test(mcp): expect the platform's line separator and shell on Windows

Listing configurations doesn't run anything, so it no longer opens the
confirmation; the run confirmation leaves out an empty working directory.
The Windows build no longer warns about an import only Unix uses.

Cargo.lock

@@ -3907,6 +3907,12 @@ version = "1.10.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6dbf3de79e51f3d586ab4cb9d5c3e2c14aa28ed23d180cf89b4df0454a69cc87"
 
+[[package]]
+name = "httpdate"
+version = "1.0.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df3b46402a9d5adb4c86a0cf463f42e19994e3ee891101b1841f30a545cb49a9"
+
 [[package]]
 name = "hybrid-array"
 version = "0.4.15"
@@ -3933,6 +3939,7 @@ dependencies = [
  "http",
  "http-body",
  "httparse",
+ "httpdate",
  "itoa",
  "pin-project-lite",
  "smallvec",
@@ -4112,6 +4119,7 @@ dependencies = [
  "encoding_rs",
  "ide-core",
  "ide-jsonrpc",
+ "ide-mcp",
  "ide-tools",
  "ide-vcs",
  "ide-vfs",
@@ -4338,6 +4346,7 @@ dependencies = [
  "dirs 6.0.0",
  "dunce",
  "encoding_rs",
+ "futures",
  "getrandom 0.3.4",
  "globset",
  "ide-agent",
@@ -4354,6 +4363,7 @@ dependencies = [
  "ide-jsonrpc",
  "ide-language",
  "ide-lsp",
+ "ide-mcp",
  "ide-notebook",
  "ide-plugin",
  "ide-remote",
@@ -4372,6 +4382,7 @@ dependencies = [
  "ignore",
  "parking_lot",
  "quick-xml 0.42.0",
+ "regex-lite",
  "regex-syntax",
  "reqwest",
  "rustix",
@@ -4529,6 +4540,25 @@ dependencies = [
  "zip",
 ]
 
+[[package]]
+name = "ide-mcp"
+version = "0.1.39"
+dependencies = [
+ "bytes",
+ "dunce",
+ "getrandom 0.3.4",
+ "http-body-util",
+ "hyper",
+ "hyper-util",
+ "percent-encoding",
+ "serde",
+ "serde_json",
+ "tempfile",
+ "tokio",
+ "tokio-util",
+ "tracing",
+]
+
 [[package]]
 name = "ide-notebook"
 version = "0.1.39"
@@ -6400,6 +6430,7 @@ dependencies = [
  "ide-jsonrpc",
  "ide-language",
  "ide-lsp",
+ "ide-mcp",
  "ide-notebook",
  "ide-plugin",
  "ide-profiler",

Cargo.toml

@@ -42,6 +42,7 @@ ide-fonts = { path = "crates/ide-fonts" }
 ide-ssh = { path = "crates/ide-ssh" }
 ide-remote = { path = "crates/ide-remote" }
 ide-host = { path = "crates/ide-host" }
+ide-mcp = { path = "crates/ide-mcp" }
 ide-notebook = { path = "crates/ide-notebook" }
 ide-extension = { path = "crates/ide-extension" }
 ide-plugin = { path = "crates/ide-plugin" }

crates/ide-agent/Cargo.toml

@@ -9,6 +9,7 @@ license.workspace = true
 encoding_rs.workspace = true
 ide-vfs.workspace = true
 ide-core.workspace = true
+ide-mcp.workspace = true
 ide-jsonrpc.workspace = true
 ide-vcs.workspace = true
 ide-tools = { path = "../ide-tools" }
@@ -21,7 +22,5 @@ tracing.workspace = true
 parking_lot.workspace = true
 dunce.workspace = true
 uuid.workspace = true
-which = "8"
-
-[dev-dependencies]
 tempfile.workspace = true
+which = "8"

crates/ide-agent/src/acp/mod.rs

@@ -92,6 +92,11 @@ pub(crate) struct Negotiated {
 }
 
 impl Negotiated {
+    pub fn mcp_stdio(&self) -> bool {
+        // Stdio is the ACP v1 baseline; v2 negotiates each transport explicitly.
+        self.capabilities.pointer("/mcpCapabilities/stdio").and_then(Value::as_bool).unwrap_or(self.generation == 1)
+    }
+
     /// Reads an `initialize` response. The shape decides, not `protocolVersion`: some v1
     /// agents report version 2 with v1 fields (`agentInfo`, `agentCapabilities`); only a
     /// v2 response has `info`.
@@ -120,7 +125,7 @@ impl Negotiated {
                 "audio": has(prompt, "audio"),
                 "embeddedContext": has(prompt, "embeddedContext"),
             },
-            "mcpCapabilities": { "http": has(mcp, "http"), "sse": false },
+            "mcpCapabilities": { "http": has(mcp, "http"), "sse": false, "stdio": has(mcp, "stdio") },
         });
         if session.is_some() {
             let mut sc = json!({ "list": {}, "resume": {}, "close": {} });

crates/ide-agent/src/acp/tests.rs

@@ -563,3 +563,13 @@ async fn v1_requests_are_sent_in_v2() {
         .collect();
     assert_eq!(commands, [&json!("28846a4c-c3e8-4a45-a3d0-c19f10d19d1a"), &json!("s1")]);
 }
+
+#[test]
+fn stdio_mcp_is_v1_baseline_and_negotiated_in_v2() {
+    assert!(super::Negotiated::from_initialize(&json!({"protocolVersion":1,"agentCapabilities":{}})).mcp_stdio());
+    assert!(!super::Negotiated::from_initialize(&json!({"info":{},"capabilities":{"session":{}}})).mcp_stdio());
+    assert!(
+        super::Negotiated::from_initialize(&json!({"info":{},"capabilities":{"session":{"mcp":{"stdio":{}}}}}))
+            .mcp_stdio()
+    );
+}

crates/ide-agent/src/lib.rs

@@ -251,6 +251,7 @@ struct Live {
     embedded: bool,
     /// `session/load`: the process can be stopped between turns and the session reloaded.
     resumable: bool,
+    mcp_stdio: bool,
 }
 
 struct Task {
@@ -696,7 +697,7 @@ impl AgentManager {
         let cwd_s = dunce::canonicalize(&cwd).unwrap_or(cwd).to_string_lossy().into_owned();
         let reply: Value = live
             .peer
-            .request("session/fork", json!({ "sessionId": live.session, "cwd": cwd_s, "mcpServers": [] }), None)
+            .request("session/fork", json!({ "sessionId": live.session, "cwd": cwd_s, "mcpServers": mcp_servers_for(live.mcp_stdio, &source.shared.paths.project_root) }), None)
             .await
             .map_err(|e| IdeError::internal(source.describe(e)))?;
         let session = reply
@@ -1449,6 +1450,7 @@ impl Task {
         let init = peer.initialize(&client_info()).await.map_err(|e| self.describe(e))?;
         let sign_in_message = spec.sign_in_message(&init.auth_methods);
         let can_load = init.load_session();
+        let mcp_stdio = init.mcp_stdio();
         let (capabilities, embedded) = capabilities_of(&init);
         // Agents that compare canonical paths fail in a symlinked directory (macOS `/tmp`).
         let cwd_s = dunce::canonicalize(&cwd).unwrap_or(cwd).to_string_lossy().into_owned();
@@ -1457,7 +1459,7 @@ impl Task {
         if let (Some(id), true) = (saved, can_load) {
             self.replaying.store(true, Ordering::Release);
             let loaded: Result<Value, RpcError> =
-                peer.request("session/load", json!({ "sessionId": id, "cwd": cwd_s, "mcpServers": [] }), None).await;
+                peer.request("session/load", json!({ "sessionId": id, "cwd": cwd_s, "mcpServers": mcp_servers_for(mcp_stdio, &self.shared.paths.project_root) }), None).await;
             tokio::time::sleep(REPLAY_GRACE).await;
             self.replaying.store(false, Ordering::Release);
             match loaded {
@@ -1470,7 +1472,11 @@ impl Task {
             Some(s) => s,
             None => {
                 let v: Value = peer
-                    .request("session/new", json!({ "cwd": cwd_s, "mcpServers": [] }), None)
+                    .request(
+                        "session/new",
+                        json!({ "cwd": cwd_s, "mcpServers": mcp_servers_for(mcp_stdio, &self.shared.paths.project_root) }),
+                        None,
+                    )
                     .await
                     .map_err(|e| self.sign_in_error(&e, Some(&sign_in_message)).unwrap_or_else(|| self.describe(e)))?;
                 let id = v.get("sessionId").and_then(Value::as_str).ok_or("the agent returned no session")?.to_owned();
@@ -1561,7 +1567,8 @@ impl Task {
         }
         self.persist();
         self.emit_task();
-        let live = Live { sign_in_message, peer, session: session_id, capabilities, embedded, resumable: can_load };
+        let live =
+            Live { sign_in_message, peer, session: session_id, capabilities, embedded, resumable: can_load, mcp_stdio };
         *self.live.lock() = Some(live.clone());
         Ok(live)
     }
@@ -2215,3 +2222,20 @@ mod replay;
 mod replay_tests;
 #[cfg(test)]
 mod tests;
+
+// The desktop advertises its relay only while the built-in server is listening.
+static MCP_EXECUTABLE: parking_lot::RwLock<Option<std::path::PathBuf>> = parking_lot::RwLock::new(None);
+
+pub fn set_mcp_executable(executable: Option<std::path::PathBuf>) {
+    *MCP_EXECUTABLE.write() = executable;
+}
+
+fn mcp_servers_for(supported: bool, root: &std::path::Path) -> Vec<Value> {
+    stdio_mcp_servers(MCP_EXECUTABLE.read().as_deref(), supported, root)
+}
+
+fn stdio_mcp_servers(executable: Option<&std::path::Path>, supported: bool, root: &std::path::Path) -> Vec<Value> {
+    let Some(executable) = executable.filter(|_| supported) else { return Vec::new() };
+    let command = ide_mcp::stdio_command(executable, root);
+    vec![json!({ "name": "OpenIDEA", "command": command[0], "args": command[1..], "env": [] })]
+}

crates/ide-agent/src/native/claude/mod.rs

@@ -98,6 +98,7 @@ pub(super) struct Shim {
 struct Session {
     id: String,
     cwd: PathBuf,
+    mcp_config: Option<tempfile::TempPath>,
     shim: Weak<Shim>,
     st: Mutex<State>,
     /// Serializes (re)starting the process.
@@ -264,9 +265,24 @@ impl Shim {
         Ok(history::chain(&entries, at.as_deref()).into_iter().cloned().collect())
     }
 
-    fn add_session(self: &Arc<Self>, id: &str, cwd: PathBuf, start: Start, pending: bool) -> Arc<Session> {
+    fn add_session(
+        self: &Arc<Self>,
+        id: &str,
+        cwd: PathBuf,
+        start: Start,
+        pending: bool,
+        mcp_config: Option<String>,
+    ) -> Arc<Session> {
+        let mcp_config = mcp_config.and_then(|json| match write_mcp_config(&json) {
+            Ok(path) => Some(path),
+            Err(e) => {
+                tracing::warn!("Claude Code session {id}: cannot write its MCP configuration: {e}");
+                None
+            }
+        });
         let session = Arc::new(Session {
             id: id.to_owned(),
+            mcp_config,
             shim: Arc::downgrade(self),
             st: Mutex::new(State {
                 proc: None,
@@ -312,6 +328,7 @@ impl Shim {
                         "loadSession": true,
                         "promptCapabilities": { "image": true, "embeddedContext": true },
                         "sessionCapabilities": { "fork": {} },
+                        "mcpCapabilities": { "stdio": true, "http": true, "sse": true },
                         "_meta": { "openidea": { "rollback": true, "steer": true, "backgroundTasks": true } },
                     },
                     "agentInfo": { "name": "claude", "title": "Claude Code", "version": self.version() },
@@ -320,7 +337,13 @@ impl Shim {
             }
             "session/new" => {
                 let id = new_uuid(false);
-                let session = self.add_session(&id, self.cwd_of(&params), Start::New { id: id.clone() }, false);
+                let session = self.add_session(
+                    &id,
+                    self.cwd_of(&params),
+                    Start::New { id: id.clone() },
+                    false,
+                    mcp_config(&params),
+                );
                 rt.block_on(session.ensure()).map_err(|e| self.start_error(&session, e))?;
                 session.announce_commands();
                 Ok(json!({ "sessionId": id, "configOptions": session.st.lock().settings.options() }))
@@ -336,7 +359,7 @@ impl Shim {
                     None => return Err(invalid(format!("no Claude Code session {id} in {}", cwd.display()))),
                 };
                 let chain = self.base_chain(&cwd, &start).map_err(internal)?;
-                let session = self.add_session(id, cwd, start, pending);
+                let session = self.add_session(id, cwd, start, pending, mcp_config(&params));
                 rt.block_on(session.ensure()).map_err(|e| self.start_error(&session, e))?;
                 if method == "session/load" {
                     session.replay(&chain);
@@ -362,7 +385,7 @@ impl Shim {
                     (start, st.settings.clone())
                 };
                 self.save_pending(&id, Some(&start));
-                let session = self.add_session(&id, source.cwd.clone(), start, true);
+                let session = self.add_session(&id, source.cwd.clone(), start, true, mcp_config(&params));
                 session.st.lock().settings = settings;
                 let options = session.st.lock().settings.options();
                 Ok(json!({ "sessionId": id, "configOptions": options }))
@@ -556,6 +579,9 @@ impl Session {
             old.end();
         }
         let mut args = shim.config.args.clone();
+        if let Some(config) = &self.mcp_config {
+            args.extend(["--mcp-config".to_owned(), config.to_string_lossy().into_owned()]);
+        }
         args.extend(start.args());
         let launch =
             Launch { program: shim.config.program.clone(), args, cwd: self.cwd.clone(), env: shim.config.env.clone() };
@@ -1345,3 +1371,38 @@ fn start_from_json(v: &Value) -> Option<Start> {
     }
     Some(Start::Fork { from: s("fork")?, id: s("id")?, at: s("at") })
 }
+
+/// Writes `json` to a new file only this user can read (removed when the path is dropped).
+fn write_mcp_config(json: &str) -> std::io::Result<tempfile::TempPath> {
+    let mut file = tempfile::Builder::new().prefix("openidea-mcp-").suffix(".json").tempfile()?;
+    std::io::Write::write_all(&mut file, json.as_bytes())?;
+    Ok(file.into_temp_path())
+}
+
+/// ACP `mcpServers` as Claude Code's `--mcp-config` JSON (`None` when there are none).
+fn mcp_config(params: &Value) -> Option<String> {
+    let servers = params.get("mcpServers")?.as_array()?;
+    let pairs = |v: Option<&Value>| -> serde_json::Map<String, Value> {
+        v.and_then(Value::as_array)
+            .into_iter()
+            .flatten()
+            .filter_map(|p| Some((p.get("name")?.as_str()?.to_owned(), p.get("value")?.clone())))
+            .collect()
+    };
+    let mut out = serde_json::Map::new();
+    for server in servers {
+        let Some(name) = server.get("name").and_then(Value::as_str) else { continue };
+        let entry = match server.get("type").and_then(Value::as_str) {
+            Some(kind @ ("http" | "sse")) => {
+                json!({ "type": kind, "url": server.get("url"), "headers": pairs(server.get("headers")) })
+            }
+            _ => json!({
+                "command": server.get("command"),
+                "args": server.get("args").cloned().unwrap_or_else(|| json!([])),
+                "env": pairs(server.get("env")),
+            }),
+        };
+        out.insert(name.to_owned(), entry);
+    }
+    (!out.is_empty()).then(|| json!({ "mcpServers": out }).to_string())
+}

crates/ide-agent/src/native/claude/tests.rs

@@ -1170,3 +1170,29 @@ async fn skipped_questions_have_no_answers() {
     let cancelled = ask_questions(&input, &json!({}), |_, _| async { None }).await;
     assert_eq!(cancelled, None);
 }
+
+#[test]
+fn mcp_servers_become_an_mcp_config() {
+    assert_eq!(mcp_config(&json!({ "mcpServers": [] })), None);
+    assert_eq!(mcp_config(&json!({})), None);
+    let config = mcp_config(&json!({ "mcpServers": [
+        { "type": "http", "name": "openidea", "url": "http://127.0.0.1:1/mcp",
+          "headers": [{ "name": "Authorization", "value": "Bearer t" }] },
+        { "name": "local", "command": "srv", "args": ["-x"], "env": [{ "name": "K", "value": "V" }] },
+    ] }))
+    .unwrap();
+    let v: Value = serde_json::from_str(&config).unwrap();
+    assert_eq!(
+        v["mcpServers"]["openidea"],
+        json!({ "type": "http", "url": "http://127.0.0.1:1/mcp", "headers": { "Authorization": "Bearer t" } })
+    );
+    assert_eq!(v["mcpServers"]["local"], json!({ "command": "srv", "args": ["-x"], "env": { "K": "V" } }));
+
+    let path = write_mcp_config(&config).unwrap();
+    assert_eq!(std::fs::read_to_string(&path).unwrap(), config);
+    #[cfg(unix)]
+    assert_eq!(std::os::unix::fs::PermissionsExt::mode(&std::fs::metadata(&path).unwrap().permissions()) & 0o077, 0);
+    let kept = path.to_path_buf();
+    drop(path);
+    assert!(!kept.exists());
+}

crates/ide-agent/src/native/codex/mod.rs

@@ -263,7 +263,7 @@ impl CodexShim {
             "agentCapabilities": {
                 "loadSession": true,
                 "promptCapabilities": { "image": true, "audio": false, "embeddedContext": true },
-                "mcpCapabilities": { "http": false, "sse": false },
+                "mcpCapabilities": { "http": false, "sse": false, "stdio": true },
                 "sessionCapabilities": { "fork": {}, "close": {} },
                 "_meta": { "openidea": { "rollback": true, "steer": true } },
             },
@@ -317,7 +317,11 @@ impl CodexShim {
 
     async fn new_session(&self, params: &Value) -> Result<Value, ResponseError> {
         let models = self.models().await;
-        let result = self.call("thread/start", json!({ "cwd": params.get("cwd") })).await?;
+        let mut request = json!({ "cwd": params.get("cwd") });
+        if let Some(config) = translate::mcp_config(params) {
+            request["config"] = config;
+        }
+        let result = self.call("thread/start", request).await?;
         let (id, options) = self.open_thread(&result, &models, None);
         if id.is_empty() {
             return Err(error(codes::INTERNAL_ERROR, "codex started no thread"));
@@ -329,7 +333,11 @@ impl CodexShim {
     async fn load_session(&self, params: &Value) -> Result<Value, ResponseError> {
         let id = str_param(params, "sessionId")?;
         let models = self.models().await;
-        let result = self.call("thread/resume", json!({ "threadId": id, "cwd": params.get("cwd") })).await?;
+        let mut request = json!({ "threadId": id, "cwd": params.get("cwd") });
+        if let Some(config) = translate::mcp_config(params) {
+            request["config"] = config;
+        }
+        let result = self.call("thread/resume", request).await?;
         let (_, options) = self.open_thread(&result, &models, None);
         let cwd = self.state.lock().threads.get(id).and_then(|t| t.cwd.clone());
         let thread = result.get("thread").unwrap_or(&Value::Null);
@@ -344,6 +352,9 @@ impl CodexShim {
         let models = self.models().await;
         let settings = self.state.lock().threads.get(source).and_then(|t| t.settings.clone());
         let mut request = json!({ "threadId": source, "cwd": params.get("cwd") });
+        if let Some(config) = translate::mcp_config(params) {
+            request["config"] = config;
+        }
         if let Some(s) = &settings {
             request["model"] = json!(s.model_slug(&models));
             request["approvalPolicy"] = json!(s.mode.approval_policy());

crates/ide-agent/src/native/codex/tests.rs

@@ -1044,3 +1044,15 @@ fn v_method(line: &str) -> Option<&str> {
     let at = line.find("\"method\":\"")? + 10;
     line[at..].split('"').next()
 }
+
+#[test]
+fn session_mcp_servers_become_thread_configuration() {
+    assert!(mcp_config(&json!({"mcpServers":[]})).is_none());
+    assert_eq!(
+        mcp_config(&json!({"mcpServers":[{"name":"OpenIDEA","command":"/app/openidea",
+        "args":["--mcp-stdio","--project","/project"],"env":[{"name":"K","value":"V"}]}]})),
+        Some(
+            json!({"mcp_servers":{"OpenIDEA":{"command":"/app/openidea","args":["--mcp-stdio","--project","/project"],"env":{"K":"V"}}}})
+        )
+    );
+}

crates/ide-agent/src/native/codex/translate.rs

@@ -836,3 +836,31 @@ pub(super) fn tail(text: &str) -> String {
 fn str_of(v: &Value, key: &str) -> Option<String> {
     v.get(key).and_then(Value::as_str).map(str::to_owned)
 }
+
+/// Session-scoped MCP configuration, carried in thread/start, resume and fork.
+pub(super) fn mcp_config(params: &Value) -> Option<Value> {
+    let mut servers = serde_json::Map::new();
+    for server in params.get("mcpServers")?.as_array()? {
+        if server.get("type").and_then(Value::as_str).is_some_and(|t| t != "stdio") {
+            continue;
+        }
+        let (Some(name), Some(command)) =
+            (server.get("name").and_then(Value::as_str), server.get("command").and_then(Value::as_str))
+        else {
+            continue;
+        };
+        let env: serde_json::Map<String, Value> = server
+            .get("env")
+            .and_then(Value::as_array)
+            .into_iter()
+            .flatten()
+            .filter_map(|v| Some((v.get("name")?.as_str()?.to_owned(), v.get("value")?.clone())))
+            .collect();
+        servers.insert(
+            name.into(),
+            json!({"command":command,
+            "args":server.get("args").cloned().unwrap_or_else(||json!([])),"env":env}),
+        );
+    }
+    (!servers.is_empty()).then(|| json!({"mcp_servers":servers}))
+}

crates/ide-agent/src/tests.rs

@@ -2255,3 +2255,17 @@ async fn delete_running_agent(no_load: bool) {
     };
     assert!(!alive, "the agent (pid {pid}) is still running");
 }
+
+#[test]
+fn mcp_servers_follow_server_state_and_agent_capabilities() {
+    let root = std::path::Path::new("/project");
+    let exe = std::path::Path::new("/app/openidea");
+    assert!(super::stdio_mcp_servers(None, true, root).is_empty());
+    assert!(super::stdio_mcp_servers(Some(exe), false, root).is_empty());
+    let servers = super::stdio_mcp_servers(Some(exe), true, root);
+    assert_eq!(
+        servers,
+        vec![json!({"name":"OpenIDEA","command":"/app/openidea",
+        "args":["--mcp-stdio","--project","/project"],"env":[]})]
+    );
+}

crates/ide-core/src/event.rs

@@ -10,9 +10,23 @@ use serde::{Deserialize, Serialize};
 use specta::Type;
 use std::sync::Arc;
 
+#[derive(Clone, Debug, Serialize, Deserialize, Type)]
+#[serde(tag = "type", rename_all = "camelCase", rename_all_fields = "camelCase")]
+pub enum McpUiRequest {
+    Confirm { client: String, tool: String, subject: String, project: String, detail: Option<String> },
+    OpenFile { path: crate::IpcPath, line: Option<u32>, column: Option<u32> },
+}
+
 #[derive(Clone, Debug, Serialize, Deserialize, Type)]
 #[serde(tag = "type", rename_all = "camelCase", rename_all_fields = "camelCase")]
 pub enum IdeEvent {
+    McpRequest {
+        id: u32,
+        request: McpUiRequest,
+    },
+    McpRequestClosed {
+        id: u32,
+    },
     /// Project window membership or selection changed.
     WindowGroupsChanged,
     /// A window entered or left full screen, itself or as a member of a full-screen window group.

crates/ide-core/src/settings.rs

@@ -61,6 +61,8 @@ pub struct Settings {
     pub cmake: CMakeSettings,
     /// Tools › Agents › Chat.
     pub agents: AgentSettings,
+    /// Tools › MCP Server (global only).
+    pub mcp_server: McpServerSettings,
     /// Plugin settings (`[contributes.settings]`): plugin id → its values by key.
     #[specta(type = BTreeMap<String, BTreeMap<String, specta_typescript::Unknown>>)]
     pub plugins: BTreeMap<String, serde_json::Map<String, serde_json::Value>>,
@@ -86,6 +88,14 @@ impl Default for AgentSettings {
     }
 }
 
+/// Tools › MCP Server: agents use the IDE's built-in tools.
+#[derive(Clone, Debug, Default, PartialEq, Eq, Serialize, Deserialize, Type)]
+#[serde(default, rename_all = "camelCase")]
+pub struct McpServerSettings {
+    /// Serve the tools on 127.0.0.1 while the IDE runs.
+    pub enabled: bool,
+}
+
 /// Absent profiles retain automatic discovery for existing projects.
 #[derive(Clone, Debug, Default, PartialEq, Serialize, Deserialize, Type)]
 #[serde(default, rename_all = "camelCase")]
@@ -230,6 +240,7 @@ impl Default for Settings {
             run_targets: Vec::new(),
             cmake: CMakeSettings::default(),
             agents: AgentSettings::default(),
+            mcp_server: McpServerSettings::default(),
             plugins: BTreeMap::new(),
         }
     }

crates/ide-host/Cargo.toml

@@ -12,9 +12,12 @@ path = "src/bin/server.rs"
 [dependencies]
 encoding_rs.workspace = true
 ide-core.workspace = true
+ide-mcp.workspace = true
+futures.workspace = true
 ide-text.workspace = true
 ide-vfs.workspace = true
 regex-syntax.workspace = true
+regex-lite = "0.1"
 ide-workspace.workspace = true
 ide-language.workspace = true
 blake3.workspace = true

crates/ide-host/src/lib.rs

@@ -8,6 +8,7 @@ pub mod environment;
 mod formatter;
 mod java_runtime;
 mod kotlin_bridge;
+pub mod mcp;
 pub mod notebook;
 pub mod ops;
 mod phpstan;
@@ -54,6 +55,8 @@ pub struct HostConfig {
 }
 
 pub struct Host {
+    pub mcp_reports: mcp::Reports,
+    pub mcp_requests: mcp::Requests,
     pub trust: trust::TrustStore,
     pub config_dir: PathBuf,
     /// Persistent user state, including credentials and recovery history.
@@ -112,6 +115,8 @@ impl Host {
         let ssh = Arc::new(ide_ssh::SshManager::new(data_dir.join("ssh-passwords.json")));
         ssh.set_configs(global_settings.effective().ssh.configs);
         let host = Self {
+            mcp_reports: Default::default(),
+            mcp_requests: Default::default(),
             trust: trust::TrustStore::load(&config_dir, &data_dir),
             proxy_password: ide_ssh::secrets::SecretFile::new(data_dir.join("proxy-password.json")),
             proxy_session_password: Mutex::default(),
@@ -219,6 +224,8 @@ impl Host {
     /// so the window can open another project at once. Returns the thread that
     /// finishes shutting down its workers.
     fn begin_close(&self, window: &str) -> Option<std::thread::JoinHandle<()>> {
+        self.mcp_reports.forget_window(window);
+        self.mcp_requests.forget_window(window);
         self.external_logs.write().remove(self.owner_window(window));
         for request in self.project_requests.write().remove(self.owner_window(window)).unwrap_or_default() {
             self.cancel_request(request);

crates/ide-host/src/mcp/edit.rs

@@ -0,0 +1,448 @@
+// Ported from JetBrains intellij-community plugins/mcp-server (mcpserver.toolsets/src/general/PatchToolset.kt, FileToolset.kt), Apache-2.0.
+//! Changing the project and the editor: new files, patches, formatting and imports,
+//! rename, open editors.
+//!
+//! Text changes go through the document layer: an open editor's buffer is
+//! patched in place and remains unsaved. Other files are opened transiently,
+//! saved and closed. Saves record Local History like the IDE's own edits.
+
+mod diff;
+mod format;
+mod patch;
+mod rename;
+
+use crate::Project;
+use crate::mcp::tool::{Call, Output, Param, ParamType, Tool};
+use ide_core::event::McpUiRequest;
+use ide_core::{DocId, FileEdit, IdeError, IdeResult, Pos, Range, TextEdit, WorkspaceEdit};
+use patch::FileOp;
+use std::fmt::Write as _;
+use std::path::{Path, PathBuf};
+
+pub fn tools() -> Vec<Tool> {
+    vec![create_new_file(), apply_patch(), format::reformat_file(), rename::rename_refactoring(), open_file_in_editor()]
+}
+
+/// What tools without a result value answer (JetBrains renders `Unit` so).
+const SUCCESS: &str = "[success]";
+
+// --- the document layer ----------------------------------------------------------
+
+/// Whether the file is open with unsaved changes.
+fn is_dirty(project: &Project, path: &Path) -> bool {
+    project.documents.by_path(path).is_some_and(|d| project.documents.is_dirty(d).unwrap_or(false))
+}
+
+async fn create_or_replace(call: &Call, path: PathBuf, text: Option<String>, overwrite: bool) -> IdeResult<()> {
+    let project = call.project.clone();
+    let edit = call
+        .host
+        .blocking(move || {
+            let mut files = Vec::new();
+            if path.exists() {
+                if !overwrite {
+                    return Err(IdeError::invalid("File already exists"));
+                }
+                if let Some(text) = text {
+                    let info = project.documents.open(&path)?;
+                    let result: IdeResult<()> = (|| {
+                        let snap = project.documents.text_snapshot(info.id)?;
+                        let doc = ide_text::Document::new(&snap.text);
+                        let edits = doc
+                            .diff(&text)
+                            .changes
+                            .into_iter()
+                            .map(|c| TextEdit {
+                                range: Range::new(doc.offset_to_pos(c.from), doc.offset_to_pos(c.to)),
+                                new_text: c.insert,
+                            })
+                            .collect();
+                        files.push(FileEdit::Edit {
+                            path: path.into(),
+                            edits,
+                            version: Some(
+                                i32::try_from(snap.version)
+                                    .map_err(|_| IdeError::invalid("document version is out of range"))?,
+                            ),
+                        });
+                        Ok(())
+                    })();
+                    project.documents.close(info.id);
+                    result?;
+                }
+            } else {
+                files.push(FileEdit::Create { path: path.clone().into(), overwrite: false });
+                if let Some(text) = text {
+                    files.push(FileEdit::Edit {
+                        path: path.into(),
+                        edits: vec![TextEdit { range: Range::point(Pos::new(0, 0)), new_text: text }],
+                        version: None,
+                    });
+                }
+            }
+            Ok(WorkspaceEdit { files, preconditions: Vec::new() })
+        })
+        .await?;
+    if edit.files.is_empty() {
+        return Ok(());
+    }
+    let edit = crate::ops::lsp::prepare_workspace_edit(&call.host, call.window(), edit).await?;
+    crate::ops::lsp::apply_workspace_edit(&call.host, call.window(), edit).await
+}
+
+/// The open document of `path`, or a transient one (`true`: close it after use).
+fn open_document(project: &Project, path: &Path) -> IdeResult<(DocId, bool)> {
+    match project.documents.by_path(path) {
+        Some(doc) => Ok((doc, false)),
+        None => Ok((project.documents.open(path)?.id, true)),
+    }
+}
+
+fn normalize_newlines(text: &str) -> String {
+    text.replace("\r\n", "\n").replace('\r', "\n")
+}
+
+/// The range of a whole text.
+fn whole_range(text: &str) -> Range {
+    let count = text.split('\n').count();
+    let last = text.rsplit('\n').next().unwrap_or("");
+    Range::new(Pos::new(0, 0), Pos::new(count.saturating_sub(1) as u32, last.encode_utf16().count() as u32))
+}
+
+/// Whether two paths name the same file (language servers report canonical paths; on a
+/// case-insensitive file system `a.txt` and `A.txt` are one file).
+fn same_file(a: &Path, b: &Path) -> bool {
+    if a == b || matches!((dunce::canonicalize(a), dunce::canonicalize(b)), (Ok(x), Ok(y)) if x == y) {
+        return true;
+    }
+    #[cfg(unix)]
+    {
+        use std::os::unix::fs::MetadataExt;
+        if let (Ok(x), Ok(y)) = (std::fs::metadata(a), std::fs::metadata(b)) {
+            return x.dev() == y.dev() && x.ino() == y.ino();
+        }
+    }
+    false
+}
+
+/// The text edits of `edit` for `path`.
+fn edits_for(edit: &WorkspaceEdit, path: &Path) -> Vec<TextEdit> {
+    edit.files
+        .iter()
+        .filter_map(|f| match f {
+            ide_core::FileEdit::Edit { path: p, edits, .. } if same_file(p, path) => Some(edits.clone()),
+            _ => None,
+        })
+        .flatten()
+        .collect()
+}
+
+/// Re-reads the open, unmodified documents of `paths` whose files changed on disk, before
+/// a tool reads or changes them: an agent that just wrote a file itself must not have
+/// that write undone from a stale buffer because the file watcher has not caught up yet
+/// (JetBrains refreshes the VFS first). Documents with unsaved changes are left alone.
+fn refresh_from_disk(project: &Project, paths: &[PathBuf]) {
+    project.documents.on_disk_changed(paths);
+}
+
+/// Project files a tool works on: `files` resolved inside the project, existing,
+/// regular, without duplicates (the first spelling is kept), changeable
+/// ([`Call::check_writable`]) and with their open documents up to date with the disk.
+async fn requested_files(call: &Call) -> IdeResult<Vec<(String, PathBuf)>> {
+    let files = call.str_list("files")?;
+    if files.is_empty() {
+        return Err(IdeError::invalid("files must contain at least one path"));
+    }
+    let mut out: Vec<(String, PathBuf)> = Vec::new();
+    for raw in files {
+        let raw = raw.trim();
+        if raw.is_empty() {
+            return Err(IdeError::invalid("files must not contain blank paths"));
+        }
+        let path = call.resolve_inside(raw)?;
+        if !path.exists() {
+            return Err(IdeError::not_found(format!("File not found: {raw}")));
+        }
+        if !path.is_file() {
+            return Err(IdeError::invalid(format!("Not a file: {raw}")));
+        }
+        if !out.iter().any(|(_, p)| *p == path) {
+            out.push((raw.to_owned(), path));
+        }
+    }
+    for (_, path) in &out {
+        call.check_writable(path).await?;
+    }
+    let (project, paths) = (call.project().clone(), out.iter().map(|(_, p)| p.clone()).collect::<Vec<_>>());
+    call.host()
+        .blocking(move || {
+            refresh_from_disk(&project, &paths);
+            Ok(())
+        })
+        .await?;
+    Ok(out)
+}
+
+// --- create_new_file ----------------------------------------------------------------
+
+fn create_new_file() -> Tool {
+    Tool::new(
+        "create_new_file",
+        "Creates a new file at the specified path within the project directory and optionally populates it with \
+text if provided.
+Use this tool to generate new files in your project structure.
+Note: Creates any necessary parent directories automatically",
+        |call| async move {
+            let raw = call.str("pathInProject")?;
+            let path = call.resolve_writable(&raw).await?;
+            let text = call.opt_str("text")?.map(|t| normalize_newlines(&t));
+            let overwrite = call.flag("overwrite", false)?;
+            let cannot =
+                |e: &dyn std::fmt::Display| IdeError::invalid(format!("Can't create file: {}: {e}", path.display()));
+            if path.is_dir() {
+                return Err(cannot(&"it is a directory"));
+            }
+            if path.exists() && !overwrite {
+                return Err(IdeError::new(
+                    ide_core::error::ErrorKind::AlreadyExists,
+                    format!("File already exists: {raw}. Specify 'overwrite=true' to overwrite it"),
+                ));
+            }
+            create_or_replace(&call, path, text, overwrite).await?;
+            Ok(Output::text(SUCCESS))
+        },
+    )
+    .write()
+    .param(Param::required(
+        "pathInProject",
+        ParamType::String,
+        "Path where the file should be created relative to the project root",
+    ))
+    .param(Param::optional("text", ParamType::String, "Content to write into the new file"))
+    .param(Param::optional(
+        "overwrite",
+        ParamType::Boolean,
+        "Whether to overwrite an existing file if exists. If false, an exception is thrown in case of a conflict.",
+    ))
+}
+
+// --- apply_patch --------------------------------------------------------------------
+
+fn apply_patch() -> Tool {
+    Tool::new(
+        "apply_patch",
+        "Apply a patch using the Codex apply_patch format or unified git diff format.
+Supports Add, Delete, and Update operations with optional Move to path for updates.
+Paths must stay inside the project directory.",
+        |call| async move {
+            let input = [call.opt_str("input")?, call.opt_str("patch")?]
+                .into_iter()
+                .flatten()
+                .find(|s| !s.trim().is_empty())
+                .ok_or_else(|| IdeError::invalid("input must be a non-empty string"))?;
+            let ops = patch::parse(&input).map_err(IdeError::invalid)?;
+            let total = ops.iter().filter(|op| !matches!(op, FileOp::Skip { .. })).count();
+            let mut applied = 0usize;
+            let mut errors = Vec::new();
+            let mut notes = Vec::new();
+            // Each operation stands alone, as in JetBrains: a failed one leaves the others applied.
+            for op in ops {
+                if let FileOp::Skip { path, note } = op {
+                    notes.push(format!("{path}: {note}"));
+                    continue;
+                }
+                let path = op.path().to_owned();
+                match apply_op(&call, op, &mut notes).await {
+                    Ok(()) => applied += 1,
+                    Err(e) if e.kind == ide_core::error::ErrorKind::Cancelled => return Err(e),
+                    Err(e) => errors.push(format!("{path}: {}", e.message)),
+                }
+            }
+            let mut out = format!("{applied} out of {total} operations applied.");
+            if !errors.is_empty() {
+                let _ = write!(
+                    out,
+                    " {} operations failed to be applied due to errors:\n{}",
+                    errors.len(),
+                    errors.join("\n")
+                );
+            }
+            if !notes.is_empty() {
+                out.push_str("\nNotes:");
+                for n in notes {
+                    let _ = write!(out, "\n- {n}");
+                }
+            }
+            Ok(Output::text(out))
+        },
+    )
+    .write()
+    .param(Param::optional(
+        "input",
+        ParamType::String,
+        "Patch text in the apply_patch format or unified git diff format.",
+    ))
+    .param(Param::optional(
+        "patch",
+        ParamType::String,
+        "Alias of `input` for compatibility with clients that send `{patch: ...}`.",
+    ))
+}
+
+/// Applies one operation of a patch; its checks come first, so a failed operation changes nothing.
+async fn apply_op(call: &Call, op: FileOp, notes: &mut Vec<String>) -> IdeResult<()> {
+    let host = call.host();
+    let project = call.project().clone();
+    match op {
+        // Noted by the caller.
+        FileOp::Skip { .. } => Ok(()),
+        FileOp::Add { path: raw, text } => {
+            let path = call.resolve_writable(&raw).await?;
+            if path.exists() {
+                return Err(IdeError::invalid(format!("File already exists: {raw}")));
+            }
+            create_or_replace(call, path, Some(text), false).await
+        }
+        FileOp::Delete { path: raw } => {
+            let path = call.resolve_writable(&raw).await?;
+            if !path.is_file() {
+                return Err(IdeError::not_found(format!("File not found: {raw}")));
+            }
+            if is_dirty(&project, &path) {
+                return Err(IdeError::invalid("cannot delete a file with unsaved editor changes"));
+            }
+            let edit = WorkspaceEdit {
+                files: vec![FileEdit::Delete { path: path.into(), recursive: false }],
+                preconditions: Vec::new(),
+            };
+            let edit = crate::ops::lsp::prepare_workspace_edit(&host, call.window(), edit).await?;
+            crate::ops::lsp::apply_workspace_edit(&host, call.window(), edit).await
+        }
+        FileOp::Update { path: first, move_to, hunks, or } => {
+            // A plain diff's other names count when its `+++` path does not exist.
+            let mut raw = first.clone();
+            let mut path = call.resolve_inside(&raw)?;
+            for other in &or {
+                if path.exists() {
+                    break;
+                }
+                let candidate = call.resolve_inside(other)?;
+                if candidate.exists() {
+                    (raw, path) = (other.clone(), candidate);
+                }
+            }
+            if !path.exists() {
+                let tried = if or.is_empty() { String::new() } else { format!(" (also tried {})", or.join(", ")) };
+                return Err(IdeError::not_found(format!("File not found: {first}{tried}")));
+            }
+            if !path.is_file() {
+                return Err(IdeError::invalid(format!("Path is not a file: {raw}")));
+            }
+            if !hunks.is_empty() || move_to.is_some() {
+                call.check_writable(&path).await?;
+            }
+            let to = match &move_to {
+                Some(m) => {
+                    let to = call.resolve_writable(m).await?;
+                    // A move that changes only the case on a case-insensitive file system finds itself.
+                    if to != path && to.exists() && !same_file(&to, &path) {
+                        return Err(IdeError::new(
+                            ide_core::error::ErrorKind::AlreadyExists,
+                            format!("File already exists: {m}"),
+                        ));
+                    }
+                    Some(to).filter(|t| *t != path)
+                }
+                None => None,
+            };
+            let shown = call.display(&path);
+            let (p, target) = (project.clone(), path.clone());
+            let (mut edit, fuzzy, dirty) = host
+                .blocking(move || {
+                    refresh_from_disk(&p, std::slice::from_ref(&target));
+                    let info = p.documents.open(&target)?;
+                    let result = (|| {
+                        let snap = p.documents.text_snapshot(info.id)?;
+                        let dirty = p.documents.is_dirty(info.id)?;
+                        let applied = patch::apply(&snap.text, &hunks).map_err(IdeError::invalid)?;
+                        let text = ide_text::Document::new(&snap.text);
+                        let edits = text
+                            .diff(&applied.text)
+                            .changes
+                            .into_iter()
+                            .map(|c| TextEdit {
+                                range: Range::new(text.offset_to_pos(c.from), text.offset_to_pos(c.to)),
+                                new_text: c.insert,
+                            })
+                            .collect();
+                        Ok((
+                            WorkspaceEdit {
+                                files: vec![FileEdit::Edit {
+                                    path: target.clone().into(),
+                                    edits,
+                                    version: Some(
+                                        i32::try_from(snap.version)
+                                            .map_err(|_| IdeError::invalid("document version is out of range"))?,
+                                    ),
+                                }],
+                                preconditions: Vec::new(),
+                            },
+                            applied.fuzzy,
+                            dirty,
+                        ))
+                    })();
+                    p.documents.close(info.id);
+                    result
+                })
+                .await?;
+            if let Some(to) = to {
+                edit.files.push(FileEdit::Rename { from: path.into(), to: to.into() });
+            }
+            let edit = crate::ops::lsp::prepare_workspace_edit(&host, call.window(), edit).await?;
+            crate::ops::lsp::apply_workspace_edit(&host, call.window(), edit).await?;
+            if dirty {
+                notes.push(format!("{shown}: patched the unsaved editor buffer"));
+            }
+            for (hunk, fuzz) in fuzzy {
+                notes.push(format!("{shown}: hunk {hunk} matched only {}", fuzz.describe()));
+            }
+            Ok(())
+        }
+    }
+}
+
+// --- the editor ------------------------------------------------------------------------
+
+fn open_file_in_editor() -> Tool {
+    Tool::new(
+        "open_file_in_editor",
+        "Opens the specified file in the IDE editor.
+Requires a filePath parameter containing the path to the file to open.
+The file path can be absolute or relative to the project root.
+Optionally puts the caret at a 1-based line and column.",
+        |call| async move {
+            let raw = call.str("filePath")?;
+            // Opening shows the file to the user: outside the project the user agrees first.
+            let path = call.resolve_readable(&raw).await?;
+            if !path.is_file() {
+                return Err(IdeError::not_found(format!("File {raw} doesn't exist or can't be opened")));
+            }
+            let positive = |name: &str| -> IdeResult<Option<u32>> {
+                match call.opt_i64(name)? {
+                    None => Ok(None),
+                    Some(n) if n < 1 || n > u32::MAX as i64 => {
+                        Err(IdeError::invalid(format!("`{name}` is 1-based and must be at least 1")))
+                    }
+                    Some(n) => Ok(Some(n as u32)),
+                }
+            };
+            let (line, column) = (positive("line")?, positive("column")?);
+            call.ask(McpUiRequest::OpenFile { path: path.into(), line, column }).await?;
+            Ok(Output::text(SUCCESS))
+        },
+    )
+    .write()
+    .param(Param::required("filePath", ParamType::String, "Path relative to the project root"))
+    .param(Param::optional("line", ParamType::Integer, "1-based line to put the caret on"))
+    .param(Param::optional("column", ParamType::Integer, "1-based column on that line"))
+}

crates/ide-host/src/mcp/edit/diff.rs

@@ -0,0 +1,380 @@
+// Ported from JetBrains intellij-community plugins/mcp-server (mcpserver.toolsets/src/general/UnifiedDiffSupport.kt), Apache-2.0.
+//! The unified diff tools answer with, so an agent sees what the IDE changed
+//! without reading the files again. Capped, so a large change cannot flood the
+//! agent's context.
+
+/// Unchanged lines kept around each change, as in a standard unified diff.
+const CONTEXT_LINES: usize = 3;
+
+/// The default cap on diff lines.
+pub const MAX_DIFF_LINES: usize = 200;
+
+/// The smallest useful hunk: the `@@` header line and one line under it.
+const MIN_HUNK_LINES: usize = 2;
+
+/// Beyond this many differing lines (after the common head and tail) the
+/// diff is not computed: the file is reported as too large to diff.
+const MAX_EDIT_DISTANCE: usize = 2000;
+
+/// One file a tool processed: the requested path, the text before and after.
+/// `None` texts are reported as unavailable, never as "nothing changed".
+pub struct ChangedFileText {
+    pub path: String,
+    pub before: Option<String>,
+    pub after: Option<String>,
+}
+
+/// A unified diff of the changes in `files`, at most `max_lines` diff lines;
+/// `None` when nothing changed. A file goes in whole, or the footer names it.
+pub fn build_unified_diff(files: &[ChangedFileText], max_lines: usize) -> Option<String> {
+    let mut lines: Vec<String> = Vec::new();
+    let mut omitted_files = Vec::new();
+    let mut omitted_lines = 0usize;
+    for file in files {
+        let Some(diff) = file_diff(file) else { continue };
+        // A header with no hunk under it helps nobody.
+        if !lines.is_empty() && max_lines.saturating_sub(lines.len()) < diff.header.len() + MIN_HUNK_LINES {
+            omitted_files.push(diff.path.clone());
+            omitted_lines += diff.line_count();
+            continue;
+        }
+        lines.extend(diff.header.iter().cloned());
+        for (index, hunk) in diff.hunks.iter().enumerate() {
+            let room = max_lines as isize - lines.len() as isize - 1;
+            if room < 1 && index > 0 {
+                omitted_lines += diff.hunks[index..].iter().map(Hunk::line_count).sum::<usize>();
+                break;
+            }
+            // The first hunk always keeps one line, so its file header never stands alone.
+            let body = room.max(1) as usize;
+            lines.extend(hunk.render(body));
+            omitted_lines += hunk.body.len().saturating_sub(body);
+        }
+    }
+    if lines.is_empty() {
+        return None;
+    }
+    let mut out = lines.join("\n");
+    if omitted_lines > 0 {
+        out.push_str(&format!("\n… and {omitted_lines} more diff line(s) omitted."));
+    }
+    if !omitted_files.is_empty() {
+        out.push_str(&format!("\n… The diff leaves out these file(s): {}.", omitted_files.join(", ")));
+    }
+    Some(out)
+}
+
+struct FileDiff {
+    path: String,
+    header: Vec<String>,
+    hunks: Vec<Hunk>,
+}
+
+impl FileDiff {
+    fn line_count(&self) -> usize {
+        self.header.len() + self.hunks.iter().map(Hunk::line_count).sum::<usize>()
+    }
+}
+
+/// One hunk: where it starts on each side (0-based), and its `-`, `+` and context lines.
+struct Hunk {
+    start0: usize,
+    start1: usize,
+    body: Vec<String>,
+}
+
+impl Hunk {
+    fn line_count(&self) -> usize {
+        self.body.len() + 1
+    }
+
+    /// The hunk with at most `max_body` body lines; the header counts the lines it prints.
+    fn render(&self, max_body: usize) -> Vec<String> {
+        let printed = &self.body[..self.body.len().min(max_body)];
+        let count0 = printed.iter().filter(|l| l.starts_with(' ') || l.starts_with('-')).count();
+        let count1 = printed.iter().filter(|l| l.starts_with(' ') || l.starts_with('+')).count();
+        // An empty range names the line before it, so it keeps the 0-based value.
+        let start = |s: usize, count: usize| if count == 0 { s } else { s + 1 };
+        let mut out =
+            vec![format!("@@ -{},{count0} +{},{count1} @@", start(self.start0, count0), start(self.start1, count1))];
+        out.extend(printed.iter().cloned());
+        out
+    }
+}
+
+/// A line of the text, and whether it ends without a line separator (the last line).
+type DiffLine<'a> = (&'a str, bool);
+
+fn file_diff(file: &ChangedFileText) -> Option<FileDiff> {
+    let path = file.path.replace('\\', "/");
+    let header = vec![format!("--- a/{path}"), format!("+++ b/{path}")];
+    let note = |text: &str| {
+        let mut header = header.clone();
+        header.push(format!("({text})"));
+        Some(FileDiff { path: path.clone(), header, hunks: Vec::new() })
+    };
+    let (Some(before), Some(after)) = (&file.before, &file.after) else {
+        return note(
+            "the content of this file is not available, so the diff cannot report what changed; read the file again",
+        );
+    };
+    if before == after {
+        return None;
+    }
+    let old = split_lines(before);
+    let new = split_lines(after);
+    let Some(changes) = changes(&old, &new) else { return note("this file changed, but it is too large to diff") };
+    // The texts differ but the lines are equal: only the line separators changed.
+    if changes.is_empty() {
+        return note("only the line separators of this file changed");
+    }
+    let hunks = group(&changes).into_iter().map(|g| build_hunk(g, &old, &new)).collect();
+    Some(FileDiff { path, header, hunks })
+}
+
+/// The lines a diff compares: no extra empty line after a final separator; a
+/// last line without one is marked, so a change of the final separator alone counts.
+fn split_lines(text: &str) -> Vec<DiffLine<'_>> {
+    if text.is_empty() {
+        return Vec::new();
+    }
+    let ends_with_newline = text.ends_with('\n');
+    let mut lines: Vec<DiffLine> = text.split('\n').map(|l| (l.strip_suffix('\r').unwrap_or(l), false)).collect();
+    if ends_with_newline {
+        lines.pop();
+    } else if let Some(last) = lines.last_mut() {
+        last.1 = true;
+    }
+    lines
+}
+
+/// A run of changed lines: at `line0` in the old text `deleted` lines, at `line1` in the new one `inserted`.
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+struct Change {
+    line0: usize,
+    line1: usize,
+    deleted: usize,
+    inserted: usize,
+}
+
+/// The changes from `a` to `b` (Myers' algorithm), `None` when they differ too much.
+fn changes(a: &[DiffLine], b: &[DiffLine]) -> Option<Vec<Change>> {
+    let head = a.iter().zip(b).take_while(|(x, y)| x == y).count();
+    let tail = a[head..].iter().rev().zip(b[head..].iter().rev()).take_while(|(x, y)| x == y).count();
+    let (a_mid, b_mid) = (&a[head..a.len() - tail], &b[head..b.len() - tail]);
+    let script = myers(a_mid, b_mid)?;
+    // `script`: per step, true = equal (both advance), Some side otherwise.
+    let mut out: Vec<Change> = Vec::new();
+    let (mut i, mut j) = (head, head);
+    for step in script {
+        match step {
+            Step::Equal => {
+                i += 1;
+                j += 1;
+                continue;
+            }
+            Step::Delete => {
+                match out.last_mut() {
+                    Some(c) if c.line0 + c.deleted == i && c.line1 + c.inserted == j => c.deleted += 1,
+                    _ => out.push(Change { line0: i, line1: j, deleted: 1, inserted: 0 }),
+                }
+                i += 1;
+            }
+            Step::Insert => {
+                match out.last_mut() {
+                    Some(c) if c.line0 + c.deleted == i && c.line1 + c.inserted == j => c.inserted += 1,
+                    _ => out.push(Change { line0: i, line1: j, deleted: 0, inserted: 1 }),
+                }
+                j += 1;
+            }
+        }
+    }
+    Some(out)
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+enum Step {
+    Equal,
+    Delete,
+    Insert,
+}
+
+/// The shortest edit script from `a` to `b`, deletions before insertions in each run.
+fn myers(a: &[DiffLine], b: &[DiffLine]) -> Option<Vec<Step>> {
+    let (n, m) = (a.len() as isize, b.len() as isize);
+    let max = (n + m) as usize;
+    let limit = max.min(MAX_EDIT_DISTANCE) as isize;
+    let off = max as isize + 1;
+    let mut v = vec![0isize; 2 * max + 3];
+    // V after each round d, for diagonals -d..=d.
+    let mut trace: Vec<Vec<isize>> = Vec::new();
+    let mut end = None;
+    'rounds: for d in 0..=limit {
+        for k in (-d..=d).step_by(2) {
+            let at = |k: isize| (off + k) as usize;
+            let mut x =
+                if k == -d || (k != d && v[at(k - 1)] < v[at(k + 1)]) { v[at(k + 1)] } else { v[at(k - 1)] + 1 };
+            let mut y = x - k;
+            while x < n && y < m && a[x as usize] == b[y as usize] {
+                x += 1;
+                y += 1;
+            }
+            v[at(k)] = x;
+            if x >= n && y >= m {
+                trace.push(v[at(-d)..=at(d)].to_vec());
+                end = Some(d);
+                break 'rounds;
+            }
+        }
+        trace.push(v[(off - d) as usize..=(off + d) as usize].to_vec());
+    }
+    let d_end = end?;
+    let mut steps = Vec::new();
+    let (mut x, mut y) = (n, m);
+    for d in (1..=d_end).rev() {
+        let prev = &trace[(d - 1) as usize];
+        let get = |k: isize| prev[(k + d - 1) as usize];
+        let k = x - y;
+        let insert = k == -d || (k != d && get(k - 1) < get(k + 1));
+        let prev_k = if insert { k + 1 } else { k - 1 };
+        let prev_x = get(prev_k);
+        let prev_y = prev_x - prev_k;
+        let (mid_x, mid_y) = if insert { (prev_x, prev_y + 1) } else { (prev_x + 1, prev_y) };
+        while x > mid_x && y > mid_y {
+            steps.push(Step::Equal);
+            x -= 1;
+            y -= 1;
+        }
+        steps.push(if insert { Step::Insert } else { Step::Delete });
+        (x, y) = (prev_x, prev_y);
+    }
+    steps.extend(std::iter::repeat_n(Step::Equal, x as usize));
+    steps.reverse();
+    // Within a run of changes, deletions first (as `-` lines precede `+` lines).
+    let mut i = 0;
+    while i < steps.len() {
+        if steps[i] == Step::Equal {
+            i += 1;
+            continue;
+        }
+        let end = steps[i..].iter().position(|s| *s == Step::Equal).map_or(steps.len(), |p| i + p);
+        steps[i..end].sort_by_key(|s| *s == Step::Insert);
+        i = end;
+    }
+    Some(steps)
+}
+
+/// Changes whose context lines touch share a hunk.
+fn group(changes: &[Change]) -> Vec<&[Change]> {
+    let mut out: Vec<&[Change]> = Vec::new();
+    let mut start = 0;
+    for i in 1..changes.len() {
+        let prev = changes[i - 1];
+        if changes[i].line0 - (prev.line0 + prev.deleted) > CONTEXT_LINES * 2 {
+            out.push(&changes[start..i]);
+            start = i;
+        }
+    }
+    if !changes.is_empty() {
+        out.push(&changes[start..]);
+    }
+    out
+}
+
+fn build_hunk(group: &[Change], old: &[DiffLine], new: &[DiffLine]) -> Hunk {
+    let (first, last) = (group[0], group[group.len() - 1]);
+    // One clamp for both sides, so the two starts in the header stay in step.
+    let leading = CONTEXT_LINES.min(first.line0).min(first.line1);
+    let (start0, start1) = (first.line0 - leading, first.line1 - leading);
+    let (end0, end1) = (last.line0 + last.deleted, last.line1 + last.inserted);
+    let trailing = CONTEXT_LINES.min(old.len() - end0).min(new.len() - end1);
+    let mut body = Vec::new();
+    let push = |body: &mut Vec<String>, prefix: char, (text, no_newline): DiffLine| {
+        body.push(format!("{prefix}{text}"));
+        if no_newline {
+            body.push("\\ No newline at end of file".into());
+        }
+    };
+    let mut line0 = start0;
+    for c in group {
+        while line0 < c.line0 {
+            push(&mut body, ' ', old[line0]);
+            line0 += 1;
+        }
+        for &l in &old[c.line0..c.line0 + c.deleted] {
+            push(&mut body, '-', l);
+        }
+        for &l in &new[c.line1..c.line1 + c.inserted] {
+            push(&mut body, '+', l);
+        }
+        line0 = c.line0 + c.deleted;
+    }
+    while line0 < end0 + trailing {
+        push(&mut body, ' ', old[line0]);
+        line0 += 1;
+    }
+    Hunk { start0, start1, body }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn diff(before: &str, after: &str) -> Option<String> {
+        build_unified_diff(
+            &[ChangedFileText { path: "src/A.java".into(), before: Some(before.into()), after: Some(after.into()) }],
+            MAX_DIFF_LINES,
+        )
+    }
+
+    #[test]
+    fn diffs_a_reformat_like_jetbrains() {
+        let out = diff("public class DiffTarget {\nint a;\n}\n", "public class DiffTarget {\n    int a;\n}\n").unwrap();
+        assert_eq!(
+            out,
+            "--- a/src/A.java\n+++ b/src/A.java\n@@ -1,3 +1,3 @@\n public class DiffTarget {\n-int a;\n+    int a;\n }"
+        );
+        assert_eq!(diff("same\n", "same\n"), None);
+    }
+
+    #[test]
+    fn splits_far_changes_into_hunks_and_marks_the_final_newline() {
+        let before: String = (1..=20).map(|i| format!("{i}\n")).collect();
+        let after: String = (1..=20)
+            .map(|i| match i {
+                2 => "two\n".to_owned(),
+                19 => "nineteen\n".to_owned(),
+                i => format!("{i}\n"),
+            })
+            .collect();
+        let out = diff(&before, &after).unwrap();
+        assert!(out.contains("@@ -1,5 +1,5 @@\n 1\n-2\n+two\n 3\n 4\n 5\n"), "{out}");
+        assert!(out.contains("@@ -16,5 +16,5 @@\n 16\n 17\n 18\n-19\n+nineteen\n 20"), "{out}");
+        let out = diff("a\nb", "a\nb\n").unwrap();
+        assert!(out.ends_with("@@ -1,2 +1,2 @@\n a\n-b\n\\ No newline at end of file\n+b"), "{out}");
+        let out = diff("a\r\n", "a\n").unwrap();
+        assert!(out.ends_with("(only the line separators of this file changed)"), "{out}");
+        let out = diff("", "x\n").unwrap();
+        assert!(out.ends_with("@@ -0,0 +1,1 @@\n+x"), "{out}");
+        let out = diff("import a;\n\nclass X {}\n", "\nclass X {}\n").unwrap();
+        assert!(out.ends_with("@@ -1,3 +1,2 @@\n-import a;\n \n class X {}"), "{out}");
+    }
+
+    #[test]
+    fn caps_the_diff_and_names_what_it_leaves_out() {
+        let before: String = (0..300).map(|i| format!("{i}\n")).collect();
+        let after: String = (0..300).map(|i| format!("x{i}\n")).collect();
+        let files = [
+            ChangedFileText { path: "a.txt".into(), before: Some(before.clone()), after: Some(after.clone()) },
+            ChangedFileText { path: "b.txt".into(), before: Some(before), after: Some(after) },
+            ChangedFileText { path: "c.bin".into(), before: None, after: None },
+        ];
+        let out = build_unified_diff(&files, 50).unwrap();
+        assert_eq!(out.lines().filter(|l| !l.starts_with('…')).count(), 50, "{out}");
+        // 553 lines of a.txt's hunk, 603 of b.txt, 3 of c.bin's note.
+        assert!(out.contains("… and 1159 more diff line(s) omitted."), "{out}");
+        assert!(out.ends_with("… The diff leaves out these file(s): b.txt, c.bin."), "{out}");
+        // The cut hunk's header counts what it prints.
+        assert!(out.contains("@@ -1,47 +0,0 @@"), "{out}");
+    }
+}

crates/ide-host/src/mcp/edit/format.rs

@@ -0,0 +1,199 @@
+// Ported from JetBrains intellij-community plugins/mcp-server (mcpserver.toolsets/src/general/FormattingToolset.kt), Apache-2.0.
+//! `reformat_file` and `optimize_imports` with the language servers: document
+//! formatting and the `source.organizeImports` code action. Both answer with a
+//! unified diff of what changed, or `ok`.
+//!
+//! JetBrains always has a formatter and an import optimizer; here a file whose
+//! language server offers none is reported after the diff (the whole call fails
+//! only when no file could be processed).
+
+use super::diff::{ChangedFileText, MAX_DIFF_LINES, build_unified_diff};
+use super::{edits_for, open_document, requested_files, whole_range};
+use crate::mcp::tool::{Call, Output, Param, ParamType, Tool};
+use ide_core::{DocId, IdeError, IdeResult};
+use std::path::Path;
+
+const ORGANIZE_IMPORTS: &str = "source.organizeImports";
+
+pub(super) fn reformat_file() -> Tool {
+    Tool::new(
+        "reformat_file",
+        "Reformats the specified files in the IDE.
+Use this tool to apply code formatting rules to files identified by their project-relative paths.
+Returns a unified diff of the changes that the formatter applied, or \"ok\" when the files already match the code \
+style.
+The diff shows the formatter changes only. It never repeats the edit that you applied yourself.
+The diff stops at 200 lines. A footer names the file(s) that it leaves out.
+To remove unused imports without reformatting, use optimize_imports.",
+        |call| async move {
+            let organize = call.flag("optimizeImports", false)?;
+            run(&call, Job { organize, format: true }).await
+        },
+    )
+    .write()
+    .param(Param::required(
+        "files",
+        ParamType::StringList,
+        "List of project-relative files to reformat. Duplicate paths are ignored after normalization.",
+    ))
+    .param(Param::optional(
+        "optimizeImports",
+        ParamType::Boolean,
+        "If true, also remove unused imports and order the remaining ones before reformatting.",
+    ))
+}
+
+#[derive(Clone, Copy)]
+struct Job {
+    organize: bool,
+    format: bool,
+}
+
+async fn run(call: &Call, job: Job) -> IdeResult<Output> {
+    let files = requested_files(call).await?;
+    let mut changed = Vec::new();
+    let mut problems = Vec::new();
+    for (raw, path) in &files {
+        match process(call, path, job).await {
+            Ok(outcome) => {
+                changed.push(ChangedFileText {
+                    path: raw.clone(),
+                    before: Some(outcome.before),
+                    after: Some(outcome.after),
+                });
+                problems.extend(outcome.notes.into_iter().map(|n| format!("{raw}: {n}")));
+            }
+            Err(e) if e.kind == ide_core::error::ErrorKind::Cancelled => return Err(e),
+            Err(e) => {
+                let what = if job.format { "not formatted" } else { "imports not optimized" };
+                problems.push(format!("{raw}: {what}: {}", e.message));
+            }
+        }
+    }
+    if changed.is_empty() {
+        return Err(IdeError::unavailable(problems.join("\n")));
+    }
+    let mut out = build_unified_diff(&changed, MAX_DIFF_LINES).unwrap_or_else(|| "ok".into());
+    if !problems.is_empty() {
+        out.push_str("\n\n");
+        out.push_str(&problems.join("\n"));
+    }
+    Ok(Output::text(out))
+}
+
+struct Outcome {
+    before: String,
+    after: String,
+    /// What went wrong without failing the file (imports not optimized before a reformat).
+    notes: Vec<String>,
+}
+
+/// Runs the job on one file's document (opened transiently when it is not open) and saves it.
+async fn process(call: &Call, path: &Path, job: Job) -> IdeResult<Outcome> {
+    let host = call.host();
+    let project = call.project().clone();
+    let (p, target) = (project.clone(), path.to_path_buf());
+    let (doc, transient) = host.blocking(move || open_document(&p, &target)).await?;
+    let result = async {
+        let info = project.documents.snapshot(doc)?;
+        if info.read_only {
+            return Err(IdeError::invalid("the file is read-only"));
+        }
+        let before = project.documents.text_snapshot(doc)?.text;
+        let mut notes = Vec::new();
+        if job.organize {
+            match organize_imports(call, doc, path).await {
+                Ok(()) => {}
+                Err(e) if job.format && e.kind != ide_core::error::ErrorKind::Cancelled => {
+                    notes.push(format!("imports not optimized: {}", e.message));
+                }
+                Err(e) => return Err(e),
+            }
+        }
+        if job.format {
+            format(call, doc, &info).await?;
+        }
+        let p = project.clone();
+        let after = host
+            .blocking(move || {
+                if !info.dirty && p.documents.is_dirty(doc)? {
+                    p.documents.save(doc)?;
+                }
+                Ok(p.documents.text_snapshot(doc)?.text)
+            })
+            .await?;
+        Ok(Outcome { before, after, notes })
+    }
+    .await;
+    if transient {
+        project.documents.close(doc);
+    }
+    result
+}
+
+/// Formats the whole document with its language server; indentation from EditorConfig, else the settings.
+async fn format(call: &Call, doc: DocId, info: &ide_workspace::DocumentInfo) -> IdeResult<()> {
+    let host = call.host();
+    let project = call.project().clone();
+    let editor = project.settings.effective().editor;
+    let ec = info.editorconfig.as_ref();
+    let insert_spaces = match ec.and_then(|e| e.indent_style) {
+        Some(style) => style != ide_workspace::editorconfig::IndentStyle::Tab,
+        None => editor.insert_spaces,
+    };
+    let tab_size = ec.and_then(|e| e.indent_size.or(e.tab_width)).unwrap_or(editor.tab_size);
+    let options = ide_lsp::types::FormatOptions { tab_size, insert_spaces, on_save: false, tool: None };
+    let version = project.documents.text_snapshot(doc)?.version;
+    let edits = tokio::select! {
+        r = crate::ops::lsp::lsp_format(&host, call.window(), doc, None, options) => r?,
+        _ = call.cancel.cancelled() => return Err(IdeError::cancelled()),
+    };
+    host.blocking(move || {
+        if project.documents.text_snapshot(doc)?.version != version {
+            return Err(IdeError::unavailable("the file changed while it was being formatted; try again"));
+        }
+        project.documents.apply_edits(doc, &edits).map(|_| ())
+    })
+    .await
+}
+
+/// Runs the `source.organizeImports` code action of the document's language server.
+/// Nothing offered: nothing to do, unless the server says it has no such action at all.
+pub(super) async fn organize_imports(call: &Call, doc: DocId, path: &Path) -> IdeResult<()> {
+    let host = call.host();
+    let window = call.window();
+    let text = call.project().documents.text_snapshot(doc)?.text;
+    let request = crate::mcp::tool::request_id();
+    let only = vec![ORGANIZE_IMPORTS.to_owned()];
+    let query = tokio::select! {
+        r = crate::ops::lsp::lsp_code_action_query(&host, window, request, doc, whole_range(&text), only) => r?,
+        _ = call.cancel.cancelled() => {
+            host.cancel_request(request);
+            return Err(IdeError::cancelled());
+        }
+    };
+    let organizes = |kind: &str| kind == ORGANIZE_IMPORTS || kind.starts_with("source.organizeImports.");
+    let action = query
+        .actions
+        .into_iter()
+        .filter(|a| a.disabled_reason.is_none() && a.kind.as_deref().is_some_and(organizes))
+        .max_by_key(|a| a.is_preferred);
+    let Some(action) = action else {
+        let offered = query.advertised_kinds.is_none_or(|kinds| kinds.iter().any(|k| k == "source" || organizes(k)));
+        return if offered {
+            Ok(())
+        } else {
+            Err(IdeError::unavailable("the language server of this file offers no organize imports action"))
+        };
+    };
+    let action = crate::ops::lsp::lsp_resolve_code_action(&host, window, doc, action).await?;
+    match &action.edit {
+        Some(edit) => {
+            let edits = edits_for(edit, path);
+            let project = call.project().clone();
+            host.blocking(move || project.documents.apply_edits(doc, &edits).map(|_| ())).await
+        }
+        // The server applies the change itself (`workspace/applyEdit` during the command).
+        None => crate::ops::lsp::lsp_apply_code_action(&host, window, doc, action).await,
+    }
+}

crates/ide-host/src/mcp/edit/patch.rs

@@ -0,0 +1,949 @@
+// Ported from JetBrains intellij-community plugins/mcp-server (mcpserver.toolsets/src/general/PatchApplyEngine.kt), Apache-2.0.
+//! Patches as AI agents write them: the Codex `apply_patch` format (with the
+//! strict `@@` pair blocks some models write) and unified (git) diffs, bare or
+//! inside `*** Begin Patch`. Parsing and applying hunks to a text are pure, so
+//! they are tested here; the tool in `edit.rs` resolves paths and writes through
+//! the documents.
+//!
+//! Beyond JetBrains: stacked `@@` anchors, unified hunk line numbers as hints,
+//! `\ No newline at end of file`, plain `diff -u` / `diff -ru` names, and errors
+//! that show where a hunk went wrong.
+
+use std::fmt::Write as _;
+
+/// One file of a patch, paths as written in it.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum FileOp {
+    Add {
+        path: String,
+        text: String,
+    },
+    Delete {
+        path: String,
+    },
+    /// `or` lists other paths the file may have, tried in order when `path` does
+    /// not exist (a plain diff's `---` name, or its names without their first
+    /// directory, as `patch -p1` reads `diff -ru old/ new/`).
+    Update {
+        path: String,
+        move_to: Option<String>,
+        hunks: Vec<Hunk>,
+        or: Vec<String>,
+    },
+    /// A git section the tool does not apply (a copy): skipped with `note`, the others go on.
+    Skip {
+        path: String,
+        note: String,
+    },
+}
+
+impl FileOp {
+    pub fn path(&self) -> &str {
+        match self {
+            FileOp::Add { path, .. }
+            | FileOp::Delete { path }
+            | FileOp::Update { path, .. }
+            | FileOp::Skip { path, .. } => path,
+        }
+    }
+}
+
+#[derive(Clone, Debug, Default, PartialEq, Eq)]
+pub struct Hunk {
+    /// `@@ <line>` anchors: found in order before the hunk's lines.
+    pub anchors: Vec<String>,
+    /// `@@ -a,b +c,d @@`: the 1-based start in the old file, a hint where to look.
+    pub old_start: Option<usize>,
+    pub lines: Vec<Line>,
+    /// `*** End of File`: the lines end the file.
+    pub at_eof: bool,
+    /// `\ No newline at end of file` after the old / new side.
+    pub old_no_newline: bool,
+    pub new_no_newline: bool,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum Line {
+    Context(String),
+    Remove(String),
+    Add(String),
+}
+
+impl Hunk {
+    fn old_lines(&self) -> Vec<&str> {
+        self.lines
+            .iter()
+            .filter_map(|l| match l {
+                Line::Context(s) | Line::Remove(s) => Some(s.as_str()),
+                Line::Add(_) => None,
+            })
+            .collect()
+    }
+
+    fn new_lines(&self) -> Vec<&str> {
+        self.lines
+            .iter()
+            .filter_map(|l| match l {
+                Line::Context(s) | Line::Add(s) => Some(s.as_str()),
+                Line::Remove(_) => None,
+            })
+            .collect()
+    }
+
+    /// How the hunk is named in errors.
+    fn label(&self, n: usize) -> String {
+        match (self.anchors.last(), self.old_start) {
+            (Some(a), _) => format!("hunk {n} (@@ {a})"),
+            (None, Some(s)) => format!("hunk {n} (at line {s})"),
+            _ => format!("hunk {n}"),
+        }
+    }
+}
+
+const BEGIN_PATCH: &str = "*** Begin Patch";
+const END_PATCH: &str = "*** End Patch";
+const ADD: &str = "*** Add File: ";
+const DELETE: &str = "*** Delete File: ";
+const UPDATE: &str = "*** Update File: ";
+const MOVE: &str = "*** Move to: ";
+const END_OF_FILE: &str = "*** End of File";
+const DIFF_GIT: &str = "diff --git ";
+
+/// Parses either format: `*** Begin Patch` … `*** End Patch` (holding the Codex
+/// format or a git diff), else a bare unified diff.
+pub fn parse(input: &str) -> Result<Vec<FileOp>, String> {
+    let lines: Vec<&str> = input.split('\n').map(|l| l.strip_suffix('\r').unwrap_or(l)).collect();
+    let ops = match lines.iter().position(|l| l.trim() == BEGIN_PATCH) {
+        Some(begin) => {
+            let end = lines[begin + 1..]
+                .iter()
+                .position(|l| l.trim() == END_PATCH)
+                .map(|e| begin + 1 + e)
+                .ok_or("patch must include *** End Patch (the patch looks truncated)")?;
+            let body = &lines[begin + 1..end];
+            // `--- x` also removes a `-- x` line (SQL, Lua comments): only a body without
+            // Codex headers is read as a diff.
+            let codex = body.iter().any(|l| {
+                let t = l.trim_start();
+                t.starts_with(ADD) || t.starts_with(DELETE) || t.starts_with(UPDATE)
+            });
+            if !codex && looks_like_git_diff(body) {
+                parse_unified(body, begin + 1)?
+            } else {
+                parse_codex(body, begin + 1)?
+            }
+        }
+        None if looks_like_git_diff(&lines) => parse_unified(&lines, 0)?,
+        None => {
+            return Err("patch must include *** Begin Patch (or be a unified diff with `--- a/path` and \
+`+++ b/path` headers)"
+                .into());
+        }
+    };
+    if ops.is_empty() {
+        return Err("patch did not contain any operations".into());
+    }
+    Ok(ops)
+}
+
+fn looks_like_git_diff(lines: &[&str]) -> bool {
+    let mut markers = false;
+    for line in lines {
+        let t = line.trim_start();
+        if t.starts_with(DIFF_GIT) || t.starts_with("rename from ") || t.starts_with("rename to ") {
+            return true;
+        }
+        markers |= line.starts_with("--- ") || line.starts_with("+++ ");
+    }
+    markers
+}
+
+/// Refuses paths with control characters, or with `\n`-style escapes a model wrote
+/// instead of a real path.
+fn ensure_safe_path(path: &str, label: &str) -> Result<(), String> {
+    let control = path.chars().any(|c| c.is_ascii_control());
+    let escaped = ["\\n", "\\r", "\\t"].iter().any(|e| path.contains(e));
+    if control || escaped {
+        Err(format!("{label} path contains control characters or escape sequences"))
+    } else {
+        Ok(())
+    }
+}
+
+// --- the Codex format -----------------------------------------------------------
+
+fn is_diff_prefix(c: char) -> bool {
+    matches!(c, ' ' | '+' | '-')
+}
+
+/// `*** Add File:` and the like (not `*** End of File`, which belongs to a hunk).
+fn is_patch_header(line: &str) -> bool {
+    match line.chars().next() {
+        None => false,
+        Some(c) if is_diff_prefix(c) => false,
+        Some(_) => {
+            let t = line.trim_start();
+            t.starts_with("*** ") && t.trim_end() != END_OF_FILE
+        }
+    }
+}
+
+fn is_hunk_header(line: &str) -> bool {
+    line.chars().next().is_some_and(|c| !is_diff_prefix(c)) && line.trim_start().starts_with("@@")
+}
+
+fn op_path(rest: &str, label: &str) -> Result<String, String> {
+    let path = rest.trim();
+    if path.is_empty() {
+        return Err(format!("{label} requires a path"));
+    }
+    ensure_safe_path(path, label)?;
+    Ok(path.to_owned())
+}
+
+/// `lines[start..]` is the body after `*** Begin Patch`; `offset` numbers lines in errors.
+fn parse_codex(body: &[&str], offset: usize) -> Result<Vec<FileOp>, String> {
+    let mut ops = Vec::new();
+    let mut i = 0;
+    let n = |i: usize| i + offset + 1;
+    while i < body.len() {
+        let line = body[i];
+        let header = line.trim_start();
+        if let Some(rest) = header.strip_prefix(ADD) {
+            let path = op_path(rest, "Add File")?;
+            i += 1;
+            // (text, written with `+`): blank separator lines before the next header are dropped.
+            let mut content: Vec<(&str, bool)> = Vec::new();
+            while let Some(&l) = body.get(i).filter(|l| !is_patch_header(l)) {
+                match l.strip_prefix('+') {
+                    Some(text) => content.push((text, true)),
+                    None if l.trim().is_empty() => content.push(("", false)),
+                    None => return Err(format!("Add File lines must start with + (line {}: `{l}`)", n(i))),
+                }
+                i += 1;
+            }
+            while content.last().is_some_and(|(_, explicit)| !explicit) {
+                content.pop();
+            }
+            let mut text = content.iter().map(|(t, _)| *t).collect::<Vec<_>>().join("\n");
+            if !content.is_empty() {
+                text.push('\n');
+            }
+            ops.push(FileOp::Add { path, text });
+        } else if let Some(rest) = header.strip_prefix(DELETE) {
+            ops.push(FileOp::Delete { path: op_path(rest, "Delete File")? });
+            i += 1;
+        } else if let Some(rest) = header.strip_prefix(UPDATE) {
+            let path = op_path(rest, "Update File")?;
+            i += 1;
+            let mut move_to = None;
+            if let Some(rest) =
+                body.get(i).filter(|l| is_patch_header(l)).and_then(|l| l.trim_start().strip_prefix(MOVE))
+            {
+                move_to = Some(op_path(rest, "Move to")?);
+                i += 1;
+            }
+            let mut hunks = Vec::new();
+            while i < body.len() && !is_patch_header(body[i]) {
+                if body[i].trim().is_empty() {
+                    i += 1;
+                    continue;
+                }
+                hunks.push(parse_codex_hunk(body, &mut i, hunks.is_empty(), offset)?);
+            }
+            // A move alone needs no hunk (JetBrains requires one).
+            if hunks.is_empty() && move_to.is_none() {
+                return Err("Update File requires at least one hunk".into());
+            }
+            ops.push(FileOp::Update { path, move_to, hunks, or: Vec::new() });
+        } else if line.trim().is_empty() {
+            i += 1;
+        } else {
+            return Err(format!("Unexpected patch line: {line}"));
+        }
+    }
+    Ok(ops)
+}
+
+fn parse_codex_hunk(body: &[&str], i: &mut usize, first: bool, offset: usize) -> Result<Hunk, String> {
+    let mut hunk = Hunk::default();
+    let mut bare = false;
+    let mut headed = false;
+    // Several `@@` lines narrow the place down, as in Codex.
+    while let Some(&line) = body.get(*i).filter(|l| is_hunk_header(l)) {
+        let trimmed = line.trim();
+        match parse_range_header(trimmed) {
+            Some((start, ..)) => hunk.old_start = Some(start),
+            None => {
+                let text = trimmed.trim_start_matches('@').trim();
+                // `@@ fn main() @@` repeats the marker at the end sometimes.
+                let text = text.trim_end_matches('@').trim_end();
+                if !text.is_empty() {
+                    hunk.anchors.push(text.to_owned());
+                }
+            }
+        }
+        bare = trimmed == "@@";
+        headed = true;
+        *i += 1;
+    }
+    let n = |i: usize| i + offset + 1;
+    if !headed {
+        let line = body[*i];
+        if !first || !line.chars().next().is_none_or(is_diff_prefix) {
+            return Err(format!("Expected @@ hunk header (line {}: `{line}`)", n(*i)));
+        }
+    }
+    let is_strict_start =
+        |l: &str| !l.is_empty() && !is_patch_header(l) && !is_hunk_header(l) && !l.starts_with(is_diff_prefix);
+    if bare && body.get(*i).is_some_and(|l| is_strict_start(l)) {
+        return parse_strict_pair(body, i);
+    }
+    // Blank lines at the end of a hunk are usually separators, not context.
+    let mut implicit_blanks = 0usize;
+    while let Some(&line) = body.get(*i).filter(|l| !is_hunk_header(l) && !is_patch_header(l)) {
+        if line.trim_end() == END_OF_FILE {
+            hunk.at_eof = true;
+            *i += 1;
+            break;
+        }
+        let parsed = match line.chars().next() {
+            None => Line::Context(String::new()),
+            Some(' ') => Line::Context(line[1..].to_owned()),
+            Some('-') => Line::Remove(line[1..].to_owned()),
+            Some('+') => Line::Add(line[1..].to_owned()),
+            Some(_) if hunk.lines.is_empty() => {
+                return Err(format!("Hunk lines must start with space, +, or - (line {}: `{line}`)", n(*i)));
+            }
+            Some(_) => break,
+        };
+        implicit_blanks = if line.is_empty() { implicit_blanks + 1 } else { 0 };
+        hunk.lines.push(parsed);
+        *i += 1;
+    }
+    hunk.lines.truncate(hunk.lines.len() - implicit_blanks);
+    if hunk.lines.is_empty() {
+        return Err("Empty hunk in Update File".into());
+    }
+    Ok(hunk)
+}
+
+/// `@@`, the old lines, `@@`, the new lines: whole lines without `-` / `+` prefixes.
+fn parse_strict_pair(body: &[&str], i: &mut usize) -> Result<Hunk, String> {
+    let mut old = Vec::new();
+    let mut closed = false;
+    while let Some(&line) = body.get(*i).filter(|l| !is_patch_header(l)) {
+        *i += 1;
+        if line.trim() == "@@" {
+            closed = true;
+            break;
+        }
+        old.push(line);
+    }
+    if !closed {
+        return Err("Strict @@ pair hunk requires second @@ delimiter".into());
+    }
+    let mut new = Vec::new();
+    while let Some(&line) = body.get(*i).filter(|l| !is_patch_header(l) && !is_hunk_header(l)) {
+        new.push(line);
+        *i += 1;
+    }
+    while new.last().is_some_and(|l| l.trim().is_empty()) {
+        new.pop();
+    }
+    if old.is_empty() && new.is_empty() {
+        return Err("Empty hunk in Update File".into());
+    }
+    let lines = old
+        .into_iter()
+        .map(|l| Line::Remove(l.to_owned()))
+        .chain(new.into_iter().map(|l| Line::Add(l.to_owned())))
+        .collect();
+    Ok(Hunk { lines, ..Hunk::default() })
+}
+
+// --- unified diffs -------------------------------------------------------------
+
+#[derive(Default)]
+struct Section {
+    git_old: Option<String>,
+    git_new: Option<String>,
+    /// `---` / `+++` seen; `None` inside is `/dev/null`.
+    old: Option<Option<String>>,
+    new: Option<Option<String>>,
+    new_file: bool,
+    deleted: bool,
+    rename_from: Option<String>,
+    rename_to: Option<String>,
+    /// `old mode` / `new mode`: a permission change, which the tool leaves alone.
+    mode_change: bool,
+    /// `copy from` / `copy to`.
+    copy_from: Option<String>,
+    copy_to: Option<String>,
+    hunks: Vec<Hunk>,
+    line: usize,
+}
+
+fn is_file_start(lines: &[&str], i: usize) -> bool {
+    let l = lines[i];
+    l.starts_with(DIFF_GIT)
+        || (l.starts_with("--- ") && lines.get(i + 1).is_some_and(|n| n.starts_with("+++ ")) && l != "--- ")
+}
+
+/// `offset` numbers lines in errors (the diff may sit inside `*** Begin Patch`).
+fn parse_unified(lines: &[&str], offset: usize) -> Result<Vec<FileOp>, String> {
+    let mut ops = Vec::new();
+    let mut i = 0;
+    let mut section: Option<Section> = None;
+    while i < lines.len() {
+        let line = lines[i];
+        let n = i + offset + 1;
+        if is_file_start(lines, i) && (line.starts_with(DIFF_GIT) || section.as_ref().is_none_or(|s| s.old.is_some())) {
+            if let Some(s) = section.take() {
+                ops.push(finish_section(s)?);
+            }
+            let mut s = Section { line: n, ..Section::default() };
+            if let Some(rest) = line.strip_prefix(DIFF_GIT) {
+                (s.git_old, s.git_new) = split_git_paths(rest);
+                i += 1;
+            }
+            section = Some(s);
+            continue;
+        }
+        let Some(s) = section.as_mut() else {
+            if line.starts_with("@@ ") {
+                return Err(format!("line {n}: a hunk without a `--- a/path` / `+++ b/path` header before it"));
+            }
+            // Text before the first file (a commit message, `Index:` lines).
+            i += 1;
+            continue;
+        };
+        let trimmed = line.trim_start();
+        if let Some(p) = line.strip_prefix("--- ") {
+            s.old = Some(diff_path(p, "a/"));
+        } else if let Some(p) = line.strip_prefix("+++ ") {
+            s.new = Some(diff_path(p, "b/"));
+        } else if trimmed.starts_with("new file mode") {
+            s.new_file = true;
+        } else if trimmed.starts_with("deleted file mode") {
+            s.deleted = true;
+        } else if let Some(p) = trimmed.strip_prefix("rename from ") {
+            s.rename_from = Some(rename_path(p)?);
+        } else if let Some(p) = trimmed.strip_prefix("rename to ") {
+            s.rename_to = Some(rename_path(p)?);
+        } else if trimmed.starts_with("Binary files ") || trimmed == "GIT binary patch" {
+            return Err(format!("Binary git patch is not supported (line {n})"));
+        } else if let Some(p) = trimmed.strip_prefix("copy from ") {
+            s.copy_from = Some(rename_path(p)?);
+        } else if let Some(p) = trimmed.strip_prefix("copy to ") {
+            s.copy_to = Some(rename_path(p)?);
+        } else if trimmed.starts_with("old mode ") || trimmed.starts_with("new mode ") {
+            s.mode_change = true;
+        } else if line.starts_with("@@") {
+            if s.old.is_none() && s.new.is_none() && s.git_old.is_none() {
+                return Err(format!("line {n}: a hunk without a `--- a/path` / `+++ b/path` header before it"));
+            }
+            i += 1;
+            let hunk = parse_unified_hunk(lines, &mut i, line, n)?;
+            s.hunks.push(hunk);
+            continue;
+        } else if !s.hunks.is_empty() && (line.starts_with('+') || line.starts_with('-') || line.starts_with(' ')) {
+            // Lines after a hunk that its counts left out (`-- ` ends `git format-patch` output).
+            if line != "-- " {
+                return Err(format!(
+                    "line {n}: `{line}` follows a hunk but is not part of it; check the hunk's counts"
+                ));
+            }
+            if let Some(s) = section.take() {
+                ops.push(finish_section(s)?);
+            }
+        }
+        // Other extended headers (`index`, modes, similarity) need nothing.
+        i += 1;
+    }
+    if let Some(s) = section {
+        ops.push(finish_section(s)?);
+    }
+    Ok(ops)
+}
+
+/// `@@ -a,b +c,d @@`: hunk lines until the counts are used up; lines beyond
+/// counts that are too small are taken too, and a bare `@@` reads to the next header.
+fn parse_unified_hunk(lines: &[&str], i: &mut usize, header: &str, n: usize) -> Result<Hunk, String> {
+    let counts = parse_range_header(header);
+    if counts.is_none() && header.starts_with("@@ -") {
+        return Err(format!("line {n}: cannot read the hunk header `{header}`"));
+    }
+    let mut hunk = Hunk { old_start: counts.map(|c| c.0), ..Hunk::default() };
+    let (mut old_left, mut new_left) = counts.map_or((usize::MAX, usize::MAX), |c| (c.1, c.2));
+    let mut implicit_blanks = 0usize;
+    let first = *i;
+    while let Some(&line) = lines.get(*i) {
+        let done = old_left == 0 && new_left == 0;
+        if line.starts_with("@@") || is_file_start(lines, *i) {
+            break;
+        }
+        if line.trim_end() == END_OF_FILE {
+            hunk.at_eof = true;
+            *i += 1;
+            break;
+        }
+        if line.starts_with('\\') {
+            match hunk.lines.last() {
+                Some(Line::Remove(_)) => hunk.old_no_newline = true,
+                Some(Line::Add(_)) => hunk.new_no_newline = true,
+                Some(Line::Context(_)) => {
+                    hunk.old_no_newline = true;
+                    hunk.new_no_newline = true;
+                }
+                None => {}
+            }
+            *i += 1;
+            continue;
+        }
+        let parsed = match line.chars().next() {
+            _ if done && (line.is_empty() || line == "-- ") => break,
+            Some(' ') => Line::Context(line[1..].to_owned()),
+            Some('-') => Line::Remove(line[1..].to_owned()),
+            Some('+') => Line::Add(line[1..].to_owned()),
+            // Editors strip the space of empty context lines.
+            None => Line::Context(String::new()),
+            Some(_) if hunk.lines.is_empty() => {
+                return Err(format!(
+                    "Hunk lines must start with space, +, or - (line {}: `{line}`)",
+                    n + 1 + *i - first
+                ));
+            }
+            Some(_) => break,
+        };
+        match parsed {
+            Line::Context(_) => {
+                old_left = old_left.saturating_sub(1);
+                new_left = new_left.saturating_sub(1);
+            }
+            Line::Remove(_) => old_left = old_left.saturating_sub(1),
+            Line::Add(_) => new_left = new_left.saturating_sub(1),
+        }
+        implicit_blanks = if line.is_empty() { implicit_blanks + 1 } else { 0 };
+        hunk.lines.push(parsed);
+        *i += 1;
+    }
+    if counts.is_none() {
+        hunk.lines.truncate(hunk.lines.len() - implicit_blanks);
+    }
+    if hunk.lines.is_empty() {
+        return Err(format!("Empty hunk in Update File (line {n}: `{header}`)"));
+    }
+    Ok(hunk)
+}
+
+/// (old start, old count, new count) of `@@ -a[,b] +c[,d] @@`; extra `@`s (`@@@`) are accepted.
+fn parse_range_header(header: &str) -> Option<(usize, usize, usize)> {
+    let rest = header.trim_start_matches('@').trim_start().strip_prefix('-')?;
+    let (ranges, _) = rest.split_once(" @@").unwrap_or((rest.trim_end_matches('@'), ""));
+    let (old, new) = ranges.split_once(" +")?;
+    let range = |r: &str| -> Option<(usize, usize)> {
+        match r.trim().split_once(',') {
+            Some((s, c)) => Some((s.parse().ok()?, c.parse().ok()?)),
+            None => Some((r.trim().parse().ok()?, 1)),
+        }
+    };
+    let (start, old_count) = range(old)?;
+    let (_, new_count) = range(new)?;
+    Some((start, old_count, new_count))
+}
+
+/// The two paths of `diff --git a/x b/y` (ambiguous with spaces: equal halves win).
+fn split_git_paths(rest: &str) -> (Option<String>, Option<String>) {
+    let rest = rest.trim();
+    if let Some((a, b)) = rest.strip_prefix('"').and_then(|r| r.split_once("\" ")) {
+        return (Some(strip_prefix(&unquote(&format!("\"{a}\"")), "a/")), Some(strip_prefix(&unquote(b), "b/")));
+    }
+    let splits: Vec<usize> = rest.match_indices(" b/").map(|(i, _)| i).collect();
+    let pick = splits.iter().find(|&&i| rest[..i].strip_prefix("a/") == Some(&rest[i + 3..])).or(splits.first());
+    match pick {
+        Some(&i) => (Some(strip_prefix(&rest[..i], "a/")), Some(rest[i + 3..].to_owned())),
+        None => (None, None),
+    }
+}
+
+/// A `---` / `+++` path: `None` for `/dev/null`; timestamps and the `a/` / `b/` prefix removed.
+fn diff_path(raw: &str, prefix: &str) -> Option<String> {
+    let raw = raw.split('\t').next().unwrap_or(raw).trim_end();
+    let path = unquote(raw);
+    if path == "/dev/null" {
+        return None;
+    }
+    Some(strip_prefix(&path, prefix))
+}
+
+fn rename_path(raw: &str) -> Result<String, String> {
+    let path = unquote(raw.trim());
+    if path.is_empty() { Err("Could not determine file path from git diff".into()) } else { Ok(path) }
+}
+
+fn strip_prefix(path: &str, prefix: &str) -> String {
+    path.strip_prefix(prefix).unwrap_or(path).to_owned()
+}
+
+/// Git quotes paths with special characters: `"a/x \"y\""`.
+fn unquote(s: &str) -> String {
+    let Some(inner) = s.strip_prefix('"').and_then(|s| s.strip_suffix('"')) else { return s.to_owned() };
+    let mut out = String::new();
+    let mut chars = inner.chars();
+    while let Some(c) = chars.next() {
+        if c != '\\' {
+            out.push(c);
+            continue;
+        }
+        match chars.next() {
+            Some('n') => out.push('\n'),
+            Some('t') => out.push('\t'),
+            Some(c) => out.push(c),
+            None => {}
+        }
+    }
+    out
+}
+
+fn finish_section(s: Section) -> Result<FileOp, String> {
+    const NO_PATH: &str = "Could not determine file path from git diff";
+    let n = s.line;
+    let old = match &s.old {
+        Some(p) => p.clone(),
+        None => s.rename_from.clone().or_else(|| s.git_old.clone()),
+    };
+    let new = match &s.new {
+        Some(p) => p.clone(),
+        None => s.rename_to.clone().or_else(|| s.git_new.clone()),
+    };
+    if s.copy_from.is_some() || s.copy_to.is_some() {
+        // Git writes a copy only with `-C`; JetBrains reads it as a change of the source.
+        let to = s.copy_to.clone().or(new).ok_or_else(|| format!("{NO_PATH} (line {n})"))?;
+        let from = s.copy_from.clone().or(old).unwrap_or_default();
+        let note = format!(
+            "the copy of {from} to {to} was skipped: copies are not supported; add the new file with `*** Add File` \
+instead"
+        );
+        return Ok(FileOp::Skip { path: to, note });
+    }
+    if s.new_file || (s.old.as_ref().is_some_and(|o| o.is_none())) {
+        let path = new.ok_or_else(|| format!("{NO_PATH} (line {n})"))?;
+        ensure_safe_path(&path, "Add File")?;
+        let mut lines = Vec::new();
+        let mut no_newline = false;
+        for h in &s.hunks {
+            for l in &h.lines {
+                match l {
+                    Line::Add(t) => lines.push(t.as_str()),
+                    _ => return Err(format!("`{path}` is a new file, but its hunk has context or removed lines")),
+                }
+            }
+            no_newline |= h.new_no_newline;
+        }
+        let mut text = lines.join("\n");
+        if !lines.is_empty() && !no_newline {
+            text.push('\n');
+        }
+        return Ok(FileOp::Add { path, text });
+    }
+    if s.deleted || (s.new.as_ref().is_some_and(|n| n.is_none())) {
+        let path = old.ok_or_else(|| format!("{NO_PATH} (line {n})"))?;
+        ensure_safe_path(&path, "Delete File")?;
+        return Ok(FileOp::Delete { path });
+    }
+    // Only git's rename headers say a file moves: plain diffs often name the sides
+    // differently (`--- a.txt.orig` / `+++ a.txt`, `diff -ru old/ new/`).
+    if s.rename_from.is_some() || s.rename_to.is_some() {
+        let path = old.or(new.clone()).ok_or_else(|| format!("{NO_PATH} (line {n})"))?;
+        ensure_safe_path(&path, "Update File")?;
+        let move_to = new.filter(|p| *p != path);
+        if let Some(m) = &move_to {
+            ensure_safe_path(m, "Move to")?;
+        }
+        if s.hunks.is_empty() && move_to.is_none() && !s.mode_change {
+            return Err(format!("line {n}: `{path}` has no changes"));
+        }
+        return Ok(FileOp::Update { path, move_to, hunks: s.hunks, or: Vec::new() });
+    }
+    let path = new.clone().or(old.clone()).ok_or_else(|| format!("{NO_PATH} (line {n})"))?;
+    ensure_safe_path(&path, "Update File")?;
+    if s.hunks.is_empty() {
+        // Only the file mode changes: nothing to do to the text, as in JetBrains.
+        if s.mode_change {
+            return Ok(FileOp::Update { path, move_to: None, hunks: Vec::new(), or: Vec::new() });
+        }
+        return Err(format!("line {n}: `{path}` has no changes"));
+    }
+    let below_first_dir = |p: &Option<String>| p.as_ref().and_then(|p| p.split_once('/')).map(|(_, r)| r.to_owned());
+    let mut or: Vec<String> = Vec::new();
+    let others =
+        if old == new { [None, None, None] } else { [old.clone(), below_first_dir(&new), below_first_dir(&old)] };
+    for p in others.into_iter().flatten() {
+        if !p.is_empty() && p != path && !or.contains(&p) {
+            or.push(p);
+        }
+    }
+    Ok(FileOp::Update { path, move_to: None, hunks: s.hunks, or })
+}
+
+// --- applying -------------------------------------------------------------------
+
+/// How exactly a hunk's lines matched the file, tried in this order.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)]
+pub enum Fuzz {
+    Exact,
+    TrailingWhitespace,
+    Whitespace,
+    /// Whitespace, and typographic dashes, quotes and spaces as their ASCII forms.
+    Punctuation,
+}
+
+impl Fuzz {
+    fn same(self, a: &str, b: &str) -> bool {
+        match self {
+            Fuzz::Exact => a == b,
+            Fuzz::TrailingWhitespace => a.trim_end() == b.trim_end(),
+            Fuzz::Whitespace => a.trim() == b.trim(),
+            Fuzz::Punctuation => a.trim().chars().map(normalize_char).eq(b.trim().chars().map(normalize_char)),
+        }
+    }
+
+    pub fn describe(self) -> &'static str {
+        match self {
+            Fuzz::Exact => "exactly",
+            Fuzz::TrailingWhitespace => "ignoring trailing whitespace",
+            Fuzz::Whitespace => "ignoring indentation and whitespace",
+            Fuzz::Punctuation => "ignoring whitespace and typographic punctuation (dashes, quotes, spaces)",
+        }
+    }
+}
+
+fn normalize_char(c: char) -> char {
+    match c {
+        '\u{2010}'..='\u{2015}' | '\u{2212}' => '-',
+        '\u{2018}'..='\u{201B}' => '\'',
+        '\u{201C}'..='\u{201F}' => '"',
+        '\u{00A0}' | '\u{2002}'..='\u{200A}' | '\u{202F}' | '\u{205F}' | '\u{3000}' => ' ',
+        c => c,
+    }
+}
+
+const LEVELS: [Fuzz; 4] = [Fuzz::Exact, Fuzz::TrailingWhitespace, Fuzz::Whitespace, Fuzz::Punctuation];
+
+/// The result of [`apply`]: the new text and the hunks that matched only loosely.
+#[derive(Debug, PartialEq, Eq)]
+pub struct Applied {
+    pub text: String,
+    /// (1-based hunk, how it matched) for hunks that did not match exactly.
+    pub fuzzy: Vec<(usize, Fuzz)>,
+}
+
+/// Applies `hunks` in order to `text` (`\n` line endings). A hunk is searched
+/// after the previous one, then (unless it ends the file) from the top. Errors
+/// name the hunk and the lines that were not found.
+pub fn apply(text: &str, hunks: &[Hunk]) -> Result<Applied, String> {
+    let trailing_newline = text.ends_with('\n');
+    let mut lines: Vec<String> = if text.is_empty() {
+        Vec::new()
+    } else {
+        let mut l: Vec<String> = text.split('\n').map(str::to_owned).collect();
+        if trailing_newline {
+            l.pop();
+        }
+        l
+    };
+    let original_len = lines.len();
+    let mut cursor = 0usize;
+    let mut fuzzy = Vec::new();
+    let mut ends_without_newline = None;
+    for (index, hunk) in hunks.iter().enumerate() {
+        let n = index + 1;
+        let file: Vec<&str> = lines.iter().map(String::as_str).collect();
+        let mut anchor_line = None;
+        for anchor in &hunk.anchors {
+            let find =
+                |from: usize| LEVELS.iter().find_map(|level| (from..file.len()).find(|&i| level.same(file[i], anchor)));
+            let found = find(cursor).or_else(|| find(0)).ok_or_else(|| {
+                format!(
+                    "Hunk context not found: {}: cannot find the line `{anchor}` its `@@` header names",
+                    hunk.label(n)
+                )
+            })?;
+            anchor_line = Some(found);
+            cursor = found + 1;
+        }
+        // Line numbers of a diff count the original file: shift them by what earlier hunks added.
+        let shift = |s: usize| (s as isize + lines.len() as isize - original_len as isize).max(0) as usize;
+        let mut old = hunk.old_lines();
+        if old.is_empty() {
+            let at = if !hunk.anchors.is_empty() {
+                cursor
+            } else if hunk.at_eof {
+                file.len()
+            } else {
+                // `@@ -5,0 +6,2 @@` inserts after line 5; without a position, at the end.
+                hunk.old_start.map_or(file.len(), |s| shift(s).min(file.len()))
+            };
+            let new: Vec<String> = hunk.new_lines().into_iter().map(str::to_owned).collect();
+            cursor = at + new.len();
+            lines.splice(at..at, new);
+            continue;
+        }
+        let hint = hunk.old_start.map(|s| shift(s.saturating_sub(1)));
+        // Models often repeat the `@@` line as the hunk's first context line: then the
+        // block starts at the anchor rather than after it.
+        let find = |old: &[&str]| {
+            find_block(&file, old, cursor, hint, hunk.at_eof)
+                .or_else(|| anchor_line.and_then(|a| find_block(&file, old, a, hint, hunk.at_eof)))
+                .or_else(|| (cursor > 0 && !hunk.at_eof).then(|| find_block(&file, old, 0, hint, false)).flatten())
+        };
+        let mut found = find(&old);
+        // A blank last line in the patch that the file does not have (Codex does the same).
+        if found.is_none() && old.last() == Some(&"") {
+            old.pop();
+            if !old.is_empty() {
+                found = find(&old);
+            }
+        }
+        let Some((at, level)) = found else {
+            return Err(mismatch(&file, &old, hint, &hunk.label(n), hunk.at_eof));
+        };
+        if level != Fuzz::Exact {
+            fuzzy.push((n, level));
+        }
+        if at + old.len() == file.len() {
+            if hunk.new_no_newline {
+                ends_without_newline = Some(true);
+            } else if hunk.old_no_newline {
+                ends_without_newline = Some(false);
+            }
+        }
+        // Context lines keep the file's spelling (a loose match must not re-indent them).
+        let mut new = Vec::new();
+        let mut matched = 0usize;
+        for line in &hunk.lines {
+            match line {
+                Line::Context(_) | Line::Remove(_) if matched >= old.len() => {}
+                Line::Context(_) => {
+                    new.push(file[at + matched].to_owned());
+                    matched += 1;
+                }
+                Line::Remove(_) => matched += 1,
+                Line::Add(s) => new.push(s.clone()),
+            }
+        }
+        let removed = old.len();
+        cursor = at + new.len();
+        lines.splice(at..at + removed, new);
+    }
+    let mut result = lines.join("\n");
+    let newline = match ends_without_newline {
+        Some(no) => !no,
+        None => trailing_newline || text.is_empty(),
+    };
+    if newline && !lines.is_empty() {
+        result.push('\n');
+    }
+    Ok(Applied { text: result, fuzzy })
+}
+
+/// Where `old` occurs at or after `from`, as exactly as possible; with a hint,
+/// the occurrence nearest to it. A hunk that ends the file must match its end.
+fn find_block(lines: &[&str], old: &[&str], from: usize, hint: Option<usize>, at_eof: bool) -> Option<(usize, Fuzz)> {
+    if old.len() > lines.len() {
+        return None;
+    }
+    let last = lines.len() - old.len();
+    let matches = |at: usize, level: Fuzz| old.iter().zip(&lines[at..]).all(|(o, l)| level.same(l, o));
+    for level in LEVELS {
+        if at_eof {
+            if last >= from && matches(last, level) {
+                return Some((last, level));
+            }
+            continue;
+        }
+        let mut best: Option<usize> = None;
+        for at in from..=last {
+            if !matches(at, level) {
+                continue;
+            }
+            match hint {
+                None => return Some((at, level)),
+                Some(h) => {
+                    if best.is_none_or(|b| at.abs_diff(h) < b.abs_diff(h)) {
+                        best = Some(at);
+                    }
+                }
+            }
+        }
+        if let Some(at) = best {
+            return Some((at, level));
+        }
+    }
+    None
+}
+
+/// The error for lines that were not found, with the closest partial match.
+fn mismatch(lines: &[&str], old: &[&str], hint: Option<usize>, label: &str, at_eof: bool) -> String {
+    let mut msg = format!("Hunk context not found: {label} does not apply: these lines were not found:\n");
+    for l in old {
+        let _ = writeln!(msg, "  {l}");
+    }
+    // The start with the longest run of matching lines (ignoring whitespace).
+    let mut best: Option<(usize, usize)> = None;
+    for at in 0..lines.len() {
+        let run = old.iter().zip(&lines[at..]).take_while(|(o, l)| Fuzz::Punctuation.same(o, l)).count();
+        let better = match best {
+            None => run > 0,
+            Some((b, r)) => run > r || (run == r && hint.is_some_and(|h| at.abs_diff(h) < b.abs_diff(h))),
+        };
+        if better {
+            best = Some((at, run));
+        }
+    }
+    match best {
+        Some((at, run)) if run < old.len() => {
+            let actual = lines.get(at + run).map_or("(end of file)".to_owned(), |l| format!("`{l}`"));
+            let _ = write!(
+                msg,
+                "Closest match at line {}: line {} is {actual}, but the patch expects `{}`.",
+                at + 1,
+                at + run + 1,
+                old[run]
+            );
+        }
+        Some((at, _)) if at_eof => {
+            let _ = write!(
+                msg,
+                "They occur at line {}, but the hunk is marked `*** End of File` and they do not end the file.",
+                at + 1
+            );
+        }
+        Some((at, _)) => {
+            let _ = write!(msg, "They occur at line {}.", at + 1);
+        }
+        None => {
+            // A common mistake: only part of a line after `-` / ` `.
+            let partial = old
+                .iter()
+                .filter(|o| !o.trim().is_empty())
+                .find_map(|o| lines.iter().position(|l| l.contains(o.trim())).map(|i| (o.trim(), i)));
+            match partial {
+                Some((o, i)) => {
+                    let _ = write!(
+                        msg,
+                        "Line {} contains `{o}` but is `{}`: patch lines must be whole lines, with their indentation.",
+                        i + 1,
+                        lines[i]
+                    );
+                }
+                None => msg.push_str("No line of them is in the file; read the file again before patching it."),
+            }
+        }
+    }
+    msg
+}
+
+#[cfg(test)]
+mod tests;

crates/ide-host/src/mcp/edit/patch/tests.rs

@@ -0,0 +1,584 @@
+//! Parser and engine tests, including JetBrains' `PatchApplyEngineTest` cases.
+
+use super::*;
+
+fn update(ops: &[FileOp]) -> &[Hunk] {
+    match &ops[0] {
+        FileOp::Update { hunks, .. } => hunks,
+        other => panic!("not an update: {other:?}"),
+    }
+}
+
+fn apply_patch(text: &str, patch: &str) -> Result<String, String> {
+    let ops = parse(patch)?;
+    apply(text, update(&ops)).map(|a| a.text)
+}
+
+fn patch(lines: &[&str]) -> String {
+    lines.iter().map(|l| format!("{l}\n")).collect()
+}
+
+fn hunk(lines: &[(char, &str)], at_eof: bool) -> Hunk {
+    let lines = lines
+        .iter()
+        .map(|&(p, t)| match p {
+            '-' => Line::Remove(t.into()),
+            '+' => Line::Add(t.into()),
+            _ => Line::Context(t.into()),
+        })
+        .collect();
+    Hunk { lines, at_eof, ..Hunk::default() }
+}
+
+// --- Codex format -------------------------------------------------------
+
+#[test]
+fn parses_every_codex_operation() {
+    let ops = parse(
+        "*** Begin Patch\n*** Add File: new.txt\n+one\n+two\n*** Delete File: old.txt\n*** Update File: a.rs\n\
+*** Move to: b.rs\n@@ fn main\n ctx\n-old\n+new\n*** End Patch\n",
+    )
+    .unwrap();
+    assert_eq!(
+        ops,
+        vec![
+            FileOp::Add { path: "new.txt".into(), text: "one\ntwo\n".into() },
+            FileOp::Delete { path: "old.txt".into() },
+            FileOp::Update {
+                path: "a.rs".into(),
+                move_to: Some("b.rs".into()),
+                hunks: vec![Hunk {
+                    anchors: vec!["fn main".into()],
+                    lines: vec![Line::Context("ctx".into()), Line::Remove("old".into()), Line::Add("new".into())],
+                    ..Hunk::default()
+                }],
+                or: vec![],
+            },
+        ]
+    );
+}
+
+#[test]
+fn codex_tolerates_wrappers_crlf_and_blank_separators() {
+    let ops = parse(
+        "apply_patch <<'EOF'\r\n*** Begin Patch\r\n*** Add File: x\r\n+a\r\n+\r\n\r\n*** Update File: y\r\n-a\r\n+b\r\n\r\n*** End Patch\r\nEOF",
+    )
+    .unwrap();
+    assert_eq!(ops[0], FileOp::Add { path: "x".into(), text: "a\n\n".into() });
+    assert_eq!(update(&ops[1..])[0].lines, vec![Line::Remove("a".into()), Line::Add("b".into())]);
+    // JetBrains: a heredoc around the patch.
+    let ops = parse(&patch(&["<<EOF", "*** Begin Patch", "*** Add File: notes.txt", "+alpha", "*** End Patch", "EOF"]))
+        .unwrap();
+    assert_eq!(ops, vec![FileOp::Add { path: "notes.txt".into(), text: "alpha\n".into() }]);
+}
+
+#[test]
+fn codex_empty_add_and_move_only() {
+    let ops = parse("*** Begin Patch\n*** Add File: e\n*** Update File: a\n*** Move to: b\n*** End Patch").unwrap();
+    assert_eq!(ops[0], FileOp::Add { path: "e".into(), text: String::new() });
+    assert_eq!(ops[1], FileOp::Update { path: "a".into(), move_to: Some("b".into()), hunks: vec![], or: vec![] });
+}
+
+/// JetBrains `PatchApplyEngineTest`: the parse errors.
+#[test]
+fn codex_errors() {
+    let fails = |lines: &[&str], expected: &str| {
+        let e = parse(&patch(lines)).unwrap_err();
+        assert!(e.contains(expected), "expected `{expected}` in: {e}");
+    };
+    fails(&["oops"], "patch must include *** Begin Patch");
+    fails(&["*** Begin Patch", "*** Add File: notes.txt", "+alpha"], "patch must include *** End Patch");
+    fails(&["*** Begin Patch", "*** End Patch"], "patch did not contain any operations");
+    fails(&["*** Begin Patch", "oops", "*** End Patch"], "Unexpected patch line: oops");
+    fails(&["*** Begin Patch", "*** Add File:   ", "*** End Patch"], "Add File requires a path");
+    fails(
+        &["*** Begin Patch", "*** Add File: notes.txt", "alpha", "*** End Patch"],
+        "Add File lines must start with +",
+    );
+    fails(
+        &["*** Begin Patch", "*** Add File: notes.txt", "+alpha", "beta", "*** End Patch"],
+        "Add File lines must start with + (line 4: `beta`)",
+    );
+    fails(&["*** Begin Patch", "*** Delete File:   ", "*** End Patch"], "Delete File requires a path");
+    fails(&["*** Begin Patch", "*** Update File:   ", "*** End Patch"], "Update File requires a path");
+    fails(
+        &["*** Begin Patch", "*** Update File: s.txt", "*** Move to:   ", "*** End Patch"],
+        "Move to requires a path",
+    );
+    fails(&["*** Begin Patch", "*** Update File: s.txt", "*** End Patch"], "Update File requires at least one hunk");
+    fails(&["*** Begin Patch", "*** Update File: s.txt", "oops", "*** End Patch"], "Expected @@ hunk header");
+    fails(
+        &["*** Begin Patch", "*** Update File: s.txt", " alpha", "-beta", "+gamma", "oops", "*** End Patch"],
+        "Expected @@ hunk header",
+    );
+    fails(
+        &["*** Begin Patch", "*** Update File: s.txt", "@@ def sample()", "oops", "*** End Patch"],
+        "Hunk lines must start with space, +, or -",
+    );
+    fails(&["*** Begin Patch", "*** Update File: s.txt", "@@", "*** End Patch"], "Empty hunk in Update File");
+    fails(
+        &["*** Begin Patch", "*** Update File: s.txt", "@@", "## Goals", "*** End Patch"],
+        "Strict @@ pair hunk requires second @@ delimiter",
+    );
+    fails(
+        &["*** Begin Patch", "*** Delete File: bad\\npath.txt", "*** End Patch"],
+        "Delete File path contains control",
+    );
+    fails(
+        &["*** Begin Patch", "*** Add File: bad\\npath.txt", "+alpha", "*** End Patch"],
+        "Add File path contains control characters or escape sequences",
+    );
+    fails(&["*** Begin Patch", "*** Update File: bad\\npath.txt", "*** End Patch"], "Update File path contains");
+    fails(
+        &["*** Begin Patch", "*** Update File: s.txt", "*** Move to: bad\\npath.txt", "*** End Patch"],
+        "Move to path contains",
+    );
+    fails(&["*** Begin Patch", "*** Update File: a", "-x", "*** End of File", "-y", "*** End Patch"], "Expected @@");
+}
+
+#[test]
+fn codex_hunks_split_on_markers_and_stack_anchors() {
+    let ops = parse(
+        "*** Begin Patch\n*** Update File: a\n@@ class A\n@@ def f():\n-x\n+y\n@@\n-p\n+q\n*** End of File\n*** End Patch",
+    )
+    .unwrap();
+    let hunks = update(&ops);
+    assert_eq!(hunks.len(), 2);
+    assert_eq!(hunks[0].anchors, vec!["class A".to_owned(), "def f():".to_owned()]);
+    assert!(!hunks[0].at_eof && hunks[1].at_eof);
+    assert!(hunks[1].anchors.is_empty());
+}
+
+#[test]
+fn codex_headers_with_line_numbers_are_hints_not_anchors() {
+    for header in ["@@@ -48,6 +48,7 @@@", "@@ -48,6 +48,7 @@", "@@ -48,6 +48,7 @@ fn sample()"] {
+        let ops = parse(&patch(&["*** Begin Patch", "*** Update File: s", header, " a", "-b", "+c", "*** End Patch"]))
+            .unwrap();
+        let h = &update(&ops)[0];
+        assert!(h.anchors.is_empty(), "{header}: {:?}", h.anchors);
+        assert_eq!(h.old_start, Some(48), "{header}");
+    }
+    let ops =
+        parse(&patch(&["*** Begin Patch", "*** Update File: s", "@@ def sample()", " a", "*** End Patch"])).unwrap();
+    assert_eq!(update(&ops)[0].anchors, vec!["def sample()".to_owned()]);
+    // JetBrains `applyHunks works with unified-diff style hunk headers`.
+    let p = patch(&[
+        "*** Begin Patch",
+        "*** Update File: s",
+        "@@ -1,3 +1,4 @@",
+        " alpha",
+        "-beta",
+        "+BETA",
+        " gamma",
+        "+delta",
+        "*** End Patch",
+    ]);
+    assert_eq!(apply_patch("alpha\nbeta\ngamma\n", &p).unwrap(), "alpha\nBETA\ngamma\ndelta\n");
+}
+
+#[test]
+fn strict_pair_hunks() {
+    let p = patch(&[
+        "*** Begin Patch",
+        "*** Update File: s",
+        "@@",
+        "## Goals",
+        "- Keep old wording",
+        "@@",
+        "## Goals",
+        "- Keep new wording",
+        "*** End Patch",
+    ]);
+    let ops = parse(&p).unwrap();
+    let h = &update(&ops)[0];
+    assert!(h.anchors.is_empty());
+    assert_eq!(
+        h.lines,
+        vec![
+            Line::Remove("## Goals".into()),
+            Line::Remove("- Keep old wording".into()),
+            Line::Add("## Goals".into()),
+            Line::Add("- Keep new wording".into()),
+        ]
+    );
+    assert_eq!(apply_patch("# T\n## Goals\n- Keep old wording\n", &p).unwrap(), "# T\n## Goals\n- Keep new wording\n");
+}
+
+#[test]
+fn applies_codex_hunks_with_anchors() {
+    let text = "class A:\n    def f():\n        return 1\nclass B:\n    def f():\n        return 1\n";
+    let patch = "*** Begin Patch\n*** Update File: a.py\n@@ class B:\n     def f():\n-        return 1\n+        return 2\n*** End Patch";
+    assert_eq!(
+        apply_patch(text, patch).unwrap(),
+        "class A:\n    def f():\n        return 1\nclass B:\n    def f():\n        return 2\n"
+    );
+}
+
+#[test]
+fn applies_several_hunks_in_order() {
+    let text = "a\nb\nc\nd\ne\nf\n";
+    let patch = "*** Begin Patch\n*** Update File: x\n@@\n a\n-b\n+B\n@@\n e\n-f\n+F\n+G\n*** End Patch";
+    assert_eq!(apply_patch(text, patch).unwrap(), "a\nB\nc\nd\ne\nF\nG\n");
+}
+
+#[test]
+fn same_lines_twice_match_in_order() {
+    let text = "x\ny\nx\ny\n";
+    let patch = "*** Begin Patch\n*** Update File: f\n@@\n-x\n+1\n@@\n-x\n+2\n*** End Patch";
+    assert_eq!(apply_patch(text, patch).unwrap(), "1\ny\n2\ny\n");
+}
+
+#[test]
+fn end_of_file_hunks_must_end_the_file() {
+    let text = "end\nmid\nend\n";
+    let patch = "*** Begin Patch\n*** Update File: f\n@@\n-end\n+END\n*** End of File\n*** End Patch";
+    assert_eq!(apply_patch(text, patch).unwrap(), "end\nmid\nEND\n");
+    let beta = hunk(&[('-', "beta"), ('+', "BETA")], true);
+    assert_eq!(apply("alpha\nbeta\n", std::slice::from_ref(&beta)).unwrap().text, "alpha\nBETA\n");
+    let e = apply("alpha\nbeta\ngamma\n", &[beta]).unwrap_err();
+    assert!(e.starts_with("Hunk context not found") && e.contains("do not end the file"), "{e}");
+}
+
+#[test]
+fn hunks_out_of_order_are_found_from_the_top() {
+    let hunks = [hunk(&[('-', "one"), ('+', "ONE")], true), hunk(&[('-', "two"), ('+', "TWO")], false)];
+    assert_eq!(apply("one\ntwo\nthree\none\n", &hunks).unwrap().text, "one\nTWO\nthree\nONE\n");
+    let text = "fn a() {\n    one();\n    two();\n}\n";
+    let p =
+        "*** Begin Patch\n*** Update File: f\n@@\n-    two();\n+    2();\n@@\n-    one();\n+    1();\n*** End Patch";
+    assert_eq!(apply_patch(text, p).unwrap(), "fn a() {\n    1();\n    2();\n}\n");
+}
+
+#[test]
+fn many_repeated_hunks_apply_deterministically() {
+    let hunks: Vec<Hunk> = (0..80).map(|i| hunk(&[('-', "alpha"), ('+', &format!("alpha-{i}"))], false)).collect();
+    let text = "alpha\n".repeat(600);
+    let expected: String = (0..80).map(|i| format!("alpha-{i}\n")).collect::<String>() + &"alpha\n".repeat(520);
+    assert_eq!(apply(&text, &hunks).unwrap().text, expected);
+}
+
+#[test]
+fn accepts_the_anchor_repeated_as_context() {
+    let text = "package greet\n\nfunc prefix() string {\n\treturn \"Merhaba, \"\n}\n";
+    let patch = "*** Begin Patch\n*** Update File: f\n@@ func prefix() string {\n func prefix() string {\n-\treturn \"Merhaba, \"\n+\treturn \"Selam, \"\n }\n*** End Patch";
+    assert_eq!(apply_patch(text, patch).unwrap(), "package greet\n\nfunc prefix() string {\n\treturn \"Selam, \"\n}\n");
+}
+
+#[test]
+fn pure_additions_go_after_the_anchor_or_at_the_end() {
+    let text = "fn a() {}\nfn b() {}\n";
+    let after = "*** Begin Patch\n*** Update File: f\n@@ fn a() {}\n+fn a2() {}\n*** End Patch";
+    assert_eq!(apply_patch(text, after).unwrap(), "fn a() {}\nfn a2() {}\nfn b() {}\n");
+    let end = "*** Begin Patch\n*** Update File: f\n@@\n+fn c() {}\n*** End Patch";
+    assert_eq!(apply_patch(text, end).unwrap(), "fn a() {}\nfn b() {}\nfn c() {}\n");
+}
+
+#[test]
+fn fuzz_levels_are_tried_in_order_and_reported() {
+    let text = "fn main() {   \n    let x = 1;\n}\n";
+    let ops =
+        parse("*** Begin Patch\n*** Update File: f\n@@\n fn main() {\n-    let x = 1;\n+    let x = 2;\n*** End Patch")
+            .unwrap();
+    let a = apply(text, update(&ops)).unwrap();
+    assert_eq!(a.text, "fn main() {   \n    let x = 2;\n}\n");
+    assert_eq!(a.fuzzy, vec![(1, Fuzz::TrailingWhitespace)]);
+    let ops = parse("*** Begin Patch\n*** Update File: f\n@@\n-let x = 1;\n+    let y = 1;\n*** End Patch").unwrap();
+    let a = apply(text, update(&ops)).unwrap();
+    assert_eq!(a.text, "fn main() {   \n    let y = 1;\n}\n");
+    assert_eq!(a.fuzzy, vec![(1, Fuzz::Whitespace)]);
+
+    // JetBrains: typographic punctuation, exact matches first.
+    let typographic = "import asyncio  # local import \u{2013} avoids top\u{2011}level dep";
+    let ascii = "import asyncio  # local import - avoids top-level dep";
+    let a =
+        apply(&format!("{typographic}\n"), &[hunk(&[('-', ascii), ('+', "import asyncio  # HELLO")], false)]).unwrap();
+    assert_eq!(a.text, "import asyncio  # HELLO\n");
+    assert_eq!(a.fuzzy, vec![(1, Fuzz::Punctuation)]);
+    let both = [hunk(&[('-', ascii), ('+', "# FIRST")], false), hunk(&[('-', ascii), ('+', "# SECOND")], false)];
+    let text = format!("first\n{typographic}\n{typographic}\n");
+    assert_eq!(apply(&text, &both).unwrap().text, "first\n# FIRST\n# SECOND\n");
+    let text = format!("first\n{typographic}\n{ascii}\n");
+    let exact = apply(&text, &[hunk(&[('-', ascii), ('+', "# EXACT")], false)]).unwrap();
+    assert_eq!(exact.text, format!("first\n{typographic}\n# EXACT\n"));
+}
+
+#[test]
+fn a_trailing_blank_context_line_is_optional() {
+    let text = "a\nb";
+    let patch = "*** Begin Patch\n*** Update File: f\n@@\n-b\n+c\n \n*** End Patch";
+    assert_eq!(apply_patch(text, patch).unwrap(), "a\nc");
+}
+
+#[test]
+fn keeps_a_missing_final_newline_and_handles_empty_files() {
+    assert_eq!(apply_patch("a\nb", "*** Begin Patch\n*** Update File: f\n-b\n+c\n*** End Patch").unwrap(), "a\nc");
+    assert_eq!(apply_patch("", "*** Begin Patch\n*** Update File: f\n+x\n*** End Patch").unwrap(), "x\n");
+    assert_eq!(apply_patch("a\n", "*** Begin Patch\n*** Update File: f\n-a\n*** End Patch").unwrap(), "");
+    let h = hunk(&[('-', "alpha"), ('+', "alpha2"), (' ', "beta")], false);
+    assert_eq!(apply("alpha   \nbeta\n", &[h]).unwrap().text, "alpha2\nbeta\n");
+}
+
+#[test]
+fn reports_where_a_hunk_went_wrong() {
+    let text = "fn a() {\n    one();\n    two();\n}\n";
+    let patch =
+        "*** Begin Patch\n*** Update File: f\n@@\n fn a() {\n     one();\n-    three();\n+    four();\n*** End Patch";
+    let e = apply_patch(text, patch).unwrap_err();
+    assert!(e.starts_with("Hunk context not found: hunk 1 does not apply"), "{e}");
+    assert!(e.contains("  fn a() {\n      one();\n      three();\n"), "{e}");
+    assert!(e.contains("Closest match at line 1: line 3 is `    two();`, but the patch expects `    three();`"), "{e}");
+    let e = apply_patch(text, "*** Begin Patch\n*** Update File: f\n@@ fn zzz\n-x\n*** End Patch").unwrap_err();
+    assert!(e.contains("hunk 1 (@@ fn zzz)") && e.contains("`fn zzz`"), "{e}");
+    let e = apply_patch(text, "*** Begin Patch\n*** Update File: f\n-nothing\n*** End Patch").unwrap_err();
+    assert!(e.contains("No line of them"), "{e}");
+    let e = apply_patch(text, "*** Begin Patch\n*** Update File: f\n-two\n+three\n*** End Patch").unwrap_err();
+    assert!(e.contains("Line 3 contains `two` but is `    two();`: patch lines must be whole lines"), "{e}");
+}
+
+// --- unified diffs ------------------------------------------------------
+
+const GIT: &str = "diff --git a/src/lib.rs b/src/lib.rs
+index 3b18e51..a9e0c2f 100644
+--- a/src/lib.rs
++++ b/src/lib.rs
+@@ -1,3 +1,3 @@ mod x;
+ fn a() {}
+-fn b() {}
++fn b() { todo!() }
+ fn c() {}
+@@ -10,2 +10,3 @@
+ fn j() {}
++fn k() {}
+ fn l() {}
+diff --git a/new.txt b/new.txt
+new file mode 100644
+index 0000000..e69de29
+--- /dev/null
++++ b/new.txt
+@@ -0,0 +1,2 @@
++hello
++world
+diff --git a/gone.txt b/gone.txt
+deleted file mode 100644
+--- a/gone.txt
++++ /dev/null
+@@ -1 +0,0 @@
+-bye
+diff --git a/old name.txt b/new name.txt
+similarity index 90%
+rename from old name.txt
+rename to new name.txt
+--- a/old name.txt
++++ b/new name.txt
+@@ -1 +1 @@
+-x
++y
+";
+
+#[test]
+fn parses_git_diffs() {
+    let ops = parse(GIT).unwrap();
+    assert_eq!(ops.len(), 4);
+    match &ops[0] {
+        FileOp::Update { path, move_to: None, hunks, or } => {
+            assert_eq!(path, "src/lib.rs");
+            assert!(or.is_empty(), "{or:?}");
+            assert_eq!(hunks.len(), 2);
+            assert_eq!(hunks[0].old_start, Some(1));
+            assert_eq!(hunks[1].lines.len(), 3);
+        }
+        other => panic!("{other:?}"),
+    }
+    assert_eq!(ops[1], FileOp::Add { path: "new.txt".into(), text: "hello\nworld\n".into() });
+    assert_eq!(ops[2], FileOp::Delete { path: "gone.txt".into() });
+    assert!(matches!(&ops[3], FileOp::Update { path, move_to: Some(to), .. }
+        if path == "old name.txt" && to == "new name.txt"));
+}
+
+#[test]
+fn parses_git_diffs_inside_begin_patch() {
+    let ops = parse(&patch(&[
+        "*** Begin Patch",
+        "diff --git a/s.txt b/s.txt",
+        "--- a/s.txt",
+        "+++ b/s.txt",
+        "@@ -1 +1 @@",
+        "-old",
+        "+new",
+        "*** End Patch",
+    ]))
+    .unwrap();
+    assert!(
+        matches!(&ops[..], [FileOp::Update { path, move_to: None, hunks, .. }] if path == "s.txt" && hunks.len() == 1)
+    );
+    // `--- x` removing a `-- x` line keeps a Codex patch a Codex patch.
+    let ops =
+        parse("*** Begin Patch\n*** Update File: q.sql\n@@\n--- old comment\n+-- new comment\n*** End Patch").unwrap();
+    assert_eq!(update(&ops)[0].lines, vec![Line::Remove("-- old comment".into()), Line::Add("-- new comment".into())]);
+}
+
+#[test]
+fn parses_plain_unified_diffs_and_pure_renames() {
+    let ops =
+        parse("--- a.txt\t2024-01-01 10:00:00\n+++ a.txt\t2024-01-02 10:00:00\n@@ -1,2 +1,2 @@\n-a\n+b\n c\n").unwrap();
+    assert!(
+        matches!(&ops[0], FileOp::Update { path, move_to: None, hunks, .. } if path == "a.txt" && hunks.len() == 1)
+    );
+    // Differently named sides are not a move: the `+++` path, else the others.
+    let ops = parse("--- a.txt.orig\n+++ a.txt\n@@ -1 +1 @@\n-a\n+b\n").unwrap();
+    assert!(matches!(&ops[0], FileOp::Update { path, move_to: None, or, .. }
+        if path == "a.txt" && or == &["a.txt.orig"]));
+    let ops = parse(
+        "diff -ru old/src/a.txt new/src/a.txt\n--- old/src/a.txt\t2024-01-01\n+++ new/src/a.txt\t2024-01-02\n@@ -1 +1 @@\n-a\n+b\n",
+    )
+    .unwrap();
+    assert!(matches!(&ops[0], FileOp::Update { path, move_to: None, or, .. }
+        if path == "new/src/a.txt" && or == &["old/src/a.txt", "src/a.txt"]));
+    let ops = parse("diff --git a/x.rs b/y/x.rs\nsimilarity index 100%\nrename from x.rs\nrename to y/x.rs\n").unwrap();
+    assert_eq!(
+        ops[0],
+        FileOp::Update { path: "x.rs".into(), move_to: Some("y/x.rs".into()), hunks: vec![], or: vec![] }
+    );
+    let ops = parse("diff --git a/e b/e\nnew file mode 100644\nindex 0000000..e69de29\n").unwrap();
+    assert_eq!(ops[0], FileOp::Add { path: "e".into(), text: String::new() });
+    let ops = parse("diff --git \"a/sp ace\" \"b/sp ace\"\ndeleted file mode 100644\n").unwrap();
+    assert_eq!(ops[0], FileOp::Delete { path: "sp ace".into() });
+}
+
+#[test]
+fn unified_counts_are_tolerated() {
+    // Counts too large: the next header ends the hunk.
+    let ops = parse("--- a/f\n+++ b/f\n@@ -1,9 +1,9 @@\n-a\n+b\n--- a/g\n+++ b/g\n@@ -1 +1 @@\n-c\n+d\n").unwrap();
+    assert_eq!(ops.len(), 2);
+    assert_eq!(update(&ops)[0].lines.len(), 2);
+    // Counts too small: following hunk lines still belong to it.
+    let ops = parse("--- a/f\n+++ b/f\n@@ -1,1 +1,1 @@\n-a\n+b\n c\n").unwrap();
+    assert_eq!(update(&ops)[0].lines.len(), 3);
+    // A bare `@@` reads to the next header; empty lines are empty context.
+    let ops = parse("--- a/f\n+++ b/f\n@@\n x\n\n-y\n+z\n\n").unwrap();
+    assert_eq!(
+        update(&ops)[0].lines,
+        vec![Line::Context("x".into()), Line::Context(String::new()), Line::Remove("y".into()), Line::Add("z".into())]
+    );
+    // `git format-patch` signature.
+    let ops = parse("Subject: x\n---\n--- a/f\n+++ b/f\n@@ -1 +1 @@\n-a\n+b\n-- \n2.43.0\n").unwrap();
+    assert_eq!(ops.len(), 1);
+    // `*** End of File` inside a unified hunk.
+    let ops = parse("--- a/f\n+++ b/f\n@@\n-a\n+b\n*** End of File\n").unwrap();
+    assert!(update(&ops)[0].at_eof);
+}
+
+#[test]
+fn unified_errors() {
+    assert!(parse("@@ -1 +1 @@\n-a\n+b\n").unwrap_err().contains("patch must include *** Begin Patch"));
+    assert!(parse("--- a/f\n+++ b/f\n@@ -x +y @@\n-a\n").unwrap_err().contains("cannot read"));
+    let e = parse("diff --git a/f b/f\nBinary files a/f and b/f differ\n").unwrap_err();
+    assert!(e.contains("Binary git patch is not supported"), "{e}");
+    assert!(parse("diff --git a/f b/f\nindex 1..2\n").unwrap_err().contains("no changes"));
+    assert!(parse("--- /dev/null\n+++ b/n\n@@ -1 +1 @@\n x\n").unwrap_err().contains("new file"));
+    let e = parse("--- a/f\n+++ b/f\n@@ -1 +1 @@\nzzz\n").unwrap_err();
+    assert!(e.contains("Hunk lines must start with space, +, or - (line 4: `zzz`)"), "{e}");
+}
+
+#[test]
+fn applies_unified_hunks_near_their_line_numbers() {
+    let text = "x\nsame\nx\nx\nx\nsame\nx\n";
+    let ops = parse("--- a/f\n+++ b/f\n@@ -6,1 +6,1 @@\n-same\n+changed\n").unwrap();
+    assert_eq!(apply(text, update(&ops)).unwrap().text, "x\nsame\nx\nx\nx\nchanged\nx\n");
+    // Wrong line numbers still apply where the context is.
+    let ops = parse("--- a/f\n+++ b/f\n@@ -40,2 +40,2 @@\n x\n-same\n+changed\n").unwrap();
+    assert_eq!(apply(text, update(&ops)).unwrap().text, "x\nsame\nx\nx\nx\nchanged\nx\n");
+    // Insertion after line 2 (`-2,0`).
+    let ops = parse("--- a/f\n+++ b/f\n@@ -2,0 +3,1 @@\n+new\n").unwrap();
+    assert_eq!(apply(text, update(&ops)).unwrap().text, "x\nsame\nnew\nx\nx\nx\nsame\nx\n");
+    // Later line numbers shift by what earlier hunks added.
+    let ops = parse("--- a/f\n+++ b/f\n@@ -0,0 +1,2 @@\n+n1\n+n2\n@@ -6,1 +8,1 @@\n-same\n+changed\n").unwrap();
+    assert_eq!(apply(text, update(&ops)).unwrap().text, "n1\nn2\nx\nsame\nx\nx\nx\nchanged\nx\n");
+}
+
+#[test]
+fn applies_the_git_example() {
+    let text = "fn a() {}\nfn b() {}\nfn c() {}\nfn d() {}\nfn e() {}\nfn f() {}\nfn g() {}\nfn h() {}\nfn i() {}\nfn j() {}\nfn l() {}\n";
+    let ops = parse(GIT).unwrap();
+    let out = apply(text, update(&ops)).unwrap().text;
+    assert_eq!(
+        out,
+        "fn a() {}\nfn b() { todo!() }\nfn c() {}\nfn d() {}\nfn e() {}\nfn f() {}\nfn g() {}\nfn h() {}\nfn i() {}\nfn j() {}\nfn k() {}\nfn l() {}\n"
+    );
+}
+
+#[test]
+fn no_newline_markers() {
+    let add = parse("--- /dev/null\n+++ b/n\n@@ -0,0 +1 @@\n+x\n\\ No newline at end of file\n").unwrap();
+    assert_eq!(add[0], FileOp::Add { path: "n".into(), text: "x".into() });
+    // Adding the final newline.
+    let ops = parse("--- a/f\n+++ b/f\n@@ -1,2 +1,2 @@\n a\n-b\n\\ No newline at end of file\n+b\n").unwrap();
+    assert_eq!(apply("a\nb", update(&ops)).unwrap().text, "a\nb\n");
+    // Removing it.
+    let ops = parse("--- a/f\n+++ b/f\n@@ -1,2 +1,2 @@\n a\n-b\n+b\n\\ No newline at end of file\n").unwrap();
+    assert_eq!(apply("a\nb\n", update(&ops)).unwrap().text, "a\nb");
+}
+
+#[test]
+fn splits_git_paths() {
+    assert_eq!(split_git_paths("a/x y b/x y"), (Some("x y".into()), Some("x y".into())));
+    assert_eq!(split_git_paths("a/x b/y"), (Some("x".into()), Some("y".into())));
+    assert_eq!(parse_range_header("@@ -3 +4,0 @@"), Some((3, 1, 0)));
+    assert_eq!(parse_range_header("@@ -1,2 +1,3 @@ fn x"), Some((1, 2, 3)));
+    assert_eq!(parse_range_header("@@@ -48,6 +48,7 @@@"), Some((48, 6, 7)));
+    assert_eq!(parse_range_header("@@ fn x"), None);
+    assert_eq!(unquote("\"a\\\"b\\\\c\""), "a\"b\\c");
+}
+
+#[test]
+fn mode_changes_and_copies_do_not_fail_the_patch() {
+    // A mode-only section is an update without hunks; the hunks of the others still apply.
+    let diff = patch(&[
+        "diff --git a/run.sh b/run.sh",
+        "old mode 100644",
+        "new mode 100755",
+        "diff --git a/a.txt b/a.txt",
+        "--- a/a.txt",
+        "+++ b/a.txt",
+        "@@ -1 +1 @@",
+        "-x",
+        "+y",
+    ]);
+    let ops = parse(&diff).unwrap();
+    assert_eq!(ops.len(), 2);
+    assert_eq!(ops[0], FileOp::Update { path: "run.sh".into(), move_to: None, hunks: Vec::new(), or: Vec::new() });
+    assert_eq!(update(&ops[1..]).len(), 1);
+
+    // A mode change together with a rename is a move.
+    let ops = parse("diff --git a/x b/y\nold mode 100644\nnew mode 100755\nrename from x\nrename to y\n").unwrap();
+    assert!(matches!(&ops[0], FileOp::Update { move_to: Some(m), .. } if m == "y"));
+
+    // A copy is skipped with a note.
+    let diff = patch(&[
+        "diff --git a/src/a.rs b/src/b.rs",
+        "similarity index 90%",
+        "copy from src/a.rs",
+        "copy to src/b.rs",
+        "--- a/src/a.rs",
+        "+++ b/src/b.rs",
+        "@@ -1 +1 @@",
+        "-a",
+        "+b",
+        "diff --git a/c.txt b/c.txt",
+        "--- a/c.txt",
+        "+++ b/c.txt",
+        "@@ -1 +1 @@",
+        "-1",
+        "+2",
+    ]);
+    let ops = parse(&diff).unwrap();
+    assert_eq!(ops.len(), 2);
+    match &ops[0] {
+        FileOp::Skip { path, note } => {
+            assert_eq!(path, "src/b.rs");
+            assert!(note.contains("copy of src/a.rs to src/b.rs") && note.contains("not supported"), "{note}");
+        }
+        other => panic!("{other:?}"),
+    }
+    assert_eq!(ops[1].path(), "c.txt");
+}

crates/ide-host/src/mcp/edit/rename.rs

@@ -0,0 +1,950 @@
+// Ported from JetBrains intellij-community plugins/mcp-server (mcpserver.toolsets/src/general/RefactoringToolset.kt, renameTarget.kt), Apache-2.0.
+//! `rename_refactoring` with the language server's rename. The target is given
+//! as in JetBrains: a `contextSnippet`, else `line` + `column`, else the one
+//! declaration of `symbolName` in the file; `targetIndex` picks from the
+//! candidates an earlier call listed. Failures are results (`ok: false` with an
+//! `error.kind`), not tool errors, so the agent can correct the call.
+//!
+//! Symbols are told apart by their definition (go to definition): the language
+//! server has no PSI elements to compare. It renames code references only;
+//! `searchInComments` / `searchInText` add whole-word occurrences found with
+//! Find in Files.
+
+use super::normalize_newlines;
+use crate::mcp::tool::{Call, Output, Param, ParamType, Tool};
+use crate::ops::search::SearchEvent;
+use ide_core::{DocId, FileEdit, IdeError, IdeResult, Pos, Range, TextEdit, WorkspaceEdit};
+use ide_lsp::types::GotoKind;
+use ide_search::{SearchContext, SearchQuery, SearchScope};
+use parking_lot::Mutex;
+use serde::Serialize;
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+
+/// Occurrences of the name whose definition is looked up when no position is given.
+const MAX_LOOKUPS: usize = 50;
+
+/// Files `searchInText` treats as plain text.
+const TEXT_EXTENSIONS: &[&str] = &["txt", "text", "md", "markdown", "rst", "adoc", "asciidoc", "properties"];
+
+pub(super) fn rename_refactoring() -> Tool {
+    Tool::new(
+        "rename_refactoring",
+        "Rename a symbol and every reference to it. Set preview=true to analyze the rename and write nothing.
+The language server resolves the symbol, so it also updates a reference that a text search cannot
+find. Always prefer this tool over a text replacement.
+
+Point at the symbol with ONE of these, in order of preference: contextSnippet, then line and column.
+With neither of them, the file must declare one symbol with this name. symbolName is always required.
+A position that resolves to another name refuses the rename.
+
+targetIndex is not a third way to point at the symbol. It picks from a candidates list an earlier call
+returned, so repeat that call with every argument it had, and add targetIndex.
+
+Read `applied`. It is the only success signal. Nothing is written in part, except after
+error.kind=write_failed, and its hint says what was written.
+ok=false with candidates asks you to pick one with targetIndex. ok=false with conflicts asks for another
+newName. ok=false with error tells you in `hint` what to correct.
+
+applyAutomaticRenamers has no effect here: the language server renames the symbol and its references. A library or \
+compiled symbol cannot be renamed.
+
+By default, the rename changes no comment, no string literal and no plain-text occurrence of the name.
+Set searchInComments or searchInText to change them too.",
+        |call| async move { run(&call).await },
+    )
+    .write()
+    .param(Param::required("pathInProject", ParamType::String, "Path relative to the project root"))
+    .param(Param::required("symbolName", ParamType::String, "Exact, case-sensitive name of the symbol to rename."))
+    .param(Param::required(
+        "newName",
+        ParamType::String,
+        "New name for the symbol. It must be a valid identifier for the symbol's language.",
+    ))
+    .param(Param::optional(
+        "contextSnippet",
+        ParamType::String,
+        "Optional. Exact fragment of the file that shows the symbol. It must match the file once, and contain \
+symbolName.",
+    ))
+    .param(Param::optional(
+        "line",
+        ParamType::Integer,
+        "Optional. 1-based line of the symbol. Copy it from search_symbol output. Needs column too.",
+    ))
+    .param(Param::optional(
+        "column",
+        ParamType::Integer,
+        "Optional. 1-based column of the symbol. Copy it from search_symbol output. Needs line too.",
+    ))
+    .param(Param::optional(
+        "targetIndex",
+        ParamType::Integer,
+        "Optional. 1-based pick from the candidates list an earlier call returned. Repeat every other argument of \
+that call.",
+    ))
+    .param(Param::optional(
+        "preview",
+        ParamType::Boolean,
+        "Optional. Analyze only: report affects and conflicts, and write nothing. The default is false.",
+    ))
+    .param(Param::optional(
+        "applyAutomaticRenamers",
+        ParamType::Boolean,
+        "Optional. Also rename what the IDE renames along with the symbol. The default is false.",
+    ))
+    .param(Param::optional(
+        "searchInComments",
+        ParamType::Boolean,
+        "Optional. Also rename the name in comments and string literals. The default is false.",
+    ))
+    .param(Param::optional(
+        "searchInText",
+        ParamType::Boolean,
+        "Optional. Also rename the name in plain-text occurrences, such as non-code files. The default is false.",
+    ))
+}
+
+// --- the result ------------------------------------------------------------------
+
+#[derive(Serialize, Default)]
+#[serde(rename_all = "camelCase")]
+struct RenameResult {
+    ok: bool,
+    applied: bool,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    resolved_symbol: Option<SymbolInfo>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    affects: Option<Affects>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    renamed_file: Option<RenamedFile>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    candidates: Option<Vec<Candidate>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    conflicts: Option<Vec<Conflict>>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    error: Option<RenameError>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    note: Option<String>,
+}
+
+impl RenameResult {
+    fn failed(kind: &'static str, hint: impl Into<String>) -> Self {
+        Self { error: Some(RenameError { kind, hint: hint.into() }), ..Self::default() }
+    }
+
+    fn with_symbol(mut self, symbol: Option<SymbolInfo>) -> Self {
+        self.resolved_symbol = symbol;
+        self
+    }
+}
+
+#[derive(Serialize, Clone)]
+#[serde(rename_all = "camelCase")]
+struct SymbolInfo {
+    name: String,
+    declaration_text: String,
+    declaration_file: String,
+    declaration_line: u32,
+    language: String,
+}
+
+/// The blast radius: files with an edit, and the edits.
+#[derive(Serialize)]
+struct Affects {
+    files: usize,
+    usages: usize,
+}
+
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+struct RenamedFile {
+    previous_path: String,
+    path: String,
+}
+
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+struct Candidate {
+    target_index: usize,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    kind: Option<String>,
+    symbol: SymbolInfo,
+}
+
+#[derive(Serialize)]
+struct Conflict {
+    description: String,
+}
+
+#[derive(Serialize)]
+struct RenameError {
+    kind: &'static str,
+    hint: String,
+}
+
+// --- the call --------------------------------------------------------------------
+
+struct Request {
+    name: String,
+    new_name: String,
+    snippet: Option<String>,
+    position: Option<(i64, i64)>,
+    target_index: Option<i64>,
+    preview: bool,
+    automatic_renamers: bool,
+    in_comments: bool,
+    in_text: bool,
+}
+
+async fn run(call: &Call) -> IdeResult<Output> {
+    let raw = call.str("pathInProject")?;
+    let name = call.str("symbolName")?;
+    let new_name = call.str("newName")?;
+    for (value, arg) in [(&raw, "pathInProject"), (&name, "symbolName"), (&new_name, "newName")] {
+        if value.trim().is_empty() {
+            return Err(IdeError::invalid(format!("{arg} is empty")));
+        }
+    }
+    let (line, column) = (call.opt_i64("line")?, call.opt_i64("column")?);
+    if line.is_some() != column.is_some() {
+        return Err(IdeError::invalid("line and column must be given together"));
+    }
+    let request = Request {
+        name,
+        new_name,
+        snippet: call.opt_str("contextSnippet")?,
+        position: line.zip(column),
+        target_index: call.opt_i64("targetIndex")?,
+        preview: call.flag("preview", false)?,
+        automatic_renamers: call.flag("applyAutomaticRenamers", false)?,
+        in_comments: call.flag("searchInComments", false)?,
+        in_text: call.flag("searchInText", false)?,
+    };
+    let path = call.resolve_inside(&raw)?;
+    if !path.is_file() {
+        return Err(IdeError::not_found(format!("File not found: {raw}")));
+    }
+    let host = call.host();
+    let project = call.project().clone();
+    let (p, target) = (project.clone(), path.clone());
+    let (doc, transient) = host
+        .blocking(move || {
+            // The rename reads and changes files across the project: no buffer may be older than its file.
+            let open: Vec<PathBuf> = p
+                .documents
+                .open_documents()
+                .into_iter()
+                .filter_map(|d| p.documents.snapshot(d).ok().map(|i| i.path.to_path_buf()))
+                .chain(std::iter::once(target.clone()))
+                .collect();
+            super::refresh_from_disk(&p, &open);
+            super::open_document(&p, &target)
+        })
+        .await?;
+    // Closed on every path out, a panic or a dropped call included.
+    let _close = CloseDocument(project.clone(), transient.then_some(doc));
+    Output::json(rename(call, doc, &path, &request).await?)
+}
+
+/// Closes a transient document when dropped.
+struct CloseDocument(Arc<crate::Project>, Option<DocId>);
+
+impl Drop for CloseDocument {
+    fn drop(&mut self) {
+        if let Some(doc) = self.1 {
+            self.0.documents.close(doc);
+        }
+    }
+}
+
+async fn rename(call: &Call, doc: DocId, path: &Path, req: &Request) -> IdeResult<RenameResult> {
+    let snap = call.project().documents.text_snapshot(doc)?;
+    let file = File { call, doc, path, text: &snap.text, language: snap.language.0.clone() };
+    let pos = match resolve_target(&file, req).await? {
+        Resolution::Resolved(pos) => pos,
+        Resolution::Unresolved(kind, hint) => return Ok(RenameResult::failed(kind, hint)),
+        Resolution::Ambiguous(positions) => {
+            let mut candidates = Vec::new();
+            for (i, pos) in positions.iter().enumerate() {
+                let (symbol, kind) = file.symbol_at(&req.name, *pos).await;
+                candidates.push(Candidate { target_index: i + 1, kind, symbol });
+            }
+            let hint = format!(
+                "'{}' matches {} symbols here. Nothing changed. Call again with every argument of this call plus \
+targetIndex, or narrow the call with a contextSnippet that shows the one you mean.",
+                req.name,
+                positions.len()
+            );
+            return Ok(RenameResult { candidates: Some(candidates), ..RenameResult::failed("ambiguous_symbol", hint) });
+        }
+    };
+    let symbol = Some(file.symbol_at(&req.name, pos).await.0);
+    if req.name == req.new_name {
+        let hint = format!("The symbol already has the name '{}'.", req.new_name);
+        return Ok(RenameResult::failed("new_name_matches_current", hint).with_symbol(symbol));
+    }
+    if !plausible_identifier(&req.new_name) {
+        let hint = format!("'{}' is not a valid identifier for {}.", req.new_name, file.language);
+        return Ok(RenameResult::failed("new_name_invalid", hint).with_symbol(symbol));
+    }
+    let host = call.host();
+    let window = call.window();
+    match crate::ops::lsp::lsp_prepare_rename(&host, window, doc, pos).await {
+        Ok(Some(_)) => {}
+        Ok(None) => {
+            let hint = "This symbol cannot be renamed. A library or compiled symbol has to change upstream.";
+            return Ok(RenameResult::failed("not_renamable", hint).with_symbol(symbol));
+        }
+        Err(e) if e.kind == ide_core::error::ErrorKind::Cancelled => return Err(e),
+        Err(e) => return Ok(RenameResult::failed("language_not_supported", no_server_hint(&e)).with_symbol(symbol)),
+    }
+    let request = crate::mcp::tool::request_id();
+    let renamed = tokio::select! {
+        r = crate::ops::lsp::lsp_rename(&host, window, request, doc, pos, req.new_name.clone()) => r,
+        _ = call.cancel.cancelled() => {
+            host.cancel_request(request);
+            return Err(IdeError::cancelled());
+        }
+    };
+    let renamed = match renamed {
+        Ok(r) => r,
+        Err(e) if e.kind == ide_core::error::ErrorKind::Cancelled => return Err(e),
+        // Servers explain a clash with an existing name in the error (gopls: "would conflict with").
+        Err(e) if e.message.to_lowercase().contains("conflict") => {
+            let hint = "A conflict refused the rename and nothing changed. Choose another newName.";
+            let conflicts = Some(vec![Conflict { description: e.message }]);
+            return Ok(RenameResult { conflicts, ..RenameResult::failed("conflicts_found", hint) }.with_symbol(symbol));
+        }
+        Err(e) => return Ok(RenameResult::failed("new_name_refused", e.message).with_symbol(symbol)),
+    };
+    let mut edit = renamed.edit;
+    if edit.files.is_empty() {
+        return Ok(RenameResult::failed("unknown", "The language server found nothing to rename.").with_symbol(symbol));
+    }
+    if req.in_comments || req.in_text {
+        add_text_occurrences(call, &mut edit, req).await?;
+    }
+    for f in &edit.files {
+        let paths: Vec<&Path> = match f {
+            FileEdit::Edit { path, .. } | FileEdit::Create { path, .. } | FileEdit::Delete { path, .. } => vec![path],
+            FileEdit::Rename { from, to } => vec![from, to],
+        };
+        for p in paths {
+            if let Err(e) = super::super::tool::ensure_inside(call.root(), p) {
+                let hint = format!(
+                    "{}. Nothing was renamed. A rename that must change a file outside the project cannot run here.",
+                    e.message
+                );
+                return Ok(RenameResult::failed("read_only_usages", hint).with_symbol(symbol));
+            }
+        }
+    }
+    let mut files: Vec<&Path> = Vec::new();
+    let mut usages = 0;
+    for f in &edit.files {
+        if let FileEdit::Edit { path, edits, .. } = f {
+            usages += edits.len();
+            if !files.contains(&&**path) {
+                files.push(path);
+            }
+        }
+    }
+    let affects = Some(Affects { files: files.len(), usages });
+    let mut notes = Vec::new();
+    if renamed.incomplete.is_some() {
+        notes.push("The language server reported that the references may be incomplete.");
+    }
+    if req.automatic_renamers {
+        notes.push(
+            "applyAutomaticRenamers had no effect: the language server renames the symbol and its references only.",
+        );
+    }
+    let note = (!notes.is_empty()).then(|| notes.join(" "));
+    if req.preview {
+        return Ok(RenameResult { ok: true, affects, resolved_symbol: symbol, note, ..RenameResult::default() });
+    }
+    // The IDE's configuration among the files: the user agrees first.
+    let mut checked: Vec<&Path> = Vec::new();
+    for f in &edit.files {
+        let paths: Vec<&Path> = match f {
+            FileEdit::Edit { path, .. } | FileEdit::Create { path, .. } | FileEdit::Delete { path, .. } => vec![path],
+            FileEdit::Rename { from, to } => vec![from, to],
+        };
+        for p in paths {
+            if !checked.contains(&p) {
+                checked.push(p);
+                call.check_writable(p).await?;
+            }
+        }
+    }
+    let renamed_file = edit.files.iter().find_map(|f| match f {
+        FileEdit::Rename { from, to } if super::same_file(from, path) => {
+            Some(RenamedFile { previous_path: call.display(from), path: call.display(to) })
+        }
+        _ => None,
+    });
+    let (h, w) = (host.clone(), window.to_owned());
+    let written = crate::ops::lsp::apply_workspace_edit(&h, &w, edit).await;
+    if let Err(e) = written {
+        let hint = format!("The rename stopped while it wrote. {} Read the files again before you retry.", e.message);
+        return Ok(RenameResult::failed("write_failed", hint).with_symbol(symbol));
+    }
+    Ok(RenameResult {
+        ok: true,
+        applied: true,
+        resolved_symbol: symbol,
+        affects,
+        renamed_file,
+        note,
+        ..RenameResult::default()
+    })
+}
+
+fn no_server_hint(e: &IdeError) -> String {
+    format!(
+        "No language server can rename in this file ({}), so nothing was renamed. Without one, change the \
+occurrences with apply_patch.",
+        e.message
+    )
+}
+
+/// Refuses only what no language accepts in a name: whitespace, separators, a leading digit.
+fn plausible_identifier(name: &str) -> bool {
+    !name.starts_with(|c: char| c.is_ascii_digit())
+        && !name.chars().any(|c| c.is_whitespace() || c.is_control() || ".,;:()[]{}<>\"'`/\\+*=!?&|^%#~".contains(c))
+}
+
+// --- the target ------------------------------------------------------------------
+
+enum Resolution {
+    Resolved(Pos),
+    /// Several symbols, in document order; `targetIndex` is 1-based.
+    Ambiguous(Vec<Pos>),
+    Unresolved(&'static str, String),
+}
+
+/// The file the rename starts in.
+struct File<'a> {
+    call: &'a Call,
+    doc: DocId,
+    path: &'a Path,
+    text: &'a str,
+    language: String,
+}
+
+impl File<'_> {
+    fn line(&self, line: u32) -> &str {
+        self.text.split('\n').nth(line as usize).unwrap_or("")
+    }
+
+    /// Where the symbol at `pos` is defined; `None` without an answer.
+    async fn definition(&self, pos: Pos) -> Option<(PathBuf, Pos)> {
+        let host = self.call.host();
+        let found = crate::ops::lsp::lsp_goto(&host, self.call.window(), self.doc, pos, GotoKind::Definition).await;
+        let loc = found.ok()?.into_iter().find(|l| l.uri.is_none())?;
+        Some((PathBuf::from(&*loc.path), loc.range.start))
+    }
+
+    /// Whether the language server can rename at `pos`; `Err` without one.
+    async fn renameable(&self, pos: Pos) -> Result<bool, Resolution> {
+        let host = self.call.host();
+        match crate::ops::lsp::lsp_prepare_rename(&host, self.call.window(), self.doc, pos).await {
+            Ok(found) => Ok(found.is_some()),
+            Err(e) => Err(Resolution::Unresolved("language_not_supported", no_server_hint(&e))),
+        }
+    }
+
+    /// The symbol (from its definition when known) and its outline kind.
+    async fn symbol_at(&self, name: &str, pos: Pos) -> (SymbolInfo, Option<String>) {
+        let (file, at) = match self.definition(pos).await {
+            Some((file, at)) if super::same_file(&file, self.path) => (self.path.to_path_buf(), at),
+            Some((file, at)) => (file, at),
+            None => (self.path.to_path_buf(), pos),
+        };
+        let declaration_text = if file == self.path {
+            self.line(at.line).trim().to_owned()
+        } else {
+            let project = self.call.project();
+            project
+                .text_of(&file)
+                .ok()
+                .and_then(|t| t.split('\n').nth(at.line as usize).map(|l| l.trim().to_owned()))
+                .unwrap_or_default()
+        };
+        let kind = if file == self.path { self.kind_at(at).await } else { None };
+        let symbol = SymbolInfo {
+            name: name.to_owned(),
+            declaration_text,
+            declaration_file: self.call.display(&file),
+            declaration_line: at.line + 1,
+            language: self.language.clone(),
+        };
+        (symbol, kind)
+    }
+
+    /// The outline kind (`field`, `method`) of the declaration whose name is at `pos`.
+    async fn kind_at(&self, pos: Pos) -> Option<String> {
+        let host = self.call.host();
+        let outline = crate::ops::doc::doc_outline(&host, self.call.window(), self.doc).await.ok()?;
+        let mut stack: Vec<&ide_core::OutlineItem> = outline.iter().collect();
+        while let Some(item) = stack.pop() {
+            let r = item.selection_range;
+            if r.start <= pos && pos <= r.end {
+                let kind = format!("{:?}", item.kind);
+                return Some(kind[..1].to_lowercase() + &kind[1..]);
+            }
+            stack.extend(item.children.iter());
+        }
+        None
+    }
+
+    /// Positions of `name` as an identifier (outside comments and strings when a grammar knows them).
+    async fn identifiers(&self, name: &str) -> Vec<Pos> {
+        let host = self.call.host();
+        match crate::ops::syntax::syntax_identifiers(&host, self.call.window(), self.doc, name.to_owned(), None).await {
+            Ok(found) if !found.is_empty() => found.into_iter().map(|o| o.range.start).collect(),
+            _ => word_positions(self.text, name),
+        }
+    }
+}
+
+/// The symbol the caller pointed at, or why the tool cannot tell which one it is.
+/// `targetIndex` picks from the list of the branch the other arguments select.
+async fn resolve_target(file: &File<'_>, req: &Request) -> IdeResult<Resolution> {
+    let resolution = if let Some(snippet) = &req.snippet {
+        by_snippet(file, snippet, &req.name).await
+    } else if let Some((line, column)) = req.position {
+        by_position(file, line, column, &req.name).await
+    } else {
+        by_declaration(file, &req.name).await?
+    };
+    let Some(index) = req.target_index else { return Ok(resolution) };
+    Ok(match resolution {
+        Resolution::Ambiguous(candidates) => pick(&candidates, index),
+        // One symbol now: only a pick of the first agrees with it; the code changed since the list.
+        Resolution::Resolved(pos) if index == 1 => Resolution::Resolved(pos),
+        Resolution::Resolved(pos) => pick(&[pos], index),
+        unresolved => unresolved,
+    })
+}
+
+fn pick(candidates: &[Pos], index: i64) -> Resolution {
+    let n = candidates.len();
+    if index < 1 || index as usize > n {
+        return Resolution::Unresolved(
+            "target_index_out_of_range",
+            format!(
+                "targetIndex {index} is outside 1..{n}. This call reports {n} candidate(s). Send the same \
+pathInProject, symbolName and contextSnippet as the call that listed them."
+            ),
+        );
+    }
+    Resolution::Resolved(candidates[index as usize - 1])
+}
+
+async fn by_snippet(file: &File<'_>, snippet: &str, name: &str) -> Resolution {
+    if snippet.trim().is_empty() {
+        return Resolution::Unresolved("snippet_not_found", "contextSnippet is blank.".into());
+    }
+    let needle = normalize_newlines(snippet);
+    if !needle.contains(name) {
+        return Resolution::Unresolved(
+            "name_mismatch",
+            format!("contextSnippet does not contain '{name}'. Pass a snippet that shows the symbol."),
+        );
+    }
+    let start = match find_snippet(file.text, &needle) {
+        SnippetMatch::NotFound => {
+            return Resolution::Unresolved(
+                "snippet_not_found",
+                "contextSnippet is not in this file. Read the file again and copy the snippet from its current text."
+                    .into(),
+            );
+        }
+        SnippetMatch::NotUnique => {
+            return Resolution::Unresolved(
+                "snippet_not_unique",
+                "contextSnippet matches this file more than once. Extend it until it is unique.".into(),
+            );
+        }
+        SnippetMatch::At(start) => start,
+    };
+    let mut symbols: Vec<(Option<(PathBuf, Pos)>, Pos)> = Vec::new();
+    // Why an occurrence could not be asked about; reported only when no other one resolves.
+    let mut refused = None;
+    for pos in snippet_occurrences(file.text, start, needle.len(), name) {
+        match file.renameable(pos).await {
+            Ok(true) => {}
+            Ok(false) => continue,
+            Err(no_server) => {
+                refused.get_or_insert(no_server);
+                continue;
+            }
+        }
+        let definition = file.definition(pos).await;
+        if definition.is_none() || !symbols.iter().any(|(d, _)| *d == definition) {
+            symbols.push((definition, pos));
+        }
+    }
+    if let (true, Some(refused)) = (symbols.is_empty(), refused) {
+        return refused;
+    }
+    match symbols.len() {
+        0 => Resolution::Unresolved(
+            "symbol_not_found",
+            format!("'{name}' inside contextSnippet does not resolve to a symbol that can be renamed."),
+        ),
+        1 => Resolution::Resolved(symbols[0].1),
+        _ => Resolution::Ambiguous(symbols.into_iter().map(|(_, p)| p).collect()),
+    }
+}
+
+async fn by_position(file: &File<'_>, line: i64, column: i64, name: &str) -> Resolution {
+    let line_count = file.text.split('\n').count() as i64;
+    if line < 1 || column < 1 || line > line_count {
+        return Resolution::Unresolved(
+            "position_out_of_bounds",
+            format!("Position {line}:{column} is outside this file. Both numbers are 1-based."),
+        );
+    }
+    let text = file.line(line as u32 - 1);
+    let units: Vec<u16> = text.encode_utf16().collect();
+    // The column has to stay on the named line: past its end it would land further down.
+    if column as usize - 1 > units.len() {
+        return Resolution::Unresolved(
+            "position_out_of_bounds",
+            format!("Column {column} is past the end of line {line}. Both numbers are 1-based."),
+        );
+    }
+    let pos = Pos::new(line as u32 - 1, column as u32 - 1);
+    let word = word_at(&units, pos.col as usize);
+    let in_code = file
+        .identifiers(name)
+        .await
+        .iter()
+        .any(|p| p.line == pos.line && p.col <= pos.col && pos.col <= p.col + units_len(name));
+    match word {
+        Some((start, w)) if w == name && in_code => {
+            let at = Pos::new(pos.line, start as u32);
+            match file.renameable(at).await {
+                Ok(true) => Resolution::Resolved(at),
+                Ok(false) => Resolution::Unresolved(
+                    "symbol_not_found",
+                    format!("No symbol that can be renamed sits at {line}:{column}."),
+                ),
+                Err(no_server) => no_server,
+            }
+        }
+        Some((_, other)) if other != name => Resolution::Unresolved(
+            "name_mismatch",
+            format!("Position {line}:{column} resolves to '{other}', not to '{name}'. Nothing was renamed."),
+        ),
+        _ => Resolution::Unresolved(
+            "symbol_not_found",
+            format!("No symbol that can be renamed sits at {line}:{column}."),
+        ),
+    }
+}
+
+/// The declarations of `name` in this file: the distinct definitions of its occurrences
+/// that lie in this file (declared-looking occurrences without go to definition).
+async fn by_declaration(file: &File<'_>, name: &str) -> IdeResult<Resolution> {
+    let occurrences = file.identifiers(name).await;
+    let mut declarations: Vec<Pos> = Vec::new();
+    let mut answered = false;
+    for pos in occurrences.iter().take(MAX_LOOKUPS) {
+        if file.call.cancel.is_cancelled() {
+            return Err(IdeError::cancelled());
+        }
+        if let Some((path, at)) = file.definition(*pos).await {
+            answered = true;
+            if super::same_file(&path, file.path) && !declarations.contains(&at) {
+                declarations.push(at);
+            }
+        }
+    }
+    if !answered {
+        declarations = occurrences.into_iter().filter(|p| is_declaration(file.text, *p)).collect();
+    }
+    declarations.sort();
+    Ok(match declarations.len() {
+        0 => Resolution::Unresolved(
+            "symbol_not_found",
+            format!("No symbol named '{name}' is declared in this file. Pass the file that declares it."),
+        ),
+        1 => Resolution::Resolved(declarations[0]),
+        _ => Resolution::Ambiguous(declarations),
+    })
+}
+
+fn units_len(s: &str) -> u32 {
+    s.encode_utf16().count() as u32
+}
+
+fn is_word_unit(u: u16) -> bool {
+    char::from_u32(u as u32).is_some_and(|c| c.is_alphanumeric() || c == '_' || c == '$') || u >= 0x80
+}
+
+/// The identifier-like word touching UTF-16 column `col`: (start column, word).
+fn word_at(units: &[u16], col: usize) -> Option<(usize, String)> {
+    let touches = |i: usize| units.get(i).is_some_and(|&u| is_word_unit(u));
+    let at = if touches(col) {
+        col
+    } else if col > 0 && touches(col - 1) {
+        col - 1
+    } else {
+        return None;
+    };
+    let start = (0..=at).rev().take_while(|&i| touches(i)).last().unwrap_or(at);
+    let end = (at..units.len()).take_while(|&i| touches(i)).last().map_or(at, |e| e + 1);
+    Some((start, String::from_utf16_lossy(&units[start..end])))
+}
+
+enum SnippetMatch {
+    NotFound,
+    NotUnique,
+    /// The byte offset of the only occurrence.
+    At(usize),
+}
+
+/// Where `needle` occurs in `text`, overlapping occurrences included.
+fn find_snippet(text: &str, needle: &str) -> SnippetMatch {
+    let Some(start) = text.find(needle) else { return SnippetMatch::NotFound };
+    // One character further, not one byte: the needle may start with a multibyte character.
+    let step = needle.chars().next().map_or(1, char::len_utf8);
+    if text[start + step..].contains(needle) { SnippetMatch::NotUnique } else { SnippetMatch::At(start) }
+}
+
+/// Whole-word occurrences of `name` inside the `len` bytes of `text` from byte `start`
+/// (a snippet's place in the file): the file's text around an occurrence decides whether
+/// it is a whole word, so a snippet cut in the middle of a word does not make one.
+fn snippet_occurrences(text: &str, start: usize, len: usize, name: &str) -> Vec<Pos> {
+    let is_word = |c: char| c.is_alphanumeric() || c == '_' || c == '$';
+    let mut out = Vec::new();
+    for (at, _) in text[start..start + len].match_indices(name) {
+        let at = start + at;
+        let before = text[..at].chars().next_back();
+        let after = text[at + name.len()..].chars().next();
+        if before.is_some_and(is_word) || after.is_some_and(is_word) {
+            continue;
+        }
+        let line_start = text[..at].rfind('\n').map_or(0, |i| i + 1);
+        out.push(Pos::new(text[..at].matches('\n').count() as u32, units_len(&text[line_start..at])));
+    }
+    out
+}
+
+/// Whole-word occurrences of `name` (0-based line, UTF-16 column).
+fn word_positions(text: &str, name: &str) -> Vec<Pos> {
+    let is_word = |c: char| c.is_alphanumeric() || c == '_' || c == '$';
+    let mut out = Vec::new();
+    for (line_no, line) in text.split('\n').enumerate() {
+        for (at, _) in line.match_indices(name) {
+            let before = line[..at].chars().next_back();
+            let after = line[at + name.len()..].chars().next();
+            if before.is_some_and(is_word) || after.is_some_and(is_word) {
+                continue;
+            }
+            out.push(Pos::new(line_no as u32, units_len(&line[..at])));
+        }
+    }
+    out
+}
+
+/// Words that introduce a declaration of the name after them.
+const DECLARATION_KEYWORDS: &[&str] = &[
+    "fn",
+    "def",
+    "class",
+    "struct",
+    "enum",
+    "trait",
+    "interface",
+    "type",
+    "func",
+    "function",
+    "fun",
+    "let",
+    "const",
+    "var",
+    "val",
+    "mod",
+    "module",
+    "object",
+    "record",
+    "typealias",
+    "protocol",
+    "union",
+    "namespace",
+    "package",
+    "static",
+    "macro_rules!",
+];
+
+/// Whether the occurrence at `p` follows a declaration keyword (`fn name`, `let mut name`).
+fn is_declaration(text: &str, p: Pos) -> bool {
+    let Some(line) = text.split('\n').nth(p.line as usize) else { return false };
+    let mut units = 0u32;
+    let byte = line
+        .char_indices()
+        .find(|(_, c)| {
+            let here = units >= p.col;
+            units += c.len_utf16() as u32;
+            here
+        })
+        .map_or(line.len(), |(i, _)| i);
+    let mut words = line[..byte].split_whitespace().rev();
+    match words.next() {
+        Some("mut") => words.next() == Some("let"),
+        Some(w) => DECLARATION_KEYWORDS.contains(&w),
+        None => false,
+    }
+}
+
+// --- comments and text -------------------------------------------------------------
+
+/// Adds whole-word occurrences of the old name to `edit`: in comments and string
+/// literals of the files it changes, and in plain-text files of the project.
+async fn add_text_occurrences(call: &Call, edit: &mut WorkspaceEdit, req: &Request) -> IdeResult<()> {
+    let edited: Vec<PathBuf> = edit
+        .files
+        .iter()
+        .filter_map(|f| match f {
+            FileEdit::Edit { path, .. } => Some(path.to_path_buf()),
+            _ => None,
+        })
+        .collect();
+    let mut found = Vec::new();
+    if req.in_comments {
+        let scope = || SearchScope::Files { paths: edited.iter().cloned().map(Into::into).collect() };
+        found.extend(occurrences(call, &req.name, scope(), SearchContext::InComments).await?);
+        found.extend(occurrences(call, &req.name, scope(), SearchContext::InStringLiterals).await?);
+    }
+    if req.in_text {
+        let text_file = |p: &Path| {
+            p.extension().and_then(|e| e.to_str()).is_some_and(|e| TEXT_EXTENSIONS.contains(&e.to_lowercase().as_str()))
+        };
+        found.extend(
+            occurrences(call, &req.name, SearchScope::Project, SearchContext::Any)
+                .await?
+                .into_iter()
+                .filter(|(p, _)| text_file(p) && !edited.iter().any(|e| super::same_file(e, p))),
+        );
+    }
+    for (path, range) in found {
+        let text_edit = TextEdit { range, new_text: req.new_name.clone() };
+        let entry = edit.files.iter_mut().find_map(|f| match f {
+            FileEdit::Edit { path: p, edits, .. } if super::same_file(p, &path) => Some(edits),
+            _ => None,
+        });
+        match entry {
+            Some(edits) => {
+                let overlaps =
+                    edits.iter().any(|e| e.range.start < range.end && range.start < e.range.end || e.range == range);
+                if !overlaps {
+                    edits.push(text_edit);
+                }
+            }
+            None => edit.files.push(FileEdit::Edit { path: path.into(), edits: vec![text_edit], version: None }),
+        }
+    }
+    Ok(())
+}
+
+/// Whole-word, case-sensitive Find in Files matches of `name`.
+async fn occurrences(
+    call: &Call,
+    name: &str,
+    scope: SearchScope,
+    context: SearchContext,
+) -> IdeResult<Vec<(PathBuf, Range)>> {
+    let query = SearchQuery {
+        pattern: name.to_owned(),
+        is_regex: false,
+        case_sensitive: true,
+        whole_word: true,
+        include: Vec::new(),
+        exclude: Vec::new(),
+        scope,
+        max_matches: 0,
+        context,
+    };
+    let host = call.host();
+    let request = crate::mcp::tool::request_id();
+    let files = Arc::new(Mutex::new(Vec::new()));
+    let emit: crate::ops::Emit<SearchEvent> = {
+        let files = files.clone();
+        Arc::new(move |event| {
+            if let SearchEvent::File { file } = event {
+                files.lock().push(file);
+            }
+        })
+    };
+    let search = crate::ops::search::start(&host, call.window(), request, query, emit);
+    tokio::pin!(search);
+    tokio::select! {
+        r = &mut search => r?,
+        _ = call.cancel.cancelled() => {
+            host.cancel_request(request);
+            let _ = search.await;
+            return Err(IdeError::cancelled());
+        }
+    }
+    let width = units_len(name);
+    let mut out = Vec::new();
+    for file in std::mem::take(&mut *files.lock()) {
+        for m in &file.matches {
+            for &(from, _) in &m.ranges {
+                let start = Pos::new(m.line, m.text_offset + from);
+                out.push((file.path.to_path_buf(), Range::new(start, Pos::new(m.line, start.col + width))));
+            }
+        }
+    }
+    Ok(out)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn finds_whole_words_in_utf16_columns() {
+        let text = "let foo = foo_bar + foo;\n// ä foo\nfoofoo";
+        assert_eq!(word_positions(text, "foo"), vec![Pos::new(0, 4), Pos::new(0, 20), Pos::new(1, 5)]);
+        let units: Vec<u16> = "  int counter;".encode_utf16().collect();
+        assert_eq!(word_at(&units, 6), Some((6, "counter".into())));
+        assert_eq!(word_at(&units, 13), Some((6, "counter".into())));
+        assert_eq!(word_at(&units, 0), None);
+    }
+
+    #[test]
+    fn finds_snippets_starting_with_multibyte_characters() {
+        let text = "let äb = 1;\nlet äb2 = äb;\n";
+        assert!(matches!(find_snippet(text, "äb"), SnippetMatch::NotUnique));
+        assert!(matches!(find_snippet(text, "äb = 1"), SnippetMatch::At(4)));
+        assert!(matches!(find_snippet(text, "ö"), SnippetMatch::NotFound));
+        // Overlapping occurrences are two.
+        assert!(matches!(find_snippet("aaa", "aa"), SnippetMatch::NotUnique));
+    }
+
+    #[test]
+    fn snippet_occurrences_are_whole_words_of_the_file() {
+        let text = "let beta = 1;\nlet x = alphabeta + beta;\n";
+        // The snippet starts inside `alphabeta`: its `beta` is not a word of the file.
+        let needle = "beta + beta";
+        let SnippetMatch::At(start) = find_snippet(text, needle) else { panic!() };
+        assert_eq!(snippet_occurrences(text, start, needle.len(), "beta"), vec![Pos::new(1, 20)]);
+        let text = "ä beta";
+        assert_eq!(snippet_occurrences(text, 0, text.len(), "beta"), vec![Pos::new(0, 2)]);
+    }
+
+    #[test]
+    fn recognizes_declarations_and_identifiers() {
+        let text = "use x;\nprint(count)\nlet mut count = 1;\nfn count() {}\n";
+        assert!(!is_declaration(text, Pos::new(1, 6)));
+        assert!(is_declaration(text, Pos::new(2, 8)) && is_declaration(text, Pos::new(3, 3)));
+        assert!(plausible_identifier("hitCount") && plausible_identifier("kebab-case") && plausible_identifier("$x"));
+        assert!(!plausible_identifier("1abc") && !plausible_identifier("bad name") && !plausible_identifier("a.b"));
+    }
+}

crates/ide-host/src/mcp/editors.rs

@@ -0,0 +1,98 @@
+use super::tool::{Call, Output, Param, ParamType, Tool};
+use ide_core::{Diagnostic, IdeResult, Severity};
+use serde_json::{Value, json};
+
+pub fn tools() -> Vec<Tool> {
+    vec![
+        Tool::new(
+            "get_all_open_file_paths",
+            "Returns active editor's and other open editors' file paths relative to the project root.
+
+Use this tool to explore current open editors.",
+            open_editors,
+        ),
+        Tool::new(
+            "get_current_file",
+            "Returns the focused editor's file and selection reported by the IDE.
+Selection lines and UTF-16 columns are 1-based, end exclusive.
+Selected text is limited to 65536 UTF-16 units.",
+            current_file,
+        ),
+        Tool::new(
+            "get_file_problems",
+            "Returns the problems for a file as reported by the IDE's Problems view, including language servers
+and inspections after profile filtering. This reflects what the Problems view shows, rather than a fresh analysis.
+Lines and UTF-16 columns are 1-based.",
+            file_problems,
+        )
+        .param(Param::required("filePath", ParamType::String, "Path relative to the project root"))
+        .param(Param::optional(
+            "errorsOnly",
+            ParamType::Boolean,
+            "Whether to include only errors or include both errors and warnings",
+        )),
+        Tool::new(
+            "get_project_problems",
+            "Returns the project's problems as reported by the IDE's Problems view, including language servers
+and inspections after profile filtering. This reflects what the Problems view shows, rather than a fresh analysis.
+Lines and UTF-16 columns are 1-based.",
+            project_problems,
+        ),
+    ]
+}
+
+async fn open_editors(call: Call) -> IdeResult<Output> {
+    let windows = call.host.mcp_windows(call.root());
+    let open = call.host.mcp_reports.editors(&windows);
+    let active = call.host.mcp_reports.focused(call.window());
+    Output::json(json!({
+        "activeFilePath": active.map(|e| call.display(&e.path.0)),
+        "openFiles": open.iter().map(|p| call.display(p)).collect::<Vec<_>>(),
+    }))
+}
+
+async fn current_file(call: Call) -> IdeResult<Output> {
+    let editor = call.host.mcp_reports.focused(call.window());
+    Output::json(match editor {
+        None => json!({}),
+        Some(e) => json!({
+            "filePath": call.display(&e.path.0), "selectedText": e.selected_text,
+            "selection": {
+                "startLine": e.selection.start.line + 1, "startColumn": e.selection.start.col + 1,
+                "endLine": e.selection.end.line + 1, "endColumn": e.selection.end.col + 1,
+            },
+        }),
+    })
+}
+
+fn problem(d: Diagnostic, text: &str) -> Value {
+    json!({
+        "severity": d.severity, "description": d.message,
+        "lineContent": text.lines().nth(d.range.start.line as usize).unwrap_or_default(),
+        "line": d.range.start.line + 1, "column": d.range.start.col + 1, "source": d.source, "code": d.code,
+    })
+}
+
+async fn file_problems(call: Call) -> IdeResult<Output> {
+    let path = call.resolve_readable(&call.str("filePath")?).await?;
+    let errors_only = call.flag("errorsOnly", true)?;
+    let files = call.host.mcp_reports.problems(&call.host.mcp_windows(call.root()));
+    let (project, file) = (call.project.clone(), path.clone());
+    let text = call.host.blocking(move || project.text_of(&file)).await.unwrap_or_default();
+    let errors: Vec<_> = files
+        .into_iter()
+        .filter(|f| f.path.0 == path)
+        .flat_map(|f| f.items)
+        .filter(|d| !errors_only || d.severity == Severity::Error)
+        .map(|d| problem(d, &text))
+        .collect();
+    Output::json(json!({"filePath": call.display(&path), "errors": errors}))
+}
+
+async fn project_problems(call: Call) -> IdeResult<Output> {
+    let files = call.host.mcp_reports.problems(&call.host.mcp_windows(call.root()));
+    let files: Vec<_> = files.into_iter().map(|f| json!({
+        "filePath":call.display(&f.path.0), "problems": f.items.into_iter().map(|d| problem(d, "")).collect::<Vec<_>>()
+    })).collect();
+    Output::json(json!({"files":files}))
+}

crates/ide-host/src/mcp/files.rs

@@ -0,0 +1,280 @@
+// Ported from JetBrains intellij-community plugins/mcp-server (mcpserver.toolsets/src/general/ReadToolset.kt,
+// the list_directory_tree part of FileToolset.kt, src/com/intellij/mcpserver/util/fs.util.kt), Apache-2.0.
+//! Reading files and listing directories.
+
+use crate::mcp::tool::{Call, Output, Param, ParamType, Tool};
+use crate::mcp::util::{
+    self, RELATIVE_PATH_IN_PROJECT_DESCRIPTION, TIMED_OUT_DESCRIPTION, TIMEOUT_MILLISECONDS_DESCRIPTION,
+};
+use ide_core::{CancellationToken, IdeError, IdeResult};
+use serde::Serialize;
+use serde_json::json;
+use std::path::Path;
+use std::time::{Duration, Instant};
+
+const DEFAULT_READ_LIMIT: i64 = 2000;
+const MAX_READ_LIMIT: i64 = 5000;
+/// Longer lines are cut (minified files would flood the context), in UTF-16 units.
+const MAX_LINE_LENGTH: usize = 2000;
+const DEFAULT_TREE_DEPTH: i64 = 5;
+
+pub fn tools() -> Vec<Tool> {
+    vec![read_file(), list_directory_tree()]
+}
+
+// --- read_file -----------------------------------------------------------------
+
+fn read_file() -> Tool {
+    Tool::new(
+        "read_file",
+        "Reads a file in the project directory or from any project dependency or other project source root.
+Can read text sources inside jar/zip archives; compiled class files are not decompiled.
+Returns numbered lines (1-indexed) as text.
+By default, reads up to 2000 lines starting from the beginning of the file.
+The maximum accepted limit is 5000 lines.",
+        |call| async move {
+            let offset = positive(&call, "offset", 1)?;
+            let limit = positive(&call, "limit", DEFAULT_READ_LIMIT)?;
+            if limit > MAX_READ_LIMIT {
+                return Err(IdeError::invalid(format!("limit must be <= {MAX_READ_LIMIT}")));
+            }
+            let path = util::resolve_read_file(&call, &call.str("file_path")?).await?;
+            if call.project().documents.by_path(&path).is_none()
+                && let probe = ide_vfs::probe(&path)?
+                && probe.binary
+            {
+                return Err(IdeError::invalid(format!(
+                    "{} is a binary file ({} bytes); read_file reads text",
+                    call.display(&path),
+                    probe.size
+                )));
+            }
+            let text = crate::ops::fs::read_text(&call.host(), call.window(), path).await?;
+            Ok(Output::text(render_slice(&text, offset as usize, limit as usize)?))
+        },
+    )
+    .param(Param::required("file_path", ParamType::String, util::FILE_PATH_DESCRIPTION))
+    .param(Param::optional("offset", ParamType::Integer, "1-based line number to start reading from"))
+    .param(Param::optional(
+        "limit",
+        ParamType::Integer,
+        "Maximum number of lines to return (default: 2000, max: 5000)",
+    ))
+}
+
+/// An integer argument that must be > 0.
+fn positive(call: &Call, name: &str, default: i64) -> IdeResult<i64> {
+    match call.opt_i64(name)?.unwrap_or(default) {
+        n if n <= 0 => Err(IdeError::invalid(format!("{name} must be > 0"))),
+        n => Ok(n),
+    }
+}
+
+/// Lines `start..` of `text` as `L<n>: <line>`; when more than `max_lines` remain, the first
+/// and the last halves of the budget with a `…N lines truncated…` marker between them.
+/// Lines are the editor's: a trailing line break starts an empty last line.
+fn render_slice(text: &str, start: usize, max_lines: usize) -> IdeResult<String> {
+    let lines: Vec<&str> = text.split('\n').map(|l| l.strip_suffix('\r').unwrap_or(l)).collect();
+    let count = lines.len();
+    if start > count {
+        return Err(IdeError::invalid("offset exceeds file length"));
+    }
+    let range = |from: usize, to: usize| {
+        (from..=to).map(|n| format!("L{n}: {}", format_line(lines[n - 1]))).collect::<Vec<_>>().join("\n")
+    };
+    let available = count - start + 1;
+    if available <= max_lines {
+        return Ok(range(start, count));
+    }
+    let head = max_lines / 2;
+    let tail = max_lines - head;
+    let head_end = start + head - 1;
+    let tail_start = count - tail + 1;
+    let mut out = String::new();
+    if head > 0 {
+        out.push_str(&range(start, head_end));
+        out.push('\n');
+    }
+    out.push_str(&format!("\u{2026}{} lines truncated\u{2026}", tail_start - head_end - 1));
+    if tail > 0 {
+        out.push('\n');
+        out.push_str(&range(tail_start, count));
+    }
+    Ok(out)
+}
+
+/// `line` cut to [`MAX_LINE_LENGTH`] UTF-16 units, or as many characters when the cut would
+/// split a surrogate pair (as JetBrains does).
+fn format_line(line: &str) -> &str {
+    let mut units = 0;
+    for (i, c) in line.char_indices() {
+        if units >= MAX_LINE_LENGTH {
+            return &line[..i];
+        }
+        if units + c.len_utf16() > MAX_LINE_LENGTH {
+            // A pair across the boundary: keep MAX_LINE_LENGTH characters instead.
+            return match line.char_indices().nth(MAX_LINE_LENGTH) {
+                Some((cut, _)) => &line[..cut],
+                None => line,
+            };
+        }
+        units += c.len_utf16();
+    }
+    line
+}
+
+// --- list_directory_tree -------------------------------------------------------
+
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+struct DirectoryTreeInfo {
+    traversed_directory: String,
+    tree: String,
+    errors: Vec<String>,
+    #[serde(skip_serializing_if = "std::ops::Not::not")]
+    listing_timed_out: bool,
+}
+
+fn list_directory_tree() -> Tool {
+    Tool::new(
+        "list_directory_tree",
+        "Provides a tree representation of the specified directory in the pseudo graphic format like `tree` utility does.
+Use this tool to explore the contents of a directory or the whole project.
+You MUST prefer this tool over listing directories via command line utilities like `ls` or `dir`.",
+        |call| async move {
+            let directory = call.str("directoryPath")?;
+            let max_depth = call.opt_i64("maxDepth")?.unwrap_or(DEFAULT_TREE_DEPTH);
+            let timeout = call.opt_i64("timeout")?.unwrap_or(util::MEDIUM_TIMEOUT.as_millis() as i64);
+            let dir = call.resolve_readable(&directory).await?;
+            if !dir.exists() {
+                return Err(IdeError::not_found(format!("No such directory: {}", dir.display())));
+            }
+            if !dir.is_dir() {
+                return Err(IdeError::invalid(format!("Not a directory: {}", dir.display())));
+            }
+            let deadline = Instant::now() + Duration::from_millis(timeout.max(0) as u64);
+            let cancel = call.cancel.clone();
+            let mut tree =
+                TreeRender { out: String::new(), errors: Vec::new(), timed_out: false, deadline, cancel: cancel.clone() };
+            let tree = call
+                .host()
+                .blocking(move || {
+                    tree.render(&dir, "", true, max_depth, true);
+                    Ok(tree)
+                })
+                .await?;
+            if cancel.is_cancelled() {
+                return Err(IdeError::cancelled());
+            }
+            Output::json(DirectoryTreeInfo {
+                traversed_directory: directory,
+                tree: tree.out,
+                errors: tree.errors,
+                listing_timed_out: tree.timed_out,
+            })
+        },
+    )
+    .param(Param::required("directoryPath", ParamType::String, RELATIVE_PATH_IN_PROJECT_DESCRIPTION))
+    .param(Param::optional("maxDepth", ParamType::Integer, "Maximum recursion depth"))
+    .param(Param::optional("timeout", ParamType::Integer, TIMEOUT_MILLISECONDS_DESCRIPTION))
+    .output(json!({
+        "type": "object",
+        "properties": {
+            "traversedDirectory": { "type": "string" },
+            "tree": { "type": "string" },
+            "errors": { "type": "array", "items": { "type": "string" } },
+            "listingTimedOut": { "type": "boolean", "description": TIMED_OUT_DESCRIPTION },
+        },
+        "required": ["traversedDirectory", "tree", "errors"],
+    }))
+}
+
+/// The `tree`-like listing: the directory's absolute path, then every entry (hidden and
+/// ignored ones too) by lower-cased name, directories marked with `/`.
+struct TreeRender {
+    out: String,
+    errors: Vec<String>,
+    timed_out: bool,
+    deadline: Instant,
+    cancel: CancellationToken,
+}
+
+impl TreeRender {
+    fn render(&mut self, path: &Path, indent: &str, is_last: bool, max_depth: i64, is_root: bool) {
+        if max_depth <= 0 || self.timed_out || self.cancel.is_cancelled() {
+            return;
+        }
+        if Instant::now() >= self.deadline {
+            self.timed_out = true;
+            return;
+        }
+        let prefix = match (is_root, is_last) {
+            (true, _) => "",
+            (false, true) => "└── ",
+            (false, false) => "├── ",
+        };
+        let name = if is_root {
+            path.display().to_string()
+        } else {
+            path.file_name().unwrap_or_default().to_string_lossy().into_owned()
+        };
+        let is_dir = path.is_dir() && !path.is_symlink();
+        self.out.push_str(&format!("{indent}{prefix}{name}{}\n", if is_dir { "/" } else { "" }));
+        if !is_dir {
+            return;
+        }
+        let mut children: Vec<_> = match std::fs::read_dir(path) {
+            Ok(entries) => entries.filter_map(|e| e.ok().map(|e| e.path())).collect(),
+            Err(e) => {
+                self.errors.push(format!("Failed to read {}: {e}", path.display()));
+                return;
+            }
+        };
+        let key = |p: &std::path::PathBuf| p.file_name().unwrap_or_default().to_string_lossy().into_owned();
+        children.sort_by_cached_key(|p| (key(p).to_lowercase(), key(p)));
+        let child_indent = format!("{indent}{}", if is_last { "    " } else { "│   " });
+        let n = children.len();
+        for (i, child) in children.iter().enumerate() {
+            self.render(child, &child_indent, i + 1 == n, max_depth - 1, false);
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn slice(text: &str, start: usize, max: usize) -> String {
+        render_slice(text, start, max).unwrap()
+    }
+
+    #[test]
+    fn numbers_lines_like_the_editor() {
+        assert_eq!(slice("a\nb", 1, 10), "L1: a\nL2: b");
+        assert_eq!(slice("a\r\nb\n", 1, 10), "L1: a\nL2: b\nL3: ");
+        assert_eq!(slice("", 1, 10), "L1: ");
+        assert_eq!(slice("a\nb\nc", 2, 10), "L2: b\nL3: c");
+        assert!(render_slice("", 2, 10).unwrap_err().message.contains("offset exceeds file length"));
+        assert!(render_slice("a\nb", 3, 10).unwrap_err().message.contains("offset exceeds file length"));
+    }
+
+    #[test]
+    fn keeps_head_and_tail_of_long_slices() {
+        let text = (1..=11).map(|n| format!("line {n}")).collect::<Vec<_>>().join("\n");
+        assert_eq!(slice(&text, 1, 4), "L1: line 1\nL2: line 2\n…7 lines truncated…\nL10: line 10\nL11: line 11");
+        assert_eq!(slice(&text, 3, 4), "L3: line 3\nL4: line 4\n…5 lines truncated…\nL10: line 10\nL11: line 11");
+        assert_eq!(slice(&text, 1, 1), "…10 lines truncated…\nL11: line 11");
+    }
+
+    #[test]
+    fn cuts_long_lines_at_utf16_units() {
+        let long = "x".repeat(2100);
+        assert_eq!(format_line(&long).len(), MAX_LINE_LENGTH);
+        // A pair across the boundary keeps 2000 characters.
+        let pair = format!("{}😀{}", "x".repeat(1999), "y".repeat(10));
+        assert_eq!(format_line(&pair).chars().count(), MAX_LINE_LENGTH);
+        assert!(format_line(&pair).ends_with('😀'));
+        let short = format!("{}😀", "x".repeat(1998));
+        assert_eq!(format_line(&short), short);
+    }
+}

crates/ide-host/src/mcp/mod.rs

@@ -0,0 +1,142 @@
+//! Built-in IDE tools. Transport and discovery live in `ide-mcp`.
+mod edit;
+mod editors;
+mod requests;
+mod run;
+mod vcs;
+pub use requests::Requests;
+mod files;
+mod reports;
+mod search;
+mod symbols;
+mod tool;
+mod util;
+
+use crate::Host;
+use ide_core::{CancellationToken, IdeError};
+use ide_mcp::{ToolCallError, ToolRegistry};
+pub use reports::{FileProblems, FocusedEditor, Reports};
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+
+pub struct Registry(Arc<Host>);
+impl Registry {
+    pub fn new(host: Arc<Host>) -> Self {
+        Self(host)
+    }
+}
+
+fn tools() -> Vec<tool::Tool> {
+    let mut tools = files::tools();
+    tools.extend(search::tools());
+    tools.extend(editors::tools());
+    tools.push(symbols::get_symbol_info());
+    tools.push(symbols::find_references());
+    tools.extend(edit::tools());
+    tools.extend(run::tools());
+    tools.extend(vcs::tools());
+    tools
+}
+
+// Checked both when listing and calling, so a later trust change takes effect immediately.
+fn allowed(tool: &ide_mcp::Tool, trusted: bool) -> bool {
+    trusted || tool.read_only
+}
+
+impl Registry {
+    fn target(&self, root: &Path) -> Result<(String, Arc<crate::Project>), String> {
+        if self.0.mcp_reports.remote_roots().iter().any(|p| p == root) {
+            return Err("not supported for remote projects yet".into());
+        }
+        let mut windows: Vec<_> = self
+            .0
+            .projects
+            .read()
+            .iter()
+            .filter(|(_, p)| p.root == root && !p.light)
+            .map(|(w, p)| (w.clone(), p.clone()))
+            .collect();
+        let focused = self.0.mcp_reports.focused_window();
+        windows.sort_by(|a, b| {
+            (Some(&b.0) == focused.as_ref()).cmp(&(Some(&a.0) == focused.as_ref())).then(a.0.cmp(&b.0))
+        });
+        windows.into_iter().next().ok_or_else(|| "project is no longer open".into())
+    }
+}
+impl ToolRegistry for Registry {
+    fn projects(&self) -> Vec<PathBuf> {
+        self.0
+            .projects()
+            .into_iter()
+            .filter(|p| !p.light)
+            .map(|p| p.root.clone())
+            .chain(self.0.mcp_reports.remote_roots())
+            .collect()
+    }
+    fn tools(&self, root: &Path) -> Result<Vec<ide_mcp::Tool>, String> {
+        let (_, project) = self.target(root)?;
+        Ok(tools().into_iter().map(|t| t.metadata).filter(|t| allowed(t, project.is_trusted())).collect())
+    }
+    fn call(
+        &self,
+        root: &Path,
+        name: &str,
+        arguments: &str,
+        cancel: CancellationToken,
+    ) -> Result<String, ToolCallError> {
+        self.call_with_client(root, name, arguments, cancel, "MCP client")
+    }
+    fn call_with_client(
+        &self,
+        root: &Path,
+        name: &str,
+        arguments: &str,
+        cancel: CancellationToken,
+        client: &str,
+    ) -> Result<String, ToolCallError> {
+        let (window, project) = self.target(root).map_err(ToolCallError::Failed)?;
+        let tool = tools()
+            .into_iter()
+            .find(|t| t.metadata.name == name && allowed(&t.metadata, project.is_trusted()))
+            .ok_or_else(|| ToolCallError::UnknownTool(format!("unknown tool: {name}")))?;
+        let args = serde_json::from_str(arguments).map_err(|e| ToolCallError::Failed(e.to_string()))?;
+        let call = tool::Call {
+            host: self.0.clone(),
+            project,
+            window,
+            args,
+            cancel: cancel.clone(),
+            client: client.to_owned(),
+            tool: name.to_owned(),
+        };
+        if cancel.is_cancelled() {
+            return Err(ToolCallError::Failed(IdeError::cancelled().message));
+        }
+        let result = self.0.runtime.block_on((tool.handler)(call));
+        if cancel.is_cancelled() {
+            return Err(ToolCallError::Failed(IdeError::cancelled().message));
+        }
+        result.map(|out| out.0).map_err(|e| ToolCallError::Failed(e.message))
+    }
+}
+
+impl Host {
+    fn mcp_windows(&self, root: &Path) -> Vec<String> {
+        let mut windows: Vec<_> =
+            self.projects.read().iter().filter(|(_, p)| p.root == root).map(|(w, _)| w.clone()).collect();
+        windows.sort();
+        windows
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn restricted_mode_excludes_execution_tools() {
+        let mut tool = super::tools().remove(0).metadata;
+        assert!(super::allowed(&tool, false));
+        tool.read_only = false;
+        assert!(!super::allowed(&tool, false));
+        assert!(super::allowed(&tool, true));
+    }
+}

crates/ide-host/src/mcp/reports.rs

@@ -0,0 +1,124 @@
+//! Window-owned snapshots. A project close drops every report from that window.
+use ide_core::{Diagnostic, IpcPath, Range};
+use parking_lot::RwLock;
+use serde::{Deserialize, Serialize};
+use specta::Type;
+use std::collections::{BTreeMap, HashMap};
+use std::path::PathBuf;
+
+#[derive(Clone, Debug, Serialize, Deserialize, Type)]
+#[serde(rename_all = "camelCase")]
+pub struct FileProblems {
+    pub path: IpcPath,
+    pub items: Vec<Diagnostic>,
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize, Type)]
+#[serde(rename_all = "camelCase")]
+pub struct FocusedEditor {
+    pub path: IpcPath,
+    /// Zero-based lines and UTF-16 columns, end exclusive.
+    pub selection: Range,
+    pub selected_text: String,
+}
+
+#[derive(Default)]
+pub struct Reports(RwLock<State>);
+#[derive(Default)]
+struct State {
+    windows: HashMap<String, Window>,
+    focused: Option<String>,
+    remote: HashMap<String, PathBuf>,
+    libraries: HashMap<String, Vec<PathBuf>>,
+}
+#[derive(Default)]
+struct Window {
+    editors: Vec<PathBuf>,
+    focused: Option<FocusedEditor>,
+    problems: BTreeMap<PathBuf, Vec<Diagnostic>>,
+}
+impl Reports {
+    pub fn set_open_editors(&self, window: &str, paths: Vec<PathBuf>) {
+        self.0.write().windows.entry(window.into()).or_default().editors = paths;
+    }
+    pub fn set_focused_editor(&self, window: &str, editor: Option<FocusedEditor>, focused: bool) {
+        let mut state = self.0.write();
+        state.windows.entry(window.into()).or_default().focused = editor;
+        if focused {
+            state.focused = Some(window.into());
+        }
+    }
+    pub fn report_problems(&self, window: &str, reset: bool, files: Vec<FileProblems>) {
+        let mut state = self.0.write();
+        let problems = &mut state.windows.entry(window.into()).or_default().problems;
+        if reset {
+            problems.clear();
+        }
+        for file in files {
+            let path = file.path.into();
+            if file.items.is_empty() {
+                problems.remove(&path);
+            } else {
+                problems.insert(path, file.items);
+            }
+        }
+    }
+    pub fn forget_window(&self, window: &str) {
+        let mut state = self.0.write();
+        state.windows.remove(window);
+        state.remote.remove(window);
+        state.libraries.remove(window);
+        if state.focused.as_deref() == Some(window) {
+            state.focused = None;
+        }
+    }
+    pub fn set_remote(&self, window: &str, root: PathBuf) {
+        self.0.write().remote.insert(window.into(), root);
+    }
+    pub fn remove_remote(&self, window: &str) {
+        self.0.write().remote.remove(window);
+    }
+    pub(crate) fn set_libraries(&self, window: &str, roots: Vec<PathBuf>) {
+        self.0.write().libraries.insert(window.into(), roots);
+    }
+    pub(super) fn libraries(&self, windows: &[String]) -> Vec<PathBuf> {
+        let state = self.0.read();
+        windows.iter().filter_map(|w| state.libraries.get(w)).flatten().cloned().collect()
+    }
+    pub(super) fn remote_roots(&self) -> Vec<PathBuf> {
+        self.0.read().remote.values().cloned().collect()
+    }
+    pub(super) fn focused_window(&self) -> Option<String> {
+        self.0.read().focused.clone()
+    }
+    pub(super) fn editors(&self, windows: &[String]) -> Vec<PathBuf> {
+        let state = self.0.read();
+        let mut paths = Vec::new();
+        for window in windows.iter().filter_map(|w| state.windows.get(w)) {
+            for path in &window.editors {
+                if !paths.contains(path) {
+                    paths.push(path.clone());
+                }
+            }
+        }
+        paths
+    }
+    pub(super) fn focused(&self, window: &str) -> Option<FocusedEditor> {
+        self.0.read().windows.get(window).and_then(|w| w.focused.clone())
+    }
+    pub(super) fn problems(&self, windows: &[String]) -> Vec<FileProblems> {
+        let state = self.0.read();
+        let mut files: BTreeMap<PathBuf, Vec<Diagnostic>> = BTreeMap::new();
+        for window in windows.iter().filter_map(|w| state.windows.get(w)) {
+            for (path, items) in &window.problems {
+                let found = files.entry(path.clone()).or_default();
+                for item in items {
+                    if !found.contains(item) {
+                        found.push(item.clone());
+                    }
+                }
+            }
+        }
+        files.into_iter().map(|(path, items)| FileProblems { path: path.into(), items }).collect()
+    }
+}

crates/ide-host/src/mcp/requests.rs

@@ -0,0 +1,71 @@
+//! Window-bound requests; missing windows, cancellation and timeout all fail closed.
+use super::tool::Call;
+use ide_core::{IdeError, IdeEvent, IdeResult, event::McpUiRequest};
+use parking_lot::Mutex;
+use std::collections::{HashMap, HashSet};
+use tokio::sync::oneshot;
+
+#[derive(Default)]
+pub struct Requests(Mutex<State>);
+#[derive(Default)]
+struct State {
+    ready: HashSet<String>,
+    pending: HashMap<u32, Pending>,
+}
+struct Pending {
+    window: String,
+    answer: oneshot::Sender<Result<bool, String>>,
+}
+impl Requests {
+    pub fn set_ready(&self, window: &str, ready: bool) {
+        if ready {
+            self.0.lock().ready.insert(window.into());
+        } else {
+            self.forget_window(window);
+        }
+    }
+    pub fn forget_window(&self, window: &str) {
+        let mut state = self.0.lock();
+        state.ready.remove(window);
+        state.pending.retain(|_, p| p.window != window);
+    }
+    pub fn answer(&self, window: &str, id: u32, allow: bool, error: Option<String>) -> IdeResult<()> {
+        let mut state = self.0.lock();
+        if !state.pending.get(&id).is_some_and(|p| p.window == window) {
+            return Err(IdeError::invalid("MCP request expired or belongs to another window"));
+        }
+        let pending = state.pending.remove(&id).unwrap();
+        let _ = pending.answer.send(error.map_or(Ok(allow), Err));
+        Ok(())
+    }
+    pub(super) async fn ask(&self, call: &Call, request: McpUiRequest) -> IdeResult<()> {
+        let id = super::tool::request_id().0;
+        let (tx, rx) = oneshot::channel();
+        {
+            let mut state = self.0.lock();
+            if !state.ready.contains(call.window()) {
+                return Err(IdeError::unavailable("MCP request denied: no project window is available"));
+            }
+            state.pending.insert(id, Pending { window: call.window.clone(), answer: tx });
+        }
+        struct Close<'a>(&'a Requests, &'a Call, u32);
+        impl Drop for Close<'_> {
+            fn drop(&mut self) {
+                self.0.0.lock().pending.remove(&self.2);
+                self.1.project.sink.emit(IdeEvent::McpRequestClosed { id: self.2 });
+            }
+        }
+        let _close = Close(self, call, id);
+        call.project.sink.emit(IdeEvent::McpRequest { id, request });
+        let result = tokio::select! {
+            result = rx => result.map_err(|_| IdeError::unavailable("MCP request denied: project window closed"))?,
+            _ = tokio::time::sleep(std::time::Duration::from_secs(180)) => return Err(IdeError::unavailable("MCP request denied: confirmation timed out")),
+            _ = call.cancel.cancelled() => return Err(IdeError::cancelled()),
+        };
+        match result {
+            Ok(true) => Ok(()),
+            Ok(false) => Err(IdeError::invalid("MCP request denied by the user")),
+            Err(message) => Err(IdeError::unavailable(message)),
+        }
+    }
+}

crates/ide-host/src/mcp/run/build.rs

@@ -0,0 +1,214 @@
+// Ported from JetBrains intellij-community plugins/mcp-server
+// (mcpserver.toolsets/src/general/AnalysisToolset.kt, build_project), Apache-2.0.
+//! `build_project`.
+
+use super::output::{MAX_TEXT_LENGTH, TRUNCATED_MARKER, truncate_tail};
+use crate::mcp::run::timeout;
+use crate::mcp::tool::{Call, Output, Param, ParamType, Tool};
+use ide_build::compile::{BuildEvent, BuildKind, BuildMessage, BuildResult};
+use ide_core::Severity;
+use ide_core::{IdeError, IdeResult};
+use parking_lot::Mutex;
+use serde_json::{Map, Value, json};
+use std::path::PathBuf;
+use std::sync::Arc;
+use std::time::Instant;
+
+const DEFAULT_TIMEOUT_MS: usize = 60_000;
+const MAX_TIMEOUT_MS: usize = 3_600_000;
+const MAX_PROBLEMS: usize = 300;
+/// Console lines attached to a failure whose messages were not parsed.
+const CONSOLE_LINES: usize = 200;
+
+/// A JetBrains `ProjectProblem`: `kind` ERROR or WARNING, the compiler's code as `group`,
+/// 1-based `line` / `column` (JetBrains reports them 0-based).
+fn problem(call: &Call, m: &BuildMessage) -> Value {
+    let mut v = json!({
+        "message": m.text,
+        "kind": if m.severity == Severity::Error { "ERROR" } else { "WARNING" },
+    });
+    if let Some(code) = &m.code {
+        v["group"] = code.clone().into();
+    }
+    if let Some(path) = &m.path {
+        v["file"] = call.display(path).into();
+    }
+    if let Some(range) = m.range {
+        v["line"] = (range.start.line + 1).into();
+        v["column"] = (range.start.col + 1).into();
+    }
+    v
+}
+
+/// Runs the build of `target` (the whole project when `None`), its console into `console`.
+/// Returns `None` when `deadline` passed first (the build is then stopped).
+pub async fn build_once(
+    call: &Call,
+    kind: BuildKind,
+    target: Option<PathBuf>,
+    deadline: Instant,
+    console: &Arc<Mutex<String>>,
+) -> IdeResult<Option<BuildResult>> {
+    let host = call.host();
+    let request = crate::mcp::tool::request_id();
+    let sink = console.clone();
+    let channel = crate::ops::Channel::new(move |e: BuildEvent| match e {
+        BuildEvent::Output { text, .. } => sink.lock().push_str(&text),
+        BuildEvent::Step { command, .. } => sink.lock().push_str(&format!("$ {command}\n")),
+        _ => {}
+    });
+    let build = crate::ops::build::build_run(&host, call.window(), kind, target, None, request, Vec::new(), channel);
+    tokio::pin!(build);
+    let remaining = deadline.saturating_duration_since(Instant::now());
+    tokio::select! {
+        r = &mut build => r.map(Some),
+        _ = tokio::time::sleep(remaining) => {
+            host.cancel_request(request);
+            let _ = build.await;
+            Ok(None)
+        }
+        _ = call.cancel.cancelled() => {
+            host.cancel_request(request);
+            let _ = build.await;
+            Err(IdeError::cancelled())
+        }
+    }
+}
+
+pub fn build_project() -> Tool {
+    Tool::new(
+        "build_project",
+        "Triggers building of the project or specified files, waits for completion, and returns build errors.
+Use this tool to build the project or compile files and get detailed information about compilation errors and warnings.
+You have to use this tool after performing edits to validate if the edits are valid.
+In OpenIDEA the project's build system builds it (Maven, Gradle, Cargo, Go or TypeScript); with `filesToRebuild`, the \
+modules containing those files. Asks the user first for every call. Problems have the project-relative \
+`file` and 1-based `line` / `column`; at most 300 problems are listed, and `isSuccess` is false whenever one of them \
+is an ERROR. On timeout (at most 1 hour; 0 times out at once) the build is stopped.",
+        |call| async move {
+            let files: Vec<String> =
+                call.str_list("filesToRebuild")?.into_iter().filter(|f| !f.trim().is_empty()).collect();
+            let rebuild = call.flag("rebuild", false)? && files.is_empty();
+            let kind = if rebuild { BuildKind::Rebuild } else { BuildKind::Build };
+            let limit = timeout(&call, DEFAULT_TIMEOUT_MS, MAX_TIMEOUT_MS)?;
+            let mut targets: Vec<Option<PathBuf>> = Vec::new();
+            let mut dirs: Vec<PathBuf> = Vec::new();
+            for f in &files {
+                let path = call.resolve_inside(f)?;
+                if !path.exists() {
+                    return Err(IdeError::not_found(format!("File not found: {f}")));
+                }
+                let dir = if path.is_dir() { path.clone() } else { path.parent().unwrap_or(&path).to_path_buf() };
+                if !dirs.contains(&dir) {
+                    dirs.push(dir);
+                    targets.push(Some(path));
+                }
+            }
+            if targets.is_empty() {
+                targets.push(None);
+            }
+            let subject = if rebuild { "Rebuild project" } else { "Build project" };
+            let detail = targets.iter().flatten().map(|p| call.display(p)).collect::<Vec<_>>().join(", ");
+            call.confirm(subject, (!detail.is_empty()).then(|| format!("modules of {detail}"))).await?;
+
+            if limit.is_zero() {
+                // JetBrains' `withTimeoutOrNull(0)`: nothing is built.
+                return Output::json(json!({ "isSuccess": false, "problems": [], "timedOut": true }));
+            }
+            let console = Arc::new(Mutex::new(String::new()));
+            let deadline = Instant::now() + limit;
+            let mut results: Vec<BuildResult> = Vec::new();
+            let mut timed_out = false;
+            for target in targets {
+                match build_once(&call, kind, target, deadline, &console).await? {
+                    Some(r) => {
+                        let failed = !r.success;
+                        results.push(r);
+                        if failed {
+                            break;
+                        }
+                    }
+                    None => {
+                        timed_out = true;
+                        break;
+                    }
+                }
+            }
+            let messages: Vec<&BuildMessage> = results
+                .iter()
+                .flat_map(|r| r.messages.iter())
+                .filter(|m| matches!(m.severity, Severity::Error | Severity::Warning))
+                .collect();
+            let mut problems: Vec<Value> = messages.iter().take(MAX_PROBLEMS).map(|m| problem(&call, m)).collect();
+            let has_errors = messages.iter().any(|m| m.severity == Severity::Error);
+            let failed = results.iter().any(|r| !r.success);
+            if failed && !has_errors {
+                let tail = truncate_tail(
+                    console.lock().trim_end(),
+                    CONSOLE_LINES,
+                    MAX_TEXT_LENGTH,
+                    TRUNCATED_MARKER,
+                );
+                problems.push(json!({
+                    "message": "Build reported errors, but detailed error messages were not captured through build events.",
+                    "kind": "ERROR",
+                    "description": tail,
+                }));
+            }
+            let mut result = Map::new();
+            result.insert("isSuccess".into(), is_success(timed_out, &results).into());
+            result.insert("problems".into(), problems.into());
+            if timed_out {
+                result.insert("timedOut".into(), true.into());
+            }
+            Output::json(Value::Object(result))
+        },
+    )
+    .write()
+    .param(Param::optional(
+        "rebuild",
+        ParamType::Boolean,
+        "Whether to perform full rebuild the project. Defaults to false. Effective only when `filesToRebuild` is not \
+specified.",
+    ))
+    .param(Param::optional(
+        "filesToRebuild",
+        ParamType::StringList,
+        "If specified, only compile files with the specified paths. Paths are relative to the project root.",
+    ))
+    .param(Param::optional("timeout", ParamType::Integer, "Timeout in milliseconds"))
+}
+
+/// JetBrains' `isSuccess`: finished in time, every build succeeded and no ERROR was reported
+/// (a build tool may exit 0 after printing errors).
+fn is_success(timed_out: bool, results: &[BuildResult]) -> bool {
+    !timed_out && results.iter().all(|r| r.success && r.messages.iter().all(|m| m.severity != Severity::Error))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn result(success: bool, severities: &[Severity]) -> BuildResult {
+        BuildResult {
+            system: ide_build::compile::BuildSystem::Cargo,
+            title: "build".into(),
+            success,
+            errors: 0,
+            warnings: 0,
+            duration_ms: 0.0,
+            messages: severities
+                .iter()
+                .map(|s| BuildMessage { severity: *s, text: "m".into(), path: None, range: None, code: None })
+                .collect(),
+        }
+    }
+
+    #[test]
+    fn an_error_problem_fails_the_build() {
+        assert!(is_success(false, &[result(true, &[Severity::Warning])]));
+        assert!(!is_success(false, &[result(true, &[Severity::Warning, Severity::Error])]));
+        assert!(!is_success(false, &[result(false, &[])]));
+        assert!(!is_success(true, &[result(true, &[])]));
+    }
+}

crates/ide-host/src/mcp/run/configs.rs

@@ -0,0 +1,709 @@
+// Ported from JetBrains intellij-community plugins/mcp-server (mcpserver.toolsets/src/general/ExecutionToolset.kt,
+// mcpserver.toolsets/src/util/execution.util.kt, mcpserver.toolsets/src/util/RunConfigurationBuildErrors.kt), Apache-2.0.
+//! `get_run_configurations` and `execute_run_configuration`.
+
+use super::build::build_once;
+use super::output::OutputCollector;
+use super::process::{quote, split_words};
+use super::targets;
+use crate::Project;
+use crate::mcp::run::timeout;
+use crate::mcp::tool::{Call, Output, Param, ParamType, Tool};
+use ide_build::compile::BuildKind;
+use ide_core::{IdeError, IdeResult, RunId, Severity};
+use ide_run::{OutputChunk, RunConfig};
+use parking_lot::Mutex;
+use serde_json::{Map, Value, json};
+use std::path::Path;
+use std::sync::Arc;
+use std::time::{Duration, Instant};
+
+const DEFAULT_TIMEOUT_MS: usize = 10_000;
+/// No limit in JetBrains; the process keeps running after the timeout anyway.
+const MAX_TIMEOUT_MS: usize = 1_800_000;
+/// Output of a failed before-launch process kept for the error message.
+const MAX_PROCESS_OUTPUT_LENGTH: usize = 20_000;
+/// A before-launch build gets this long.
+const BEFORE_LAUNCH_BUILD_TIMEOUT: Duration = Duration::from_secs(3600);
+
+async fn load_configs(call: &Call) -> IdeResult<Vec<RunConfig>> {
+    let host = call.host();
+    let window = call.window().to_owned();
+    let h = host.clone();
+    host.blocking(move || crate::ops::run::configs(&h, &window)).await
+}
+
+fn supports_overrides(config: &RunConfig) -> bool {
+    config.extras.compound.is_empty() && !config.command.trim().is_empty()
+}
+
+fn command_line(config: &RunConfig) -> String {
+    std::iter::once(config.command.clone()).chain(config.args.iter().map(|a| quote(a))).collect::<Vec<_>>().join(" ")
+}
+
+fn describe_config(call: &Call, c: &RunConfig) -> Value {
+    let mut v = json!({
+        "name": c.name,
+        "description": c.kind,
+        "supportsDynamicLaunchOverrides": supports_overrides(c),
+    });
+    if supports_overrides(c) {
+        v["commandLine"] = command_line(c).into();
+        if let Some(cwd) = c.cwd.as_deref() {
+            v["workingDirectory"] = call.display(&call.root().join(cwd)).into();
+        }
+        if !c.env.is_empty() {
+            v["environment"] = json!(c.env);
+        }
+    }
+    v
+}
+
+/// A file of the project to look for run points in: its `/`-separated project-relative path
+/// and current text (unsaved edits included).
+fn read_file(project: &Project, path: &Path, file: &str) -> IdeResult<(String, String)> {
+    let meta = std::fs::metadata(path).map_err(|_| IdeError::not_found(format!("File not found: {file}")))?;
+    if !meta.is_file() {
+        return Err(IdeError::invalid(format!("Not a file: {file}")));
+    }
+    let rel = path.strip_prefix(&project.root).unwrap_or(path).to_string_lossy().replace('\\', "/");
+    let text = match project.documents.text_of(path) {
+        Some(text) => text,
+        None => std::fs::read_to_string(path).map_err(|e| IdeError::invalid(format!("Cannot read {file}: {e}")))?,
+    };
+    Ok((rel, text))
+}
+
+/// Reads `file` and runs `scan` (root, relative path, text) over it off the async threads:
+/// the run point patterns go over up to 400 KB of text.
+async fn scan_file<T: Send + 'static>(
+    call: &Call,
+    file: &str,
+    scan: impl FnOnce(&Path, &str, &str) -> IdeResult<T> + Send + 'static,
+) -> IdeResult<T> {
+    let path = call.resolve_inside(file)?;
+    let project = call.project().clone();
+    let file = file.to_owned();
+    call.host()
+        .blocking(move || {
+            let (rel, text) = read_file(&project, &path, &file)?;
+            scan(&project.root, &rel, &text)
+        })
+        .await
+}
+
+pub fn get_run_configurations() -> Tool {
+    Tool::new(
+        "get_run_configurations",
+        "Returns either project run configurations or executable code locations, depending on the input.
+
+Without `filePath`, this tool lists the project's existing run configurations. The result includes configuration
+names and, when available, launch details such as program arguments, working directory, environment variables,
+and `supportsDynamicLaunchOverrides`.
+
+`supportsDynamicLaunchOverrides` is the source-of-truth capability flag for one-time launch overrides
+(`programArguments`, `workingDirectory`, `envs`) in `execute_run_configuration` and `xdebug_start_debugger_session`.
+Only pass those override parameters when this flag is `true` for the selected configuration.
+
+With `filePath`, this tool discovers executable entry points (run points) in that file, such as test methods,
+main methods, or other executable entry points where the IDE shows a Run gutter icon. The result contains `filePath` and
+`runPoints`; use the returned line numbers with `execute_run_configuration` to run from code.
+In OpenIDEA the configurations are the saved ones and those detected from the build files (package.json scripts, \
+Cargo targets, Gradle/Maven tasks, Go, Python, Makefile…); `description` is the configuration type and `commandLine` \
+the whole command. Run points are found in Rust, JavaScript/TypeScript, Python and Go files.",
+        |call| async move {
+            let configs = load_configs(&call).await?;
+            if let Some(file) = call.opt_str("filePath")? {
+                let points = scan_file(&call, &file, move |root, rel, text| {
+                    let mut points: Vec<Value> = Vec::new();
+                    let mut lines = std::collections::HashSet::new();
+                    for t in targets::detect(text, rel) {
+                        if lines.contains(&t.line) {
+                            continue;
+                        }
+                        if let Some(config) = targets::target_config(root, &t, rel, &configs, text) {
+                            lines.insert(t.line);
+                            points.push(json!({
+                                "line": t.line + 1,
+                                "description": format!("Run '{}'", config.name),
+                                "elementText": t.name,
+                            }));
+                        }
+                    }
+                    Ok(points)
+                })
+                .await?;
+                return Output::json(json!({ "filePath": file, "runPoints": points }));
+            }
+            let list: Vec<Value> = configs.iter().map(|c| describe_config(&call, c)).collect();
+            Output::json(json!({ "configurations": list }))
+        },
+    )
+    .write()
+    .param(Param::optional(
+        "filePath",
+        ParamType::String,
+        "Optional file path relative to the project root. When provided, returns run points (executable entry points) \
+in the file instead of project-wide run configurations.",
+    ))
+}
+
+/// What `execute_run_configuration` runs.
+enum ExecutionTarget {
+    ByName(String),
+    ByContext(String, i64),
+}
+
+fn execution_target(name: Option<String>, file: Option<String>, line: Option<i64>) -> IdeResult<ExecutionTarget> {
+    let name = name.filter(|n| !n.trim().is_empty());
+    let file = file.filter(|f| !f.trim().is_empty());
+    match (name, file, line) {
+        (Some(_), f, l) if f.is_some() || l.is_some() => {
+            Err(IdeError::invalid("Pass either configurationName or filePath + line, but not both."))
+        }
+        (Some(name), _, _) => Ok(ExecutionTarget::ByName(name)),
+        (None, Some(file), Some(line)) => Ok(ExecutionTarget::ByContext(file, line)),
+        (None, Some(_), None) | (None, None, Some(_)) => {
+            Err(IdeError::invalid("Pass both filePath and line together, or use configurationName."))
+        }
+        (None, None, None) => Err(IdeError::invalid("Pass either configurationName or filePath + line.")),
+    }
+}
+
+/// The temporary configuration of the run point at `file:line` (1-based): the innermost target
+/// enclosing that line (as JetBrains walks up to the enclosing test), else the whole file's
+/// (its tests, its main function).
+async fn config_from_code_location(
+    call: &Call,
+    configs: Vec<RunConfig>,
+    file: &str,
+    line: i64,
+) -> IdeResult<RunConfig> {
+    let file_name = file.to_owned();
+    scan_file(call, file, move |root, rel, text| {
+        if line < 1 {
+            return Err(IdeError::invalid(format!("Line number must be >= 1, got: {line}")));
+        }
+        let count = text.split('\n').count();
+        if line as usize > count {
+            return Err(IdeError::invalid(format!("Line {line} is out of range (file has {count} lines)")));
+        }
+        targets::enclosing(text, rel, line as usize - 1)
+            .iter()
+            .find_map(|t| targets::target_config(root, t, rel, &configs, text))
+            .or_else(|| targets::context_config(root, rel, &configs, text))
+            .ok_or_else(|| {
+                IdeError::not_found(format!(
+                    "No run configuration could be created from {file_name}:{line}. Use get_run_configurations with \
+filePath to find valid run locations."
+                ))
+            })
+    })
+    .await
+}
+
+/// Applies the one-off overrides (JetBrains' `prepareRunConfigurationForExecution`): a missing or
+/// empty string keeps the value, a whitespace-only one clears it; `envs` merge over the configuration's.
+fn apply_overrides(
+    config: &mut RunConfig,
+    root: &Path,
+    args: Option<String>,
+    cwd: Option<String>,
+    envs: Option<Vec<(String, String)>>,
+) -> IdeResult<()> {
+    let args = args.filter(|a| !a.is_empty());
+    let cwd = cwd.filter(|d| !d.is_empty());
+    if args.is_none() && cwd.is_none() && envs.is_none() {
+        return Ok(());
+    }
+    if !supports_overrides(config) {
+        return Err(IdeError::invalid(format!(
+            "Run configuration '{}' of type '{}' doesn't support dynamic launch overrides (programArguments, \
+workingDirectory, envs).",
+            config.name,
+            if config.extras.compound.is_empty() { config.kind.as_str() } else { "Compound" }
+        )));
+    }
+    if let Some(args) = args {
+        let words = split_words(&args)?;
+        // A configuration that is one shell line (`npm run dev`, no separate arguments)
+        // keeps its command and gets the new line's arguments appended.
+        let shell_line = config.args.is_empty() && config.command.trim().contains(char::is_whitespace);
+        if shell_line {
+            if !words.is_empty() {
+                config.command = format!("{} {}", config.command.trim(), args.trim());
+            }
+        } else {
+            config.args = words;
+        }
+    }
+    if let Some(dir) = cwd {
+        if dir.trim().is_empty() {
+            config.cwd = None;
+        } else {
+            let path = crate::mcp::tool::resolve_inside(root, &dir)?;
+            if !path.is_dir() {
+                return Err(IdeError::not_found(format!("workingDirectory {} is not a directory", path.display())));
+            }
+            config.cwd = Some(path.into());
+        }
+    }
+    config.env.extend(envs.into_iter().flatten());
+    Ok(())
+}
+
+/// Polls how run `id` ended: `None` while running, else its exit code (if known).
+fn run_exit(host: &crate::Host, id: RunId) -> Option<Option<i32>> {
+    match host.processes.exit_code(id) {
+        Ok(exit) => exit,
+        // Remote (SSH) runs, or a finished run already forgotten: the run list knows whether it runs.
+        Err(_) => match crate::ops::run::list(host).into_iter().find(|r| r.id == id) {
+            Some(r) if r.running => None,
+            _ => Some(None),
+        },
+    }
+}
+
+/// Waits for run `id` to exit, until `deadline`: `None` when it is still running. Cancelling
+/// the call stops the run.
+async fn wait_exit(call: &Call, id: RunId, deadline: Option<Instant>) -> IdeResult<Option<Option<i32>>> {
+    let host = call.host();
+    loop {
+        if let Some(exit) = run_exit(&host, id) {
+            return Ok(Some(exit));
+        }
+        if deadline.is_some_and(|d| Instant::now() >= d) {
+            return Ok(None);
+        }
+        tokio::select! {
+            _ = tokio::time::sleep(Duration::from_millis(50)) => {}
+            _ = call.cancel.cancelled() => {
+                let _ = crate::ops::run::stop(&host, call.window(), id);
+                return Err(IdeError::cancelled());
+            }
+        }
+    }
+}
+
+/// An output callback that skips the IDE's own lines (`Process finished…`), as JetBrains
+/// skips `ProcessOutputType.SYSTEM`.
+fn process_output(mut f: impl FnMut(&str) + Send + 'static) -> crate::ops::Emit<OutputChunk> {
+    let f = Mutex::new(move |t: &str| f(t));
+    Arc::new(move |chunk: OutputChunk| match &chunk {
+        OutputChunk::Stdout { text } | OutputChunk::Stderr { text } => (f.lock())(text),
+        OutputChunk::System { .. } => {}
+    })
+}
+
+/// What failed before launch (JetBrains' `RunConfigurationBuildErrors`): build errors as
+/// `path:line: message`, else the output of before-launch processes that failed.
+#[derive(Default)]
+struct BuildErrors {
+    errors: Vec<String>,
+    process_outputs: Vec<String>,
+}
+
+impl BuildErrors {
+    fn text(&self) -> Option<String> {
+        let mut seen = std::collections::HashSet::new();
+        let errors: Vec<&String> = self.errors.iter().filter(|e| seen.insert(*e)).collect();
+        if !errors.is_empty() {
+            return Some(errors.iter().map(|e| e.as_str()).collect::<Vec<_>>().join("\n"));
+        }
+        let outputs: Vec<&str> = self.process_outputs.iter().map(|o| o.trim()).filter(|o| !o.is_empty()).collect();
+        (!outputs.is_empty()).then(|| outputs.join("\n"))
+    }
+}
+
+/// Runs `config` to its end; `Ok(false)` (with its output recorded) when it failed.
+async fn run_to_end(call: &Call, config: RunConfig, errors: &mut BuildErrors) -> IdeResult<bool> {
+    let tail = Arc::new(Mutex::new(String::new()));
+    let sink = tail.clone();
+    let emit = process_output(move |text| {
+        let mut t = sink.lock();
+        t.push_str(text);
+        if t.len() > 2 * MAX_PROCESS_OUTPUT_LENGTH {
+            let mut cut = t.len() - MAX_PROCESS_OUTPUT_LENGTH;
+            while !t.is_char_boundary(cut) {
+                cut += 1;
+            }
+            t.drain(..cut);
+        }
+    });
+    let info = crate::ops::run::start(&call.host(), call.window(), config, emit).await?;
+    let exit = wait_exit(call, info.id, None).await?.flatten();
+    if exit == Some(0) {
+        return Ok(true);
+    }
+    let t = tail.lock();
+    let start = t.char_indices().rev().nth(MAX_PROCESS_OUTPUT_LENGTH - 1).map_or(0, |(i, _)| i);
+    errors.process_outputs.push(t[start..].to_owned());
+    Ok(false)
+}
+
+/// The configuration's before-launch tasks, as the Run tool window runs them; returns why
+/// the launch is aborted, if it is. Tool windows are not activated.
+async fn before_launch(
+    call: &Call,
+    config: &RunConfig,
+    configs: &[RunConfig],
+    chain: &mut Vec<String>,
+    errors: &mut BuildErrors,
+) -> IdeResult<Option<String>> {
+    chain.push(config.id.clone());
+    for task in &config.extras.before_launch {
+        let target = task.target.as_str();
+        let (label, failure) = match task.kind.as_str() {
+            "build" => {
+                let console = Arc::new(Mutex::new(String::new()));
+                let deadline = Instant::now() + BEFORE_LAUNCH_BUILD_TIMEOUT;
+                let failure = match build_once(call, BuildKind::Build, None, deadline, &console).await {
+                    Ok(Some(r)) => {
+                        for m in r.messages.iter().filter(|m| m.severity == Severity::Error) {
+                            errors.errors.push(match (&m.path, m.range) {
+                                (Some(p), Some(r)) => format!("{}:{}: {}", p.display(), r.start.line + 1, m.text),
+                                _ => m.text.clone(),
+                            });
+                        }
+                        (!r.success).then(|| "Build failed".to_owned())
+                    }
+                    Ok(None) => Some("The build timed out".to_owned()),
+                    Err(e) => Some(e.message),
+                };
+                ("Build Project".to_owned(), failure)
+            }
+            "run" => {
+                let other = configs.iter().find(|c| c.id == target);
+                let label = format!("Run '{}'", other.map_or(target, |c| c.name.as_str()));
+                let failure = if chain.iter().any(|c| c == target) {
+                    Some("The before launch tasks run in a cycle".to_owned())
+                } else if let Some(other) = other {
+                    let ok = Box::pin(before_launch(call, other, configs, chain, errors)).await?.is_none()
+                        && run_to_end(call, other.clone(), errors).await?;
+                    (!ok).then(|| format!("'{}' failed", other.name))
+                } else {
+                    Some(format!("Configuration '{target}' no longer exists"))
+                };
+                (label, failure)
+            }
+            "command" => {
+                let failure = if target.trim().is_empty() {
+                    Some("No command".to_owned())
+                } else {
+                    let run = RunConfig {
+                        id: format!("before-launch:{}:{target}", config.id),
+                        name: target.to_owned(),
+                        kind: "shell".into(),
+                        command: target.to_owned(),
+                        args: Vec::new(),
+                        cwd: config.cwd.clone(),
+                        env: Default::default(),
+                        detected: true,
+                        is_test: false,
+                        debug_adapter: None,
+                        allow_parallel: false,
+                        extras: Default::default(),
+                    };
+                    (!run_to_end(call, run, errors).await?).then(|| format!("'{target}' failed"))
+                };
+                (format!("Run '{target}'"), failure)
+            }
+            "toolWindow" => continue,
+            "tool" => (format!("External tool '{target}'"), Some("External tools cannot run through MCP".to_owned())),
+            other => (other.to_owned(), Some(format!("Unknown before launch task '{other}'"))),
+        };
+        if let Some(failure) = failure {
+            chain.pop();
+            return Ok(Some(format!("Before launch: {label}: {failure}")));
+        }
+    }
+    chain.pop();
+    Ok(None)
+}
+
+/// The before-launch tasks of `config` as the confirmation lists them, nested ones indented.
+fn describe_before_launch(
+    config: &RunConfig,
+    configs: &[RunConfig],
+    depth: usize,
+    chain: &mut Vec<String>,
+    out: &mut String,
+) {
+    chain.push(config.id.clone());
+    let indent = "  ".repeat(depth + 1);
+    for task in &config.extras.before_launch {
+        let target = task.target.as_str();
+        match task.kind.as_str() {
+            "build" => out.push_str(&format!("\n{indent}Build Project")),
+            "command" => out.push_str(&format!("\n{indent}Run command: {target}")),
+            "run" => match configs.iter().find(|c| c.id == target) {
+                Some(other) => {
+                    let line = if other.extras.compound.is_empty() { command_line(other) } else { "compound".into() };
+                    out.push_str(&format!("\n{indent}Run '{}': {line}", other.name));
+                    if !chain.contains(&other.id) {
+                        describe_before_launch(other, configs, depth + 1, chain, out);
+                    }
+                }
+                None => out.push_str(&format!("\n{indent}Run '{target}' (missing)")),
+            },
+            "toolWindow" => {}
+            "tool" => out.push_str(&format!("\n{indent}External tool '{target}'")),
+            other => out.push_str(&format!("\n{indent}{other} '{target}'")),
+        }
+    }
+    chain.pop();
+}
+
+/// What the user approves for `config` besides its command line: everything else that runs
+/// or applies — before-launch tasks, the stored environment (for a configuration made from
+/// code, the one of the configuration it derives from), `.env` files, the `envs` overrides
+/// (`NODE_OPTIONS`, `PATH`, ...), the stop command and a remote run target.
+fn confirmation_detail(
+    config: &RunConfig,
+    cwd: &str,
+    stored_env: &std::collections::BTreeMap<String, String>,
+    overrides: &[(String, String)],
+    configs: &[RunConfig],
+) -> String {
+    let mut detail = command_line(config);
+    if !cwd.is_empty() {
+        detail.push_str(&format!("\nin {cwd}"));
+    }
+    if let Some(target) = config.extras.target.as_deref().filter(|t| !t.is_empty()) {
+        detail.push_str(&format!("\non run target {target}"));
+    }
+    let mut tasks = String::new();
+    describe_before_launch(config, configs, 0, &mut Vec::new(), &mut tasks);
+    if !tasks.is_empty() {
+        detail.push_str(&format!("\nbefore launch:{tasks}"));
+    }
+    if !config.extras.env_files.is_empty() {
+        detail.push_str(&format!("\nenv files: {}", config.extras.env_files.join(", ")));
+    }
+    if !config.extras.include_system_env {
+        detail.push_str("\nwithout the system environment");
+    }
+    if !stored_env.is_empty() {
+        detail.push_str("\nenvironment:");
+        for (k, v) in stored_env {
+            detail.push_str(&format!("\n  {k}={v}"));
+        }
+    }
+    if !overrides.is_empty() {
+        detail.push_str("\nenvironment overrides:");
+        for (k, v) in overrides {
+            detail.push_str(&format!("\n  {k}={v}"));
+        }
+    }
+    if let Some(stop) = config.extras.stop_command.as_deref().filter(|s| !s.trim().is_empty()) {
+        detail.push_str(&format!("\non stop: {stop}"));
+    }
+    detail
+}
+
+fn execution_failed(details: &[Option<String>]) -> IdeError {
+    let details: Vec<&str> = details.iter().flatten().map(String::as_str).collect();
+    IdeError::invalid(format!("Execution failed: {}", details.join("\n")))
+}
+
+pub fn execute_run_configuration() -> Tool {
+    Tool::new(
+        "execute_run_configuration",
+        "Run either an existing run configuration by name or a temporary run configuration created from a code location \
+(`filePath` + `line`) in the current project, then wait up to specified timeout for it to finish.
+
+Use this tool with either a configuration name returned by `get_run_configurations`, or with a run point
+(`filePath` + `line`) returned by `get_run_configurations(filePath = ...)`.
+
+Optional launch overrides (`programArguments`, `workingDirectory`, `envs`) are applied only for this run and are not persisted.
+Do not pass these override parameters unless you explicitly need to change the configured launch values for this run.
+Missing/null override parameters keep existing run configuration values unchanged.
+For string overrides (`programArguments`, `workingDirectory`), missing/null or empty string (`\"\"`) keeps the existing value unchanged.
+Pass a whitespace-only string such as `\" \"` to clear an existing value for this launch.
+
+Pass either `configurationName`, or `filePath` together with `line`. These modes are mutually exclusive.
+
+Behavior:
+- When `waitForExit=true`, waits up to `timeout` milliseconds for process termination. If the timeout expires,
+  the process keeps running in the background and `exitCode` is omitted from the result.
+- When `waitForExit=false`, waits only for the process to start, then returns immediately without applying `timeout`.
+- `fullOutputPath` points to a temp file with the full raw output and may continue growing while the process is alive.
+
+Returns the execution result including current output snapshot, optional exit code, and optional `fullOutputPath`.
+In OpenIDEA the user is asked first for every call; `programArguments` replace the configuration's \
+arguments (appended to a command that is one shell line, such as `npm run dev`); the run does not appear in the Run \
+tool window; output files are private and deleted after a day.",
+        |call| async move {
+            let target = execution_target(
+                call.opt_str("configurationName")?,
+                call.opt_str("filePath")?,
+                call.opt_i64("line")?,
+            )?;
+            let wait = call.flag("waitForExit", true)?;
+            // As JetBrains: `timeout` is ignored without waiting, and 0 returns without waiting.
+            let limit = if wait { Some(timeout(&call, DEFAULT_TIMEOUT_MS, MAX_TIMEOUT_MS)?) } else { None };
+            let envs = call.args.get("envs").filter(|v| !v.is_null()).map(|_| call.str_map("envs")).transpose()?;
+            let configs = load_configs(&call).await?;
+            let mut config = match &target {
+                ExecutionTarget::ByName(name) => configs
+                    .iter()
+                    .find(|c| c.name == *name)
+                    .cloned()
+                    .ok_or_else(|| IdeError::not_found(format!("Run configuration with name '{name}' not found.")))?,
+                ExecutionTarget::ByContext(file, line) => {
+                    config_from_code_location(&call, configs.clone(), file, *line).await?
+                }
+            };
+            let stored_env = config.env.clone();
+            let overrides: Vec<(String, String)> = envs.clone().unwrap_or_default();
+            apply_overrides(
+                &mut config,
+                call.root(),
+                call.opt_str("programArguments")?,
+                call.opt_str("workingDirectory")?,
+                envs,
+            )?;
+            if !config.extras.compound.is_empty() {
+                return Err(IdeError::invalid(format!(
+                    "`{}` is a compound configuration, which cannot run through MCP; run its configurations ({}) \
+one by one",
+                    config.name,
+                    config.extras.compound.join(", ")
+                )));
+            }
+            let cwd = match config.cwd.as_deref() {
+                Some(p) => call.root().join(p),
+                None => call.root().to_path_buf(),
+            };
+            let detail = confirmation_detail(&config, &call.display(&cwd), &stored_env, &overrides, &configs);
+            call.confirm(&config.name, Some(detail)).await?;
+
+            let mut errors = BuildErrors::default();
+            if let Some(reason) = before_launch(&call, &config, &configs, &mut Vec::new(), &mut errors).await? {
+                return Err(execution_failed(&[errors.text(), Some(reason)]));
+            }
+            let collector = Arc::new(Mutex::new(OutputCollector::create(&config.name)?));
+            let output_path = collector.lock().path.clone();
+            let sink = collector.clone();
+            let emit = process_output(move |text| sink.lock().append(text));
+            let info = match crate::ops::run::start(&call.host(), call.window(), config, emit).await {
+                Ok(info) => info,
+                Err(e) => {
+                    let _ = std::fs::remove_file(&output_path);
+                    return Err(execution_failed(&[errors.text(), Some(e.message)]));
+                }
+            };
+
+            let exit = match limit {
+                Some(limit) if !limit.is_zero() => wait_exit(&call, info.id, Some(Instant::now() + limit)).await?,
+                _ => None,
+            };
+            let c = collector.lock();
+            let mut result = Map::new();
+            if let Some(Some(code)) = exit {
+                result.insert("exitCode".into(), code.into());
+            }
+            result.insert("output".into(), c.preview().into());
+            // An exited run whose whole output is in `output` needs no file.
+            if exit.is_none() || c.truncated {
+                result.insert("fullOutputPath".into(), c.path.to_string_lossy().into_owned().into());
+            } else {
+                let _ = std::fs::remove_file(&c.path);
+            }
+            Output::json(Value::Object(result))
+        },
+    )
+    .write()
+    .param(Param::optional("configurationName", ParamType::String, "Name of the existing run configuration to execute"))
+    .param(Param::optional(
+        "filePath",
+        ParamType::String,
+        "File path relative to the project root. Provide together with `line` to create and execute a temporary run \
+configuration from code context.",
+    ))
+    .param(Param::optional(
+        "line",
+        ParamType::Integer,
+        "1-based line number for `filePath`. Provide together with `filePath` and do not combine with \
+`configurationName`.",
+    ))
+    .param(Param::optional("timeout", ParamType::Integer, "Timeout in milliseconds"))
+    .param(Param::optional(
+        "waitForExit",
+        ParamType::Boolean,
+        "Whether to wait for process termination. If false, the tool returns immediately after the process starts and \
+ignores `timeout`.",
+    ))
+    .param(Param::optional(
+        "programArguments",
+        ParamType::String,
+        "Optional program arguments override for this launch only. Missing/null or empty string keeps the existing \
+value; whitespace-only string clears it.",
+    ))
+    .param(Param::optional(
+        "workingDirectory",
+        ParamType::String,
+        "Optional working directory override for this launch only. Missing/null or empty string keeps the existing \
+value; whitespace-only string clears it.",
+    ))
+    .param(Param::optional(
+        "envs",
+        ParamType::StringMap,
+        "Optional environment variable overrides for this launch only. Missing/null keeps existing env unchanged; when \
+provided, values are merged over existing env.",
+    ))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn config() -> RunConfig {
+        RunConfig {
+            id: "user:x".into(),
+            name: "x".into(),
+            kind: "shell".into(),
+            command: "prog".into(),
+            args: vec!["a".into()],
+            cwd: Some(std::path::PathBuf::from("sub").into()),
+            env: [("A".to_owned(), "1".to_owned())].into(),
+            detected: false,
+            is_test: false,
+            debug_adapter: None,
+            allow_parallel: false,
+            extras: Default::default(),
+        }
+    }
+
+    #[test]
+    fn empty_overrides_keep_and_blank_ones_clear() {
+        let root = Path::new("/");
+        let mut c = config();
+        apply_overrides(&mut c, root, Some(String::new()), Some(String::new()), None).unwrap();
+        assert_eq!(c, config());
+        apply_overrides(&mut c, root, Some(" ".into()), Some(" ".into()), Some(vec![("C".into(), "3".into())]))
+            .unwrap();
+        assert!(c.args.is_empty());
+        assert!(c.cwd.is_none());
+        assert_eq!(c.env.keys().collect::<Vec<_>>(), ["A", "C"]);
+        apply_overrides(&mut c, root, Some("x 'y z'".into()), None, None).unwrap();
+        assert_eq!(c.args, ["x", "y z"]);
+    }
+
+    #[test]
+    fn execution_targets_are_exclusive() {
+        let err = |n: Option<&str>, f: Option<&str>, l| {
+            execution_target(n.map(Into::into), f.map(Into::into), l).err().map(|e| e.message)
+        };
+        assert_eq!(
+            err(Some("a"), Some("f"), Some(1)).as_deref(),
+            Some("Pass either configurationName or filePath + line, but not both.")
+        );
+        assert_eq!(
+            err(None, Some("f"), None).as_deref(),
+            Some("Pass both filePath and line together, or use configurationName.")
+        );
+        assert_eq!(err(None, None, None).as_deref(), Some("Pass either configurationName or filePath + line."));
+        assert!(err(Some("a"), None, None).is_none());
+    }
+}

crates/ide-host/src/mcp/run/mod.rs

@@ -0,0 +1,25 @@
+//! Run configurations and builds; every call asks the user first.
+
+mod build;
+mod configs;
+mod output;
+mod process;
+mod targets;
+
+use crate::mcp::tool::{Call, Tool};
+use ide_core::IdeResult;
+use std::time::Duration;
+
+pub fn tools() -> Vec<Tool> {
+    vec![configs::get_run_configurations(), configs::execute_run_configuration(), build::build_project()]
+}
+
+/// The `timeout` argument: `default` when absent, at most `max` milliseconds. As in JetBrains
+/// (`withTimeoutOrNull`), zero or a negative value times out at once.
+fn timeout(call: &Call, default: usize, max: usize) -> IdeResult<Duration> {
+    Ok(match call.opt_i64("timeout")? {
+        None => Duration::from_millis(default as u64),
+        Some(n) if n <= 0 => Duration::ZERO,
+        Some(n) => Duration::from_millis((n as u64).min(max as u64)),
+    })
+}

crates/ide-host/src/mcp/run/output.rs

@@ -0,0 +1,188 @@
+// Ported from JetBrains intellij-community plugins/mcp-server (src/com/intellij/mcpserver/util/text.util.kt,
+// mcpserver.toolsets/src/util/OutputCollector.kt), Apache-2.0.
+//! Output of commands and runs: truncation, the run output collector and the private
+//! directory of full output files.
+
+use ide_core::IdeResult;
+use std::io::Write as _;
+use std::path::{Path, PathBuf};
+
+/// Marker of text cut by [`truncate_tail`].
+pub const TRUNCATED_MARKER: &str = "<<<...content truncated...>>>";
+/// Longest text [`truncate_tail`] returns (before its marker).
+pub const MAX_TEXT_LENGTH: usize = 64 * 1024;
+/// Characters of a run's output returned inline.
+pub const RUN_PREVIEW_MAX_LENGTH: usize = 10_000;
+pub const RUN_PREVIEW_TRUNCATED_MARKER: &str = "<truncated>";
+
+/// Console tail bounded by line count and character count.
+pub fn truncate_tail(text: &str, max_lines: usize, max_length: usize, marker: &str) -> String {
+    let lines: Vec<&str> = text.split('\n').collect();
+    let text = if lines.len() > max_lines {
+        [vec![marker], lines[lines.len() - (max_lines - 1)..].to_vec()].concat().join("\n")
+    } else {
+        text.to_owned()
+    };
+    if text.chars().count() <= max_length {
+        return text;
+    }
+    let start = text.char_indices().rev().nth(max_length - 1).map_or(0, |(i, _)| i);
+    format!("{marker}{}", &text[start..])
+}
+
+/// A run's output: all of it to a file, its first [`RUN_PREVIEW_MAX_LENGTH`] characters
+/// in memory (then [`RUN_PREVIEW_TRUNCATED_MARKER`]).
+pub struct OutputCollector {
+    pub path: PathBuf,
+    preview: String,
+    preview_chars: usize,
+    pub truncated: bool,
+    file: Option<std::fs::File>,
+}
+
+impl OutputCollector {
+    pub fn create(name: &str) -> IdeResult<Self> {
+        let (path, file) = temp_output_file(&format!("run-{name}"))?;
+        Ok(Self { path, preview: String::new(), preview_chars: 0, truncated: false, file: Some(file) })
+    }
+
+    pub fn append(&mut self, text: &str) {
+        // A failed write keeps the preview going; the file is then incomplete.
+        if let Some(f) = &mut self.file
+            && f.write_all(text.as_bytes()).is_err()
+        {
+            self.file = None;
+        }
+        if self.truncated {
+            return;
+        }
+        // As JetBrains: reaching the limit marks the preview truncated, even without more output.
+        let room = RUN_PREVIEW_MAX_LENGTH - self.preview_chars;
+        let chars = text.chars().count();
+        if chars < room {
+            self.preview_chars += chars;
+            self.preview.push_str(text);
+        } else {
+            let cut = text.char_indices().nth(room).map_or(text.len(), |(i, _)| i);
+            self.preview.push_str(&text[..cut]);
+            self.preview.push_str(RUN_PREVIEW_TRUNCATED_MARKER);
+            self.preview_chars = RUN_PREVIEW_MAX_LENGTH;
+            self.truncated = true;
+        }
+    }
+
+    pub fn preview(&self) -> &str {
+        &self.preview
+    }
+}
+
+/// Output files older than this are removed when a new one is created.
+const OUTPUT_MAX_AGE: std::time::Duration = std::time::Duration::from_secs(24 * 60 * 60);
+
+pub fn temp_output_file(prefix: &str) -> IdeResult<(PathBuf, std::fs::File)> {
+    let dir = output_dir()?;
+    remove_old_logs(&dir, OUTPUT_MAX_AGE);
+    let safe: String =
+        prefix.chars().map(|c| if c.is_ascii_alphanumeric() || c == '-' { c } else { '_' }).take(40).collect();
+    let path = dir.join(format!("{safe}-{}.log", uuid::Uuid::new_v4().simple()));
+    let mut options = std::fs::OpenOptions::new();
+    options.write(true).create_new(true);
+    #[cfg(unix)]
+    std::os::unix::fs::OpenOptionsExt::mode(&mut options, 0o600);
+    let file = options.open(&path)?;
+    Ok((path, file))
+}
+
+/// Best effort: removes `*.log` files in `dir` last modified more than `max_age` ago.
+fn remove_old_logs(dir: &Path, max_age: std::time::Duration) {
+    let Ok(entries) = std::fs::read_dir(dir) else { return };
+    let now = std::time::SystemTime::now();
+    for entry in entries.flatten() {
+        let path = entry.path();
+        if path.extension().is_none_or(|e| e != "log") {
+            continue;
+        }
+        let old = entry
+            .metadata()
+            .ok()
+            .filter(std::fs::Metadata::is_file)
+            .and_then(|m| m.modified().ok())
+            .and_then(|modified| now.duration_since(modified).ok())
+            .is_some_and(|age| age > max_age);
+        if old {
+            let _ = std::fs::remove_file(&path);
+        }
+    }
+}
+
+/// A directory only this user can read: output may hold secrets, and `/tmp` is shared on Linux.
+fn output_dir() -> IdeResult<PathBuf> {
+    #[cfg(unix)]
+    {
+        use std::os::unix::fs::{DirBuilderExt, MetadataExt};
+        let uid = rustix::process::getuid().as_raw();
+        let dir = std::env::temp_dir().join(format!("openidea-mcp-{uid}"));
+        match std::fs::DirBuilder::new().mode(0o700).create(&dir) {
+            Ok(()) => {}
+            Err(e) if e.kind() == std::io::ErrorKind::AlreadyExists => {}
+            Err(e) => return Err(e.into()),
+        }
+        let meta = std::fs::symlink_metadata(&dir)?;
+        if !meta.is_dir() || meta.uid() != uid || meta.mode() & 0o077 != 0 {
+            return Err(ide_core::IdeError::new(
+                ide_core::error::ErrorKind::PermissionDenied,
+                format!("{} is not a private directory of this user", dir.display()),
+            ));
+        }
+        Ok(dir)
+    }
+    #[cfg(not(unix))]
+    {
+        let dir = std::env::temp_dir().join("openidea-mcp");
+        std::fs::create_dir_all(&dir)?;
+        Ok(dir)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::time::Duration;
+
+    #[test]
+    fn preview_line_keeps_a_fixed_length() {
+        // JetBrains' `truncateRunConfigurationPreviewLine`: 1000 characters including the marker.
+        let line = "a".repeat(2000);
+        let cut = truncate_tail(&line, 3, 1000 - RUN_PREVIEW_TRUNCATED_MARKER.len(), RUN_PREVIEW_TRUNCATED_MARKER);
+        assert!(cut.starts_with("<truncated>"));
+        assert_eq!(cut.len(), 1000);
+    }
+
+    #[test]
+    fn collector_limits_the_preview_and_keeps_everything_in_the_file() {
+        let mut c = OutputCollector::create("test").unwrap();
+        let output = "a".repeat(RUN_PREVIEW_MAX_LENGTH + 1);
+        c.append(&output[..10]);
+        c.append(&output[10..]);
+        assert_eq!(c.preview(), format!("{}{RUN_PREVIEW_TRUNCATED_MARKER}", &output[..RUN_PREVIEW_MAX_LENGTH]));
+        assert!(c.truncated);
+        assert_eq!(std::fs::read_to_string(&c.path).unwrap(), output);
+        let _ = std::fs::remove_file(&c.path);
+    }
+
+    #[test]
+    fn removes_day_old_logs() {
+        let dir = tempfile::tempdir().unwrap();
+        let old = std::time::SystemTime::now() - Duration::from_secs(25 * 60 * 60);
+        for name in ["old.log", "new.log", "old.txt"] {
+            let file = std::fs::File::create(dir.path().join(name)).unwrap();
+            if name.starts_with("old") {
+                file.set_modified(old).unwrap();
+            }
+        }
+        remove_old_logs(dir.path(), OUTPUT_MAX_AGE);
+        assert!(!dir.path().join("old.log").exists());
+        assert!(dir.path().join("new.log").exists());
+        assert!(dir.path().join("old.txt").exists(), "only logs are removed");
+    }
+}

crates/ide-host/src/mcp/run/process.rs

@@ -0,0 +1,65 @@
+use ide_core::{IdeError, IdeResult};
+/// POSIX-like word splitting: whitespace separates, quotes group, `\` escapes (not inside `'…'`).
+pub fn split_words(line: &str) -> IdeResult<Vec<String>> {
+    let mut words = Vec::new();
+    let mut word = String::new();
+    let mut in_word = false;
+    let mut chars = line.chars();
+    while let Some(c) = chars.next() {
+        match c {
+            '\'' => {
+                in_word = true;
+                loop {
+                    match chars.next() {
+                        Some('\'') => break,
+                        Some(c) => word.push(c),
+                        None => return Err(IdeError::invalid("unterminated ' quote")),
+                    }
+                }
+            }
+            '"' => {
+                in_word = true;
+                loop {
+                    match chars.next() {
+                        Some('"') => break,
+                        Some('\\') => match chars.next() {
+                            Some(c @ ('"' | '\\' | '$' | '`')) => word.push(c),
+                            Some(c) => {
+                                word.push('\\');
+                                word.push(c);
+                            }
+                            None => return Err(IdeError::invalid("unterminated \" quote")),
+                        },
+                        Some(c) => word.push(c),
+                        None => return Err(IdeError::invalid("unterminated \" quote")),
+                    }
+                }
+            }
+            '\\' if !cfg!(windows) => {
+                in_word = true;
+                if let Some(c) = chars.next() {
+                    word.push(c);
+                }
+            }
+            c if c.is_whitespace() => {
+                if in_word {
+                    words.push(std::mem::take(&mut word));
+                    in_word = false;
+                }
+            }
+            c => {
+                in_word = true;
+                word.push(c);
+            }
+        }
+    }
+    if in_word {
+        words.push(word);
+    }
+    Ok(words)
+}
+
+pub fn quote(arg: &str) -> String {
+    let plain = !arg.is_empty() && arg.chars().all(|c| c.is_ascii_alphanumeric() || "-_./=:@%+,".contains(c));
+    if plain { arg.to_owned() } else { format!("'{}'", arg.replace('\'', "'\\''")) }
+}

crates/ide-host/src/mcp/run/targets.rs

@@ -0,0 +1,975 @@
+//! Run points inside a file (the editor's gutter ▶ icons) and the run configuration of
+//! one: a port of the frontend's `features/run/targets.ts` and `context.ts` for Rust,
+//! JavaScript/TypeScript, Python and Go. JVM files are not covered (the editor scans
+//! them with a parser of its own).
+
+use ide_run::RunConfig;
+use regex_lite::Regex;
+use std::path::Path;
+use std::sync::LazyLock;
+
+/// Above this size files are not scanned (generated / minified files).
+const MAX_SCAN: usize = 400_000;
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Kind {
+    Main,
+    Test,
+    Suite,
+}
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Target {
+    /// 0-based line of the declaration.
+    pub line: usize,
+    pub kind: Kind,
+    /// Display name (`adds_numbers`, `math > adds`).
+    pub name: String,
+    /// Rust module path, describe chain, Python class chain…
+    pub path: Vec<String>,
+}
+
+macro_rules! re {
+    ($name:ident, $re:expr) => {
+        static $name: LazyLock<Regex> = LazyLock::new(|| Regex::new($re).expect("valid regex"));
+    };
+}
+
+fn indent_of(s: &str) -> usize {
+    s.chars().take_while(|c| c.is_whitespace()).map(|c| if c == '\t' { 4 } else { 1 }).sum()
+}
+
+// ---------------------------------------------------------------- Rust
+
+re!(LINE_COMMENT, r"//.*$");
+re!(STRING, r#""(?:[^"\\]|\\.)*""#);
+re!(CHAR, r"'(?:[^'\\]|\\.)'");
+
+/// Strips string literals and line comments (rough) so braces inside them don't count.
+fn code_only(line: &str) -> String {
+    let line = LINE_COMMENT.replace(line, "");
+    let line = STRING.replace_all(&line, "\"\"");
+    CHAR.replace_all(&line, "''").into_owned()
+}
+
+re!(RUST_SRC, r"(?:^|/)src/(.+)\.rs$");
+
+fn rust_module_prefix(rel: &str) -> Vec<String> {
+    let Some(m) = RUST_SRC.captures(rel) else { return Vec::new() };
+    let mut parts: Vec<String> = m[1].split('/').map(str::to_owned).collect();
+    let last = parts.last().cloned().unwrap_or_default();
+    if parts.len() == 1 && (last == "lib" || last == "main") || parts[0] == "bin" {
+        return Vec::new();
+    }
+    if last == "mod" {
+        parts.pop();
+    }
+    parts
+}
+
+re!(RUST_TEST_ATTR, r"^#\[(?:[\w:]+::)?test\b|^#\[(?:tokio|async_std|actix_rt|rstest|test_case)(?:::\w+)?\b");
+re!(RUST_CFG_TEST, r"^#\[cfg\(test\)\]");
+re!(RUST_FN, r"^(?:pub(?:\([^)]*\))?\s+)?(?:async\s+)?(?:unsafe\s+)?fn\s+(\w+)");
+re!(RUST_MOD, r"^(?:pub(?:\([^)]*\))?\s+)?mod\s+(\w+)\s*\{");
+re!(RUST_MAIN_FILE, r"(?:^|/)(?:src/main|src/bin/[^/]+|examples/[^/]+)\.rs$");
+
+fn rust_targets(lines: &[&str], rel: &str) -> Vec<Target> {
+    let mut out: Vec<Target> = Vec::new();
+    let prefix = rust_module_prefix(rel);
+    let mut mods: Vec<(String, i64)> = Vec::new();
+    let mut depth: i64 = 0;
+    let mut pending_test = false;
+    let mut pending_cfg_test = false;
+    for (i, raw) in lines.iter().enumerate() {
+        let line = code_only(raw);
+        let trimmed = line.trim();
+        if RUST_TEST_ATTR.is_match(trimmed) {
+            pending_test = true;
+        }
+        if RUST_CFG_TEST.is_match(trimmed) {
+            pending_cfg_test = true;
+        }
+        let mod_path = || prefix.iter().cloned().chain(mods.iter().map(|m| m.0.clone())).collect::<Vec<_>>();
+        if let Some(f) = RUST_FN.captures(trimmed) {
+            let name = f[1].to_owned();
+            if pending_test {
+                let mut path = mod_path();
+                path.push(name.clone());
+                out.push(Target { line: i, kind: Kind::Test, name, path });
+            } else if name == "main" && depth == 0 && RUST_MAIN_FILE.is_match(rel) {
+                out.push(Target { line: i, kind: Kind::Main, name, path: Vec::new() });
+            }
+            pending_test = false;
+            pending_cfg_test = false;
+        } else if let Some(m) = RUST_MOD.captures(trimmed) {
+            let name = m[1].to_owned();
+            let mut path = mod_path();
+            path.push(name.clone());
+            if pending_cfg_test || name == "tests" {
+                out.push(Target { line: i, kind: Kind::Suite, name: name.clone(), path });
+            }
+            mods.push((name, depth));
+            pending_test = false;
+            pending_cfg_test = false;
+        } else if !trimmed.is_empty() && !trimmed.starts_with("#[") && !trimmed.starts_with("//") {
+            pending_test = false;
+            if !trimmed.starts_with('#') {
+                pending_cfg_test = false;
+            }
+        }
+        for ch in line.chars() {
+            if ch == '{' {
+                depth += 1;
+            } else if ch == '}' {
+                depth -= 1;
+                while mods.last().is_some_and(|m| m.1 >= depth) {
+                    mods.pop();
+                }
+            }
+        }
+    }
+    // A suite that contains no tests is noise.
+    let tests: Vec<Vec<String>> = out.iter().filter(|t| t.kind == Kind::Test).map(|t| t.path.clone()).collect();
+    out.retain(|t| t.kind != Kind::Suite || tests.iter().any(|p| p.len() > t.path.len() && p.starts_with(&t.path)));
+    out
+}
+
+// ---------------------------------------------------------------- JavaScript / TypeScript
+
+re!(
+    JS_CALL,
+    r"^(\s*)(describe|suite|context|test|it)\b(?:\.(?:only|skip|todo|concurrent|failing|sequential))*(\.each\s*(?:\(.*?\)|`[^`]*`))?\s*\(\s*"
+);
+
+/// The string literal at the start of `s` (quote, then text up to the same unescaped quote).
+fn js_string(s: &str) -> Option<(char, String)> {
+    let mut chars = s.chars();
+    let quote = chars.next().filter(|q| matches!(q, '\'' | '"' | '`'))?;
+    let mut raw = String::new();
+    while let Some(c) = chars.next() {
+        if c == quote {
+            return Some((quote, raw));
+        }
+        raw.push(c);
+        if c == '\\' {
+            raw.push(chars.next()?);
+        }
+    }
+    None
+}
+
+re!(JS_ESCAPE, r"\\(.)");
+
+fn js_targets(lines: &[&str]) -> Vec<Target> {
+    let mut out = Vec::new();
+    let mut stack: Vec<(usize, String)> = Vec::new();
+    for (i, line) in lines.iter().enumerate() {
+        let Some(m) = JS_CALL.captures(line) else { continue };
+        let Some((_quote, raw)) = js_string(&line[m.get(0).map_or(0, |g| g.end())..]) else { continue };
+        let indent = indent_of(&m[1]);
+        while stack.last().is_some_and(|s| s.0 >= indent) {
+            stack.pop();
+        }
+        let name = JS_ESCAPE.replace_all(&raw, "$1").into_owned();
+        let mut path: Vec<String> = stack.iter().map(|s| s.1.clone()).collect();
+        path.push(name.clone());
+        let suite = matches!(&m[2], "describe" | "suite" | "context");
+        out.push(Target { line: i, kind: if suite { Kind::Suite } else { Kind::Test }, name: path.join(" > "), path });
+        if suite {
+            stack.push((indent, name));
+        }
+    }
+    out
+}
+
+fn escape_regexp(s: &str) -> String {
+    let mut out = String::with_capacity(s.len());
+    for c in s.chars() {
+        if ".*+?^${}()|[]\\".contains(c) {
+            out.push('\\');
+        }
+        out.push(c);
+    }
+    out
+}
+
+re!(JS_PATTERN_PLACEHOLDER, r"%[sdifjo#p]|\\\$\\\{[^}]*\\\}|\$\w+");
+
+/// Jest / Vitest `-t` pattern for a test (full name = describe chain + name, space separated).
+fn js_name_pattern(target: &Target) -> String {
+    let pattern = escape_regexp(&target.path.join(" "));
+    // `test.each` placeholders (%s, $name, ${…}) match anything.
+    let pattern = JS_PATTERN_PLACEHOLDER.replace_all(&pattern, ".*");
+    if target.kind == Kind::Suite { format!("^{pattern}") } else { format!("^{pattern}$") }
+}
+
+// ---------------------------------------------------------------- Python
+
+re!(PY_COMMENT, r"^\s*#");
+re!(PY_CLASS, r"^\s*class\s+(\w+)");
+re!(PY_TEST_DEF, r"^\s*(?:async\s+)?def\s+(test\w*)\s*\(");
+re!(PY_MAIN, r#"^if\s+__name__\s*==\s*['"]__main__['"]\s*:"#);
+
+fn python_targets(lines: &[&str]) -> Vec<Target> {
+    let mut out = Vec::new();
+    let mut classes: Vec<(usize, String, bool)> = Vec::new();
+    for (i, line) in lines.iter().enumerate() {
+        if line.trim().is_empty() || PY_COMMENT.is_match(line) {
+            continue;
+        }
+        let indent = indent_of(line);
+        while classes.last().is_some_and(|c| c.0 >= indent) {
+            classes.pop();
+        }
+        if let Some(c) = PY_CLASS.captures(line) {
+            let test = c[1].starts_with("Test") && classes.iter().all(|c| c.2);
+            classes.push((indent, c[1].to_owned(), test));
+            if test {
+                let path: Vec<String> = classes.iter().map(|c| c.1.clone()).collect();
+                out.push(Target { line: i, kind: Kind::Suite, name: c[1].to_owned(), path });
+            }
+            continue;
+        }
+        if let Some(d) = PY_TEST_DEF.captures(line)
+            && classes.iter().all(|c| c.2)
+        {
+            let mut path: Vec<String> = classes.iter().map(|c| c.1.clone()).collect();
+            path.push(d[1].to_owned());
+            out.push(Target { line: i, kind: Kind::Test, name: path.join("."), path });
+            continue;
+        }
+        if indent == 0 && PY_MAIN.is_match(line) {
+            out.push(Target { line: i, kind: Kind::Main, name: "main".into(), path: Vec::new() });
+        }
+    }
+    out
+}
+
+// ---------------------------------------------------------------- Go
+
+re!(GO_PACKAGE_MAIN, r"^package\s+main\b");
+re!(GO_TEST, r"^func\s+(Test\w*|Benchmark\w*|Example\w*|Fuzz\w*)\s*\(\s*(?:\w+\s+\*testing\.[TFB])?\s*\)?");
+re!(GO_TESTING_ARG, r"\*testing\.[TFB]");
+re!(GO_TESTING_TB, r"\*testing\.[TB]\b");
+re!(GO_MAIN, r"^func\s+main\s*\(\s*\)");
+re!(GO_ONE_LINE, r"\}\s*(?://.*)?$");
+re!(GO_RUN_LITERAL, r#"\b\w+\.Run\(\s*"((?:[^"\\]|\\.)*)"\s*,"#);
+re!(GO_RUN_FIELD, r"\b\w+\.Run\(\s*\w+\.(\w+)\s*,");
+re!(GO_RUN_KEY, r"\b\w+\.Run\(\s*(\w+)\s*,");
+re!(GO_MAP_KEY, r#"^\s*"((?:[^"\\]|\\.)*)"\s*:\s*\{"#);
+re!(WHITESPACE, r"\s");
+
+fn go_targets(lines: &[&str]) -> Vec<Target> {
+    let mut out = Vec::new();
+    let is_main = lines.iter().any(|l| GO_PACKAGE_MAIN.is_match(l));
+    for (i, line) in lines.iter().enumerate() {
+        if let Some(t) = GO_TEST.captures(line) {
+            let name = t[1].to_owned();
+            if name.starts_with("Example") || GO_TESTING_ARG.is_match(line) {
+                out.push(Target { line: i, kind: Kind::Test, name: name.clone(), path: vec![name.clone()] });
+                if GO_TESTING_TB.is_match(line) {
+                    out.extend(go_subtests(lines, i, &name));
+                }
+                continue;
+            }
+        }
+        if is_main && GO_MAIN.is_match(line) {
+            out.push(Target { line: i, kind: Kind::Main, name: "main".into(), path: Vec::new() });
+        }
+    }
+    out
+}
+
+/// Subtests of the test function at `start`: `t.Run("name", …)`, and table entries run with
+/// `t.Run(tt.name, …)` (`{name: "…", …}`) or keyed by name (`"…": {…}`).
+fn go_subtests(lines: &[&str], start: usize, test: &str) -> Vec<Target> {
+    if GO_ONE_LINE.is_match(lines[start]) {
+        return Vec::new();
+    }
+    let mut end = start;
+    while end + 1 < lines.len() && !lines[end].starts_with('}') {
+        end += 1;
+    }
+    let body = &lines[start + 1..end.max(start + 1)];
+    let mut out: Vec<Target> = Vec::new();
+    let mut add = |offset: usize, name: &str| {
+        let sub = WHITESPACE.replace_all(&JS_ESCAPE.replace_all(name, "$1"), "_").into_owned();
+        if !out.iter().any(|t| t.path[1] == sub) {
+            out.push(Target {
+                line: start + 1 + offset,
+                kind: Kind::Test,
+                name: format!("{test}/{sub}"),
+                path: vec![test.to_owned(), sub],
+            });
+        }
+    };
+    let mut fields: Vec<String> = Vec::new();
+    let mut keys: Vec<String> = Vec::new();
+    for (i, l) in body.iter().enumerate() {
+        if let Some(m) = GO_RUN_LITERAL.captures(l) {
+            add(i, &m[1]);
+        }
+        if let Some(m) = GO_RUN_FIELD.captures(l) {
+            fields.push(m[1].to_owned());
+        }
+        if let Some(m) = GO_RUN_KEY.captures(l) {
+            let range = Regex::new(&format!(r"\bfor\s+{}\s*,\s*\w+\s*:=\s*range\b", &m[1])).expect("valid regex");
+            if body[..i].iter().any(|b| range.is_match(b)) {
+                keys.push(m[1].to_owned());
+            }
+        }
+    }
+    if !fields.is_empty() || !keys.is_empty() {
+        let field_res: Vec<Regex> = fields
+            .iter()
+            .map(|f| Regex::new(&format!(r#"\b{f}\s*:\s*"((?:[^"\\]|\\.)*)""#)).expect("valid regex"))
+            .collect();
+        for (i, l) in body.iter().enumerate() {
+            for re in &field_res {
+                if let Some(m) = re.captures(l) {
+                    add(i, &m[1]);
+                }
+            }
+            if !keys.is_empty()
+                && let Some(m) = GO_MAP_KEY.captures(l)
+            {
+                add(i, &m[1]);
+            }
+        }
+    }
+    out.sort_by_key(|t| t.line);
+    out
+}
+
+// ---------------------------------------------------------------- detection
+
+re!(JS_FILE, r"\.[cm]?[jt]sx?$");
+re!(JS_TEST_FILE, r"\.(test|spec)\.[cm]?[jt]sx?$|(^|/)__tests__/");
+re!(PY_TEST_FILE, r"(^|/)(test_[^/]*|[^/]*_test)\.py$|(^|/)tests?/");
+
+/// Run targets of a file (`rel`: project-relative with `/`, picks the language).
+pub fn detect(text: &str, rel: &str) -> Vec<Target> {
+    if text.len() > MAX_SCAN {
+        return Vec::new();
+    }
+    let lines: Vec<&str> = text.split('\n').map(|l| l.strip_suffix('\r').unwrap_or(l)).collect();
+    if rel.ends_with(".rs") {
+        rust_targets(&lines, rel)
+    } else if JS_FILE.is_match(rel) {
+        if JS_TEST_FILE.is_match(rel) { js_targets(&lines) } else { Vec::new() }
+    } else if rel.ends_with(".py") {
+        let test_file = PY_TEST_FILE.is_match(rel);
+        python_targets(&lines).into_iter().filter(|t| t.kind == Kind::Main || test_file).collect()
+    } else if rel.ends_with(".go") {
+        let test_file = rel.ends_with("_test.go");
+        go_targets(&lines).into_iter().filter(|t| t.kind == Kind::Main || test_file).collect()
+    } else {
+        Vec::new()
+    }
+}
+
+/// The last line (0-based) of the block declared at `start`: by indentation in Python, else
+/// where the braces opened on (or, for a Rust signature, after) the declaration close again.
+fn block_end(lines: &[&str], start: usize, rel: &str) -> usize {
+    if rel.ends_with(".py") {
+        let indent = indent_of(lines[start]);
+        let mut end = start;
+        for (i, line) in lines.iter().enumerate().skip(start + 1) {
+            if line.trim().is_empty() || PY_COMMENT.is_match(line) {
+                continue;
+            }
+            if indent_of(line) <= indent {
+                break;
+            }
+            end = i;
+        }
+        return end;
+    }
+    let rust = rel.ends_with(".rs");
+    let mut depth: i64 = 0;
+    let mut opened = false;
+    for (i, raw) in lines.iter().enumerate().skip(start) {
+        let line = code_only(raw);
+        for ch in line.chars() {
+            match ch {
+                '{' => {
+                    depth += 1;
+                    opened = true;
+                }
+                '}' => depth -= 1,
+                // A Rust declaration without a body (`fn f();`).
+                ';' if rust && !opened => return i,
+                _ => {}
+            }
+            if opened && depth <= 0 {
+                return i;
+            }
+        }
+        // Only a Rust signature continues on the next lines; a call without a block ends here.
+        if !opened && !rust {
+            return i;
+        }
+    }
+    lines.len().saturating_sub(1)
+}
+
+/// The run targets whose declaration or body contains `line` (0-based), innermost first.
+pub fn enclosing(text: &str, rel: &str, line: usize) -> Vec<Target> {
+    let lines: Vec<&str> = text.split('\n').map(|l| l.strip_suffix('\r').unwrap_or(l)).collect();
+    let mut out: Vec<Target> =
+        detect(text, rel).into_iter().filter(|t| t.line <= line && line <= block_end(&lines, t.line, rel)).collect();
+    out.sort_by_key(|t| std::cmp::Reverse(t.line));
+    out
+}
+
+// ---------------------------------------------------------------- configurations
+
+/// A configuration's working directory relative to the project root, with `/` (Go: its module).
+fn cwd_of(root: &Path, c: &RunConfig) -> String {
+    let module = (c.kind == "go").then(|| c.extras.params.get("module").cloned()).flatten();
+    let cwd = module
+        .or_else(|| c.cwd.as_deref().map(|p| p.strip_prefix(root).unwrap_or(p).to_string_lossy().replace('\\', "/")));
+    let cwd = cwd.unwrap_or_default();
+    let cwd = cwd.strip_prefix("./").or_else(|| cwd.strip_prefix('.')).unwrap_or(&cwd);
+    cwd.trim_end_matches('/').to_owned()
+}
+
+/// Configs whose working directory most specifically contains `rel` (ties in their original order).
+fn all_closest<'a>(root: &Path, configs: &[&'a RunConfig], rel: &str) -> Vec<&'a RunConfig> {
+    let score = |c: &RunConfig| -> Option<usize> {
+        let cwd = cwd_of(root, c);
+        if cwd.is_empty() { Some(0) } else { (rel == cwd || rel.starts_with(&format!("{cwd}/"))).then_some(cwd.len()) }
+    };
+    let scored: Vec<(&RunConfig, usize)> = configs.iter().filter_map(|c| score(c).map(|s| (*c, s))).collect();
+    let best = scored.iter().map(|s| s.1).max();
+    scored.into_iter().filter(|s| Some(s.1) == best).map(|s| s.0).collect()
+}
+
+fn closest<'a>(root: &Path, configs: &[&'a RunConfig], rel: &str) -> Option<&'a RunConfig> {
+    all_closest(root, configs, rel).into_iter().next()
+}
+
+fn rel_to_cwd(root: &Path, rel: &str, c: &RunConfig) -> String {
+    let cwd = cwd_of(root, c);
+    match rel.strip_prefix(&format!("{cwd}/")) {
+        Some(inner) if !cwd.is_empty() => inner.to_owned(),
+        _ => rel.to_owned(),
+    }
+}
+
+fn file_name(rel: &str) -> &str {
+    rel.rsplit('/').next().unwrap_or(rel)
+}
+
+fn dir_of(p: &str) -> &str {
+    p.rfind('/').map_or("", |i| &p[..i])
+}
+
+fn derived(base: &RunConfig, rel: &str, args: Vec<String>) -> RunConfig {
+    RunConfig {
+        id: format!("context:{}:{rel}", base.id),
+        name: file_name(rel).to_owned(),
+        args,
+        detected: true,
+        ..base.clone()
+    }
+}
+
+/// Kinds whose test configs can run a file of this extension.
+fn test_kinds(rel: &str) -> &'static [&'static str] {
+    if JS_FILE.is_match(rel) {
+        &["npm", "deno", "bun"]
+    } else if rel.ends_with(".py") {
+        &["pytest", "python"]
+    } else if rel.ends_with(".go") {
+        &["go"]
+    } else if rel.ends_with(".rs") {
+        &["cargo"]
+    } else {
+        &[]
+    }
+}
+
+/// The project's Python interpreter as `(command, leading args)`, from detected configs.
+fn project_python(configs: &[RunConfig]) -> Option<(String, Vec<String>)> {
+    if let Some(py) = configs.iter().find(|c| c.kind == "python") {
+        let prefix = match py.args.iter().position(|a| a == "-m") {
+            Some(m) => py.args[..m].to_vec(),
+            None => py.args.iter().filter(|a| !a.ends_with(".py")).cloned().collect(),
+        };
+        return Some((py.command.clone(), prefix));
+    }
+    let pytest = configs.iter().find(|c| c.kind == "pytest")?;
+    static VENV: LazyLock<Regex> =
+        LazyLock::new(|| Regex::new(r"^(.*[/\\](?:bin|Scripts)[/\\])pytest(\.exe)?$").expect("valid regex"));
+    if let Some(m) = VENV.captures(&pytest.command) {
+        return Some((format!("{}python{}", &m[1], m.get(2).map_or("", |g| g.as_str())), Vec::new()));
+    }
+    if let Some(m) = pytest.args.iter().position(|a| a == "-m")
+        && pytest.args.get(m + 1).is_some_and(|a| a == "pytest")
+    {
+        return Some((pytest.command.clone(), pytest.args[..m].to_vec()));
+    }
+    if pytest.args.first().is_some_and(|a| a == "run") && pytest.args.get(1).is_some_and(|a| a == "pytest") {
+        return Some((pytest.command.clone(), vec!["run".into(), "python".into()]));
+    }
+    None
+}
+
+fn blank(id: String, name: &str, kind: &str, command: String, args: Vec<String>) -> RunConfig {
+    RunConfig {
+        id,
+        name: name.to_owned(),
+        kind: kind.to_owned(),
+        command,
+        args,
+        cwd: None,
+        env: Default::default(),
+        detected: true,
+        is_test: false,
+        debug_adapter: None,
+        allow_parallel: false,
+        extras: Default::default(),
+    }
+}
+
+/// PyCharm runs pytest for a test file even when the project declares no test setup.
+fn implicit_pytest(rel: &str, configs: &[RunConfig]) -> Option<RunConfig> {
+    if !rel.ends_with(".py") {
+        return None;
+    }
+    let (command, mut args) = project_python(configs).unwrap_or_else(|| ("python3".into(), Vec::new()));
+    args.extend(["-m".to_owned(), "pytest".to_owned()]);
+    let mut c = blank("pytest:implicit".into(), "pytest", "pytest", command, args);
+    c.is_test = true;
+    c.debug_adapter = Some("debugpy".into());
+    Some(c)
+}
+
+fn test_base_for(root: &Path, rel: &str, configs: &[RunConfig]) -> Option<RunConfig> {
+    let kinds = test_kinds(rel);
+    // Configurations produced from a test or file are results of narrowing, never bases for it.
+    let candidates: Vec<&RunConfig> = configs
+        .iter()
+        .filter(|c| c.is_test && kinds.contains(&c.kind.as_str()) && !c.id.starts_with("context:"))
+        .collect();
+    closest(root, &candidates, rel).or(candidates.first().copied()).cloned().or_else(|| implicit_pytest(rel, configs))
+}
+
+/// Go test flags may come before or after package targets; binary arguments start at `-args`.
+fn go_test_parts(args: &[String]) -> (Vec<String>, Vec<String>, Vec<String>) {
+    const BOOLEAN_FLAGS: &[&str] = &[
+        "-a",
+        "-n",
+        "-race",
+        "-msan",
+        "-asan",
+        "-cover",
+        "-linkshared",
+        "-modcacherw",
+        "-trimpath",
+        "-v",
+        "-work",
+        "-x",
+        "-json",
+        "-c",
+        "-i",
+        "-short",
+        "-failfast",
+        "-benchmem",
+        "-fullpath",
+        "-buildvcs",
+    ];
+    let (mut flags, mut targets, mut program) = (Vec::new(), Vec::new(), Vec::new());
+    let mut i = 1;
+    while i < args.len() {
+        let arg = &args[i];
+        if arg == "-args" || arg == "--" {
+            program = args[i..].to_vec();
+            break;
+        }
+        if arg.starts_with('-') {
+            flags.push(arg.clone());
+            if !arg.contains('=') && !BOOLEAN_FLAGS.contains(&arg.as_str()) && i + 1 < args.len() {
+                i += 1;
+                flags.push(args[i].clone());
+            }
+        } else {
+            targets.push(arg.clone());
+        }
+        i += 1;
+    }
+    (flags, targets, program)
+}
+
+fn without_go_selection(flags: &[String]) -> Vec<String> {
+    let mut out = Vec::new();
+    let mut i = 0;
+    while i < flags.len() {
+        let f = flags[i].as_str();
+        if matches!(f, "-run" | "-skip" | "-bench" | "-fuzz") {
+            i += 2;
+            continue;
+        }
+        if ["-run=", "-skip=", "-bench=", "-fuzz="].iter().any(|p| f.starts_with(p)) {
+            i += 1;
+            continue;
+        }
+        out.push(flags[i].clone());
+        i += 1;
+    }
+    out
+}
+
+/// File-level test configuration for `rel` (the closest matching test config narrowed to the file).
+fn test_config_for(root: &Path, rel: &str, configs: &[RunConfig]) -> Option<RunConfig> {
+    let base = test_base_for(root, rel, configs)?;
+    let file = rel_to_cwd(root, rel, &base);
+    let with = |extra: &[String]| [base.args.clone(), extra.to_vec()].concat();
+    Some(match base.kind.as_str() {
+        // `npm run test -- file` works for npm, pnpm, yarn and bun.
+        "npm" | "bun" if base.args.iter().any(|a| a == "--") => derived(&base, rel, with(&[file])),
+        "npm" | "bun" => derived(&base, rel, with(&["--".into(), file])),
+        "deno" | "pytest" | "python" => derived(&base, rel, with(&[file])),
+        "go" => {
+            let dir = dir_of(&file);
+            let target = if dir.is_empty() { ".".to_owned() } else { format!("./{dir}") };
+            let (flags, _, program) = go_test_parts(&base.args);
+            let args = [vec!["test".to_owned()], flags, vec![target.clone()], program].concat();
+            let mut c = derived(&base, rel, args);
+            c.name = format!("go test {target}");
+            if c.extras.params.contains_key("goKind") {
+                c.extras.params.insert("scope".into(), "directory".into());
+                c.extras.params.insert("target".into(), target);
+            }
+            c
+        }
+        "cargo" => {
+            static TESTS: LazyLock<Regex> =
+                LazyLock::new(|| Regex::new(r"(?:^|/)tests/([^/]+)\.rs$").expect("valid regex"));
+            match TESTS.captures(rel) {
+                Some(m) => {
+                    // Cargo's own options go before the test binary's `--`.
+                    let at = base.args.iter().position(|a| a == "--").unwrap_or(base.args.len());
+                    let mut args = base.args.clone();
+                    args.splice(at..at, ["--test".to_owned(), m[1].to_owned()]);
+                    derived(&base, rel, args)
+                }
+                None => base,
+            }
+        }
+        _ => base,
+    })
+}
+
+fn main_config_for(root: &Path, rel: &str, configs: &[RunConfig]) -> Option<RunConfig> {
+    if rel.ends_with(".rs") {
+        static BIN: LazyLock<Regex> = LazyLock::new(|| Regex::new(r"src/bin/([^/]+)\.rs$").expect("valid regex"));
+        let bin = BIN.captures(rel).map(|m| m[1].to_owned());
+        let runs: Vec<&RunConfig> =
+            configs.iter().filter(|c| c.kind == "cargo" && c.id.starts_with("cargo:run")).collect();
+        let by_bin =
+            bin.and_then(|b| runs.iter().find(|c| c.id == format!("cargo:run:{b}") || c.args.contains(&b)).copied());
+        return by_bin.or_else(|| closest(root, &runs, rel)).or(runs.first().copied()).cloned();
+    }
+    if rel.ends_with(".go") {
+        let gos: Vec<&RunConfig> = configs.iter().filter(|c| c.kind == "go").collect();
+        let runs: Vec<&RunConfig> =
+            gos.iter().filter(|c| c.args.first().is_some_and(|a| a == "run")).copied().collect();
+        // The module containing the file (nested modules run from their own directory).
+        let base = closest(root, &runs, rel)
+            .or_else(|| closest(root, &gos, rel))
+            .or(runs.first().copied())
+            .or(gos.first().copied())?;
+        let dir = rel_to_cwd(root, rel, base);
+        let dir = dir_of(&dir);
+        let target = if dir.is_empty() { ".".to_owned() } else { format!("./{dir}") };
+        if let Some(hit) = runs.iter().find(|c| c.cwd == base.cwd && c.args.get(1) == Some(&target)) {
+            return Some((*hit).clone());
+        }
+        let mut c = derived(base, rel, vec!["run".into(), target.clone()]);
+        c.name = format!("go run {target}");
+        c.is_test = false;
+        return Some(c);
+    }
+    None
+}
+
+fn script_config_for(rel: &str, configs: &[RunConfig]) -> Option<RunConfig> {
+    let id = format!("context:file:{rel}");
+    let name = file_name(rel);
+    let script = |command: &str, args: Vec<String>| blank(id.clone(), name, "shell", command.to_owned(), args);
+    if rel.ends_with(".py") {
+        // Reuse the project's interpreter (venv / uv / poetry) when detected.
+        let (command, mut args) = project_python(configs).unwrap_or_else(|| ("python3".into(), Vec::new()));
+        args.push(rel.to_owned());
+        let mut c = blank(id, name, "python", command, args);
+        c.debug_adapter = Some("debugpy".into());
+        return Some(c);
+    }
+    static JS: LazyLock<Regex> = LazyLock::new(|| Regex::new(r"\.[cm]?js$").expect("valid regex"));
+    if JS.is_match(rel) {
+        return Some(script("node", vec![rel.to_owned()]));
+    }
+    if rel.ends_with(".ts") {
+        return Some(script("npx", vec!["tsx".into(), rel.to_owned()]));
+    }
+    for (ext, shell) in [(".zsh", "zsh"), (".bash", "bash"), (".sh", "sh")] {
+        if rel.ends_with(ext) {
+            return Some(script(shell, vec![rel.to_owned()]));
+        }
+    }
+    None
+}
+
+re!(TEST_FILE, r"\.(test|spec)\.[cm]?[jt]sx?$|(^|/)__tests__/|(^|/)(test_[^/]*\.py|[^/]*_test\.py|[^/]*_test\.go)$");
+re!(RUST_TESTS_FILE, r"(^|/)tests/[^/]+\.rs$");
+re!(RUST_MAIN_ROLE, r"(^|/)src/main\.rs$|(^|/)src/bin/[^/]+\.rs$");
+re!(GO_PACKAGE_MAIN_MULTILINE, r"(?m)^\s*package\s+main\b");
+re!(SCRIPT_FILE, r"\.(py|sh|bash|zsh|[cm]?js|ts)$");
+
+/// "Run Context Configuration" for the whole file: its tests, its main target or the script.
+pub fn context_config(root: &Path, rel: &str, configs: &[RunConfig], content: &str) -> Option<RunConfig> {
+    let name = file_name(rel);
+    if TEST_FILE.is_match(rel) || (RUST_TESTS_FILE.is_match(rel) && name != "mod.rs") {
+        return test_config_for(root, rel, configs);
+    }
+    if RUST_MAIN_ROLE.is_match(rel) || (rel.ends_with(".go") && GO_PACKAGE_MAIN_MULTILINE.is_match(content)) {
+        return main_config_for(root, rel, configs).or_else(|| script_config_for(rel, configs));
+    }
+    if SCRIPT_FILE.is_match(name) {
+        return script_config_for(rel, configs);
+    }
+    None
+}
+
+fn replace_last(mut args: Vec<String>, f: impl FnOnce(&str) -> String) -> Vec<String> {
+    if let Some(last) = args.last_mut() {
+        *last = f(last);
+    }
+    args
+}
+
+/// The run configuration of one target, or `None` when the project has no matching runner.
+pub fn target_config(
+    root: &Path,
+    target: &Target,
+    rel: &str,
+    configs: &[RunConfig],
+    content: &str,
+) -> Option<RunConfig> {
+    if target.kind == Kind::Main {
+        return context_config(root, rel, configs, content);
+    }
+    let file = test_config_for(root, rel, configs)?;
+    let short =
+        if target.kind == Kind::Suite { target.path.last().cloned().unwrap_or_default() } else { target.name.clone() };
+    let named = |args: Vec<String>| RunConfig {
+        id: format!("context:target:{}:{rel}:{}", file.id, target.path.join("/")),
+        name: short.clone(),
+        args,
+        detected: true,
+        ..file.clone()
+    };
+    let with = |extra: Vec<String>| [file.args.clone(), extra].concat();
+    match file.kind.as_str() {
+        "npm" | "bun" | "deno" => Some(named(with(vec!["-t".into(), js_name_pattern(target)]))),
+        "pytest" | "python" => {
+            Some(named(replace_last(file.args.clone(), |f| format!("{f}::{}", target.path.join("::")))))
+        }
+        "go" => {
+            let pattern = format!("^{}$", target.path.iter().map(|p| escape_regexp(p)).collect::<Vec<_>>().join("$/^"));
+            let benchmark = target.path.first().is_some_and(|p| p.starts_with("Benchmark"));
+            let (flags, targets, program) = go_test_parts(&file.args);
+            let selection: Vec<String> = if benchmark {
+                vec!["-run".into(), "^$".into(), "-bench".into(), pattern.clone()]
+            } else {
+                vec!["-run".into(), pattern.clone()]
+            };
+            let flags = without_go_selection(&flags);
+            let mut c = named([vec!["test".to_owned()], flags.clone(), targets, selection, program].concat());
+            if c.extras.params.contains_key("goKind") {
+                let mut tool_args: Vec<String> = flags;
+                if benchmark {
+                    tool_args.extend(["-bench".to_owned(), pattern.clone()]);
+                }
+                c.extras.params.insert("pattern".into(), if benchmark { "^$".into() } else { pattern });
+                c.extras.params.insert(
+                    "toolArgs".into(),
+                    tool_args.iter().map(|a| super::process::quote(a)).collect::<Vec<_>>().join(" "),
+                );
+            }
+            Some(c)
+        }
+        "cargo" => {
+            let path = target.path.join("::");
+            // Test-binary arguments follow the one `--` (`cargo test -- --nocapture` has it already).
+            let separator: Vec<String> =
+                if file.args.iter().any(|a| a == "--") { Vec::new() } else { vec!["--".into()] };
+            Some(named(if target.kind == Kind::Suite {
+                with([separator, vec![format!("{path}::")]].concat())
+            } else {
+                with([separator, vec![path, "--exact".into()]].concat())
+            }))
+        }
+        _ => None,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn pick(ts: &[Target]) -> Vec<(usize, Kind, String)> {
+        ts.iter().map(|t| (t.line, t.kind, t.path.join("/"))).collect()
+    }
+
+    #[test]
+    fn rust_main_tests_and_test_modules() {
+        let src = [
+            "fn main() {}",
+            "#[cfg(test)]",
+            "mod tests {",
+            "    use super::*;",
+            "    #[test]",
+            "    fn adds() { let s = \"}\"; }",
+            "    #[tokio::test]",
+            "    #[ignore]",
+            "    async fn async_one() {}",
+            "    fn helper() {}",
+            "}",
+            "fn after() {}",
+        ]
+        .join("\n");
+        assert_eq!(
+            pick(&detect(&src, "src/main.rs")),
+            [
+                (0, Kind::Main, String::new()),
+                (2, Kind::Suite, "tests".into()),
+                (5, Kind::Test, "tests/adds".into()),
+                (8, Kind::Test, "tests/async_one".into()),
+            ]
+        );
+        assert_eq!(
+            pick(&detect("#[test]\nfn x() {}", "crates/a/src/foo/bar.rs")),
+            [(1, Kind::Test, "foo/bar/x".into())]
+        );
+        assert!(detect("fn main() {}", "src/lib.rs").is_empty());
+    }
+
+    #[test]
+    fn js_describe_chains() {
+        let src = [
+            "describe('math', () => {",
+            "  it('adds', () => {});",
+            "  describe(\"nested\", () => {",
+            "    test.each([[1]])('n=%i', () => {});",
+            "  });",
+            "  test.skip(`subs`, () => {});",
+            "});",
+            "const item = items.find((x) => x);",
+            "test('top', () => {});",
+        ]
+        .join("\n");
+        let ts = detect(&src, "src/math.test.ts");
+        assert_eq!(
+            pick(&ts),
+            [
+                (0, Kind::Suite, "math".into()),
+                (1, Kind::Test, "math/adds".into()),
+                (2, Kind::Suite, "math/nested".into()),
+                (3, Kind::Test, "math/nested/n=%i".into()),
+                (5, Kind::Test, "math/subs".into()),
+                (8, Kind::Test, "top".into()),
+            ]
+        );
+        assert_eq!(js_name_pattern(&ts[1]), "^math adds$");
+        assert_eq!(js_name_pattern(&ts[3]), "^math nested n=.*$");
+        assert_eq!(js_name_pattern(&ts[0]), "^math");
+        assert!(detect("test('x', () => {})", "src/math.ts").is_empty());
+    }
+
+    #[test]
+    fn python_and_go() {
+        let src = "class TestCalc:\n    def test_add(self):\n        pass\ndef test_top():\n    pass\nclass Helper:\n    def test_no(self):\n        pass\nif __name__ == '__main__':\n    main()\n";
+        assert_eq!(
+            pick(&detect(src, "tests/test_calc.py")),
+            [
+                (0, Kind::Suite, "TestCalc".into()),
+                (1, Kind::Test, "TestCalc/test_add".into()),
+                (3, Kind::Test, "test_top".into()),
+                (8, Kind::Main, String::new()),
+            ]
+        );
+        let go = "package calc\n\nfunc TestAdd(t *testing.T) {\n\tt.Run(\"zero case\", func(t *testing.T) {})\n}\n";
+        assert_eq!(
+            pick(&detect(go, "calc_test.go")),
+            [(2, Kind::Test, "TestAdd".into()), (3, Kind::Test, "TestAdd/zero_case".into())]
+        );
+    }
+
+    #[test]
+    fn narrows_cargo_test_configs() {
+        let root = Path::new("/p");
+        let mut test = blank("cargo:test".into(), "test", "cargo", "cargo".into(), vec!["test".into()]);
+        test.is_test = true;
+        let configs = vec![test];
+        let src = "#[cfg(test)]\nmod tests {\n    #[test]\n    fn adds() {}\n}\n";
+        let ts = detect(src, "src/math.rs");
+        let c = target_config(root, &ts[1], "src/math.rs", &configs, src).unwrap();
+        assert_eq!(c.args, ["test", "--", "math::tests::adds", "--exact"]);
+        let c = target_config(root, &ts[0], "src/math.rs", &configs, src).unwrap();
+        assert_eq!(c.args, ["test", "--", "math::tests::"]);
+    }
+
+    #[test]
+    fn cargo_test_args_get_one_separator() {
+        let root = Path::new("/p");
+        let mut test =
+            blank("cargo:test".into(), "test", "cargo", "cargo".into(), vec!["test".into(), "--".into(), "-q".into()]);
+        test.is_test = true;
+        let configs = vec![test];
+        let src = "#[test]\nfn adds() {}\n";
+        let ts = detect(src, "tests/math.rs");
+        let c = target_config(root, &ts[0], "tests/math.rs", &configs, src).unwrap();
+        assert_eq!(c.args, ["test", "--test", "math", "--", "-q", "adds", "--exact"]);
+    }
+
+    #[test]
+    fn a_line_in_a_body_picks_the_enclosing_target() {
+        let names = |src: &str, rel: &str, line: usize| -> Vec<String> {
+            enclosing(src, rel, line).iter().map(|t| t.path.join("/")).collect()
+        };
+        let rust = [
+            "#[cfg(test)]",
+            "mod tests {",
+            "    #[test]",
+            "    fn adds(",
+            "        x: u8,",
+            "    ) {",
+            "        let s = \"}\";",
+            "        assert!(true);",
+            "    }",
+            "",
+            "    fn helper() {}",
+            "}",
+        ]
+        .join("\n");
+        assert_eq!(names(&rust, "src/math.rs", 7), ["math/tests/adds", "math/tests"]);
+        assert_eq!(names(&rust, "src/math.rs", 4), ["math/tests/adds", "math/tests"]);
+        assert_eq!(names(&rust, "src/math.rs", 10), ["math/tests"]);
+
+        let js = "describe('math', () => {\n  it('adds', () => {\n    expect(1).toBe(1);\n  });\n  it('one', fn);\n  const x = 1;\n});\n";
+        assert_eq!(names(js, "src/math.test.ts", 2), ["math/adds", "math"]);
+        assert_eq!(names(js, "src/math.test.ts", 5), ["math"]);
+
+        let py = "class TestCalc:\n    def test_add(self):\n        x = 1\n\n        assert x\n    def helper(self):\n        pass\n";
+        assert_eq!(names(py, "tests/test_calc.py", 4), ["TestCalc/test_add", "TestCalc"]);
+        assert_eq!(names(py, "tests/test_calc.py", 6), ["TestCalc"]);
+
+        let go = "package calc\n\nfunc TestAdd(t *testing.T) {\n\tt.Run(\"zero\", func(t *testing.T) {\n\t\tx := 0\n\t})\n\ty := 1\n}\n";
+        assert_eq!(names(go, "calc_test.go", 4), ["TestAdd/zero", "TestAdd"]);
+        assert_eq!(names(go, "calc_test.go", 6), ["TestAdd"]);
+        assert!(names(go, "calc_test.go", 0).is_empty());
+    }
+}

crates/ide-host/src/mcp/search.rs

@@ -0,0 +1,901 @@
+// Ported from JetBrains intellij-community plugins/mcp-server (mcpserver.toolsets/src/general/SearchToolset.kt,
+// SearchSymbolSupport.kt), Apache-2.0.
+//! Text, regex, file and symbol search.
+//!
+//! Coordinates are 1-based, end exclusive; columns count UTF-16 code units like
+//! the editor (one per character except emoji and other astral characters).
+
+use crate::mcp::tool::{Call, Output, Param, ParamType, Tool};
+use crate::mcp::util::{INDEXING_PARTIAL_RESULT_REASON, MEDIUM_TIMEOUT};
+use crate::ops::search::SearchEvent;
+use globset::{GlobBuilder, GlobSet, GlobSetBuilder};
+use ide_core::{CancellationToken, IdeError, IdeResult, Location, Range};
+use ide_search::{FileMask, FileMatches, SearchQuery, SearchScope, SearchSummary};
+use ide_vfs::EntryKind;
+use parking_lot::Mutex;
+use serde::Serialize;
+use serde_json::{Value, json};
+use std::cell::Cell;
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+use std::time::{Duration, Instant};
+
+pub const MAX_RESULTS_UPPER_BOUND: usize = 5000;
+const DEFAULT_LIMIT: i64 = 1000;
+pub const SYMBOL_SEARCH_DEFAULT_LIMIT: i64 = 50;
+pub const SEARCH_TIMEOUT_PARTIAL_RESULT_REASON: &str =
+    "The search timed out after 10 s. Narrow the query or pass paths.";
+/// Symbols requested from the index per result when `paths` filters them afterwards.
+const SYMBOL_POOL_FACTOR: usize = 20;
+const MAX_SYMBOL_POOL: usize = 20_000;
+/// Matches Find in Files may report, per result asked for, when `paths` are filtered afterwards.
+const UNMASKED_MATCH_FACTOR: usize = 20;
+const MIN_UNMASKED_MATCHES: usize = 10_000;
+/// UTF-16 units of a line Find in Files reports (`ide_search`'s line window); matches
+/// outside the window of a longer line are left out.
+const LINE_WINDOW: usize = 500;
+
+const PATHS_DESCRIPTION: &str = "Optional list of project-relative glob patterns to filter results. Supports '!' \
+excludes. Trailing '/' expands to '**'. Patterns without '/' are treated as '**/pattern'. Empty strings are ignored.";
+const LIMIT_DESCRIPTION: &str = "Maximum number of results to return";
+
+pub fn tools() -> Vec<Tool> {
+    vec![search_text(), search_regex(), search_symbol(), search_file()]
+}
+
+fn search_text() -> Tool {
+    Tool::new(
+        "search_text",
+        "Searches for a text substring within project files.
+Use this tool for fast text search with match coordinates.
+Results include match coordinates when available (1-based line/column, end exclusive).
+
+Paths are glob patterns relative to the project root.
+Examples: [\"src/**\", \"!**/test/**\"], [\"**/*.kt\"], [\"foo/\"].",
+        |call| async move { text_search(call, false).await },
+    )
+    .param(Param::required("q", ParamType::String, "Text to search for"))
+    .param(Param::optional("paths", ParamType::StringList, PATHS_DESCRIPTION))
+    .param(Param::optional("limit", ParamType::Integer, LIMIT_DESCRIPTION))
+    .output(result_schema())
+}
+
+fn search_regex() -> Tool {
+    Tool::new(
+        "search_regex",
+        "Searches for regex matches within project files.
+Use this tool when you need regex search with match coordinates.
+Results include match coordinates when available (1-based line/column, end exclusive).
+The pattern uses Rust regex syntax and is case-sensitive; prefix `(?i)` to ignore case.
+
+Paths are glob patterns relative to the project root.
+Examples: [\"src/**\", \"!**/test/**\"], [\"**/*.kt\"], [\"foo/\"].",
+        |call| async move { text_search(call, true).await },
+    )
+    .param(Param::required("q", ParamType::String, "Regex pattern to search for"))
+    .param(Param::optional("paths", ParamType::StringList, PATHS_DESCRIPTION))
+    .param(Param::optional("limit", ParamType::Integer, LIMIT_DESCRIPTION))
+    .output(result_schema())
+}
+
+fn search_symbol() -> Tool {
+    Tool::new(
+        "search_symbol",
+        "Searches for symbols (classes, methods, fields).
+Use this tool for semantic lookup by identifier fragments.
+Results include match coordinates when available (1-based line/column, end exclusive).
+
+Paths are glob patterns relative to the project root.
+By default this searches project symbols only.
+If you don't find a suitable result, try again with include_external=true to search SDK and library symbols too.",
+        |call| async move { symbol_search(call).await },
+    )
+    .param(Param::required("q", ParamType::String, "Symbol query text"))
+    .param(Param::optional("paths", ParamType::StringList, PATHS_DESCRIPTION))
+    .param(Param::optional(
+        "include_external",
+        ParamType::Boolean,
+        "Whether to include SDK and library symbols. Disabled by default; if nothing suitable is found, try again \
+with include_external=true.",
+    ))
+    .param(Param::optional("limit", ParamType::Integer, LIMIT_DESCRIPTION))
+    .output(result_schema())
+}
+
+fn search_file() -> Tool {
+    Tool::new(
+        "search_file",
+        "Searches for files by glob pattern within the project.
+Use this tool when you need to match file paths using glob syntax.
+
+Glob patterns are relative to the project root.
+Examples: \"**/*.kt\", \"src/**/Foo*.java\", \"build.gradle.kts\".
+Patterns without '/' are treated as \"**/pattern\".
+Paths are optional additional glob filters relative to the project root.",
+        |call| async move { file_search(call).await },
+    )
+    .param(Param::required("q", ParamType::String, "Glob pattern to search for"))
+    .param(Param::optional("paths", ParamType::StringList, PATHS_DESCRIPTION))
+    .param(Param::optional(
+        "includeExcluded",
+        ParamType::Boolean,
+        "Whether to include excluded/ignored files in results",
+    ))
+    .param(Param::optional("limit", ParamType::Integer, LIMIT_DESCRIPTION))
+    .output(result_schema())
+}
+
+// --- results -------------------------------------------------------------------
+
+/// One hit. Every search tool returns these, so they share one schema: `search_file`
+/// fills only `filePath`, only `search_symbol` fills `name` and `container`.
+#[derive(Serialize, Debug, Default, Clone, PartialEq)]
+#[serde(rename_all = "camelCase")]
+struct SearchItem {
+    file_path: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    start_line: Option<u32>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    start_column: Option<u32>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    end_line: Option<u32>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    end_column: Option<u32>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    name: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    container: Option<String>,
+}
+
+impl SearchItem {
+    fn at(file_path: String, r: Range) -> Self {
+        Self {
+            file_path,
+            start_line: Some(r.start.line + 1),
+            start_column: Some(r.start.col + 1),
+            end_line: Some(r.end.line + 1),
+            end_column: Some(r.end.col + 1),
+            ..Default::default()
+        }
+    }
+}
+
+/// Empty fields are left out, so a search without hits is `{}`.
+#[derive(Serialize, Default)]
+#[serde(rename_all = "camelCase")]
+struct SearchResult {
+    #[serde(skip_serializing_if = "Vec::is_empty")]
+    items: Vec<SearchItem>,
+    #[serde(skip_serializing_if = "std::ops::Not::not")]
+    more: bool,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    partial_result_reason: Option<&'static str>,
+}
+
+fn result_schema() -> Value {
+    let int = json!({ "type": "integer" });
+    let string = json!({ "type": "string" });
+    json!({
+        "type": "object",
+        "properties": {
+            "items": { "type": "array", "items": {
+                "type": "object",
+                "properties": {
+                    "filePath": string, "startLine": int, "startColumn": int, "endLine": int, "endColumn": int,
+                    "name": string, "container": string,
+                },
+                "required": ["filePath"],
+            } },
+            "more": { "type": "boolean" },
+            "partialResultReason": string,
+        },
+    })
+}
+
+fn limit(call: &Call, default: i64) -> IdeResult<usize> {
+    match call.opt_i64("limit")?.unwrap_or(default) {
+        n if n <= 0 => Err(IdeError::invalid("limit must be > 0")),
+        n => Ok((n as usize).min(MAX_RESULTS_UPPER_BOUND)),
+    }
+}
+
+fn query(call: &Call, empty: &str) -> IdeResult<String> {
+    let q = call.str("q")?;
+    if q.trim().is_empty() {
+        return Err(IdeError::invalid(empty));
+    }
+    Ok(q)
+}
+
+// --- path globs ----------------------------------------------------------------
+
+/// The `paths` argument: project-relative globs, `!` excludes.
+struct PathScope {
+    /// `None` when only excludes were given (everything is included).
+    include: Option<GlobSet>,
+    exclude: GlobSet,
+    /// The globs as `FileMask` masks for Find in Files (`{a,b}` expanded, as masks
+    /// split on commas), `None` when they cannot be expressed.
+    masks: Option<(Vec<String>, Vec<String>)>,
+}
+
+impl PathScope {
+    fn new(root: &Path, patterns: &[String]) -> IdeResult<Self> {
+        let (mut include, mut exclude) = (GlobSetBuilder::new(), GlobSetBuilder::new());
+        let (mut include_masks, mut exclude_masks) = (Vec::new(), Vec::new());
+        let mut has_include = false;
+        let mut maskable = true;
+        for raw in patterns {
+            let raw = raw.trim();
+            if raw.is_empty() {
+                continue;
+            }
+            let (negated, pattern) = match raw.strip_prefix('!') {
+                Some(rest) if rest.trim().is_empty() => return Err(IdeError::invalid("Exclude pattern is empty")),
+                Some(rest) => (true, rest.trim()),
+                None => (false, raw),
+            };
+            let mut glob = normalize_glob(pattern, root)?;
+            // A path naming an existing directory covers the files below it.
+            if index_of_glob_char(&glob).is_none() && root.join(&glob).is_dir() {
+                glob.push_str("/**");
+            }
+            let alternatives = expand_braces(&glob);
+            maskable &= alternatives.is_some();
+            let (set, masks) =
+                if negated { (&mut exclude, &mut exclude_masks) } else { (&mut include, &mut include_masks) };
+            set.add(build_glob(&glob)?);
+            masks.extend(alternatives.into_iter().flatten());
+            has_include |= !negated;
+        }
+        let build = |b: GlobSetBuilder| b.build().map_err(|e| IdeError::invalid(format!("Invalid glob pattern: {e}")));
+        Ok(Self {
+            include: if has_include { Some(build(include)?) } else { None },
+            exclude: build(exclude)?,
+            masks: maskable.then_some((include_masks, exclude_masks)),
+        })
+    }
+
+    fn is_all(&self) -> bool {
+        self.include.is_none() && self.exclude.is_empty()
+    }
+
+    /// `path` is project-relative with `/` (absolute outside the project).
+    fn matches(&self, path: &str) -> bool {
+        self.include.as_ref().is_none_or(|s| s.is_match(path)) && !self.exclude.is_match(path)
+    }
+}
+
+/// A glob as a project-relative pattern: `\` → `/`, leading `./` dropped, `dir/` → `dir/**`,
+/// `name` → `**/name`, and its leading directories (`..`, absolute paths) resolved against
+/// `root`. Errors when that points outside the project.
+fn normalize_glob(raw: &str, root: &Path) -> IdeResult<String> {
+    let mut value = raw.trim().replace('\\', "/");
+    if value.is_empty() {
+        return Err(IdeError::invalid("Glob pattern is empty"));
+    }
+    while let Some(rest) = value.strip_prefix("./") {
+        value = rest.to_owned();
+    }
+    if value.ends_with('/') {
+        let dir = value.trim_end_matches('/');
+        value = if dir.is_empty() { "**".into() } else { format!("{dir}/**") };
+    }
+    if !value.contains('/') {
+        value = format!("**/{value}");
+    }
+    let value = normalize_path_pattern(&value, root)?;
+    if value.is_empty() {
+        return Err(IdeError::invalid(format!("Invalid glob pattern: {raw}")));
+    }
+    Ok(value)
+}
+
+/// Resolves the whole directory segments before the first glob character against `root`.
+/// (JetBrains resolves up to the glob character itself, turning `src/Foo*.java` into
+/// `src/Foo/*.java`; only whole segments are resolved here.)
+fn normalize_path_pattern(pattern: &str, root: &Path) -> IdeResult<String> {
+    let outside = || {
+        IdeError::invalid(format!("Specified path '{pattern}' points to the location outside of the project directory"))
+    };
+    let prefix_len = match index_of_glob_char(pattern) {
+        None => pattern.len(),
+        Some(i) => pattern[..i].rfind('/').map_or(0, |slash| slash + 1),
+    };
+    let prefix = pattern[..prefix_len].trim_end_matches('/');
+    if prefix.is_empty() {
+        if is_absolute_pattern(pattern) {
+            return Err(outside());
+        }
+        return Ok(pattern.to_owned());
+    }
+    let prefix_path = Path::new(prefix);
+    let absolute = crate::mcp::tool::normalize(&if prefix_path.is_absolute() {
+        prefix_path.to_path_buf()
+    } else {
+        root.join(prefix_path)
+    });
+    let relative = relative_to_root(root, &absolute).ok_or_else(outside)?;
+    let suffix = pattern[prefix_len..].trim_start_matches('/');
+    Ok(match (relative.is_empty(), suffix.is_empty()) {
+        (true, _) => suffix.to_owned(),
+        (false, true) => relative,
+        (false, false) => format!("{relative}/{suffix}"),
+    })
+}
+
+/// `path` relative to `root` with `/`, also when one of them is spelled through a symlink
+/// (`/var` and `/private/var`); `None` outside `root`.
+fn relative_to_root(root: &Path, path: &Path) -> Option<String> {
+    let rel = match path.strip_prefix(root) {
+        Ok(rel) => rel.to_path_buf(),
+        Err(_) => {
+            let canon_root = dunce::canonicalize(root).ok()?;
+            let existing = path.ancestors().find(|a| a.exists())?;
+            let real = dunce::canonicalize(existing).ok()?.join(path.strip_prefix(existing).ok()?);
+            real.strip_prefix(&canon_root).ok()?.to_path_buf()
+        }
+    };
+    Some(rel.to_string_lossy().replace('\\', "/"))
+}
+
+fn is_absolute_pattern(pattern: &str) -> bool {
+    let b = pattern.as_bytes();
+    pattern.starts_with('/') || (b.len() >= 3 && b[1] == b':' && b[2] == b'/')
+}
+
+fn index_of_glob_char(pattern: &str) -> Option<usize> {
+    pattern.find(['*', '?', '[', ']', '{', '}'])
+}
+
+/// At most this many masks per glob from expanding its `{a,b}` groups.
+const MAX_BRACE_ALTERNATIVES: usize = 64;
+
+/// `glob` with its `{a,b}` groups expanded into separate globs without commas, for
+/// `FileMask` (which splits on them). `None` for nested groups, braces or commas in a
+/// character class, a comma outside a group, an unbalanced brace, or too many results.
+fn expand_braces(glob: &str) -> Option<Vec<String>> {
+    let mut out = vec![String::new()];
+    let mut chars = glob.chars();
+    let mut in_class = false;
+    while let Some(c) = chars.next() {
+        match c {
+            '{' | '}' | ',' if in_class => return None,
+            '[' => {
+                in_class = true;
+                out.iter_mut().for_each(|o| o.push(c));
+            }
+            ']' => {
+                in_class = false;
+                out.iter_mut().for_each(|o| o.push(c));
+            }
+            '{' => {
+                let mut group = String::new();
+                loop {
+                    match chars.next()? {
+                        '}' => break,
+                        '{' | '[' | ']' => return None,
+                        g => group.push(g),
+                    }
+                }
+                let options: Vec<&str> = group.split(',').collect();
+                if out.len() * options.len() > MAX_BRACE_ALTERNATIVES {
+                    return None;
+                }
+                out = out.iter().flat_map(|o| options.iter().map(move |a| format!("{o}{a}"))).collect();
+            }
+            '}' | ',' => return None,
+            _ => out.iter_mut().for_each(|o| o.push(c)),
+        }
+    }
+    (!in_class).then_some(out)
+}
+
+/// `**/` matches zero or more directories; case follows the file system (insensitive on
+/// macOS and Windows, like Find in Files' masks).
+fn build_glob(glob: &str) -> IdeResult<globset::Glob> {
+    GlobBuilder::new(glob)
+        .literal_separator(true)
+        .backslash_escape(false)
+        .case_insensitive(cfg!(any(target_os = "macos", target_os = "windows")))
+        .build()
+        .map_err(|_| IdeError::invalid(format!("Invalid glob pattern: {glob}")))
+}
+
+// --- text / regex --------------------------------------------------------------
+
+/// A match before it becomes a [`SearchItem`]; 1-based, end exclusive.
+struct TextHit {
+    file_path: String,
+    line: u32,
+    column: u32,
+    end_line: u32,
+    end_column: u32,
+}
+
+async fn text_search(call: Call, is_regex: bool) -> IdeResult<Output> {
+    let pattern = query(&call, if is_regex { "Regex pattern is empty" } else { "Search text is empty" })?;
+    let limit = limit(&call, DEFAULT_LIMIT)?;
+    let scope = PathScope::new(call.root(), &call.str_list("paths")?)?;
+    // Globs Find in Files cannot take are applied afterwards, so the engine must not
+    // stop at `limit` matches the filter may drop.
+    let (masks, max_matches) = match scope.masks.clone() {
+        // One more than asked tells whether there are more.
+        Some(masks) => (masks, (limit + 1) as u32),
+        // Bounded all the same (as the symbol pool): past it the result reports `more`.
+        None => {
+            let budget = ((limit + 1) * UNMASKED_MATCH_FACTOR).max(MIN_UNMASKED_MATCHES);
+            (Default::default(), u32::try_from(budget).unwrap_or(u32::MAX))
+        }
+    };
+    let (include, exclude) = masks;
+    let query = SearchQuery {
+        pattern: pattern.clone(),
+        is_regex,
+        case_sensitive: true,
+        whole_word: false,
+        include,
+        exclude,
+        scope: SearchScope::Project,
+        max_matches,
+        context: Default::default(),
+    };
+    if is_regex && let Err(e) = ide_search::match_ranges("", &query) {
+        return Err(IdeError::invalid(format!("Invalid regex pattern: {pattern} ({})", e.message)));
+    }
+    let (files, summary, timed_out) = run_search(&call, query.clone()).await?;
+    // Content roots outside the project are reported by absolute path.
+    let mut files: Vec<(String, FileMatches)> =
+        files.into_iter().map(|f| (call.display(&f.path.0), f)).filter(|(path, _)| scope.matches(path)).collect();
+    files.sort_by(|a, b| a.0.cmp(&b.0));
+    // Only these can match a line break.
+    let may_span = is_regex || pattern.contains('\n');
+    let mut hits = Vec::new();
+    let mut spanning = Vec::new();
+    let host = call.host();
+    for (path, file) in &files {
+        if hits.len() > limit {
+            break;
+        }
+        // Find in Files keeps a window of very long lines and drops the matches outside it:
+        // such lines are matched again in the file's whole text.
+        let long = |m: &ide_search::LineMatch| m.text_offset > 0 || m.text.encode_utf16().count() + 1 >= LINE_WINDOW;
+        let whole = if file.matches.iter().any(long) {
+            crate::ops::fs::read_text(&host, call.window(), file.path.0.clone())
+                .await
+                .ok()
+                .and_then(|text| Some((ide_search::match_ranges(&text, &query).ok()?, text)))
+        } else {
+            None
+        };
+        for m in &file.matches {
+            if let Some((ranges, text)) = &whole
+                && long(m)
+            {
+                hits.extend(line_hits(path, text, ranges, m.line));
+                continue;
+            }
+            let line_end = m.text_offset + m.text.encode_utf16().count() as u32;
+            for &(a, b) in &m.ranges {
+                let (a, b) = (m.text_offset + a, m.text_offset + b);
+                if may_span && b == line_end && hits.len() < limit {
+                    spanning.push((hits.len(), file.path.0.clone()));
+                }
+                hits.push(TextHit {
+                    file_path: path.clone(),
+                    line: m.line + 1,
+                    column: a + 1,
+                    end_line: m.line + 1,
+                    end_column: b + 1,
+                });
+            }
+        }
+    }
+    let more = hits.len() > limit || summary.limit_hit || timed_out;
+    hits.truncate(limit);
+    extend_spanning(&call, &query, &mut hits, spanning).await;
+    let items = hits
+        .into_iter()
+        .map(|h| SearchItem {
+            file_path: h.file_path,
+            start_line: Some(h.line),
+            start_column: Some(h.column),
+            end_line: Some(h.end_line),
+            end_column: Some(h.end_column),
+            ..Default::default()
+        })
+        .collect();
+    let partial_result_reason = timed_out.then_some(SEARCH_TIMEOUT_PARTIAL_RESULT_REASON);
+    Output::json(SearchResult { items, more, partial_result_reason })
+}
+
+/// The matches of `ranges` (byte ranges in `text`) that start on 0-based `line`, with their
+/// real end (on a later line for a match spanning lines).
+fn line_hits(path: &str, text: &str, ranges: &[(usize, usize)], line: u32) -> Vec<TextHit> {
+    let starts: Vec<usize> = std::iter::once(0).chain(text.match_indices('\n').map(|(i, _)| i + 1)).collect();
+    let Some(&line_start) = starts.get(line as usize) else { return Vec::new() };
+    let line_end = starts.get(line as usize + 1).map_or(text.len(), |s| s - 1);
+    let column = |at: usize| -> (u32, u32) {
+        let l = starts.partition_point(|&s| s <= at) - 1;
+        (l as u32 + 1, text[starts[l]..at].encode_utf16().count() as u32 + 1)
+    };
+    let first = ranges.partition_point(|r| r.0 < line_start);
+    ranges[first..]
+        .iter()
+        .take_while(|r| r.0 <= line_end)
+        .map(|&(a, b)| {
+            let (end_line, end_column) = column(b);
+            TextHit { file_path: path.to_owned(), line: line + 1, column: column(a).1, end_line, end_column }
+        })
+        .collect()
+}
+
+/// A file's path, text, line start offsets and match byte ranges.
+type FileText = (PathBuf, String, Vec<usize>, Vec<(usize, usize)>);
+
+/// Find in Files reports only the first line of a match that spans lines: matches
+/// ending at a line end get their real end from matching the file's text again.
+async fn extend_spanning(call: &Call, query: &SearchQuery, hits: &mut [TextHit], spanning: Vec<(usize, PathBuf)>) {
+    let host = call.host();
+    let mut current: Option<FileText> = None;
+    for (i, path) in spanning {
+        if current.as_ref().is_none_or(|(p, ..)| p != &path) {
+            let Ok(text) = crate::ops::fs::read_text(&host, call.window(), path.clone()).await else { continue };
+            let Ok(ranges) = ide_search::match_ranges(&text, query) else { continue };
+            let starts = std::iter::once(0).chain(text.match_indices('\n').map(|(i, _)| i + 1)).collect();
+            current = Some((path, text, starts, ranges));
+        }
+        let Some((_, text, starts, ranges)) = &current else { continue };
+        let h = &mut hits[i];
+        let Some(&line_start) = starts.get(h.line as usize - 1) else { continue };
+        let Some(start) = byte_at(&text[line_start..], h.column - 1).map(|b| line_start + b) else { continue };
+        let Ok(found) = ranges.binary_search_by_key(&start, |r| r.0) else { continue };
+        let end = ranges[found].1;
+        let end_line = starts.partition_point(|&s| s <= end) - 1;
+        h.end_line = end_line as u32 + 1;
+        h.end_column = text[starts[end_line]..end].encode_utf16().count() as u32 + 1;
+    }
+}
+
+/// The byte offset of UTF-16 column `col` in `line`.
+fn byte_at(line: &str, col: u32) -> Option<usize> {
+    let mut units = 0;
+    for (i, c) in line.char_indices() {
+        if units == col {
+            return Some(i);
+        }
+        units += c.len_utf16() as u32;
+    }
+    (units == col).then_some(line.len())
+}
+
+/// Runs Find in Files for at most [`MEDIUM_TIMEOUT`], cancelling it when the call is
+/// cancelled. Returns what was found and whether the time ran out.
+async fn run_search(call: &Call, query: SearchQuery) -> IdeResult<(Vec<FileMatches>, SearchSummary, bool)> {
+    let host = call.host();
+    let request = crate::mcp::tool::request_id();
+    let files = Arc::new(Mutex::new(Vec::new()));
+    let done = Arc::new(Mutex::new(None));
+    let emit: crate::ops::Emit<SearchEvent> = {
+        let (files, done) = (files.clone(), done.clone());
+        Arc::new(move |event| match event {
+            SearchEvent::File { file } => files.lock().push(file),
+            SearchEvent::Done { summary } => *done.lock() = Some(summary),
+        })
+    };
+    let search = crate::ops::search::start(&host, call.window(), request, query, emit);
+    tokio::pin!(search);
+    let mut timed_out = false;
+    tokio::select! {
+        r = &mut search => r?,
+        _ = call.cancel.cancelled() => {
+            host.cancel_request(request);
+            let _ = search.await;
+            return Err(IdeError::cancelled());
+        }
+        _ = tokio::time::sleep(MEDIUM_TIMEOUT) => {
+            host.cancel_request(request);
+            let _ = search.await;
+            timed_out = true;
+        }
+    }
+    let summary = done.lock().take().unwrap_or_default();
+    if summary.cancelled && !timed_out {
+        return Err(IdeError::cancelled());
+    }
+    let files = std::mem::take(&mut *files.lock());
+    Ok((files, summary, timed_out))
+}
+
+// --- files ---------------------------------------------------------------------
+
+async fn file_search(call: Call) -> IdeResult<Output> {
+    let q = query(&call, "Glob pattern is empty")?;
+    let limit = limit(&call, DEFAULT_LIMIT)?;
+    let scope = PathScope::new(call.root(), &call.str_list("paths")?)?;
+    let include_excluded = call.flag("includeExcluded", false)?;
+    let glob = GlobSetBuilder::new()
+        .add(build_glob(&normalize_glob(&q, call.root())?)?)
+        .build()
+        .map_err(|_| IdeError::invalid(format!("Invalid glob pattern: {q}")))?;
+    // Ignored names and "Exclude files" patterns, which `read_dir` does not flag.
+    let excludes = if include_excluded { None } else { Some(FileMask::new(&[], &call.project().search_excludes())?) };
+    let root = call.root().to_path_buf();
+    // The project folder and the content roots outside it.
+    let roots: Vec<PathBuf> = std::iter::once(root.clone())
+        .chain(call.project().content_roots().into_iter().filter(|r| relative_to_root(&root, r).is_none()))
+        .collect();
+    let host = call.host();
+    let walk = Walk {
+        host: host.clone(),
+        window: call.window().to_owned(),
+        root,
+        include_excluded,
+        excludes,
+        glob,
+        scope,
+        limit,
+        cancel: call.cancel.clone(),
+        deadline: Instant::now() + MEDIUM_TIMEOUT,
+        timed_out: Cell::new(false),
+    };
+    let (paths, more, timed_out) = host
+        .blocking(move || {
+            let mut found = Vec::new();
+            let more = roots.iter().any(|base| walk.dir(base, base, &mut found));
+            if walk.cancel.is_cancelled() {
+                return Err(IdeError::cancelled());
+            }
+            Ok((found, more, walk.timed_out.get()))
+        })
+        .await?;
+    let items = paths.into_iter().map(|file_path| SearchItem { file_path, ..Default::default() }).collect();
+    let partial_result_reason = timed_out.then_some(SEARCH_TIMEOUT_PARTIAL_RESULT_REASON);
+    Output::json(SearchResult { items, more, partial_result_reason })
+}
+
+struct Walk {
+    host: Arc<crate::Host>,
+    window: String,
+    root: PathBuf,
+    include_excluded: bool,
+    excludes: Option<FileMask>,
+    glob: GlobSet,
+    scope: PathScope,
+    limit: usize,
+    cancel: CancellationToken,
+    deadline: Instant,
+    timed_out: Cell<bool>,
+}
+
+impl Walk {
+    /// Collects matching files under `dir` (inside the walked root `base`) depth first in
+    /// name order; true when it stopped early: more than `limit` match or the time ran out.
+    fn dir(&self, dir: &Path, base: &Path, found: &mut Vec<String>) -> bool {
+        let Ok(mut entries) = tokio::runtime::Handle::current().block_on(crate::ops::fs::read_dir(
+            &self.host,
+            &self.window,
+            dir.to_path_buf(),
+        )) else {
+            return false;
+        };
+        entries.sort_by(|a, b| a.name.cmp(&b.name));
+        for entry in entries {
+            if self.cancel.is_cancelled() {
+                return false;
+            }
+            if Instant::now() >= self.deadline {
+                self.timed_out.set(true);
+                return true;
+            }
+            if entry.name == ".git" || (!self.include_excluded && (entry.ignored || entry.excluded)) {
+                continue;
+            }
+            let Ok(in_base) = entry.path.strip_prefix(base) else { continue };
+            if self.excludes.as_ref().is_some_and(|m| !m.matches(&in_base.to_string_lossy().replace('\\', "/"))) {
+                continue;
+            }
+            match entry.kind {
+                // Symlinked directories are not followed (they may loop).
+                EntryKind::Dir => {
+                    if self.dir(&entry.path, base, found) {
+                        return true;
+                    }
+                }
+                EntryKind::File => {
+                    // Files of content roots outside the project go by absolute path.
+                    let path = relative_to_root(&self.root, &entry.path)
+                        .unwrap_or_else(|| entry.path.to_string_lossy().into_owned());
+                    if self.glob.is_match(&path) && self.scope.matches(&path) {
+                        if found.len() == self.limit {
+                            return true;
+                        }
+                        found.push(path);
+                    }
+                }
+                _ => {}
+            }
+        }
+        false
+    }
+}
+
+// --- symbols -------------------------------------------------------------------
+
+async fn symbol_search(call: Call) -> IdeResult<Output> {
+    let started = Instant::now();
+    let q = query(&call, "Search query is empty")?;
+    let limit = limit(&call, SYMBOL_SEARCH_DEFAULT_LIMIT)?;
+    let scope = PathScope::new(call.root(), &call.str_list("paths")?)?;
+    let external = call.flag("include_external", false)?;
+    let host = call.host();
+    let project = call.project().clone();
+    let indexing_before = project.index.status().indexing;
+    let pool = if scope.is_all() { limit + 1 } else { ((limit + 1) * SYMBOL_POOL_FACTOR).min(MAX_SYMBOL_POOL) };
+    let found = {
+        let (project, q) = (project.clone(), q.clone());
+        host.blocking(move || Ok(project.index.find_symbols(&q, ide_index::SymbolFilter::All, pool))).await?
+    };
+    let mut items: Vec<SearchItem> = found
+        .into_iter()
+        .filter(|s| scope.matches(&s.rel_path))
+        .map(|s| SearchItem {
+            name: Some(s.name),
+            container: s.container.filter(|c| !c.is_empty()),
+            ..SearchItem::at(s.rel_path, s.range)
+        })
+        .collect();
+    let mut timed_out = false;
+    if external && items.len() <= limit {
+        let budget = MEDIUM_TIMEOUT.saturating_sub(started.elapsed());
+        let (symbols, out_of_time) = workspace_symbols(&call, &q, budget).await;
+        timed_out = out_of_time;
+        for (name, container, location) in symbols {
+            let path = location.uri.clone().unwrap_or_else(|| call.display(&location.path));
+            // Project files obey `paths`; library symbols are what was asked for.
+            let inside = location.uri.is_none() && !Path::new(&path).is_absolute();
+            if inside && !scope.matches(&path) {
+                continue;
+            }
+            let item = SearchItem {
+                name: Some(name),
+                container: container.filter(|c| !c.is_empty()),
+                ..SearchItem::at(path, location.range)
+            };
+            if !items
+                .iter()
+                .any(|e| e.name == item.name && e.file_path == item.file_path && e.start_line == item.start_line)
+            {
+                items.push(item);
+            }
+            if items.len() > limit {
+                break;
+            }
+        }
+    }
+    let more = items.len() > limit || timed_out;
+    items.truncate(limit);
+    let indexing = indexing_before || project.index.status().indexing;
+    let partial_result_reason = if indexing {
+        Some(INDEXING_PARTIAL_RESULT_REASON)
+    } else {
+        timed_out.then_some(SEARCH_TIMEOUT_PARTIAL_RESULT_REASON)
+    };
+    Output::json(SearchResult { items, more, partial_result_reason })
+}
+
+/// The language servers' workspace symbols, and whether `budget` ran out first; empty
+/// when none runs or they fail.
+async fn workspace_symbols(call: &Call, q: &str, budget: Duration) -> (Vec<(String, Option<String>, Location)>, bool) {
+    let host = call.host();
+    let request = crate::mcp::tool::request_id();
+    let symbols = crate::ops::lsp::lsp_workspace_symbols(&host, call.window(), request, q.to_owned());
+    tokio::pin!(symbols);
+    let result = tokio::select! {
+        r = tokio::time::timeout(budget, &mut symbols) => r.ok(),
+        _ = call.cancel.cancelled() => None,
+    };
+    match result {
+        Some(Ok(symbols)) => (symbols.into_iter().map(|s| (s.name, s.container, s.location)).collect(), false),
+        Some(Err(e)) => {
+            tracing::debug!("MCP search_symbol: workspace symbols: {e}");
+            (Vec::new(), false)
+        }
+        None => {
+            host.cancel_request(request);
+            let _ = symbols.await;
+            (Vec::new(), !call.cancel.is_cancelled())
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn root() -> (tempfile::TempDir, PathBuf) {
+        let dir = tempfile::tempdir().unwrap();
+        let root = dunce::canonicalize(dir.path()).unwrap().join("project");
+        std::fs::create_dir_all(root.join("subdir1/nested")).unwrap();
+        (dir, root)
+    }
+
+    fn scope(root: &Path, p: &[&str]) -> PathScope {
+        PathScope::new(root, &p.iter().map(|s| s.to_string()).collect::<Vec<_>>()).unwrap()
+    }
+
+    #[test]
+    fn normalizes_globs() {
+        let (_dir, root) = root();
+        let n = |p: &str| normalize_glob(p, &root);
+        assert_eq!(n("*.rs").unwrap(), "**/*.rs");
+        assert_eq!(n("./foo/bar.txt").unwrap(), "foo/bar.txt");
+        assert_eq!(n("foo/").unwrap(), "foo/**");
+        assert_eq!(n("/").unwrap(), "**/**");
+        assert_eq!(n("./src/**/*.ts").unwrap(), "src/**/*.ts");
+        assert_eq!(n("src\\gen\\*.rs").unwrap(), "src/gen/*.rs");
+        assert_eq!(n("src/a/../Foo*.java").unwrap(), "src/Foo*.java");
+        assert_eq!(n(&root.join("sub/Foo.kt").to_string_lossy()).unwrap(), "sub/Foo.kt");
+        assert_eq!(n(&format!("{}/**/*.kt", root.display())).unwrap(), "**/*.kt");
+        for outside in ["../outside/**", "/elsewhere/*.rs", "/**"] {
+            let err = n(outside).unwrap_err().message;
+            assert!(err.contains("outside of the project directory"), "{outside}: {err}");
+        }
+        assert!(n("  ").unwrap_err().message.contains("Glob pattern is empty"));
+    }
+
+    #[test]
+    fn expands_brace_groups() {
+        let e = |g: &str| expand_braces(g);
+        assert_eq!(e("src/**/*.rs"), Some(vec!["src/**/*.rs".to_owned()]));
+        assert_eq!(e("src/**/*.{ts,tsx}"), Some(vec!["src/**/*.ts".to_owned(), "src/**/*.tsx".to_owned()]));
+        assert_eq!(e("{a,b}/*.{x,y}"), Some(["a/*.x", "a/*.y", "b/*.x", "b/*.y"].map(String::from).to_vec()));
+        assert_eq!(e("a{,.bak}"), Some(vec!["a".to_owned(), "a.bak".to_owned()]));
+        assert_eq!(e("[{]x"), None);
+        assert_eq!(e("{a,{b,c}}"), None);
+        assert_eq!(e("a,b"), None);
+        assert_eq!(e("{a,b"), None);
+        assert_eq!(e("a}"), None);
+        assert_eq!(e(&"{a,b}".repeat(7)), None);
+        assert_eq!(e(&"{a,b}".repeat(6)).map(|v| v.len()), Some(64));
+    }
+
+    #[test]
+    fn utf16_columns_to_bytes() {
+        assert_eq!(byte_at("a😀b", 0), Some(0));
+        assert_eq!(byte_at("a😀b", 3), Some(5));
+        assert_eq!(byte_at("a😀b", 4), Some(6));
+        assert_eq!(byte_at("a😀b", 2), None);
+        assert_eq!(byte_at("ab", 5), None);
+    }
+
+    #[test]
+    fn path_scopes() {
+        let (_dir, root) = root();
+        let root = root.as_path();
+        assert!(scope(root, &[]).is_all());
+        assert!(scope(root, &["", " "]).is_all());
+        let s = scope(root, &["subdir1/**", "!**/*.java"]);
+        assert!(s.matches("subdir1/foo.txt"));
+        assert!(!s.matches("subdir1/foo.java"));
+        assert!(!s.matches("subdir2/foo.txt"));
+        let s = scope(root, &["subdir1/**", "!subdir1/excluded/**"]);
+        assert!(s.matches("subdir1/foo.txt") && !s.matches("subdir1/excluded/foo.txt"));
+        // An existing directory covers the files below it; other names match files only.
+        let s = scope(root, &["subdir1/nested"]);
+        assert!(s.matches("subdir1/nested/foo.txt") && !s.matches("subdir1/other/foo.txt"));
+        let s = scope(root, &["!gen"]);
+        assert!(s.matches("src/gen/a.rs") && !s.matches("src/gen"));
+        let s = scope(root, &["*.rs"]);
+        assert!(s.matches("a.rs") && s.matches("x/y/a.rs") && !s.matches("a.ts"));
+        assert!(s.matches("/abs/content/root/a.rs"));
+        let s = scope(root, &["!*.md"]);
+        assert!(s.matches("a.rs") && !s.matches("docs/a.md"));
+        assert!(scope(root, &["*.{rs,ts}"]).masks.is_some());
+        assert!(scope(root, &["*.{rs,{ts,js}}"]).masks.is_none());
+        let err = |p: &str| PathScope::new(root, &[p.to_owned()]).err().unwrap().message;
+        assert!(err("a[").contains("Invalid glob pattern"));
+        assert!(err("!").contains("Exclude pattern is empty"));
+        assert!(err("../x/**").contains("outside of the project directory"));
+    }
+}

crates/ide-host/src/mcp/symbols.rs

@@ -0,0 +1,264 @@
+//! Quick Documentation through the project's language services.
+use super::tool::{Call, Output, Param, ParamType, Tool};
+use ide_core::{IdeError, IdeResult, Pos, Range};
+use ide_lsp::types::GotoKind;
+use serde::Serialize;
+use serde_json::json;
+use std::path::Path;
+
+pub fn get_symbol_info() -> Tool {
+    Tool::new("get_symbol_info", "Retrieves information about the symbol at the specified position in the specified file.
+Provides the same information as the Quick Documentation feature of the IDE does (the language server's hover).
+
+This tool is useful for getting information about the symbol at the specified position in the specified file.
+The information may include the symbol's name, signature, type, documentation, etc. It depends on a particular language.
+
+If the position has a reference to a symbol the tool will return a piece of code with the declaration of the symbol if possible.
+
+Use this tool to understand symbols declaration, semantics, where it's declared, etc.", get_info)
+    .param(Param::required("filePath", ParamType::String, "Path relative to the project root"))
+    .param(Param::required("line", ParamType::Integer, "1-based line number"))
+    .param(Param::required("column", ParamType::Integer, "1-based UTF-16 column number"))
+}
+
+async fn get_info(call: Call) -> IdeResult<Output> {
+    let path = call.resolve_readable(&call.str("filePath")?).await?;
+    let line = call.opt_i64("line")?.ok_or_else(|| IdeError::invalid("missing line"))?;
+    let col = call.opt_i64("column")?.ok_or_else(|| IdeError::invalid("missing column"))?;
+    let project = call.project.clone();
+    let p = path.clone();
+    struct Document(std::sync::Arc<crate::Project>, ide_core::DocId);
+    impl Drop for Document {
+        fn drop(&mut self) {
+            self.0.documents.close(self.1);
+        }
+    }
+    let (text, document) = call
+        .host
+        .blocking(move || {
+            let text = project.text_of(&p)?;
+            let doc = project.documents.open(&p)?;
+            Ok((text, Document(project, doc.id)))
+        })
+        .await?;
+    let doc = document.1;
+    if line < 1 || line > u32::MAX as i64 {
+        return Err(IdeError::invalid("line is out of bounds"));
+    }
+    let line_text = usize::try_from(line.saturating_sub(1))
+        .ok()
+        .and_then(|l| text.split('\n').nth(l))
+        .ok_or_else(|| IdeError::invalid("Line number is out of bounds of the document"))?;
+    if col < 1 || col as usize > line_text.encode_utf16().count() + 1 {
+        return Err(IdeError::invalid("Column number is out of bounds of the document"));
+    }
+    let pos = Pos::new((line - 1) as u32, (col - 1) as u32);
+    let word = word_at(line_text, char_column(line_text, col as u32));
+    let mut output = json!({"documentation":""});
+    let work = async {
+        let hover = call.project.lsp.hover(doc, pos, call.cancel.clone()).await;
+        let definitions = call.project.lsp.goto(doc, pos, GotoKind::Definition).await;
+        Ok::<_, IdeError>((hover, definitions))
+    };
+    let result = tokio::select! {
+        result = tokio::time::timeout(std::time::Duration::from_secs(20), work) => result,
+        _ = call.cancel.cancelled() => return Err(IdeError::cancelled()),
+    };
+    match result {
+        Ok(Ok((hover, definitions))) => {
+            if let Ok(Some(hover)) = hover {
+                output["documentation"] = hover.contents.value.into();
+            }
+            if let Ok(definitions) = definitions
+                && let Some(location) = definitions.iter().find(|l| l.uri.is_none())
+                && let Some(info) = symbol_info(&call, &location.path, word.clone(), location.range, 1)
+            {
+                output["symbolInfo"] = serde_json::to_value(info).map_err(|e| IdeError::internal(e.to_string()))?;
+            }
+        }
+        Ok(Err(e)) => {
+            output["partialResultReason"] = e.message.into();
+        }
+        Err(_) => {
+            output["partialResultReason"] = "The language server did not answer in time; retry later.".into();
+        }
+    }
+    if output.get("symbolInfo").is_none()
+        && let Some(word) = word
+    {
+        let project = call.project.clone();
+        let path = path.clone();
+        let found = call
+            .host
+            .blocking(move || {
+                let mut symbols = project.index.symbols_named(&word, None, 50);
+                symbols.sort_by_key(|s| s.path != path);
+                Ok(symbols.into_iter().next())
+            })
+            .await?;
+        if let Some(symbol) = found
+            && let Some(info) = symbol_info(&call, &symbol.path, Some(symbol.name), symbol.range, 1)
+        {
+            output["symbolInfo"] = serde_json::to_value(info).map_err(|e| IdeError::internal(e.to_string()))?;
+        }
+    }
+    if call.project.index.status().indexing {
+        output["partialResultReason"] = super::util::INDEXING_PARTIAL_RESULT_REASON.into();
+    }
+    Ok(Output::text(output.to_string()))
+}
+
+/// The 1-based character index of 1-based UTF-16 `column` in `line`.
+fn char_column(line: &str, column: u32) -> u32 {
+    let mut units = 0u32;
+    let mut chars = 0u32;
+    for c in line.chars() {
+        if units + 1 >= column {
+            break;
+        }
+        units += c.len_utf16() as u32;
+        chars += 1;
+    }
+    chars + 1
+}
+
+fn is_word(c: char) -> bool {
+    c.is_alphanumeric() || c == '_' || c == '$'
+}
+
+/// The identifier at (or just before) 1-based character `column` of `line`.
+fn word_at(line: &str, column: u32) -> Option<String> {
+    let chars: Vec<char> = line.chars().collect();
+    let mut at = (column as usize).saturating_sub(1).min(chars.len());
+    if !chars.get(at).is_some_and(|c| is_word(*c)) {
+        if at > 0 && is_word(chars[at - 1]) {
+            at -= 1;
+        } else {
+            return None;
+        }
+    }
+    let start = (0..=at).rev().take_while(|i| is_word(chars[*i])).last()?;
+    let end = (at..chars.len()).take_while(|i| is_word(chars[*i])).last()? + 1;
+    Some(chars[start..end].iter().collect())
+}
+
+/// Lines of comments and annotations above a declaration that count as part of it.
+const MAX_LEADING_LINES: usize = 30;
+
+/// JetBrains' `SymbolInfo`.
+#[derive(Serialize)]
+#[serde(rename_all = "camelCase")]
+struct SymbolInfo {
+    #[serde(skip_serializing_if = "Option::is_none")]
+    name: Option<String>,
+    declaration_text: String,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    declaration_file: Option<String>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    declaration_line: Option<u32>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    language: Option<String>,
+}
+
+/// JetBrains' `getElementSymbolInfo` over a declaration's name range: from the comments and
+/// annotations right above it to the line where the name ends, plus `extra_lines`.
+fn symbol_info(
+    call: &Call,
+    path: &Path,
+    name: Option<String>,
+    name_range: Range,
+    extra_lines: u32,
+) -> Option<SymbolInfo> {
+    let project = call.project();
+    let text = project.text_of(path).ok()?;
+    let text = text.replace("\r\n", "\n");
+    let lines: Vec<&str> = text.split('\n').collect();
+    let name_line = name_range.start.line as usize;
+    if name_line >= lines.len() {
+        return None;
+    }
+    let language = project.languages.detect(path, lines.first().copied());
+    let config = project.languages.get(&language);
+    let line_comment = config.as_ref().and_then(|c| c.line_comment.clone());
+    let mut start = name_line;
+    while start > 0
+        && name_line - start < MAX_LEADING_LINES
+        && leads_declaration(lines[start - 1], line_comment.as_deref())
+    {
+        start -= 1;
+    }
+    let end = (name_range.end.line.max(name_range.start.line) as usize + extra_lines as usize).min(lines.len() - 1);
+    Some(SymbolInfo {
+        name,
+        declaration_text: format!("<…>\n{}\n<…>", lines[start..=end].join("\n")),
+        declaration_file: Some(call.display(path)),
+        declaration_line: Some(name_line as u32 + 1),
+        language: config.map(|c| c.name),
+    })
+}
+
+/// Doc comments, comments and annotations / attributes / decorators belong to the declaration below.
+fn leads_declaration(line: &str, line_comment: Option<&str>) -> bool {
+    let t = line.trim_start();
+    if t.is_empty() {
+        return false;
+    }
+    ["//", "/*", "*", "#[", "#![", "@"].iter().any(|p| t.starts_with(p))
+        || line_comment.is_some_and(|c| !c.is_empty() && t.starts_with(c))
+}
+
+pub fn find_references() -> Tool {
+    Tool::new("find_references", "Find references using the language service and the IDE's project index. Positions are 1-based UTF-16. Reports incomplete results when analysis is still running.", |call| async move {
+        let path = call.resolve_readable(&call.str("filePath")?).await?;
+        let line = call.opt_i64("line")?.ok_or_else(|| IdeError::invalid("missing line"))?;
+        let column = call.opt_i64("column")?.ok_or_else(|| IdeError::invalid("missing column"))?;
+        let project = call.project.clone();
+        let (doc, text) = call.host.blocking(move || {
+            let text = project.text_of(&path)?;
+            let doc = project.documents.open(&path)?;
+            Ok((doc.id, text))
+        }).await?;
+        struct Close(std::sync::Arc<crate::Project>, ide_core::DocId);
+        impl Drop for Close { fn drop(&mut self) { self.0.documents.close(self.1); } }
+        let _close = Close(call.project.clone(), doc);
+        let pos = mcp_position(&text, line, column)?;
+        let request = super::tool::request_id();
+        let work = crate::ops::lsp::lsp_references(&call.host, &call.window, request, doc, pos, call.flag("includeDeclaration", true)?, true, false, crate::ops::Channel::new(|_| {}));
+        tokio::pin!(work);
+        let result = tokio::select! {
+            result = &mut work => result?,
+            _ = call.cancel.cancelled() => { call.host.cancel_request(request); let _ = work.await; return Err(IdeError::cancelled()); }
+            _ = tokio::time::sleep(std::time::Duration::from_secs(60)) => { call.host.cancel_request(request); let _ = work.await; return Err(IdeError::unavailable("references timed out; retry when analysis finishes")); }
+        };
+        let mut value = serde_json::to_value(&result).map_err(|e| IdeError::internal(e.to_string()))?;
+        // Convert every Location range at this boundary, including declarations.
+        fn positions(value: &mut serde_json::Value) {
+            match value {
+                serde_json::Value::Object(map) => {
+                    if let (Some(line), Some(col)) = (map.get("line").and_then(|v| v.as_u64()), map.get("col").and_then(|v| v.as_u64())) {
+                        map.insert("line".into(), (line + 1).into()); map.insert("col".into(), (col + 1).into());
+                    } else { for v in map.values_mut() { positions(v); } }
+                }
+                serde_json::Value::Array(items) => { for v in items { positions(v); } }
+                _ => {}
+            }
+        }
+        positions(&mut value);
+        Output::json(value)
+    })
+    .param(Param::required("filePath", ParamType::String, "Path relative to the project root"))
+    .param(Param::required("line", ParamType::Integer, "1-based line"))
+    .param(Param::required("column", ParamType::Integer, "1-based UTF-16 column"))
+    .param(Param::optional("includeDeclaration", ParamType::Boolean, "Include declarations (default true)"))
+}
+
+fn mcp_position(text: &str, line: i64, column: i64) -> IdeResult<Pos> {
+    if line < 1 || line > u32::MAX as i64 || column < 1 || column > u32::MAX as i64 {
+        return Err(IdeError::invalid("line and column must be positive 1-based positions"));
+    }
+    let row = text.split('\n').nth((line - 1) as usize).ok_or_else(|| IdeError::invalid("line is out of bounds"))?;
+    if column as usize > row.encode_utf16().count() + 1 {
+        return Err(IdeError::invalid("column is out of bounds"));
+    }
+    Ok(Pos::new((line - 1) as u32, (column - 1) as u32))
+}

crates/ide-host/src/mcp/tool.rs

@@ -0,0 +1,297 @@
+use crate::{Host, Project};
+use ide_core::{CancellationToken, IdeError, IdeResult};
+use serde::Serialize;
+use serde_json::{Value, json};
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+
+pub struct Call {
+    pub client: String,
+    pub tool: String,
+    pub host: Arc<Host>,
+    pub project: Arc<Project>,
+    pub window: String,
+    pub args: Value,
+    pub cancel: CancellationToken,
+}
+
+impl Call {
+    pub fn opt_str(&self, name: &str) -> IdeResult<Option<String>> {
+        self.args
+            .get(name)
+            .filter(|v| !v.is_null())
+            .map(|v| v.as_str().map(str::to_owned).ok_or_else(|| IdeError::invalid(format!("{name} must be a string"))))
+            .transpose()
+    }
+    pub fn str_map(&self, name: &str) -> IdeResult<Vec<(String, String)>> {
+        self.args
+            .get(name)
+            .and_then(Value::as_object)
+            .ok_or_else(|| IdeError::invalid(format!("{name} must be an object")))?
+            .iter()
+            .map(|(k, v)| {
+                v.as_str()
+                    .map(|v| (k.clone(), v.to_owned()))
+                    .ok_or_else(|| IdeError::invalid(format!("{name} must contain strings")))
+            })
+            .collect()
+    }
+    pub fn resolve_inside(&self, path: &str) -> IdeResult<PathBuf> {
+        resolve_inside(self.root(), path)
+    }
+    pub async fn resolve_writable(&self, path: &str) -> IdeResult<PathBuf> {
+        let path = self.resolve_inside(path)?;
+        self.check_writable(&path).await?;
+        Ok(path)
+    }
+    pub async fn check_writable(&self, path: &Path) -> IdeResult<()> {
+        self.project.require_trust()?;
+        ensure_inside(self.root(), path)
+    }
+    pub async fn ask(&self, request: ide_core::event::McpUiRequest) -> IdeResult<()> {
+        self.host.mcp_requests.ask(self, request).await
+    }
+    pub async fn confirm(&self, subject: &str, detail: Option<String>) -> IdeResult<()> {
+        self.ask(ide_core::event::McpUiRequest::Confirm {
+            client: self.client.clone(),
+            tool: self.tool.clone(),
+            subject: subject.into(),
+            project: self.root().to_string_lossy().into_owned(),
+            detail,
+        })
+        .await?;
+        self.project.require_trust()
+    }
+    pub fn host(&self) -> Arc<Host> {
+        self.host.clone()
+    }
+    pub fn project(&self) -> &Arc<Project> {
+        &self.project
+    }
+    pub fn root(&self) -> &Path {
+        &self.project.root
+    }
+    pub fn window(&self) -> &str {
+        &self.window
+    }
+    pub fn str(&self, name: &str) -> IdeResult<String> {
+        self.args
+            .get(name)
+            .and_then(Value::as_str)
+            .map(str::to_owned)
+            .ok_or_else(|| IdeError::invalid(format!("missing or invalid argument `{name}`")))
+    }
+    pub fn opt_i64(&self, name: &str) -> IdeResult<Option<i64>> {
+        self.args
+            .get(name)
+            .map(|v| v.as_i64().ok_or_else(|| IdeError::invalid(format!("{name} must be an integer"))))
+            .transpose()
+    }
+    pub fn flag(&self, name: &str, default: bool) -> IdeResult<bool> {
+        self.args
+            .get(name)
+            .map(|v| v.as_bool().ok_or_else(|| IdeError::invalid(format!("{name} must be a boolean"))))
+            .unwrap_or(Ok(default))
+    }
+    pub fn str_list(&self, name: &str) -> IdeResult<Vec<String>> {
+        match self.args.get(name) {
+            None => Ok(Vec::new()),
+            Some(Value::Array(values)) => values
+                .iter()
+                .map(|v| {
+                    v.as_str()
+                        .map(str::to_owned)
+                        .ok_or_else(|| IdeError::invalid(format!("{name} must contain strings")))
+                })
+                .collect(),
+            _ => Err(IdeError::invalid(format!("{name} must be an array"))),
+        }
+    }
+    pub fn display(&self, path: &Path) -> String {
+        path.strip_prefix(self.root()).unwrap_or(path).to_string_lossy().replace('\\', "/")
+    }
+    pub async fn resolve_readable(&self, path: &str) -> IdeResult<PathBuf> {
+        let root = self.root().to_path_buf();
+        let mut roots = self.project.content_roots();
+        roots.extend(self.host.mcp_reports.libraries(&self.host.mcp_windows(self.root())));
+        roots.extend(
+            self.project
+                .settings
+                .effective()
+                .project_structure
+                .libraries
+                .iter()
+                .flat_map(|l| l.sources.iter().chain(&l.classes).chain(&l.javadocs))
+                .map(|p| self.root().join(p)),
+        );
+        let path = path.to_owned();
+        self.host
+            .blocking(move || {
+                let path = if path.starts_with("file://") {
+                    ide_lsp::uri_to_path(&path).ok_or_else(|| IdeError::invalid("invalid file URL"))?
+                } else {
+                    PathBuf::from(path)
+                };
+                let path = if path.is_absolute() { path } else { root.join(path) };
+                let (local, entry) =
+                    ide_vfs::split_archive_path(&path).map_or((path.clone(), None), |(p, e)| (p, Some(e)));
+                let real = if let Ok(real) = dunce::canonicalize(&local) {
+                    real
+                } else {
+                    let parent =
+                        local.ancestors().find(|p| p.exists()).ok_or_else(|| IdeError::not_found("path not found"))?;
+                    normalize(
+                        &dunce::canonicalize(parent)?
+                            .join(local.strip_prefix(parent).map_err(|e| IdeError::invalid(e.to_string()))?),
+                    )
+                };
+                if !std::iter::once(root).chain(roots).any(|r| {
+                    let r = ide_vfs::split_archive_path(&r).map_or(r.clone(), |(archive, _)| archive);
+                    dunce::canonicalize(r).is_ok_and(|r| real.starts_with(r))
+                }) {
+                    return Err(IdeError::invalid("path is outside the project's content roots"));
+                }
+                Ok(entry.map_or_else(|| real.clone(), |entry| PathBuf::from(format!("{}!/{entry}", real.display()))))
+            })
+            .await
+    }
+}
+
+pub struct Output(pub String);
+impl Output {
+    pub fn text(text: impl Into<String>) -> Self {
+        Self(text.into())
+    }
+    pub fn json(value: impl Serialize) -> IdeResult<Self> {
+        serde_json::to_string(&value).map(Self).map_err(|e| IdeError::internal(e.to_string()))
+    }
+}
+
+#[derive(Clone, Copy)]
+pub enum ParamType {
+    String,
+    Integer,
+    Boolean,
+    StringList,
+    StringMap,
+}
+pub struct Param {
+    name: &'static str,
+    kind: ParamType,
+    description: &'static str,
+    required: bool,
+}
+impl Param {
+    pub fn required(name: &'static str, kind: ParamType, description: &'static str) -> Self {
+        Self { name, kind, description, required: true }
+    }
+    pub fn optional(name: &'static str, kind: ParamType, description: &'static str) -> Self {
+        Self { name, kind, description, required: false }
+    }
+}
+
+type Handler = Arc<dyn Fn(Call) -> futures::future::BoxFuture<'static, IdeResult<Output>> + Send + Sync>;
+pub struct Tool {
+    pub metadata: ide_mcp::Tool,
+    pub handler: Handler,
+}
+impl Tool {
+    pub fn new<F, Fut>(name: &str, description: &str, handler: F) -> Self
+    where
+        F: Fn(Call) -> Fut + Send + Sync + 'static,
+        Fut: Future<Output = IdeResult<Output>> + Send + 'static,
+    {
+        Self {
+            metadata: ide_mcp::Tool {
+                name: name.into(),
+                description: description.into(),
+                read_only: true,
+                destructive: false,
+                output_schema: None,
+                input_schema: json!({ "type": "object", "properties": {
+                    "projectPath": { "type": "string", "description": "Any directory inside an open project. Optional when only one project is open." }
+                }, "required": [] }),
+            },
+            handler: Arc::new(move |call| Box::pin(handler(call))),
+        }
+    }
+    pub fn write(mut self) -> Self {
+        self.metadata.read_only = false;
+        self
+    }
+    pub fn param(mut self, param: Param) -> Self {
+        let mut schema = match param.kind {
+            ParamType::String => json!({"type":"string"}),
+            ParamType::Integer => json!({"type":"integer"}),
+            ParamType::Boolean => json!({"type":"boolean"}),
+            ParamType::StringMap => json!({"type":"object","additionalProperties":{"type":"string"}}),
+            ParamType::StringList => json!({"type":"array","items":{"type":"string"}}),
+        };
+        schema["description"] = param.description.into();
+        self.metadata.input_schema["properties"][param.name] = schema;
+        if param.required {
+            self.metadata.input_schema["required"].as_array_mut().unwrap().push(param.name.into());
+        }
+        self
+    }
+    pub fn output(mut self, schema: Value) -> Self {
+        self.metadata.output_schema = Some(schema);
+        self
+    }
+}
+
+pub fn normalize(path: &Path) -> PathBuf {
+    let mut out = PathBuf::new();
+    for part in path.components() {
+        match part {
+            std::path::Component::CurDir => {}
+            std::path::Component::ParentDir => {
+                out.pop();
+            }
+            p => out.push(p.as_os_str()),
+        }
+    }
+    out
+}
+
+pub fn request_id() -> ide_core::RequestId {
+    static NEXT: std::sync::atomic::AtomicU32 = std::sync::atomic::AtomicU32::new(0x8000_0000);
+    ide_core::RequestId(NEXT.fetch_add(1, std::sync::atomic::Ordering::Relaxed))
+}
+
+/// Resolve existing ancestors too, so symlinks cannot escape the project.
+pub fn resolve_inside(root: &Path, raw: &str) -> IdeResult<PathBuf> {
+    let path = if raw.starts_with("file://") {
+        ide_lsp::uri_to_path(raw).ok_or_else(|| IdeError::invalid("invalid file URL"))?
+    } else {
+        PathBuf::from(raw)
+    };
+    let path = if path.is_absolute() { path } else { root.join(path) };
+    if path.components().any(|c| c.as_os_str().to_string_lossy().eq_ignore_ascii_case(".git")) {
+        return Err(IdeError::invalid("VCS metadata cannot be changed"));
+    }
+    let path = normalize(&path);
+    let ancestor =
+        path.ancestors().find(|p| p.exists()).ok_or_else(|| IdeError::invalid("path has no existing parent"))?;
+    let mut real = dunce::canonicalize(ancestor)?;
+    let suffix = path.strip_prefix(ancestor).map_err(|e| IdeError::invalid(e.to_string()))?;
+    if !suffix.as_os_str().is_empty() {
+        real.push(suffix);
+    }
+    let root = dunce::canonicalize(root)?;
+    if !real.starts_with(&root) {
+        return Err(IdeError::invalid("path is outside the project"));
+    }
+    if real
+        .strip_prefix(&root)
+        .unwrap()
+        .components()
+        .any(|c| c.as_os_str().to_string_lossy().eq_ignore_ascii_case(".git"))
+    {
+        return Err(IdeError::invalid("VCS metadata cannot be changed"));
+    }
+    Ok(real)
+}
+pub fn ensure_inside(root: &Path, path: &Path) -> IdeResult<()> {
+    resolve_inside(root, &path.to_string_lossy()).map(|_| ())
+}

crates/ide-host/src/mcp/util.rs

@@ -0,0 +1,69 @@
+// Ported from JetBrains intellij-community plugins/mcp-server (src/com/intellij/mcpserver/util/fs.util.kt,
+// util/text.util.kt, toolsets/Constants.kt), Apache-2.0.
+//! Helpers shared by the tools: the strings and timeouts of JetBrains' `Constants`,
+//! resolving the paths `read_file` accepts, and text truncation.
+
+use crate::mcp::tool::Call;
+use ide_core::{IdeError, IdeResult};
+use std::path::PathBuf;
+use std::time::Duration;
+
+pub const RELATIVE_PATH_IN_PROJECT_DESCRIPTION: &str = "Path relative to the project root";
+pub const FILE_PATH_DESCRIPTION: &str = "Path to the file. Supports project-relative paths, paths with '..', \
+absolute paths, archive entries like '/path/lib.jar!/pkg/Foo.java', and URLs such as 'file://' and 'jar://'. \
+Any path returned from the other tools can be passed as is (e.g. paths from 'search_*' tools).";
+pub const TIMEOUT_MILLISECONDS_DESCRIPTION: &str = "Timeout in milliseconds";
+pub const TIMED_OUT_DESCRIPTION: &str = "Indicates whether the operation was timed out. 'true' value may mean that \
+the results may be incomplete or partial. 'false', 'null' or missing value means that the operation has not been \
+timed out.";
+pub const MEDIUM_TIMEOUT: Duration = Duration::from_secs(10);
+pub const INDEXING_PARTIAL_RESULT_REASON: &str =
+    "Project indexing was in progress; results may be incomplete — retry once indexing completes.";
+
+/// Whether `path` starts with a URL scheme (`file://`, `jar://`, `jrt://` …).
+pub fn looks_like_vfs_url(path: &str) -> bool {
+    path.find("://")
+        .is_some_and(|i| i > 0 && path[..i].chars().all(|c| c.is_ascii_alphanumeric() || matches!(c, '+' | '-' | '.')))
+}
+
+/// Resolves `read_file`'s `file_path`: project-relative or absolute paths, archive entries
+/// (`/lib.jar!/pkg/Foo.java`) and `file://` / `jar://` URLs, within known content or library roots.
+pub async fn resolve_read_file(call: &Call, file_path: &str) -> IdeResult<PathBuf> {
+    let normalized = file_path.trim().replace('\\', "/");
+    if normalized.is_empty() {
+        return Err(IdeError::invalid("file_path is empty"));
+    }
+    let missing = || IdeError::not_found(format!("File {file_path} doesn't exist or can't be opened"));
+    let local = if looks_like_vfs_url(&normalized) {
+        let (scheme, rest) = normalized.split_once("://").unwrap_or_default();
+        match scheme.to_ascii_lowercase().as_str() {
+            // `file://` URLs are percent-decoded by `resolve`.
+            "file" => normalized.clone(),
+            "jar" => rest.to_owned(),
+            "jrt" => {
+                return Err(IdeError::invalid(format!(
+                    "File {file_path} can't be opened: OpenIDEA does not read jrt:// (Java runtime image) entries"
+                )));
+            }
+            _ => return Err(missing()),
+        }
+    } else {
+        normalized
+    };
+    let path = call.resolve_readable(&local).await?;
+    match ide_vfs::split_archive_path(&path) {
+        Some((archive, entry)) => {
+            if !archive.is_file() {
+                return Err(missing());
+            }
+            if entry.is_empty() || ide_vfs::read_archive_dir(&archive, &entry).is_ok() {
+                return Err(IdeError::invalid(format!("File {file_path} is a directory")));
+            }
+            ide_vfs::probe(&path).map_err(|_| missing())?;
+        }
+        None if path.is_dir() => return Err(IdeError::invalid(format!("File {file_path} is a directory"))),
+        None if !path.is_file() && call.project().documents.by_path(&path).is_none() => return Err(missing()),
+        None => {}
+    }
+    Ok(path)
+}

crates/ide-host/src/mcp/vcs.rs

@@ -0,0 +1,362 @@
+// Ported from JetBrains intellij-community plugins/mcp-server
+// (mcpserver.vcs/src/com/intellij/mcpserver/toolsets/vcs/VcsToolset.kt), Apache-2.0.
+//! Version control: repositories and git status.
+
+use crate::mcp::tool::{Call, Output, Param, ParamType, Tool};
+use ide_core::{IdeError, IdeResult};
+use serde_json::{Value, json};
+use std::path::{Path, PathBuf};
+
+const STATUS_DEFAULT_LIMIT: i64 = 1000;
+
+pub fn tools() -> Vec<Tool> {
+    vec![get_repositories(), git_status(), git_diff()]
+}
+
+/// `path` with symbolic links resolved (macOS `/var` is `/private/var`), as given when it
+/// does not exist.
+fn canonical(path: &Path) -> PathBuf {
+    dunce::canonicalize(path).unwrap_or_else(|_| path.to_path_buf())
+}
+
+/// A path relative to the project root with `/`; empty for the root itself. Either may
+/// name the other through a symbolic link.
+fn relative_to(root: &Path, path: &Path) -> String {
+    let rel = match path.strip_prefix(root) {
+        Ok(rel) => Some(rel.to_path_buf()),
+        Err(_) => canonical(path).strip_prefix(canonical(root)).ok().map(Path::to_path_buf),
+    };
+    match rel {
+        Some(rel) => rel.to_string_lossy().replace('\\', "/"),
+        None => path.to_string_lossy().into_owned(),
+    }
+}
+
+fn relative_to_project(call: &Call, path: &Path) -> String {
+    relative_to(call.root(), path)
+}
+
+/// The repository whose roots contain `path` most specifically (paths compared canonically).
+fn innermost_repo<T>(repos: Vec<(PathBuf, T)>, path: &Path) -> Option<(PathBuf, T)> {
+    let path = canonical(path);
+    repos.into_iter().filter(|r| path.starts_with(canonical(&r.0))).max_by_key(|r| canonical(&r.0).components().count())
+}
+
+// Read tools must never invoke repository-configured executables, including in Restricted Mode.
+fn read_command(git: &str, root: &Path) -> std::process::Command {
+    let mut command = std::process::Command::new(git);
+    command
+        .current_dir(root)
+        .args([
+            "-c",
+            "core.fsmonitor=false",
+            "-c",
+            "core.hooksPath=",
+            "-c",
+            "diff.external=",
+            "-c",
+            "core.attributesFile=",
+            "-c",
+            "submodule.recurse=false",
+            "-c",
+            "color.ui=false",
+        ])
+        .env("GIT_NO_LAZY_FETCH", "1")
+        .env("GIT_TERMINAL_PROMPT", "0")
+        .env("GIT_OPTIONAL_LOCKS", "0")
+        .env_remove("GIT_EXTERNAL_DIFF")
+        .env_remove("GIT_DIR")
+        .env_remove("GIT_WORK_TREE")
+        .env_remove("GIT_INDEX_FILE");
+    ide_core::process::prepare(&mut command);
+    command
+}
+
+/// The branch HEAD is on (unborn too); `None` when HEAD is detached or git fails.
+fn read_branch(git: &str, root: &Path) -> Option<String> {
+    let mut cmd = read_command(git, root);
+    cmd.args(["symbolic-ref", "--short", "-q", "HEAD"]);
+    ide_core::process::prepare(&mut cmd);
+    let out = cmd.output().ok().filter(|o| o.status.success())?;
+    Some(String::from_utf8_lossy(&out.stdout).trim().to_owned()).filter(|b| !b.is_empty())
+}
+
+fn get_repositories() -> Tool {
+    Tool::new(
+        "get_repositories",
+        "Retrieves the list of VCS roots in the project.
+This is useful to detect all repositories in a multi-repository project.
+In OpenIDEA each root also tells its current `branch` (absent when HEAD is detached), `headCommit` and a merge, \
+rebase or cherry-pick in progress (`operationInProgress`).",
+        |call| async move {
+            let host = call.host();
+            let window = call.window.clone();
+            let roots = call.host.blocking(move || crate::ops::vcs::vcs_roots(&host, &window)).await?;
+            let list: Vec<Value> = roots
+                .into_iter()
+                .map(|r| {
+                    let mut v =
+                        json!({ "pathRelativeToProject": relative_to_project(&call, &r.root), "vcsName": "Git" });
+                    if let Some(head) = r.head {
+                        v["branch"] = head.into();
+                    }
+                    if let Some(commit) = r.head_commit {
+                        v["headCommit"] = commit.into();
+                    }
+                    if let Some(op) = r.operation {
+                        v["operationInProgress"] = op.into();
+                    }
+                    v
+                })
+                .collect();
+            Output::json(json!({ "roots": list }))
+        },
+    )
+}
+
+/// One entry of `git status --porcelain -z`.
+#[derive(Debug, PartialEq)]
+struct StatusEntry {
+    index: char,
+    work_tree: char,
+    path: String,
+    orig_path: Option<String>,
+}
+
+impl StatusEntry {
+    fn untracked(&self) -> bool {
+        self.index == '?'
+    }
+    fn ignored(&self) -> bool {
+        self.index == '!'
+    }
+    fn conflicted(&self) -> bool {
+        matches!((self.index, self.work_tree), ('D', 'D') | ('A', 'U') | ('U', _) | ('A', 'A') | ('D', 'U'))
+    }
+    fn staged(&self) -> bool {
+        !self.conflicted() && !matches!(self.index, ' ' | '?' | '!')
+    }
+    fn unstaged(&self) -> bool {
+        !self.conflicted() && !matches!(self.work_tree, ' ' | '?' | '!')
+    }
+}
+
+fn parse_status(out: &str) -> Vec<StatusEntry> {
+    let mut fields = out.split('\0').filter(|f| !f.is_empty());
+    let mut entries = Vec::new();
+    while let Some(field) = fields.next() {
+        let mut chars = field.chars();
+        let (Some(index), Some(work_tree)) = (chars.next(), chars.next()) else { continue };
+        let path = field.get(3..).unwrap_or_default().to_owned();
+        let orig_path = matches!(index, 'R' | 'C').then(|| fields.next().map(str::to_owned)).flatten();
+        entries.push(StatusEntry { index, work_tree, path, orig_path });
+    }
+    entries
+}
+
+fn git_executable(call: &Call) -> String {
+    let settings = if call.project.is_trusted() {
+        call.project.settings.effective()
+    } else {
+        call.host.global_settings.effective()
+    };
+    let exe = settings.vcs.git.executable.trim().to_owned();
+    if exe.is_empty() { "git".to_owned() } else { exe }
+}
+
+/// `git status` of the repository at `root`, paths relative to it.
+fn read_status(git: &str, root: &Path, untracked: bool, ignored: bool) -> IdeResult<Vec<StatusEntry>> {
+    let mut cmd = read_command(git, root);
+    cmd.args(["-c", "core.quotepath=false", "status", "--porcelain", "-z", "--find-renames"]);
+    // git refuses `--ignored=matching` with `--untracked-files=no`: untracked files are dropped below.
+    cmd.arg(if untracked || ignored { "--untracked-files=all" } else { "--untracked-files=no" });
+    if ignored {
+        cmd.arg("--ignored=matching");
+    }
+    ide_core::process::prepare(&mut cmd);
+    let out = cmd.output().map_err(|e| IdeError::unavailable(format!("cannot run git: {e}")))?;
+    if !out.status.success() {
+        return Err(IdeError::internal(String::from_utf8_lossy(&out.stderr).trim().to_owned()));
+    }
+    let mut entries = parse_status(&String::from_utf8_lossy(&out.stdout));
+    entries.retain(|e| untracked || !e.untracked());
+    Ok(entries)
+}
+
+/// A git repository in the project, for paths outside the repositories IDEA knows: the
+/// closest folder with `.git` from `start` up to the project root.
+fn find_git_root(root: &Path, start: &Path) -> Option<PathBuf> {
+    let (root, start) = (canonical(root), canonical(start));
+    let mut current = if start.is_dir() { start.as_path() } else { start.parent().unwrap_or(&start) };
+    while current.starts_with(&root) {
+        if current.join(".git").exists() {
+            return Some(current.to_path_buf());
+        }
+        current = current.parent()?;
+    }
+    None
+}
+
+fn git_status() -> Tool {
+    Tool::new(
+        "git_status",
+        "Retrieves Git status for one or more repositories in the current project.
+Returns porcelain-style index/worktree status codes and summary counters.
+By default all Git repositories are returned.",
+        |call| async move {
+            let include_untracked = call.flag("includeUntracked", true)?;
+            let include_ignored = call.flag("includeIgnored", false)?;
+            let limit = call.opt_i64("limit")?.unwrap_or(STATUS_DEFAULT_LIMIT);
+            if limit <= 0 {
+                return Err(IdeError::invalid("limit must be > 0"));
+            }
+            let limit = limit as usize;
+            let host = call.host();
+            let h = host.clone();
+            let w = call.window.clone();
+            let repos: Vec<(PathBuf, Option<String>)> = host
+                .blocking(move || crate::ops::vcs::vcs_roots(&h, &w))
+                .await?
+                .into_iter()
+                .map(|r| (r.root.into_path_buf(), r.head))
+                .collect();
+            let wanted = call.opt_str("repositoryPathRelativeToProject")?;
+            let git = git_executable(&call);
+            let mut roots: Vec<(PathBuf, Option<String>)> = match &wanted {
+                None => repos,
+                Some(wanted) => {
+                    let path = call.resolve_inside(wanted)?;
+                    // The innermost repository containing the path.
+                    match innermost_repo(repos, &path) {
+                        Some(repo) => vec![repo],
+                        None => match find_git_root(call.root(), &path) {
+                            Some(root) => {
+                                // JetBrains reads the branch of any repository it reports.
+                                let (git, dir) = (git.clone(), root.clone());
+                                let branch = host.blocking(move || Ok(read_branch(&git, &dir))).await?;
+                                vec![(root, branch)]
+                            }
+                            None => {
+                                return Err(IdeError::not_found(format!("No git repository found for path: {wanted}")));
+                            }
+                        },
+                    }
+                }
+            };
+            roots.sort_by_key(|r| relative_to_project(&call, &r.0));
+            let mut repositories = Vec::new();
+            for (root, branch) in roots {
+                let rel = relative_to_project(&call, &root);
+                let (git, dir) = (git.clone(), root.clone());
+                let entries = host
+                    .blocking(move || read_status(&git, &dir, include_untracked, include_ignored))
+                    .await
+                    .map_err(|e| {
+                        IdeError::internal(format!("Failed to get git status for repository '{rel}': {}", e.message))
+                    })?;
+                let count = |f: fn(&StatusEntry) -> bool| entries.iter().filter(|e| f(e)).count();
+                let listed: Vec<Value> = entries
+                    .iter()
+                    .take(limit)
+                    .map(|e| {
+                        let mut v = json!({
+                            "pathRelativeToRepository": e.path.trim_end_matches('/'),
+                            "indexStatus": e.index.to_string(),
+                            "workTreeStatus": e.work_tree.to_string(),
+                        });
+                        if let Some(orig) = &e.orig_path {
+                            v["originalPathRelativeToRepository"] = orig.clone().into();
+                        }
+                        v
+                    })
+                    .collect();
+                repositories.push(json!({
+                    "repositoryPathRelativeToProject": rel,
+                    "currentBranch": branch,
+                    "isClean": entries.is_empty(),
+                    "totalEntries": entries.len(),
+                    "hasMoreEntries": entries.len() > listed.len(),
+                    "stagedCount": count(StatusEntry::staged),
+                    "unstagedCount": count(StatusEntry::unstaged),
+                    "untrackedCount": count(StatusEntry::untracked),
+                    "ignoredCount": count(StatusEntry::ignored),
+                    "conflictedCount": count(StatusEntry::conflicted),
+                    "entries": listed,
+                }));
+            }
+            Output::json(json!({ "repositories": repositories }))
+        },
+    )
+    .param(Param::optional(
+        "repositoryPathRelativeToProject",
+        ParamType::String,
+        "Optional path relative to project root used to select a single containing repository",
+    ))
+    .param(Param::optional("includeUntracked", ParamType::Boolean, "Whether to include untracked files"))
+    .param(Param::optional("includeIgnored", ParamType::Boolean, "Whether to include ignored files"))
+    .param(Param::optional("limit", ParamType::Integer, "Maximum number of entries returned per repository"))
+}
+
+fn git_diff() -> Tool {
+    Tool::new("git_diff", "Read a Git diff for a file or the working tree. staged=true compares the index with HEAD; otherwise compares disk with the index. Unsaved editor text is not part of this diff.", |call| async move {
+        let wanted = call.opt_str("repositoryPathRelativeToProject")?;
+        let path = wanted.as_deref().map(|p| call.resolve_inside(p)).transpose()?.unwrap_or_else(|| call.root().to_path_buf());
+        let root = find_git_root(call.root(), &path).ok_or_else(|| IdeError::not_found("No git repository found"))?;
+        let file = call.opt_str("filePath")?.map(|p| call.resolve_inside(&p)).transpose()?;
+        if file.as_ref().is_some_and(|p| !p.starts_with(&root)) { return Err(IdeError::invalid("file is outside the repository")); }
+        let staged = call.flag("staged", false)?;
+        let git = git_executable(&call);
+        let cancel = call.cancel.clone();
+        let text = call.host.blocking(move || {
+            let mut cmd = read_command(&git, &root);
+            cmd.args(["--no-pager", "diff", "--no-ext-diff", "--no-textconv"]);
+            if staged { cmd.arg("--cached"); }
+            cmd.arg("--");
+            if let Some(file) = file { cmd.arg(file.strip_prefix(&root).map_err(|e| IdeError::invalid(e.to_string()))?); }
+            ide_core::process::prepare(&mut cmd);
+            if cancel.is_cancelled() { return Err(IdeError::cancelled()); }
+            let out = cmd.output()?;
+            if !out.status.success() { return Err(IdeError::unavailable(String::from_utf8_lossy(&out.stderr).trim())); }
+            Ok(String::from_utf8_lossy(&out.stdout).into_owned())
+        }).await?;
+        Ok(Output::text(text))
+    })
+    .param(Param::optional("repositoryPathRelativeToProject", ParamType::String, "Select the containing repository"))
+    .param(Param::optional("filePath", ParamType::String, "Optional project-relative file; omit for the working tree"))
+    .param(Param::optional("staged", ParamType::Boolean, "Show staged changes"))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn parses_porcelain_z_with_renames() {
+        let out = "M  a.txt\0R  new.txt\0old.txt\0?? u.txt\0UU c.txt\0";
+        let e = parse_status(out);
+        assert_eq!(e.len(), 4);
+        assert_eq!(e[1].path, "new.txt");
+        assert_eq!(e[1].orig_path.as_deref(), Some("old.txt"));
+        assert!(e[0].staged() && !e[0].unstaged());
+        assert!(e[2].untracked() && !e[2].staged());
+        assert!(e[3].conflicted() && !e[3].staged() && !e[3].unstaged());
+    }
+
+    #[cfg(unix)]
+    #[test]
+    fn paths_through_a_symlinked_root_compare_canonically() {
+        // As macOS `/var` → `/private/var`: the project opened through the link, git reporting real paths.
+        let dir = tempfile::tempdir().unwrap();
+        let real = dunce::canonicalize(dir.path()).unwrap().join("real");
+        std::fs::create_dir_all(real.join("sub/.git")).unwrap();
+        std::fs::write(real.join("sub/f.txt"), "x").unwrap();
+        let link = dir.path().join("link");
+        std::os::unix::fs::symlink(&real, &link).unwrap();
+        assert_eq!(relative_to(&link, &real.join("sub")), "sub");
+        assert_eq!(relative_to(&real, &link.join("sub")), "sub");
+        assert_eq!(relative_to(&link, &link), "");
+        let repos = vec![(real.clone(), 1), (real.join("sub"), 2)];
+        assert_eq!(innermost_repo(repos, &link.join("sub/f.txt")).map(|r| r.1), Some(2));
+        assert_eq!(find_git_root(&link, &real.join("sub/f.txt")), Some(real.join("sub")));
+    }
+}

crates/ide-host/src/ops/sdk.rs

@@ -207,7 +207,13 @@ pub async fn sdk_project_libraries(
     if cancel.is_cancelled() {
         return Err(IdeError::cancelled());
     }
-    Ok(ide_sdk::libraries::merge_groups([libraries.map_err(join_err)?, dependencies.map_err(join_err)?].concat()))
+    let groups =
+        ide_sdk::libraries::merge_groups([libraries.map_err(join_err)?, dependencies.map_err(join_err)?].concat());
+    if host.project(window).is_ok_and(|current| std::sync::Arc::ptr_eq(&current, &project)) {
+        host.mcp_reports
+            .set_libraries(window, groups.iter().flat_map(|g| g.roots.iter().map(|r| r.path.0.clone())).collect());
+    }
+    Ok(groups)
 }
 
 /// Looks up `names` (bare command names): `node_modules/.bin` above `near`, then the search path.

crates/ide-host/tests/mcp.rs

@@ -0,0 +1,418 @@
+use ide_core::{CancellationToken, ChangeSet, Diagnostic, IdeEvent, Pos, Range, Severity, TextChange};
+use ide_host::mcp::{FileProblems, FocusedEditor, Registry};
+use ide_host::{Host, HostConfig};
+use ide_mcp::ToolRegistry;
+use serde_json::{Value, json};
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+
+struct Harness {
+    host: Arc<Host>,
+    root: PathBuf,
+    tmp: tempfile::TempDir,
+    events: Arc<std::sync::Mutex<Vec<IdeEvent>>>,
+}
+impl Harness {
+    fn new() -> Self {
+        let tmp = tempfile::tempdir().unwrap();
+        let root = dunce::canonicalize(tmp.path()).unwrap().join("project");
+        std::fs::create_dir_all(root.join("src")).unwrap();
+        std::fs::write(root.join("src/a.txt"), "old text\nneedle needle\n").unwrap();
+        std::fs::write(root.join("src/b.txt"), "needle\n").unwrap();
+        std::fs::create_dir_all(root.join("ignored")).unwrap();
+        std::fs::write(root.join("ignored/a.txt"), "needle\n").unwrap();
+        std::fs::write(root.join(".gitignore"), "ignored/\n").unwrap();
+        let events = Arc::new(std::sync::Mutex::new(Vec::new()));
+        let sink = events.clone();
+        let host = Arc::new(Host::new(HostConfig {
+            config_dir: tmp.path().join("config"),
+            data_dir: tmp.path().join("data"),
+            local_data_dir: tmp.path().join("local"),
+            languages: Arc::new(ide_language::LanguageRegistry::load(None).unwrap()),
+            syntax: Arc::default(),
+            sink_for: Box::new(move |_| {
+                let events = sink.clone();
+                Arc::new(move |e| events.lock().unwrap().push(e))
+            }),
+            owner: |w| w,
+            runtime: tokio::runtime::Handle::current(),
+            project_environment: false,
+        }));
+        host.open_project("main", &root).unwrap();
+        Self { host, root, tmp, events }
+    }
+    async fn trust(&self) {
+        self.host.set_project_trust(&self.root, true, false).await.unwrap();
+    }
+    async fn error(&self, name: &str, args: Value) -> String {
+        let (host, root, name) = (self.host.clone(), self.root.clone(), name.to_owned());
+        let e = tokio::task::spawn_blocking(move || {
+            Registry::new(host).call(&root, &name, &args.to_string(), CancellationToken::new())
+        })
+        .await
+        .unwrap()
+        .unwrap_err();
+        match e {
+            ide_mcp::ToolCallError::Failed(e) | ide_mcp::ToolCallError::UnknownTool(e) => e,
+        }
+    }
+    async fn request(&self) -> u32 {
+        tokio::time::timeout(std::time::Duration::from_secs(10), async {
+            loop {
+                if let Some(id) = self.events.lock().unwrap().iter().rev().find_map(|e| match e {
+                    IdeEvent::McpRequest { id, .. } => Some(*id),
+                    _ => None,
+                }) {
+                    return id;
+                }
+                tokio::time::sleep(std::time::Duration::from_millis(10)).await;
+            }
+        })
+        .await
+        .unwrap()
+    }
+    async fn call(&self, name: &str, args: Value) -> String {
+        let (host, root, name) = (self.host.clone(), self.root.clone(), name.to_owned());
+        tokio::task::spawn_blocking(move || {
+            Registry::new(host).call(&root, &name, &args.to_string(), CancellationToken::new())
+        })
+        .await
+        .unwrap()
+        .unwrap()
+    }
+    async fn json(&self, name: &str, args: Value) -> Value {
+        serde_json::from_str(&self.call(name, args).await).unwrap()
+    }
+}
+impl Drop for Harness {
+    fn drop(&mut self) {
+        self.host.close_project("main");
+        self.host.close_project("second");
+    }
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn reads_unsaved_text_and_searches_the_overlay_with_a_limit() {
+    let h = Harness::new();
+    let p = h.host.project("main").unwrap();
+    let doc = p.documents.open(&h.root.join("src/a.txt")).unwrap();
+    p.documents
+        .edit(
+            doc.id,
+            doc.version,
+            ChangeSet { changes: vec![TextChange { from: 0, to: 3, insert: "fresh needle".into() }] },
+        )
+        .unwrap();
+    assert_eq!(
+        h.call("read_file", json!({"file_path":"src/a.txt","offset":1,"limit":5})).await,
+        "L1: fresh needle text\nL2: needle needle\nL3: "
+    );
+    let found = h.json("search_text", json!({"q":"needle","limit":2})).await;
+    assert_eq!(found["items"].as_array().unwrap().len(), 2);
+    assert_eq!(found["more"], true);
+    let all = h.json("search_text", json!({"q":"fresh","limit":20})).await;
+    assert_eq!(all["items"][0]["filePath"], "src/a.txt");
+    let all = h.json("search_text", json!({"q":"needle","limit":20})).await;
+    assert!(all["items"].as_array().unwrap().iter().all(|v| !v["filePath"].as_str().unwrap().contains("ignored")));
+    let files = h.json("search_file", json!({"q":"*.txt","paths":["src/**"]})).await;
+    assert_eq!(files["items"], json!([{"filePath":"src/a.txt"},{"filePath":"src/b.txt"}]));
+    let regex = h.json("search_regex", json!({"q":"fresh\\s+needle"})).await;
+    assert_eq!(regex["items"][0]["startColumn"], 1);
+    assert_eq!(std::fs::read_to_string(h.root.join("src/a.txt")).unwrap(), "old text\nneedle needle\n");
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn window_reports_supply_editor_selection_and_problems_then_disappear_on_close() {
+    let h = Harness::new();
+    let path = h.root.join("src/a.txt");
+    h.host.mcp_reports.set_open_editors("main", vec![path.clone()]);
+    h.host.mcp_reports.set_focused_editor(
+        "main",
+        Some(FocusedEditor {
+            path: path.clone().into(),
+            selection: Range::new(Pos::new(1, 2), Pos::new(1, 4)),
+            selected_text: "ed".into(),
+        }),
+        true,
+    );
+    let d = Diagnostic {
+        range: Range::point(Pos::new(1, 2)),
+        severity: Severity::Warning,
+        message: "reported warning".into(),
+        source: Some("inspection".into()),
+        code: None,
+        unnecessary: false,
+        deprecated: false,
+        server: None,
+    };
+    h.host.mcp_reports.report_problems("main", true, vec![FileProblems { path: path.clone().into(), items: vec![d] }]);
+    assert_eq!(h.json("get_all_open_file_paths", json!({})).await["openFiles"], json!(["src/a.txt"]));
+    let focused = h.json("get_current_file", json!({})).await;
+    assert_eq!(focused["selectedText"], "ed");
+    assert_eq!(focused["selection"]["startColumn"], 3);
+    let problems = h.json("get_file_problems", json!({"filePath":"src/a.txt","errorsOnly":false})).await;
+    assert_eq!(problems["errors"][0]["description"], "reported warning");
+    assert_eq!(h.json("get_project_problems", json!({})).await["files"].as_array().unwrap().len(), 1);
+    h.host.close_project("main");
+    h.host.open_project("main", &h.root).unwrap();
+    assert_eq!(h.json("get_all_open_file_paths", json!({})).await["openFiles"], json!([]));
+    assert_eq!(h.json("get_current_file", json!({})).await, json!({}));
+    assert_eq!(h.json("get_project_problems", json!({})).await["files"], json!([]));
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn restricted_projects_have_only_read_tools_and_remote_projects_explain_the_limitation() {
+    let h = Harness::new();
+    assert!(!h.host.project("main").unwrap().is_trusted());
+    let registry = Registry::new(h.host.clone());
+    assert!(registry.tools(&h.root).unwrap().iter().all(|t| t.read_only && !t.destructive));
+    assert!(!h.host.global_settings.effective().mcp_server.enabled);
+    h.host.mcp_reports.set_remote("remote", PathBuf::from("/remote/project"));
+    assert_eq!(registry.tools(Path::new("/remote/project")).unwrap_err(), "not supported for remote projects yet");
+    h.host.close_project_detached("remote");
+    assert!(!registry.projects().contains(&PathBuf::from("/remote/project")));
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn project_path_argument_routes_to_another_open_project() {
+    let h = Harness::new();
+    let second = h.tmp.path().join("second");
+    std::fs::create_dir_all(second.join("nested")).unwrap();
+    std::fs::write(second.join("unique.txt"), "second project").unwrap();
+    h.host.open_project("second", &second).unwrap();
+    let discovery = ide_mcp::discovery_path(h.tmp.path());
+    let _server = ide_mcp::McpServer::start(
+        Arc::new(Registry::new(h.host.clone())),
+        Some(discovery.clone()),
+        &tokio::runtime::Handle::current(),
+    )
+    .unwrap();
+    let request = json!({"jsonrpc":"2.0","id":1,"method":"tools/call","params":{"name":"read_file","arguments":{
+        "projectPath":second.join("nested"),"file_path":"unique.txt"}}});
+    let input = format!("{request}\n");
+    let mut output = Vec::new();
+    ide_mcp::stdio::bridge(&discovery, &h.root, input.as_bytes(), &mut output).await.unwrap();
+    let reply: Value = serde_json::from_slice(&output).unwrap();
+    assert_eq!(reply["result"]["content"][0]["text"], "L1: second project");
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn mutations_preserve_unsaved_text_and_reject_metadata_and_escapes() {
+    let h = Harness::new();
+    h.trust().await;
+    let p = h.host.project("main").unwrap();
+    let path = h.root.join("src/a.txt");
+    let doc = p.documents.open(&path).unwrap();
+    p.documents
+        .edit(doc.id, doc.version, ChangeSet { changes: vec![TextChange { from: 0, to: 3, insert: "unsaved".into() }] })
+        .unwrap();
+    let output = h.call("apply_patch", json!({"input":"*** Begin Patch\n*** Update File: src/a.txt\n@@\n-unsaved text\n+agent text\n*** End Patch"})).await;
+    assert!(output.starts_with("1 out of 1"), "{output}");
+    assert_eq!(p.documents.text_snapshot(doc.id).unwrap().text, "agent text\nneedle needle\n");
+    assert!(p.documents.is_dirty(doc.id).unwrap());
+    assert_eq!(std::fs::read_to_string(&path).unwrap(), "old text\nneedle needle\n");
+    assert!(
+        h.events.lock().unwrap().iter().any(|e| matches!(e, IdeEvent::DocPatched { doc: id, .. } if *id == doc.id))
+    );
+    let edit_id = h
+        .events
+        .lock()
+        .unwrap()
+        .iter()
+        .rev()
+        .find_map(|event| match event {
+            IdeEvent::WorkspaceEditApplied { id, .. } => Some(*id),
+            _ => None,
+        })
+        .unwrap();
+    p.documents.undo_workspace_edit(edit_id).unwrap();
+    assert_eq!(p.documents.text_snapshot(doc.id).unwrap().text, "unsaved text\nneedle needle\n");
+    p.documents.redo_workspace_edit(edit_id).unwrap();
+    assert_eq!(p.documents.text_snapshot(doc.id).unwrap().text, "agent text\nneedle needle\n");
+    h.call("create_new_file", json!({"pathInProject":"new/deep.txt","text":"hello\r\n"})).await;
+    // A new file gets the platform's default line separator.
+    let expected = if cfg!(windows) { "hello\r\n" } else { "hello\n" };
+    assert_eq!(std::fs::read_to_string(h.root.join("new/deep.txt")).unwrap(), expected);
+    h.call("create_new_file", json!({"pathInProject":"src/a.txt","text":"buffer only","overwrite":true})).await;
+    assert_eq!(p.documents.text_snapshot(doc.id).unwrap().text, "buffer only");
+    assert_eq!(std::fs::read_to_string(&path).unwrap(), "old text\nneedle needle\n");
+    for path in [".git/config", "nested/.git/HEAD", "../escape.txt"] {
+        let e = h.error("create_new_file", json!({"pathInProject":path,"text":"no"})).await;
+        assert!(e.contains("VCS metadata") || e.contains("outside"), "{path}: {e}");
+    }
+    #[cfg(unix)]
+    {
+        std::os::unix::fs::symlink(h.tmp.path(), h.root.join("escape")).unwrap();
+        assert!(h.error("create_new_file", json!({"pathInProject":"escape/outside.txt"})).await.contains("outside"));
+    }
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn execution_requires_a_window_and_denial_never_runs_a_build() {
+    let h = Harness::new();
+    h.trust().await;
+    assert!(h.error("build_project", json!({})).await.contains("no project window"));
+    h.host.mcp_requests.set_ready("main", true);
+    let denied = h.error("build_project", json!({}));
+    let answer = async {
+        let id = h.request().await;
+        assert!(h.host.mcp_requests.answer("other", id, true, None).is_err());
+        h.host.mcp_requests.answer("main", id, false, None).unwrap();
+    };
+    let (error, ()) = tokio::join!(denied, answer);
+    assert!(error.contains("denied by the user"), "{error}");
+    assert!(h.host.processes.list().is_empty());
+    assert!(h.events.lock().unwrap().iter().any(|e| matches!(e, IdeEvent::McpRequestClosed { .. })));
+    h.events.lock().unwrap().clear();
+    let closed = h.error("build_project", json!({}));
+    let close = async {
+        h.request().await;
+        h.host.mcp_requests.forget_window("main");
+    };
+    let (error, ()) = tokio::join!(closed, close);
+    assert!(error.contains("window closed"), "{error}");
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn git_status_and_diff_on_a_temporary_repository() {
+    let h = Harness::new();
+    let git = |args: &[&str]| {
+        let output = std::process::Command::new("git").current_dir(&h.root).args(args).output().unwrap();
+        assert!(output.status.success(), "{}", String::from_utf8_lossy(&output.stderr));
+    };
+    git(&["init"]);
+    git(&["add", "."]);
+    git(&["-c", "user.name=Test", "-c", "[email protected]", "commit", "-m", "Initial"]);
+    #[cfg(unix)]
+    {
+        use std::os::unix::fs::PermissionsExt;
+        let helper = h.tmp.path().join("fsmonitor");
+        std::fs::write(&helper, format!("#!/bin/sh\ntouch '{}'\n", h.tmp.path().join("executed").display())).unwrap();
+        std::fs::set_permissions(&helper, std::fs::Permissions::from_mode(0o755)).unwrap();
+        git(&["config", "core.fsmonitor", helper.to_str().unwrap()]);
+    }
+    std::fs::write(h.root.join("src/a.txt"), "changed\n").unwrap();
+    let status = h.json("git_status", json!({"repositoryPathRelativeToProject":"."})).await;
+    assert_eq!(status["repositories"][0]["unstagedCount"], 1);
+    assert!(h.call("git_diff", json!({"filePath":"src/a.txt"})).await.contains("+changed"));
+    assert!(h.call("git_diff", json!({})).await.contains("src/a.txt"));
+    assert!(h.call("git_diff", json!({"staged":true})).await.is_empty());
+    assert!(!h.tmp.path().join("executed").exists());
+}
+
+#[cfg(unix)]
+#[tokio::test(flavor = "multi_thread")]
+async fn reformat_uses_the_formatter_chain_and_preserves_a_dirty_buffer() {
+    use std::os::unix::fs::PermissionsExt;
+    let h = Harness::new();
+    h.trust().await;
+    std::fs::create_dir_all(h.root.join("vendor/bin")).unwrap();
+    std::fs::write(h.root.join("vendor/bin/php-cs-fixer"), "").unwrap();
+    std::fs::write(h.root.join(".php-cs-fixer.dist.php"), "<?php").unwrap();
+    let php = h.root.join("fake-php");
+    std::fs::write(&php, "#!/bin/sh\nfor last; do :; done\nsed 's/  echo/    echo/' \"$last\" > \"$last.new\" && mv \"$last.new\" \"$last\"\n").unwrap();
+    std::fs::set_permissions(&php, std::fs::Permissions::from_mode(0o755)).unwrap();
+    let p = h.host.project("main").unwrap();
+    p.settings.set(ide_workspace::SettingsScope::Project, "languages.php.interpreter", json!(php)).unwrap();
+    let path = h.root.join("src/Example.php");
+    std::fs::write(&path, "<?php\n  echo 1;\n").unwrap();
+    let doc = p.documents.open(&path).unwrap();
+    p.documents
+        .edit(doc.id, doc.version, ChangeSet { changes: vec![TextChange { from: 13, to: 14, insert: "2".into() }] })
+        .unwrap();
+    let before = p.documents.text_snapshot(doc.id).unwrap().text;
+    let diff = h.call("reformat_file", json!({"files":["src/Example.php"]})).await;
+    assert!(diff.contains("+    echo"), "{diff}");
+    assert_eq!(p.documents.text_snapshot(doc.id).unwrap().text, before.replace("  echo", "    echo"));
+    assert_eq!(std::fs::read_to_string(path).unwrap(), "<?php\n  echo 1;\n");
+    assert!(p.documents.is_dirty(doc.id).unwrap());
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn execute_reports_output_exit_code_and_requires_confirmation() {
+    let h = Harness::new();
+    h.trust().await;
+    let config = ide_run::RunConfig {
+        id: "test".into(),
+        name: "MCP test".into(),
+        kind: "shell".into(),
+        command: if cfg!(windows) { "echo captured-output& exit 7" } else { "echo captured-output; exit 7" }.into(),
+        args: vec![],
+        cwd: None,
+        env: Default::default(),
+        detected: false,
+        is_test: false,
+        debug_adapter: None,
+        allow_parallel: false,
+        extras: Default::default(),
+    };
+    ide_run::save_user_configs(&h.root, &[config]).unwrap();
+    assert!(
+        h.error("execute_run_configuration", json!({"configurationName":"MCP test"}))
+            .await
+            .contains("no project window")
+    );
+    h.host.mcp_requests.set_ready("main", true);
+    let denied = h.error("execute_run_configuration", json!({"configurationName":"MCP test"}));
+    let deny = async {
+        let id = h.request().await;
+        h.host.mcp_requests.answer("main", id, false, None).unwrap();
+    };
+    let (error, ()) = tokio::join!(denied, deny);
+    assert!(error.contains("denied by the user"));
+    assert!(h.host.processes.list().is_empty());
+    h.events.lock().unwrap().clear();
+    let run = h.json("execute_run_configuration", json!({"configurationName":"MCP test","timeout":10000}));
+    let allow = async {
+        let id = h.request().await;
+        h.host.mcp_requests.answer("main", id, true, None).unwrap();
+    };
+    let (result, ()) = tokio::join!(run, allow);
+    assert_eq!(result["exitCode"], 7);
+    assert!(result["output"].as_str().unwrap().contains("captured-output"));
+}
+
+#[tokio::test(flavor = "multi_thread")]
+#[ignore = "requires rust-analyzer, like language_smoke::rust"]
+async fn rust_references_and_rename_through_mcp() {
+    let h = Harness::new();
+    h.trust().await;
+    let fixture = Path::new(env!("CARGO_MANIFEST_DIR")).join("../../fixtures/rust-app");
+    for name in ["Cargo.toml", "Cargo.lock"] {
+        std::fs::copy(fixture.join(name), h.root.join(name)).unwrap();
+    }
+    for name in ["lib.rs", "main.rs", "parser.rs"] {
+        std::fs::copy(fixture.join("src").join(name), h.root.join("src").join(name)).unwrap();
+    }
+    let project = h.host.project("main").unwrap();
+    let doc = project.documents.open(&h.root.join("src/lib.rs")).unwrap();
+    let text = project.documents.text_snapshot(doc.id).unwrap().text;
+    let (line, row) = text.lines().enumerate().find(|(_, row)| row.contains("fn format_price")).unwrap();
+    let column = row[..row.find("format_price").unwrap()].encode_utf16().count() + 1;
+    let args = json!({"filePath":"src/lib.rs", "line":line + 1, "column":column});
+    let deadline = std::time::Instant::now() + std::time::Duration::from_secs(120);
+    loop {
+        let result = tokio::task::spawn_blocking({
+            let host = h.host.clone();
+            let root = h.root.clone();
+            let args = args.to_string();
+            move || Registry::new(host).call(&root, "find_references", &args, CancellationToken::new())
+        })
+        .await
+        .unwrap();
+        if let Ok(result) = result {
+            let refs: Value = serde_json::from_str(&result).unwrap();
+            if refs["locations"].as_array().is_some_and(|locations| {
+                locations.iter().any(|l| l["path"].as_str().is_some_and(|p| p.ends_with("main.rs")))
+            }) {
+                break;
+            }
+        }
+        assert!(std::time::Instant::now() < deadline, "language server did not find format_price references");
+        tokio::time::sleep(std::time::Duration::from_millis(500)).await;
+    }
+    let result = h.json("rename_refactoring", json!({"pathInProject":"src/lib.rs", "symbolName":"format_price", "newName":"format_amount", "line":line + 1, "column":column})).await;
+    assert_eq!(result["applied"], true, "{result}");
+    assert!(project.documents.text_snapshot(doc.id).unwrap().text.contains("format_amount"));
+    assert!(std::fs::read_to_string(h.root.join("src/main.rs")).unwrap().contains("format_amount"));
+}

crates/ide-mcp/Cargo.toml

@@ -0,0 +1,24 @@
+[package]
+name = "ide-mcp"
+description = "The IDE's MCP server: Streamable HTTP on 127.0.0.1 for AI agents outside the IDE, its discovery file and the stdio bridge"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[dependencies]
+bytes = "1"
+dunce.workspace = true
+getrandom = "0.3"
+http-body-util = "0.1"
+hyper = { version = "1", features = ["client", "http1", "server"] }
+hyper-util = { version = "0.1", default-features = false, features = ["tokio"] }
+percent-encoding = "2"
+serde.workspace = true
+serde_json.workspace = true
+tokio = { workspace = true, features = ["net", "io-std"] }
+tracing.workspace = true
+tokio-util.workspace = true
+
+[dev-dependencies]
+tempfile.workspace = true
+tokio = { workspace = true, features = ["net", "io-std", "rt-multi-thread", "macros"] }

crates/ide-mcp/src/discovery.rs

@@ -0,0 +1,94 @@
+//! `<app-data>/mcp/server.json`: where the running IDE's server listens and
+//! its token, for the stdio bridge. Readable only by the user; removed when
+//! the server stops.
+
+use serde::{Deserialize, Serialize};
+use std::io;
+use std::path::{Path, PathBuf};
+
+/// The discovery file, relative to the app data directory.
+pub const DISCOVERY_FILE: &str = "mcp/server.json";
+
+/// The discovery file of the IDE whose app data directory is `app_data`.
+pub fn discovery_path(app_data: &Path) -> PathBuf {
+    app_data.join(DISCOVERY_FILE)
+}
+
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub struct Discovery {
+    pub port: u16,
+    pub token: String,
+    /// The IDE's process.
+    pub pid: u32,
+    /// The IDE's version.
+    pub version: String,
+}
+
+impl Discovery {
+    pub fn read(path: &Path) -> io::Result<Self> {
+        let bytes = std::fs::read(path)?;
+        serde_json::from_slice(&bytes).map_err(|e| io::Error::new(io::ErrorKind::InvalidData, e))
+    }
+
+    /// Writes the file atomically, readable only by the user.
+    pub fn write(&self, path: &Path) -> io::Result<()> {
+        let dir = path.parent().ok_or_else(|| io::Error::other("no parent directory"))?;
+        std::fs::create_dir_all(dir)?;
+        let tmp = path.with_extension(format!("tmp{}", std::process::id()));
+        let bytes = serde_json::to_vec_pretty(self).map_err(io::Error::other)?;
+        let written = write_private(&tmp, &bytes).and_then(|()| std::fs::rename(&tmp, path));
+        if written.is_err() {
+            let _ = std::fs::remove_file(&tmp);
+        }
+        written
+    }
+
+    /// Removes the file at `path` if it still describes this process's server.
+    pub fn remove_if_ours(path: &Path) {
+        if Self::read(path).is_ok_and(|d| d.pid == std::process::id()) {
+            let _ = std::fs::remove_file(path);
+        }
+    }
+}
+
+#[cfg(unix)]
+fn write_private(path: &Path, bytes: &[u8]) -> io::Result<()> {
+    use std::io::Write;
+    use std::os::unix::fs::OpenOptionsExt;
+    let _ = std::fs::remove_file(path);
+    let mut file = std::fs::OpenOptions::new().write(true).create_new(true).mode(0o600).open(path)?;
+    file.write_all(bytes)?;
+    file.sync_all()
+}
+
+/// The app data directory is the user's own on Windows.
+#[cfg(not(unix))]
+fn write_private(path: &Path, bytes: &[u8]) -> io::Result<()> {
+    std::fs::write(path, bytes)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn round_trips_privately_and_only_its_owner_removes_it() {
+        let tmp = tempfile::tempdir().unwrap();
+        let path = discovery_path(tmp.path());
+        let ours = Discovery { port: 1234, token: "t".into(), pid: std::process::id(), version: "0.1.0".into() };
+        ours.write(&path).unwrap();
+        assert_eq!(Discovery::read(&path).unwrap(), ours);
+        #[cfg(unix)]
+        {
+            use std::os::unix::fs::PermissionsExt;
+            assert_eq!(std::fs::metadata(&path).unwrap().permissions().mode() & 0o777, 0o600);
+        }
+        let theirs = Discovery { pid: ours.pid.wrapping_add(1), ..ours.clone() };
+        theirs.write(&path).unwrap();
+        Discovery::remove_if_ours(&path);
+        assert!(path.is_file(), "another process's file stays");
+        ours.write(&path).unwrap();
+        Discovery::remove_if_ours(&path);
+        assert!(!path.exists());
+    }
+}

crates/ide-mcp/src/lib.rs

@@ -0,0 +1,154 @@
+//! The IDE's MCP server: AI agents outside the IDE (Claude Code, Codex…) call
+//! the IDE's built-in tools.
+//!
+//! - **Transport:** MCP Streamable HTTP (2025-06-18; 2025-03-26 and 2024-11-05
+//!   clients too) on `127.0.0.1:<random port>`, endpoint `/mcp`. Responses are
+//!   plain JSON (no SSE streams: `GET` is 405). Every request carries
+//!   `Authorization: Bearer <token>` (random, per run); requests from another
+//!   `Origin` or `Host` are refused (DNS rebinding).
+//! - **Projects:** the `X-OpenIDEA-Project` header or the `?project=` query
+//!   names a folder; the server picks the open project containing it.
+//! - **Discovery:** `<app-data>/mcp/server.json` (`port`, `token`, `pid`,
+//!   `version`; readable only by the user) while the server runs.
+//! - **Stdio:** `<app exe> --mcp-stdio [--project <path>]` reads the discovery
+//!   file and relays newline-delimited JSON-RPC to the server ([`stdio`]), so
+//!   persisted client configurations hold no token.
+//!
+//! The tools themselves come from a [`ToolRegistry`] (the IDE host); this
+//! crate knows nothing about plugins.
+
+mod discovery;
+mod protocol;
+mod server;
+pub mod stdio;
+
+pub use discovery::{DISCOVERY_FILE, Discovery, discovery_path};
+pub use server::McpServer;
+pub use tokio_util::sync::CancellationToken;
+
+use std::path::{Path, PathBuf};
+
+/// The header naming the project a request is about (an absolute path).
+pub const PROJECT_HEADER: &str = "x-openidea-project";
+/// The command-line flag that runs the executable as the stdio bridge.
+pub const STDIO_FLAG: &str = "--mcp-stdio";
+
+/// A tool as `tools/list` shows it.
+#[derive(Clone, Debug, PartialEq)]
+pub struct Tool {
+    pub name: String,
+    pub description: String,
+    /// A JSON Schema of the `arguments` object.
+    pub input_schema: serde_json::Value,
+    pub output_schema: Option<serde_json::Value>,
+    /// Only reads (`annotations.readOnlyHint`).
+    pub read_only: bool,
+    /// May destroy data (`annotations.destructiveHint`).
+    pub destructive: bool,
+}
+
+/// A failed `tools/call`.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub enum ToolCallError {
+    /// No such tool for the project: a protocol error.
+    UnknownTool(String),
+    /// The tool ran and failed, or couldn't run: a result with `isError`.
+    Failed(String),
+}
+
+/// Where the tools come from (the IDE host). Calls block; the server runs
+/// them off its async threads.
+pub trait ToolRegistry: Send + Sync + 'static {
+    /// Roots of the projects open in the IDE that the server serves.
+    fn projects(&self) -> Vec<PathBuf>;
+    /// The tools callable for `project` (one of [`Self::projects`]). `Err`
+    /// says why there are none (an unsupported project).
+    fn tools(&self, project: &Path) -> Result<Vec<Tool>, String>;
+    fn call_with_client(
+        &self,
+        project: &Path,
+        name: &str,
+        arguments: &str,
+        cancel: CancellationToken,
+        _client: &str,
+    ) -> Result<String, ToolCallError> {
+        self.call(project, name, arguments, cancel)
+    }
+
+    /// Runs tool `name` with `arguments` (a JSON object, as text) for `project`.
+    fn call(
+        &self,
+        project: &Path,
+        name: &str,
+        arguments: &str,
+        cancel: CancellationToken,
+    ) -> Result<String, ToolCallError>;
+}
+
+/// The URL of the server at `port` for `project`.
+pub fn endpoint_url(port: u16, project: &Path) -> String {
+    format!("http://127.0.0.1:{port}/mcp?project={}", encode_query(&project.to_string_lossy()))
+}
+
+/// The stdio bridge's command line for `project`: `exe --mcp-stdio --project <project>`.
+pub fn stdio_command(exe: &Path, project: &Path) -> Vec<String> {
+    vec![
+        exe.to_string_lossy().into_owned(),
+        STDIO_FLAG.to_owned(),
+        "--project".to_owned(),
+        project.to_string_lossy().into_owned(),
+    ]
+}
+
+/// Whether `args` (the process's, program name first) ask for the stdio
+/// bridge; then the project it is for (`--project <path>`, `None`: the
+/// current directory).
+pub fn stdio_request(args: &[String]) -> Option<Option<PathBuf>> {
+    let rest = args.get(1..).unwrap_or_default();
+    if !rest.iter().any(|a| a == STDIO_FLAG) {
+        return None;
+    }
+    let project = rest
+        .iter()
+        .position(|a| a == "--project")
+        .and_then(|i| rest.get(i + 1))
+        .map(PathBuf::from)
+        .or_else(|| rest.iter().find_map(|a| a.strip_prefix("--project=").map(PathBuf::from)));
+    Some(project)
+}
+
+/// Characters escaped in a query value: everything but unreserved characters and `/`.
+const QUERY: &percent_encoding::AsciiSet =
+    &percent_encoding::NON_ALPHANUMERIC.remove(b'-').remove(b'_').remove(b'.').remove(b'~').remove(b'/');
+
+pub(crate) fn encode_query(value: &str) -> String {
+    percent_encoding::utf8_percent_encode(value, QUERY).to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn urls_and_commands_name_the_project() {
+        let url = endpoint_url(4321, Path::new("/home/me/my app/项目"));
+        assert_eq!(url, "http://127.0.0.1:4321/mcp?project=/home/me/my%20app/%E9%A1%B9%E7%9B%AE");
+        assert_eq!(
+            stdio_command(Path::new("/Applications/OpenIDEA.app/Contents/MacOS/openidea"), Path::new("/p")),
+            ["/Applications/OpenIDEA.app/Contents/MacOS/openidea", "--mcp-stdio", "--project", "/p"]
+        );
+    }
+
+    #[test]
+    fn stdio_requests_are_recognized() {
+        let args = |a: &[&str]| a.iter().map(|s| (*s).to_owned()).collect::<Vec<_>>();
+        assert_eq!(stdio_request(&args(&["openidea"])), None);
+        assert_eq!(stdio_request(&args(&["openidea", "/some/project"])), None);
+        assert_eq!(stdio_request(&args(&["openidea", "--mcp-stdio"])), Some(None));
+        assert_eq!(
+            stdio_request(&args(&["openidea", "--mcp-stdio", "--project", "/p"])),
+            Some(Some(PathBuf::from("/p")))
+        );
+        assert_eq!(stdio_request(&args(&["openidea", "--project=/q", "--mcp-stdio"])), Some(Some(PathBuf::from("/q"))));
+    }
+}

crates/ide-mcp/src/protocol.rs

@@ -0,0 +1,298 @@
+//! MCP over JSON-RPC 2.0: `initialize`, `ping`, `tools/list`, `tools/call`
+//! and notifications, for one POST body (a message or a batch). Blocking: the
+//! server runs it on a blocking thread.
+
+use crate::{CancellationToken, Tool, ToolCallError, ToolRegistry};
+use serde_json::{Value, json};
+use std::collections::HashMap;
+use std::path::{Path, PathBuf};
+use std::sync::Mutex;
+
+#[derive(Default)]
+pub(crate) struct Requests(Mutex<RequestState>);
+#[derive(Default)]
+struct RequestState {
+    clients: HashMap<String, String>,
+    running: HashMap<(String, String), CancellationToken>,
+    early: HashMap<(String, String), std::time::Instant>,
+}
+struct InFlight<'a> {
+    requests: &'a Requests,
+    key: (String, String),
+}
+impl Drop for InFlight<'_> {
+    fn drop(&mut self) {
+        self.requests.0.lock().unwrap().running.remove(&self.key);
+    }
+}
+
+/// The protocol version answered when the client asks for one this server doesn't know.
+pub(crate) const LATEST: &str = "2025-06-18";
+pub(crate) const SUPPORTED: [&str; 3] = ["2025-06-18", "2025-03-26", "2024-11-05"];
+
+const PARSE_ERROR: i64 = -32700;
+const INVALID_REQUEST: i64 = -32600;
+const METHOD_NOT_FOUND: i64 = -32601;
+const INVALID_PARAMS: i64 = -32602;
+/// The requested folder isn't a project open in the IDE (or has no tools there).
+pub(crate) const NOT_OPEN: i64 = -32001;
+
+pub(crate) struct RpcError {
+    code: i64,
+    message: String,
+}
+
+impl RpcError {
+    fn new(code: i64, message: impl Into<String>) -> Self {
+        Self { code, message: message.into() }
+    }
+}
+
+pub(crate) fn error_response(id: Value, code: i64, message: &str) -> Value {
+    json!({ "jsonrpc": "2.0", "id": id, "error": { "code": code, "message": message } })
+}
+
+/// Answers one POST body: `Ok(None)` when it held only notifications and
+/// responses (HTTP 202), `Err` with the error response when it isn't JSON.
+pub(crate) fn handle_body(
+    registry: &dyn ToolRegistry,
+    project: Option<&str>,
+    body: &[u8],
+    requests: &Requests,
+    scope: &str,
+    cancel: CancellationToken,
+) -> Result<Option<Value>, Value> {
+    let message: Value = serde_json::from_slice(body)
+        .map_err(|e| error_response(Value::Null, PARSE_ERROR, &format!("not JSON: {e}")))?;
+    let session = Session { registry, project, requests, scope, cancel };
+    Ok(match message {
+        Value::Array(batch) if batch.is_empty() => Some(error_response(Value::Null, INVALID_REQUEST, "an empty batch")),
+        Value::Array(batch) => {
+            let replies: Vec<Value> = batch.into_iter().filter_map(|m| session.handle(m)).collect();
+            (!replies.is_empty()).then_some(Value::Array(replies))
+        }
+        message => session.handle(message),
+    })
+}
+
+struct Session<'a> {
+    registry: &'a dyn ToolRegistry,
+    project: Option<&'a str>,
+    requests: &'a Requests,
+    scope: &'a str,
+    cancel: CancellationToken,
+}
+
+impl Session<'_> {
+    /// The response to one message (`None` for notifications and responses).
+    fn handle(&self, message: Value) -> Option<Value> {
+        let Value::Object(mut message) = message else {
+            return Some(error_response(Value::Null, INVALID_REQUEST, "not a JSON-RPC message"));
+        };
+        let id = message.remove("id");
+        if message.get("jsonrpc") != Some(&json!("2.0"))
+            || id.as_ref().is_some_and(|id| !id.is_null() && !id.is_string() && !id.is_number())
+        {
+            return Some(error_response(Value::Null, INVALID_REQUEST, "invalid JSON-RPC envelope"));
+        }
+        let Some(method) = message.get("method").and_then(Value::as_str).map(str::to_owned) else {
+            // A response to a request of ours (we send none), or garbage.
+            return id.map(|id| error_response(id, INVALID_REQUEST, "not a JSON-RPC request"));
+        };
+        if method == "notifications/cancelled" {
+            if let Some(id) = message.get("params").and_then(|p| p.get("requestId")) {
+                let key = (self.scope.to_owned(), id.to_string());
+                let mut state = self.requests.0.lock().unwrap();
+                if let Some(cancel) = state.running.get(&key) {
+                    cancel.cancel();
+                } else if state.early.len() < 1024 {
+                    state.early.insert(key, std::time::Instant::now());
+                }
+            }
+            return None;
+        }
+        let id = id?;
+        let key = (self.scope.to_owned(), id.to_string());
+        let cancel = self.cancel.child_token();
+        {
+            let mut requests = self.requests.0.lock().unwrap();
+            requests.early.retain(|_, at| at.elapsed() < std::time::Duration::from_secs(60));
+            if requests.running.contains_key(&key) {
+                return Some(error_response(id, INVALID_REQUEST, "request id already in flight"));
+            }
+            if requests.early.remove(&key).is_some() {
+                cancel.cancel();
+            }
+            requests.running.insert(key.clone(), cancel.clone());
+        }
+        let _in_flight = InFlight { requests: self.requests, key };
+        let params = message.remove("params").unwrap_or(Value::Null);
+        let result = match self.request(&method, params, cancel) {
+            Ok(result) => json!({ "jsonrpc": "2.0", "id": id, "result": result }),
+            Err(e) => error_response(id, e.code, &e.message),
+        };
+        Some(result)
+    }
+
+    fn request(&self, method: &str, params: Value, cancel: CancellationToken) -> Result<Value, RpcError> {
+        match method {
+            "initialize" => Ok(self.initialize(&params)),
+            "ping" => Ok(json!({})),
+            "tools/list" => {
+                let project = self.project()?;
+                let tools = self.registry.tools(&project).map_err(|e| RpcError::new(NOT_OPEN, e))?;
+                Ok(json!({ "tools": tools.iter().map(tool_json).collect::<Vec<_>>() }))
+            }
+            "tools/call" => self.call(params, cancel),
+            _ => Err(RpcError::new(METHOD_NOT_FOUND, format!("no method {method:?}"))),
+        }
+    }
+
+    fn initialize(&self, params: &Value) -> Value {
+        if let Some(name) = params.pointer("/clientInfo/name").and_then(Value::as_str) {
+            let mut requests = self.requests.0.lock().unwrap();
+            if requests.clients.len() < 1024 {
+                requests.clients.insert(self.scope.into(), name.chars().take(128).collect());
+            }
+        }
+        let asked = params.get("protocolVersion").and_then(Value::as_str).unwrap_or(LATEST);
+        let version = if SUPPORTED.contains(&asked) { asked } else { LATEST };
+        let about = match self.project() {
+            Ok(root) => format!("the project open in OpenIDEA at {}", root.display()),
+            Err(_) => "a project open in OpenIDEA".to_owned(),
+        };
+        json!({
+            "protocolVersion": version,
+            "capabilities": { "tools": { "listChanged": false } },
+            "serverInfo": { "name": "OpenIDEA", "version": env!("CARGO_PKG_VERSION") },
+            "instructions": format!(
+                "Built-in OpenIDEA tools for {about}: they see the files and editors the IDE has open."
+            ),
+        })
+    }
+
+    fn call(&self, params: Value, cancel: CancellationToken) -> Result<Value, RpcError> {
+        let name = params
+            .get("name")
+            .and_then(Value::as_str)
+            .ok_or_else(|| RpcError::new(INVALID_PARAMS, "tools/call needs a tool `name`"))?;
+        let arguments = match params.get("arguments") {
+            None | Some(Value::Null) => "{}".to_owned(),
+            Some(args @ Value::Object(_)) => args.to_string(),
+            Some(_) => return Err(RpcError::new(INVALID_PARAMS, "`arguments` must be an object")),
+        };
+        let requested = params.pointer("/arguments/projectPath");
+        if requested.is_some_and(|v| !v.is_string()) {
+            return Err(RpcError::new(INVALID_PARAMS, "projectPath must be a string"));
+        }
+        let project = self.resolve_project(requested.and_then(Value::as_str).or(self.project))?;
+        let outcome = if cancel.is_cancelled() {
+            Err(ToolCallError::Failed("cancelled".into()))
+        } else {
+            let client =
+                self.requests.0.lock().unwrap().clients.get(self.scope).cloned().unwrap_or_else(|| "MCP client".into());
+            self.registry.call_with_client(&project, name, &arguments, cancel, &client)
+        };
+        let (text, is_error) = match outcome {
+            Ok(text) => (text, false),
+            Err(ToolCallError::Failed(message)) => (message, true),
+            Err(ToolCallError::UnknownTool(message)) => return Err(RpcError::new(INVALID_PARAMS, message)),
+        };
+        let mut result = json!({ "content": [{ "type": "text", "text": text }], "isError": is_error });
+        if !is_error && let Ok(value @ Value::Object(_)) = serde_json::from_str::<Value>(&text) {
+            result["structuredContent"] = value;
+        }
+        Ok(result)
+    }
+
+    /// The open project the request names.
+    fn project(&self) -> Result<PathBuf, RpcError> {
+        self.resolve_project(self.project)
+    }
+
+    fn resolve_project(&self, requested: Option<&str>) -> Result<PathBuf, RpcError> {
+        let mut roots = self.registry.projects();
+        roots.sort();
+        roots.dedup();
+        if let Some(requested) = requested.filter(|p| !p.trim().is_empty()) {
+            return resolve(&roots, Path::new(requested)).ok_or_else(|| {
+                RpcError::new(
+                    NOT_OPEN,
+                    format!(
+                        "this folder isn't open in OpenIDEA: {requested}. Open projects: {}",
+                        roots.iter().map(|p| p.display().to_string()).collect::<Vec<_>>().join(", ")
+                    ),
+                )
+            });
+        }
+        if roots.len() == 1 {
+            return Ok(roots.remove(0));
+        }
+        Err(RpcError::new(
+            INVALID_PARAMS,
+            format!(
+                "Specify projectPath, X-OpenIDEA-Project or ?project=. Open projects: {}",
+                roots.iter().map(|p| p.display().to_string()).collect::<Vec<_>>().join(", ")
+            ),
+        ))
+    }
+}
+
+/// The project among `roots` containing `path` (the innermost one).
+fn resolve(roots: &[PathBuf], path: &Path) -> Option<PathBuf> {
+    if !path.is_absolute() {
+        return None;
+    }
+    let path = dunce::canonicalize(path).unwrap_or_else(|_| {
+        let mut out = PathBuf::new();
+        for part in path.components() {
+            match part {
+                std::path::Component::CurDir => {}
+                std::path::Component::ParentDir => {
+                    out.pop();
+                }
+                part => out.push(part.as_os_str()),
+            }
+        }
+        out
+    });
+    roots
+        .iter()
+        .filter_map(|root| {
+            let canonical = dunce::canonicalize(root).unwrap_or_else(|_| root.clone());
+            path.starts_with(&canonical).then(|| (canonical.components().count(), root))
+        })
+        .max_by_key(|(depth, _)| *depth)
+        .map(|(_, root)| root.clone())
+}
+
+fn tool_json(tool: &Tool) -> Value {
+    let mut value = json!({
+        "name": tool.name, "description": tool.description, "inputSchema": tool.input_schema,
+        "annotations": { "readOnlyHint": tool.read_only, "destructiveHint": tool.destructive },
+    });
+    if let Some(schema) = &tool.output_schema {
+        value["outputSchema"] = schema.clone();
+    }
+    value
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn the_innermost_open_project_containing_the_path_answers() {
+        let tmp = tempfile::tempdir().unwrap();
+        let outer = dunce::canonicalize(tmp.path()).unwrap();
+        let inner = outer.join("inner");
+        std::fs::create_dir_all(inner.join("src")).unwrap();
+        let roots = [outer.clone(), inner.clone()];
+        assert_eq!(resolve(&roots, &inner.join("src")), Some(inner.clone()));
+        assert_eq!(resolve(&roots, &outer.join("other")), Some(outer.clone()));
+        assert_eq!(resolve(&roots[1..], &outer), None);
+        assert_eq!(resolve(&roots, Path::new("relative/path")), None);
+        // Siblings sharing a prefix are not inside.
+        assert_eq!(resolve(&roots[1..], &outer.join("inner-two")), None);
+    }
+}

crates/ide-mcp/src/server.rs

@@ -0,0 +1,301 @@
+//! The HTTP side: one endpoint, `/mcp`, on the loopback interface.
+
+use crate::discovery::Discovery;
+use crate::{CancellationToken, PROJECT_HEADER, ToolRegistry, protocol};
+use bytes::Bytes;
+use http_body_util::{BodyExt, Full, Limited};
+use hyper::body::Incoming;
+use hyper::header::{self, HeaderMap, HeaderValue};
+use hyper::{Method, Request, Response, StatusCode};
+use std::convert::Infallible;
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+use tokio::sync::watch;
+
+/// Largest request body.
+const MAX_BODY: usize = 8 << 20;
+
+struct Shared {
+    registry: Arc<dyn ToolRegistry>,
+    token: String,
+    port: u16,
+    requests: protocol::Requests,
+    cancel: CancellationToken,
+}
+
+/// The running server. Stopping it (or dropping it) closes the port and
+/// removes its discovery file.
+pub struct McpServer {
+    port: u16,
+    token: String,
+    discovery: Option<PathBuf>,
+    shutdown: watch::Sender<bool>,
+    cancel: CancellationToken,
+}
+
+impl McpServer {
+    /// Starts listening on `127.0.0.1:<random port>` with a new token, on
+    /// `runtime`, and writes the discovery file at `discovery` if given.
+    pub fn start(
+        registry: Arc<dyn ToolRegistry>,
+        discovery: Option<PathBuf>,
+        runtime: &tokio::runtime::Handle,
+    ) -> std::io::Result<Self> {
+        let listener = std::net::TcpListener::bind(("127.0.0.1", 0))?;
+        listener.set_nonblocking(true)?;
+        let port = listener.local_addr()?.port();
+        let token = new_token()?;
+        let listener = {
+            let _entered = runtime.enter();
+            tokio::net::TcpListener::from_std(listener)?
+        };
+        if let Some(path) = &discovery {
+            let info = Discovery {
+                port,
+                token: token.clone(),
+                pid: std::process::id(),
+                version: env!("CARGO_PKG_VERSION").to_owned(),
+            };
+            info.write(path)?;
+        }
+        let (shutdown, stopped) = watch::channel(false);
+        let cancel = CancellationToken::new();
+        let shared = Arc::new(Shared {
+            registry,
+            token: token.clone(),
+            port,
+            requests: Default::default(),
+            cancel: cancel.clone(),
+        });
+        runtime.spawn(accept(listener, shared, stopped));
+        tracing::info!("MCP server on 127.0.0.1:{port}");
+        Ok(Self { port, token, discovery, shutdown, cancel })
+    }
+
+    pub fn port(&self) -> u16 {
+        self.port
+    }
+
+    /// The bearer token of this run.
+    pub fn token(&self) -> &str {
+        &self.token
+    }
+
+    /// The endpoint URL for `project`.
+    pub fn url(&self, project: &Path) -> String {
+        crate::endpoint_url(self.port, project)
+    }
+
+    pub fn stop(self) {}
+}
+
+impl Drop for McpServer {
+    fn drop(&mut self) {
+        self.cancel.cancel();
+        let _ = self.shutdown.send(true);
+        if let Some(path) = &self.discovery {
+            Discovery::remove_if_ours(path);
+        }
+    }
+}
+
+pub(crate) fn new_token() -> std::io::Result<String> {
+    let mut bytes = [0u8; 32];
+    getrandom::fill(&mut bytes).map_err(|e| std::io::Error::other(e.to_string()))?;
+    Ok(bytes.iter().map(|b| format!("{b:02x}")).collect())
+}
+
+async fn accept(listener: tokio::net::TcpListener, shared: Arc<Shared>, mut stopped: watch::Receiver<bool>) {
+    loop {
+        let stream = tokio::select! {
+            _ = stopped.changed() => return,
+            accepted = listener.accept() => match accepted {
+                Ok((stream, _)) => stream,
+                Err(e) => {
+                    tracing::warn!("MCP server accept: {e}");
+                    tokio::time::sleep(std::time::Duration::from_millis(100)).await;
+                    continue;
+                }
+            },
+        };
+        let (shared, mut stopped) = (shared.clone(), stopped.clone());
+        tokio::spawn(async move {
+            let scope = match new_token() {
+                Ok(scope) => scope,
+                Err(_) => return,
+            };
+            let service = hyper::service::service_fn(move |req| serve(req, shared.clone(), scope.clone()));
+            let conn = hyper::server::conn::http1::Builder::new()
+                .serve_connection(hyper_util::rt::TokioIo::new(stream), service);
+            tokio::pin!(conn);
+            tokio::select! {
+                result = conn.as_mut() => {
+                    if let Err(e) = result {
+                        tracing::debug!("MCP connection: {e}");
+                    }
+                }
+                _ = stopped.changed() => {}
+            }
+        });
+    }
+}
+
+async fn serve(
+    req: Request<Incoming>,
+    shared: Arc<Shared>,
+    scope: String,
+) -> Result<Response<Full<Bytes>>, Infallible> {
+    Ok(respond(req, &shared, scope).await)
+}
+
+type Reply = Response<Full<Bytes>>;
+
+async fn respond(req: Request<Incoming>, shared: &Arc<Shared>, scope: String) -> Reply {
+    if req.uri().path() != "/mcp" {
+        return plain(StatusCode::NOT_FOUND, "not found: the endpoint is /mcp");
+    }
+    if !local_request(req.headers(), shared.port) {
+        return plain(StatusCode::FORBIDDEN, "requests from web pages are refused");
+    }
+    if !authorized(req.headers(), &shared.token) {
+        let mut response = plain(StatusCode::UNAUTHORIZED, "missing or wrong bearer token");
+        response.headers_mut().insert(header::WWW_AUTHENTICATE, HeaderValue::from_static("Bearer"));
+        return response;
+    }
+    if req.method() != Method::POST {
+        // No server-sent event streams: every answer is in the POST's response.
+        let mut response = plain(StatusCode::METHOD_NOT_ALLOWED, "only POST");
+        response.headers_mut().insert(header::ALLOW, HeaderValue::from_static("POST"));
+        return response;
+    }
+    if let Some(version) = req.headers().get("mcp-protocol-version")
+        && !version.to_str().is_ok_and(|v| protocol::SUPPORTED.contains(&v))
+    {
+        return plain(StatusCode::BAD_REQUEST, "unsupported MCP-Protocol-Version");
+    }
+    let scope = req.headers().get("mcp-session-id").and_then(|v| v.to_str().ok()).unwrap_or(&scope).to_owned();
+    let project = project_of(&req);
+    let body = match Limited::new(req.into_body(), MAX_BODY).collect().await {
+        Ok(body) => body.to_bytes(),
+        Err(e) => return plain(StatusCode::PAYLOAD_TOO_LARGE, &format!("request body: {e}")),
+    };
+    let initializing = serde_json::from_slice::<serde_json::Value>(&body)
+        .is_ok_and(|m| m.get("method").and_then(|v| v.as_str()) == Some("initialize"));
+    let response_scope = scope.clone();
+    let registry = shared.registry.clone();
+    let shared = shared.clone();
+    let cancel = shared.cancel.child_token();
+    let _guard = cancel.clone().drop_guard();
+    let handled = tokio::task::spawn_blocking(move || {
+        protocol::handle_body(registry.as_ref(), project.as_deref(), &body, &shared.requests, &scope, cancel)
+    })
+    .await;
+    match handled {
+        Ok(Ok(Some(reply))) => {
+            let mut response = json(StatusCode::OK, &reply);
+            if initializing && let Ok(value) = HeaderValue::from_str(&response_scope) {
+                response.headers_mut().insert("mcp-session-id", value);
+            }
+            response
+        }
+        Ok(Ok(None)) => empty(StatusCode::ACCEPTED),
+        Ok(Err(parse_error)) => json(StatusCode::BAD_REQUEST, &parse_error),
+        Err(e) => plain(StatusCode::INTERNAL_SERVER_ERROR, &format!("the request failed: {e}")),
+    }
+}
+
+/// No `Origin` other than this server's own, and a loopback `Host`: a web
+/// page (DNS rebinding) can't reach the tools even before the token check.
+fn local_request(headers: &HeaderMap, port: u16) -> bool {
+    let ours = |authority: &str| {
+        ["127.0.0.1", "localhost", "[::1]"].iter().any(|host| authority.eq_ignore_ascii_case(&format!("{host}:{port}")))
+    };
+    let host_ok = headers.get(header::HOST).is_none_or(|h| h.to_str().is_ok_and(ours));
+    let origin_ok = headers.get(header::ORIGIN).is_none_or(|o| {
+        o.to_str()
+            .is_ok_and(|o| o.strip_prefix("http://").is_some_and(|authority| ours(authority.trim_end_matches('/'))))
+    });
+    host_ok && origin_ok
+}
+
+fn authorized(headers: &HeaderMap, token: &str) -> bool {
+    let Some(given) = headers.get(header::AUTHORIZATION).and_then(|v| v.to_str().ok()) else { return false };
+    let Some((scheme, given)) = given.trim().split_once(' ') else { return false };
+    scheme.eq_ignore_ascii_case("bearer") && constant_time_eq(given.trim().as_bytes(), token.as_bytes())
+}
+
+fn constant_time_eq(a: &[u8], b: &[u8]) -> bool {
+    a.len() == b.len() && a.iter().zip(b).fold(0u8, |acc, (x, y)| acc | (x ^ y)) == 0
+}
+
+/// The project the request names: the header (UTF-8), else `?project=` (percent-encoded).
+fn project_of(req: &Request<Incoming>) -> Option<String> {
+    if let Some(value) = req.headers().get(PROJECT_HEADER) {
+        return String::from_utf8(value.as_bytes().to_vec()).ok();
+    }
+    req.uri().query()?.split('&').find_map(|pair| {
+        let (key, value) = pair.split_once('=')?;
+        (key == "project").then(|| {
+            let value = value.replace('+', " ");
+            percent_encoding::percent_decode_str(&value).decode_utf8_lossy().into_owned()
+        })
+    })
+}
+
+fn plain(status: StatusCode, text: &str) -> Response<Full<Bytes>> {
+    let mut response = Response::new(Full::new(Bytes::from(text.to_owned())));
+    *response.status_mut() = status;
+    response.headers_mut().insert(header::CONTENT_TYPE, HeaderValue::from_static("text/plain; charset=utf-8"));
+    response
+}
+
+fn json(status: StatusCode, value: &serde_json::Value) -> Response<Full<Bytes>> {
+    let mut response = Response::new(Full::new(Bytes::from(value.to_string())));
+    *response.status_mut() = status;
+    response.headers_mut().insert(header::CONTENT_TYPE, HeaderValue::from_static("application/json"));
+    response
+}
+
+fn empty(status: StatusCode) -> Response<Full<Bytes>> {
+    let mut response = Response::new(Full::new(Bytes::new()));
+    *response.status_mut() = status;
+    response
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn only_loopback_hosts_and_origins_of_this_server_pass() {
+        let headers = |pairs: &[(header::HeaderName, &str)]| {
+            let mut h = HeaderMap::new();
+            for (k, v) in pairs {
+                h.insert(k.clone(), HeaderValue::from_str(v).unwrap());
+            }
+            h
+        };
+        assert!(local_request(&headers(&[]), 80));
+        assert!(local_request(&headers(&[(header::HOST, "127.0.0.1:80")]), 80));
+        assert!(local_request(
+            &headers(&[(header::HOST, "localhost:80"), (header::ORIGIN, "http://localhost:80")]),
+            80
+        ));
+        assert!(!local_request(&headers(&[(header::HOST, "evil.example:80")]), 80));
+        assert!(!local_request(&headers(&[(header::HOST, "127.0.0.1:81")]), 80));
+        assert!(!local_request(&headers(&[(header::ORIGIN, "https://evil.example")]), 80));
+        assert!(!local_request(&headers(&[(header::ORIGIN, "null")]), 80));
+    }
+
+    #[test]
+    fn bearer_tokens_compare_exactly() {
+        let mut h = HeaderMap::new();
+        assert!(!authorized(&h, "abc"));
+        h.insert(header::AUTHORIZATION, HeaderValue::from_static("Bearer abc"));
+        assert!(authorized(&h, "abc"));
+        assert!(!authorized(&h, "abcd"));
+        h.insert(header::AUTHORIZATION, HeaderValue::from_static("Basic abc"));
+        assert!(!authorized(&h, "abc"));
+        assert_eq!(new_token().unwrap().len(), 64);
+    }
+}

crates/ide-mcp/src/stdio.rs

@@ -0,0 +1,130 @@
+//! The stdio bridge: `<app exe> --mcp-stdio [--project <path>]`. MCP clients
+//! that start servers as processes (and configurations that must not hold a
+//! token) talk newline-delimited JSON-RPC to it; it relays each message to the
+//! running IDE's server, found through the discovery file.
+
+use crate::discovery::Discovery;
+use crate::protocol::{NOT_OPEN, error_response};
+use bytes::Bytes;
+use http_body_util::{BodyExt, Full};
+use hyper::{Request, StatusCode, header};
+use serde_json::Value;
+use std::path::{Path, PathBuf};
+use tokio::io::{AsyncBufRead, AsyncBufReadExt, AsyncWrite, AsyncWriteExt};
+
+/// Runs the bridge on this process's stdin and stdout until stdin closes.
+/// `project` defaults to the current directory. Returns the exit code.
+pub fn run(discovery: &Path, project: Option<PathBuf>) -> i32 {
+    let cwd = std::env::current_dir().unwrap_or_default();
+    let project = project.map_or_else(|| cwd.clone(), |p| if p.is_absolute() { p } else { cwd.join(p) });
+    let runtime = match tokio::runtime::Builder::new_current_thread().enable_all().build() {
+        Ok(rt) => rt,
+        Err(e) => {
+            eprintln!("openidea --mcp-stdio: {e}");
+            return 1;
+        }
+    };
+    let stdin = tokio::io::BufReader::new(tokio::io::stdin());
+    match runtime.block_on(bridge(discovery, &project, stdin, tokio::io::stdout())) {
+        Ok(()) => 0,
+        Err(e) => {
+            eprintln!("openidea --mcp-stdio: {e}");
+            1
+        }
+    }
+}
+
+/// Relays each line of `input` (a JSON-RPC message or batch) to the IDE and
+/// writes its answer, if any, as one line to `output`.
+pub async fn bridge<R, W>(discovery: &Path, project: &Path, input: R, mut output: W) -> std::io::Result<()>
+where
+    R: AsyncBufRead + Unpin,
+    W: AsyncWrite + Unpin,
+{
+    let scope = crate::server::new_token()?;
+    let mut lines = input.lines();
+    let mut pending = tokio::task::JoinSet::new();
+    let mut eof = false;
+    loop {
+        let reply = tokio::select! {
+            line = lines.next_line(), if !eof => {
+                let Some(line) = line? else { eof = true; continue };
+                if line.trim().is_empty() { continue; }
+                match serde_json::from_str::<Value>(&line) {
+                    Ok(message) => {
+                        let (discovery, project, scope) = (discovery.to_owned(), project.to_owned(), scope.clone());
+                        pending.spawn(async move { relay(&discovery, &project, &message, &scope).await });
+                        continue;
+                    }
+                    Err(e) => Some(error_response(Value::Null, -32700, &format!("not JSON: {e}"))),
+                }
+            }
+            reply = pending.join_next(), if !pending.is_empty() => match reply { Some(reply) => reply.map_err(std::io::Error::other)?, None => None },
+            else => break,
+        };
+        if let Some(reply) = reply {
+            output.write_all(reply.to_string().as_bytes()).await?;
+            output.write_all(b"\n").await?;
+            output.flush().await?;
+        }
+    }
+    Ok(())
+}
+
+/// The IDE's answer to `message`, or an error response for each request in
+/// it when the IDE can't be reached.
+async fn relay(discovery: &Path, project: &Path, message: &Value, scope: &str) -> Option<Value> {
+    let failure = match post(discovery, project, message, scope).await {
+        Ok((StatusCode::ACCEPTED, _)) => return None,
+        Ok((_, body)) if !body.is_empty() => match serde_json::from_slice::<Value>(&body) {
+            Ok(reply) => return Some(reply),
+            Err(_) => String::from_utf8_lossy(&body).trim().to_owned(),
+        },
+        Ok((status, _)) => format!("OpenIDEA answered {status}"),
+        Err(e) => e,
+    };
+    let errors: Vec<Value> = requests(message).into_iter().map(|id| error_response(id, NOT_OPEN, &failure)).collect();
+    match (message, errors.len()) {
+        (_, 0) => None,
+        (Value::Array(_), _) => Some(Value::Array(errors)),
+        (_, _) => errors.into_iter().next(),
+    }
+}
+
+/// Ids of the requests in a message or batch (notifications have none).
+fn requests(message: &Value) -> Vec<Value> {
+    let ids = |m: &Value| m.get("method").is_some().then(|| m.get("id").cloned()).flatten();
+    match message {
+        Value::Array(batch) => batch.iter().filter_map(ids).collect(),
+        m => ids(m).into_iter().collect(),
+    }
+}
+
+/// POSTs `message` to the server in the discovery file; a message for the
+/// user when that fails.
+async fn post(discovery: &Path, project: &Path, message: &Value, scope: &str) -> Result<(StatusCode, Bytes), String> {
+    let not_running = || {
+        format!(
+            "OpenIDEA's MCP server is not running. Start OpenIDEA, open {} in it, and turn on Settings › Tools › MCP Server",
+            project.display()
+        )
+    };
+    let info = Discovery::read(discovery).map_err(|_| not_running())?;
+    let stream = tokio::net::TcpStream::connect(("127.0.0.1", info.port)).await.map_err(|_| not_running())?;
+    let (mut sender, conn) = hyper::client::conn::http1::handshake(hyper_util::rt::TokioIo::new(stream))
+        .await
+        .map_err(|e| format!("cannot reach OpenIDEA: {e}"))?;
+    tokio::spawn(conn);
+    let request = Request::post(format!("/mcp?project={}", crate::encode_query(&project.to_string_lossy())))
+        .header(header::HOST, format!("127.0.0.1:{}", info.port))
+        .header(header::AUTHORIZATION, format!("Bearer {}", info.token))
+        .header("mcp-session-id", scope)
+        .header(header::CONTENT_TYPE, "application/json")
+        .header(header::ACCEPT, "application/json, text/event-stream")
+        .body(Full::new(Bytes::from(message.to_string())))
+        .map_err(|e| e.to_string())?;
+    let response = sender.send_request(request).await.map_err(|e| format!("cannot reach OpenIDEA: {e}"))?;
+    let status = response.status();
+    let body = response.into_body().collect().await.map_err(|e| format!("OpenIDEA's answer: {e}"))?.to_bytes();
+    Ok((status, body))
+}

crates/ide-mcp/tests/server.rs

@@ -0,0 +1,350 @@
+//! The server over real HTTP, and the stdio bridge in front of it, with a
+//! registry standing in for the IDE host.
+
+use ide_mcp::{Discovery, McpServer, Tool, ToolCallError, ToolRegistry, discovery_path, stdio};
+use serde_json::{Value, json};
+use std::path::{Path, PathBuf};
+use std::sync::Arc;
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
+
+struct Registry {
+    project: PathBuf,
+}
+
+impl ToolRegistry for Registry {
+    fn projects(&self) -> Vec<PathBuf> {
+        vec![self.project.clone()]
+    }
+
+    fn tools(&self, project: &Path) -> Result<Vec<Tool>, String> {
+        assert_eq!(project, self.project);
+        Ok(vec![Tool {
+            name: "echo".into(),
+            description: "Says it back".into(),
+            input_schema: json!({ "type": "object", "properties": { "text": { "type": "string" } } }),
+            read_only: true,
+            destructive: false,
+            output_schema: None,
+        }])
+    }
+
+    fn call(
+        &self,
+        project: &Path,
+        name: &str,
+        arguments: &str,
+        _cancel: ide_mcp::CancellationToken,
+    ) -> Result<String, ToolCallError> {
+        let args: Value = serde_json::from_str(arguments).unwrap();
+        match name {
+            "echo" if args["text"] == "fail" => Err(ToolCallError::Failed("it failed".into())),
+            "echo" => Ok(format!("{} in {}", args["text"].as_str().unwrap_or(""), project.display())),
+            _ => Err(ToolCallError::UnknownTool(format!("no tool {name:?}"))),
+        }
+    }
+}
+
+struct Setup {
+    _tmp: tempfile::TempDir,
+    project: PathBuf,
+    discovery: PathBuf,
+    server: Option<McpServer>,
+}
+
+fn setup() -> Setup {
+    let tmp = tempfile::tempdir().unwrap();
+    let project = dunce::canonicalize(tmp.path()).unwrap().join("project");
+    std::fs::create_dir_all(project.join("src")).unwrap();
+    let discovery = discovery_path(&tmp.path().join("app-data"));
+    let registry = Arc::new(Registry { project: project.clone() });
+    let server = McpServer::start(registry, Some(discovery.clone()), &tokio::runtime::Handle::current()).unwrap();
+    Setup { _tmp: tmp, project, discovery, server: Some(server) }
+}
+
+impl Setup {
+    fn server(&self) -> &McpServer {
+        self.server.as_ref().unwrap()
+    }
+}
+
+/// A raw HTTP/1.1 exchange: (status, body).
+async fn http(port: u16, request: &str) -> (u16, String) {
+    let mut stream = tokio::net::TcpStream::connect(("127.0.0.1", port)).await.unwrap();
+    stream.write_all(request.as_bytes()).await.unwrap();
+    let mut out = String::new();
+    stream.read_to_string(&mut out).await.unwrap();
+    let status = out.split(' ').nth(1).unwrap().parse().unwrap();
+    let body = out.split_once("\r\n\r\n").map(|(_, b)| b.to_owned()).unwrap_or_default();
+    (status, body)
+}
+
+/// POSTs `body` to `path` with extra header lines; closes the connection after.
+async fn post(s: &Setup, path: &str, headers: &[&str], body: &Value) -> (u16, String) {
+    let body = body.to_string();
+    let port = s.server().port();
+    let mut head = format!(
+        "POST {path} HTTP/1.1\r\nHost: 127.0.0.1:{port}\r\nContent-Type: application/json\r\nAccept: application/json, text/event-stream\r\nContent-Length: {}\r\nConnection: close\r\n",
+        body.len()
+    );
+    for h in headers {
+        head.push_str(h);
+        head.push_str("\r\n");
+    }
+    http(port, &format!("{head}\r\n{body}")).await
+}
+
+fn bearer(s: &Setup) -> String {
+    format!("Authorization: Bearer {}", s.server().token())
+}
+
+async fn rpc(s: &Setup, method: &str, params: Value) -> Value {
+    let project = format!("X-OpenIDEA-Project: {}", s.project.display());
+    let (status, body) = post(
+        s,
+        "/mcp",
+        &[&bearer(s), &project],
+        &json!({ "jsonrpc": "2.0", "id": 7, "method": method, "params": params }),
+    )
+    .await;
+    assert_eq!(status, 200, "{body}");
+    let reply: Value = serde_json::from_str(&body).unwrap();
+    assert_eq!(reply["id"], 7);
+    reply
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn initialize_list_and_call_tools() {
+    let s = setup();
+    let init = rpc(
+        &s,
+        "initialize",
+        json!({ "protocolVersion": "2025-03-26", "capabilities": {}, "clientInfo": { "name": "t", "version": "1" } }),
+    )
+    .await;
+    assert_eq!(init["result"]["protocolVersion"], "2025-03-26");
+    assert_eq!(init["result"]["serverInfo"]["name"], "OpenIDEA");
+    assert!(init["result"]["capabilities"]["tools"].is_object());
+    let newer = rpc(&s, "initialize", json!({ "protocolVersion": "2099-01-01" })).await;
+    assert_eq!(newer["result"]["protocolVersion"], "2025-06-18");
+
+    // Notifications are accepted without a body.
+    let (status, body) =
+        post(&s, "/mcp", &[&bearer(&s)], &json!({ "jsonrpc": "2.0", "method": "notifications/initialized" })).await;
+    assert_eq!((status, body.as_str()), (202, ""));
+
+    let list = rpc(&s, "tools/list", json!({})).await;
+    let tool = &list["result"]["tools"][0];
+    assert_eq!(tool["name"], "echo");
+    assert_eq!(tool["inputSchema"]["type"], "object");
+    assert_eq!(tool["annotations"], json!({ "readOnlyHint": true, "destructiveHint": false }));
+
+    let call = rpc(&s, "tools/call", json!({ "name": "echo", "arguments": { "text": "hi" } })).await;
+    let expected = format!("hi in {}", s.project.display());
+    assert_eq!(call["result"], json!({ "content": [{ "type": "text", "text": expected }], "isError": false }));
+    let failed = rpc(&s, "tools/call", json!({ "name": "echo", "arguments": { "text": "fail" } })).await;
+    assert_eq!(failed["result"]["isError"], true);
+    assert_eq!(failed["result"]["content"][0]["text"], "it failed");
+    let unknown = rpc(&s, "tools/call", json!({ "name": "nope" })).await;
+    assert_eq!(unknown["error"]["code"], -32602);
+    assert_eq!(rpc(&s, "ping", json!({})).await["result"], json!({}));
+    assert_eq!(rpc(&s, "resources/list", json!({})).await["error"]["code"], -32601);
+
+    // The project by query, from a folder inside it; a batch.
+    let query = format!("/mcp?project={}", ide_mcp::endpoint_url(1, &s.project.join("src")).split_once('=').unwrap().1);
+    let batch = json!([
+        { "jsonrpc": "2.0", "id": 1, "method": "tools/call", "params": { "name": "echo", "arguments": { "text": "a" } } },
+        { "jsonrpc": "2.0", "method": "notifications/cancelled", "params": { "requestId": 9 } },
+        { "jsonrpc": "2.0", "id": 2, "method": "ping" }
+    ]);
+    let (status, body) = post(&s, &query, &[&bearer(&s)], &batch).await;
+    assert_eq!(status, 200, "{body}");
+    let replies: Value = serde_json::from_str(&body).unwrap();
+    assert_eq!(replies.as_array().unwrap().len(), 2);
+    assert_eq!(replies[0]["result"]["content"][0]["text"], expected.replacen("hi", "a", 1));
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn requests_without_the_token_or_from_web_pages_are_refused() {
+    let s = setup();
+    let ping = json!({ "jsonrpc": "2.0", "id": 1, "method": "ping" });
+    assert_eq!(post(&s, "/mcp", &[], &ping).await.0, 401);
+    assert_eq!(post(&s, "/mcp", &["Authorization: Bearer wrong"], &ping).await.0, 401);
+    assert_eq!(post(&s, "/mcp", &[&bearer(&s), "Origin: https://evil.example"], &ping).await.0, 403);
+    let port = s.server().port();
+    let (status, _) = http(
+        port,
+        &format!(
+            "POST /mcp HTTP/1.1\r\nHost: evil.example:{port}\r\nContent-Length: 2\r\nConnection: close\r\n\r\n{{}}"
+        ),
+    )
+    .await;
+    assert_eq!(status, 403, "a rebound host name");
+    // No SSE stream to open; other paths don't exist.
+    let get = format!("GET /mcp HTTP/1.1\r\nHost: 127.0.0.1:{port}\r\n{}\r\nConnection: close\r\n\r\n", bearer(&s));
+    assert_eq!(http(port, &get).await.0, 405);
+    assert_eq!(post(&s, "/other", &[&bearer(&s)], &ping).await.0, 404);
+    assert_eq!(post(&s, "/mcp", &[&bearer(&s), "MCP-Protocol-Version: 1999-01-01"], &ping).await.0, 400);
+    let (status, body) = post(&s, "/mcp", &[&bearer(&s)], &json!("{")).await;
+    assert_eq!(status, 200, "a JSON string is a message, just not a request: {body}");
+    let garbage = format!(
+        "POST /mcp HTTP/1.1\r\nHost: 127.0.0.1:{port}\r\n{}\r\nContent-Length: 1\r\nConnection: close\r\n\r\n{{",
+        bearer(&s)
+    );
+    let (status, body) = http(port, &garbage).await;
+    assert_eq!(status, 400);
+    assert_eq!(serde_json::from_str::<Value>(&body).unwrap()["error"]["code"], -32700);
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn folders_that_are_not_open_are_named_in_the_error() {
+    let s = setup();
+    let elsewhere = s.project.parent().unwrap().join("elsewhere");
+    let header = format!("X-OpenIDEA-Project: {}", elsewhere.display());
+    let (status, body) =
+        post(&s, "/mcp", &[&bearer(&s), &header], &json!({"jsonrpc":"2.0","id":3,"method":"tools/list"})).await;
+    assert_eq!(status, 200);
+    let reply: Value = serde_json::from_str(&body).unwrap();
+    assert!(reply["error"]["message"].as_str().unwrap().contains("isn't open in OpenIDEA"));
+    let (_, body) = post(&s, "/mcp", &[&bearer(&s)], &json!({"jsonrpc":"2.0","id":3,"method":"tools/list"})).await;
+    assert!(serde_json::from_str::<Value>(&body).unwrap()["result"]["tools"].is_array());
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn the_discovery_file_lives_while_the_server_runs() {
+    let mut s = setup();
+    let info = Discovery::read(&s.discovery).unwrap();
+    assert_eq!((info.port, info.token.as_str(), info.pid), (s.server().port(), s.server().token(), std::process::id()));
+    let port = info.port;
+    s.server.take().unwrap().stop();
+    assert!(!s.discovery.exists());
+    tokio::time::sleep(std::time::Duration::from_millis(50)).await;
+    assert!(tokio::net::TcpStream::connect(("127.0.0.1", port)).await.is_err(), "the port is closed");
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn the_stdio_bridge_relays_lines_and_explains_a_missing_ide() {
+    let mut s = setup();
+    let input = [
+        json!({ "jsonrpc": "2.0", "id": 1, "method": "initialize", "params": { "protocolVersion": "2025-06-18" } }),
+        json!({ "jsonrpc": "2.0", "method": "notifications/initialized" }),
+        json!({ "jsonrpc": "2.0", "id": 2, "method": "tools/call", "params": { "name": "echo", "arguments": { "text": "x" } } }),
+    ]
+    .iter()
+    .map(|m| format!("{m}\n"))
+    .collect::<String>()
+        + "\n";
+    let mut output = Vec::new();
+    stdio::bridge(&s.discovery, &s.project.join("src"), input.as_bytes(), &mut output).await.unwrap();
+    let mut replies: Vec<Value> =
+        String::from_utf8(output).unwrap().lines().map(|l| serde_json::from_str(l).unwrap()).collect();
+    replies.sort_by_key(|r| r["id"].as_i64());
+    assert_eq!(replies.len(), 2, "nothing for the notification: {replies:?}");
+    assert_eq!(replies[0]["result"]["protocolVersion"], "2025-06-18");
+    assert_eq!(replies[1]["result"]["content"][0]["text"], format!("x in {}", s.project.display()));
+
+    // The IDE quit: each request gets an error saying what to do.
+    s.server.take().unwrap().stop();
+    let mut output = Vec::new();
+    let input = format!("{}\n", json!({ "jsonrpc": "2.0", "id": 5, "method": "initialize", "params": {} }));
+    stdio::bridge(&s.discovery, &s.project, input.as_bytes(), &mut output).await.unwrap();
+    let reply: Value = serde_json::from_slice(&output).unwrap();
+    assert_eq!(reply["id"], 5);
+    assert!(reply["error"]["message"].as_str().unwrap().contains("MCP server is not running"), "{reply}");
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn routing_an_argument_overrides_the_header_and_ambiguity_lists_projects() {
+    struct Many(Vec<PathBuf>);
+    impl ToolRegistry for Many {
+        fn projects(&self) -> Vec<PathBuf> {
+            self.0.clone()
+        }
+        fn tools(&self, _: &Path) -> Result<Vec<Tool>, String> {
+            Ok(Vec::new())
+        }
+        fn call(
+            &self,
+            project: &Path,
+            _: &str,
+            _: &str,
+            _: ide_mcp::CancellationToken,
+        ) -> Result<String, ToolCallError> {
+            Ok(json!({"project":project}).to_string())
+        }
+    }
+    let mut s = setup();
+    s.server.take().unwrap().stop();
+    let second = s.project.parent().unwrap().join("second");
+    std::fs::create_dir_all(second.join("nested")).unwrap();
+    s.server = Some(
+        McpServer::start(
+            Arc::new(Many(vec![s.project.clone(), second.clone()])),
+            None,
+            &tokio::runtime::Handle::current(),
+        )
+        .unwrap(),
+    );
+    let (_, body) = post(&s, "/mcp", &[&bearer(&s)], &json!({"jsonrpc":"2.0","id":1,"method":"tools/list"})).await;
+    let reply: Value = serde_json::from_str(&body).unwrap();
+    let message = reply["error"]["message"].as_str().unwrap();
+    assert!(message.contains(s.project.to_str().unwrap()) && message.contains(second.to_str().unwrap()));
+    let result = rpc(&s, "tools/call", json!({"name":"where","arguments":{"projectPath":second.join("nested")}})).await;
+    assert_eq!(result["result"]["structuredContent"]["project"], json!(second));
+    let unknown = rpc(&s, "tools/call", json!({"name":"where","arguments":{"projectPath":"/unknown/project"}})).await;
+    assert_eq!(unknown["error"]["code"], -32001);
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn cancellation_reaches_a_running_tool_without_affecting_another_client() {
+    struct Waiting(Arc<tokio::sync::Notify>);
+    impl ToolRegistry for Waiting {
+        fn projects(&self) -> Vec<PathBuf> {
+            vec![PathBuf::from("/project")]
+        }
+        fn tools(&self, _: &Path) -> Result<Vec<Tool>, String> {
+            Ok(Vec::new())
+        }
+        fn call(
+            &self,
+            _: &Path,
+            _: &str,
+            _: &str,
+            cancel: ide_mcp::CancellationToken,
+        ) -> Result<String, ToolCallError> {
+            self.0.notify_one();
+            tokio::runtime::Handle::current().block_on(cancel.cancelled());
+            Err(ToolCallError::Failed("cancelled".into()))
+        }
+    }
+    let mut s = setup();
+    s.server.take().unwrap().stop();
+    let started = Arc::new(tokio::sync::Notify::new());
+    s.server =
+        Some(McpServer::start(Arc::new(Waiting(started.clone())), None, &tokio::runtime::Handle::current()).unwrap());
+    let body = json!({"jsonrpc":"2.0","id":11,"method":"tools/call","params":{"name":"wait"}});
+    let auth = bearer(&s);
+    let headers = [&*auth, "Mcp-Session-Id: client-one"];
+    let call = post(&s, "/mcp", &headers, &body);
+    let cancel = async {
+        started.notified().await;
+        let notification = json!({"jsonrpc":"2.0","method":"notifications/cancelled","params":{"requestId":11}});
+        assert_eq!(post(&s, "/mcp", &[&bearer(&s), "Mcp-Session-Id: client-two"], &notification).await.0, 202);
+        assert_eq!(post(&s, "/mcp", &[&bearer(&s), "Mcp-Session-Id: client-one"], &notification).await.0, 202);
+    };
+    let ((status, body), ()) =
+        tokio::time::timeout(std::time::Duration::from_secs(5), async { tokio::join!(call, cancel) }).await.unwrap();
+    assert_eq!(status, 200);
+    assert_eq!(serde_json::from_str::<Value>(&body).unwrap()["result"]["isError"], true);
+}
+
+#[tokio::test(flavor = "multi_thread")]
+async fn a_cancellation_that_arrives_before_the_call_is_remembered() {
+    let s = setup();
+    let auth = bearer(&s);
+    let headers = [auth.as_str(), "Mcp-Session-Id: early-cancel"];
+    let notification = json!({"jsonrpc":"2.0","method":"notifications/cancelled","params":{"requestId":8}});
+    assert_eq!(post(&s, "/mcp", &headers, &notification).await.0, 202);
+    let call = json!({"jsonrpc":"2.0","id":8,"method":"tools/call","params":{"name":"echo","arguments":{"text":"hi"}}});
+    let (_, body) = post(&s, "/mcp", &headers, &call).await;
+    assert_eq!(serde_json::from_str::<Value>(&body).unwrap()["result"]["isError"], true);
+}

crates/ide-run/src/process.rs

@@ -57,6 +57,7 @@ struct Entry {
     stop: Option<StopCommand>,
     output: OutputFn,
     exited: AtomicBool,
+    code: Mutex<Option<i32>>,
     stopping: AtomicBool,
 }
 
@@ -436,6 +437,7 @@ impl ProcessManager {
             stop,
             output: on_output.clone(),
             exited: AtomicBool::new(false),
+            code: Mutex::new(None),
             stopping: AtomicBool::new(false),
         });
         self.register(entry.clone());
@@ -547,6 +549,7 @@ impl ProcessManager {
             stop,
             output: on_output.clone(),
             exited: AtomicBool::new(false),
+            code: Mutex::new(None),
             stopping: AtomicBool::new(false),
         });
         self.register(entry.clone());
@@ -685,6 +688,15 @@ impl ProcessManager {
         Ok(())
     }
 
+    /// Returns `None` while running, or the exit code once output has drained.
+    pub fn exit_code(&self, id: RunId) -> IdeResult<Option<Option<i32>>> {
+        let entry = self.entry(id)?;
+        if !entry.exited.load(Ordering::Acquire) {
+            return Ok(None);
+        }
+        Ok(Some(*entry.code.lock()))
+    }
+
     pub fn list(&self) -> Vec<RunInfo> {
         self.runs.lock().values().map(|e| e.info()).collect()
     }
@@ -1078,6 +1090,7 @@ fn spawn_pump(
                 std::thread::sleep(Duration::from_millis(50));
             }
         }
+        *entry.code.lock() = code;
         entry.exited.store(true, Ordering::Release);
         tracing::debug!(id = %entry.id, ?code, "run exited");
         sink.emit(IdeEvent::RunExited { run: entry.id, code });

crates/ide-search/src/lib.rs

@@ -253,6 +253,18 @@ pub fn validate_query(query: &SearchQuery) -> IdeResult<()> {
     Ok(())
 }
 
+/// Byte ranges of the matches of `query` in `text`, matched as [`search`] does.
+/// Unlike [`LineMatch`]es, a match spanning lines comes back whole.
+pub fn match_ranges(text: &str, query: &SearchQuery) -> IdeResult<Vec<(usize, usize)>> {
+    if query.pattern.is_empty() {
+        return Ok(Vec::new());
+    }
+    let compiled = query::compile(query)?;
+    let mut out = Vec::new();
+    iter::for_each_match(&compiled.matcher, text.as_bytes(), 0, |m| out.push((m.start(), m.end())));
+    Ok(out)
+}
+
 /// Computes the replacement text for every match of `query` in `text`
 /// (supports `$1` group references for regex queries).
 ///

crates/ide-workspace/src/settings.rs

@@ -27,7 +27,10 @@ pub enum SettingsScope {
     Project,
 }
 
-fn remove_custom_schemes(layer: &mut Json) {
+fn remove_global_settings(layer: &mut Json) {
+    if let Some(layer) = layer.as_object_mut() {
+        layer.remove("mcpServer");
+    }
     if let Some(editor) = layer.get_mut("editor").and_then(Json::as_object_mut) {
         editor.remove("customSchemes");
     }
@@ -187,7 +190,7 @@ impl SettingsStore {
         for (scope, file) in self.layers() {
             let Some(mut layer) = read_layer(&file) else { continue };
             if scope == SettingsScope::Project {
-                remove_custom_schemes(&mut layer);
+                remove_global_settings(&mut layer);
             }
             if let Err(e) = try_merge(&mut merged, layer) {
                 tracing::warn!("{} has invalid settings, ignoring it: {e}", file.display());
@@ -220,6 +223,9 @@ impl SettingsStore {
         {
             return Err(IdeError::invalid("custom color schemes belong to user settings"));
         }
+        if scope == SettingsScope::Project && (key == "mcpServer" || key.starts_with("mcpServer.")) {
+            return Err(IdeError::invalid("MCP server belongs to user settings"));
+        }
         let file = self.file(scope).ok_or_else(|| IdeError::invalid("no project is open"))?.to_path_buf();
         let segments: Vec<&str> = key.split('.').collect();
         if segments.iter().any(|s| s.is_empty()) {
@@ -259,7 +265,7 @@ impl SettingsStore {
             let layer = if is_target { parse_layer(&new_text).ok() } else { read_layer(&layer_file) };
             let Some(mut layer) = layer else { continue };
             if layer_scope == SettingsScope::Project {
-                remove_custom_schemes(&mut layer);
+                remove_global_settings(&mut layer);
             }
             if let Err(e) = try_merge(&mut merged, layer)
                 && is_target
@@ -637,4 +643,22 @@ mod tests {
         let s = store.set(SettingsScope::Global, "appearance.mainToolbar", Json::Null).unwrap();
         assert_eq!(s.appearance.main_toolbar, None);
     }
+    #[test]
+    fn mcp_server_is_default_off_and_cannot_be_enabled_by_a_project() {
+        let tmp = tempfile::tempdir().unwrap();
+        let config = tmp.path().join("config");
+        let project = tmp.path().join("project");
+        std::fs::create_dir_all(project.join(".openidea")).unwrap();
+        std::fs::write(project.join(".openidea/settings.toml"), "[mcpServer]\nenabled = true\n").unwrap();
+        let settings = SettingsStore::load(&config, Some(&project));
+        assert!(!settings.effective().mcp_server.enabled);
+        assert!(settings.set(SettingsScope::Project, "mcpServer.enabled", serde_json::json!(true)).is_err());
+        assert!(
+            settings
+                .set(SettingsScope::Global, "mcpServer.enabled", serde_json::json!(true))
+                .unwrap()
+                .mcp_server
+                .enabled
+        );
+    }
 }

src-tauri/Cargo.toml

@@ -66,6 +66,7 @@ ide-spell.workspace = true
 ide-ssh.workspace = true
 ide-remote.workspace = true
 ide-host.workspace = true
+ide-mcp.workspace = true
 ide-notebook.workspace = true
 ide-jsonrpc.workspace = true
 ide-tools = { path = "../crates/ide-tools" }

src-tauri/src/commands/app.rs

@@ -179,6 +179,9 @@ pub fn settings_set(
     value: String,
 ) -> IdeResult<Settings> {
     let applied = ide_host::ops::project::set_settings(&state.host, window.label(), scope, &key, &value)?;
+    if key == "mcpServer" || key.starts_with("mcpServer.") {
+        crate::commands::mcp::apply(&state);
+    }
     // A project value concerns only that project's window (and its settings window).
     let event = ide_core::IdeEvent::SettingsChanged { key };
     if applied.project_scope {
@@ -231,6 +234,7 @@ pub async fn settings_import(window: Window, state: State<'_, AppState>, path: P
         tauri::async_runtime::spawn(async move { lsp.reconfigure().await });
     }
     crate::commands::ssh::apply_ssh_settings(&state);
+    crate::commands::mcp::apply(&state);
     state.host.apply_proxy();
     state.sink.emit(ide_core::IdeEvent::SettingsChanged { key: String::new() });
     let settings = ide_host::ops::project::settings(&state.host, window.label());

src-tauri/src/commands/mcp.rs

@@ -0,0 +1,150 @@
+//! Tools › MCP Server: runs `ide_mcp::McpServer` over built-in host tools
+//! while `mcpServer.enabled` is on, and reports where it listens.
+
+use crate::state::AppState;
+use ide_core::{IdeResult, IpcPath};
+use ide_host::mcp::{FileProblems, FocusedEditor};
+use parking_lot::Mutex;
+use serde::Serialize;
+use specta::Type;
+use std::path::PathBuf;
+use std::sync::Arc;
+use tauri::{State, Window};
+
+/// The server while it runs, or why it doesn't.
+#[derive(Default)]
+pub struct McpService {
+    server: Mutex<Option<ide_mcp::McpServer>>,
+    error: Mutex<Option<String>>,
+}
+
+/// Starts or stops the server to match the global `mcpServer.enabled`.
+pub fn apply(state: &AppState) {
+    let enabled = state.global_settings.effective().mcp_server.enabled;
+    let mut server = state.mcp.server.lock();
+    if !enabled {
+        if let Some(running) = server.take() {
+            running.stop();
+        }
+        ide_agent::set_mcp_executable(None);
+        *state.mcp.error.lock() = None;
+        return;
+    }
+    if server.is_some() {
+        return;
+    }
+    let discovery = ide_mcp::discovery_path(&state.data_dir);
+    match ide_mcp::McpServer::start(
+        Arc::new(ide_host::mcp::Registry::new(state.host.clone())),
+        Some(discovery),
+        &state.host.runtime,
+    ) {
+        Ok(started) => {
+            let exe = std::env::current_exe().unwrap_or_default();
+            ide_agent::set_mcp_executable(Some(exe));
+            *server = Some(started);
+            *state.mcp.error.lock() = None;
+        }
+        Err(e) => {
+            tracing::warn!("MCP server: {e}");
+            *state.mcp.error.lock() = Some(e.to_string());
+        }
+    }
+}
+
+/// Stops the server on exit (its discovery file goes with it).
+pub fn stop(state: &AppState) {
+    ide_agent::set_mcp_executable(None);
+    if let Some(server) = state.mcp.server.lock().take() {
+        server.stop();
+    }
+}
+
+/// What Settings › Tools › MCP Server shows.
+#[derive(Serialize, Type)]
+#[serde(rename_all = "camelCase")]
+pub struct McpServerStatus {
+    pub running: bool,
+    /// Why it isn't running though turned on.
+    pub error: Option<String>,
+    pub port: Option<u16>,
+    /// The window's local project, which the URL and command below are for.
+    pub project: Option<IpcPath>,
+    /// `http://127.0.0.1:<port>/mcp?project=<root>`.
+    pub url: Option<String>,
+    /// Bearer token of `url` (changes with every run).
+    pub token: Option<String>,
+    /// The stdio bridge: this executable and its arguments.
+    pub stdio_command: Vec<String>,
+}
+
+#[tauri::command]
+#[specta::specta]
+pub fn mcp_server_status(window: Window, state: State<'_, AppState>) -> IdeResult<McpServerStatus> {
+    let root: Option<PathBuf> = state.project(window.label()).ok().map(|p| p.root.clone());
+    let server = state.mcp.server.lock();
+    let exe = std::env::current_exe().unwrap_or_default();
+    Ok(McpServerStatus {
+        running: server.is_some(),
+        error: state.mcp.error.lock().clone(),
+        port: server.as_ref().map(|s| s.port()),
+        url: server.as_ref().zip(root.as_ref()).map(|(s, r)| s.url(r)),
+        token: server.as_ref().map(|s| s.token().to_owned()),
+        stdio_command: root.as_ref().map(|r| ide_mcp::stdio_command(&exe, r)).unwrap_or_default(),
+        project: root.map(IpcPath::from),
+    })
+}
+
+#[tauri::command]
+#[specta::specta]
+pub fn mcp_set_open_editors(window: Window, state: State<'_, AppState>, paths: Vec<IpcPath>) -> IdeResult<()> {
+    state.project(window.label())?;
+    state.host.mcp_reports.set_open_editors(window.label(), paths.into_iter().map(PathBuf::from).collect());
+    Ok(())
+}
+
+#[tauri::command]
+#[specta::specta]
+pub fn mcp_set_focused_editor(
+    window: Window,
+    state: State<'_, AppState>,
+    editor: Option<FocusedEditor>,
+    focused: bool,
+) -> IdeResult<()> {
+    state.project(window.label())?;
+    state.host.mcp_reports.set_focused_editor(window.label(), editor, focused);
+    Ok(())
+}
+
+#[tauri::command]
+#[specta::specta]
+pub fn mcp_report_problems(
+    window: Window,
+    state: State<'_, AppState>,
+    reset: bool,
+    files: Vec<FileProblems>,
+) -> IdeResult<()> {
+    state.project(window.label())?;
+    state.host.mcp_reports.report_problems(window.label(), reset, files);
+    Ok(())
+}
+
+#[tauri::command]
+#[specta::specta]
+pub fn mcp_ui_ready(window: Window, state: State<'_, AppState>, ready: bool) -> IdeResult<()> {
+    state.project(window.label())?;
+    state.host.mcp_requests.set_ready(window.label(), ready);
+    Ok(())
+}
+
+#[tauri::command]
+#[specta::specta]
+pub fn mcp_respond(
+    window: Window,
+    state: State<'_, AppState>,
+    id: u32,
+    allow: bool,
+    error: Option<String>,
+) -> IdeResult<()> {
+    state.host.mcp_requests.answer(window.label(), id, allow, error)
+}

src-tauri/src/commands/mod.rs

@@ -29,6 +29,7 @@ pub mod history;
 pub mod http;
 pub mod java;
 pub mod lsp;
+pub mod mcp;
 pub mod nav;
 pub mod notebook;
 pub mod perf;
@@ -65,6 +66,12 @@ pub(crate) fn sender<T: tauri::ipc::IpcResponse + Send + Sync + 'static>(
 pub fn builder() -> tauri_specta::Builder<tauri::Wry> {
     tauri_specta::Builder::<tauri::Wry>::new().commands(collect_commands![
         app::app_info,
+        mcp::mcp_ui_ready,
+        mcp::mcp_respond,
+        mcp::mcp_server_status,
+        mcp::mcp_set_open_editors,
+        mcp::mcp_set_focused_editor,
+        mcp::mcp_report_problems,
         android::android_devices,
         android::android_logcat,
         app::recent_projects,

src-tauri/src/events.rs

@@ -63,9 +63,24 @@ impl EventSink for TauriSink {
         ) {
             flash_taskbar_unless_focused(&self.app);
         }
+        if matches!(&event, IdeEvent::McpRequest { .. })
+            && let Some(label) = self.window.clone()
+        {
+            let app = self.app.clone();
+            let _ = self.app.run_on_main_thread(move || {
+                if let Some(window) = app.get_webview_window(&label) {
+                    let _ = window.unminimize();
+                    let _ = window.show();
+                    let _ = window.set_focus();
+                }
+            });
+        }
         let result = match &self.window {
             Some(label) => {
-                for target in crate::windows::document_windows(&self.app, label) {
+                for target in crate::windows::document_windows(&self.app, label)
+                    .into_iter()
+                    .filter(|_| !matches!(&event, IdeEvent::McpRequest { .. } | IdeEvent::McpRequestClosed { .. }))
+                {
                     let _ = self.app.emit_to(target.as_str(), IDE_EVENT, &event);
                 }
                 self.app.emit_to(label.as_str(), IDE_EVENT, &event)

src-tauri/src/lib.rs

@@ -73,6 +73,10 @@ pub fn run() {
     let context = tauri::generate_context!();
     #[cfg(debug_assertions)]
     let context = dev::configure(context);
+    if let Some(project) = ide_mcp::stdio_request(&std::env::args().collect::<Vec<_>>()) {
+        let app_data = dirs::data_dir().unwrap_or_default().join(&context.config().identifier);
+        std::process::exit(ide_mcp::stdio::run(&ide_mcp::discovery_path(&app_data), project));
+    }
     // The `openidea` command: answer and exit, no UI.
     if let Some(code) = cli::run(&context.config().identifier) {
         std::process::exit(code);
@@ -190,6 +194,7 @@ pub fn run() {
         let menu_state = menu::MenuState::default();
         menu::install(app.handle(), &menu_state, &state.recent.list());
         app.manage(state);
+        commands::mcp::apply(&app.state::<AppState>());
         app.manage(windows);
         app.manage(application_focus::ApplicationFocus::default());
         #[cfg(target_os = "macos")]
@@ -268,6 +273,7 @@ pub fn run() {
         if let tauri::RunEvent::Exit = event {
             if let Some(state) = app.try_state::<AppState>() {
                 state.host.stop_processes_on_exit();
+                commands::mcp::stop(&state);
                 state.host.clear_workspace_edit_history_on_exit();
                 state.host.shutdown_notebooks_on_exit();
             }

src-tauri/src/remote_dev.rs

@@ -533,6 +533,7 @@ pub async fn remote_connect(
     }
     state.remote_dev.disconnect(&label);
     state.host.close_project(&label);
+    state.host.mcp_reports.set_remote(&label, std::path::PathBuf::from(&connection.root));
     state.remote_dev.0.lock().insert(label.clone(), connection.clone());
     let weak = Arc::downgrade(&connection);
     let peer = connection.peer.clone();
@@ -764,6 +765,7 @@ pub async fn remote_stop_forwarding(window: Window, state: State<'_, AppState>,
 #[tauri::command]
 #[specta::specta]
 pub fn remote_disconnect(window: Window, state: State<'_, AppState>) {
+    state.host.mcp_reports.remove_remote(AppState::owner_window(window.label()));
     state.remote_dev.disconnect(AppState::owner_window(window.label()));
 }
 

src-tauri/src/state.rs

@@ -20,6 +20,8 @@ pub struct AppState {
     pub plugins: Arc<ide_host::plugins::PluginHost>,
     /// The built-in web server (Open In › Browser, the editor's browser bar).
     pub web: ide_web::WebServer,
+    /// Tools › MCP Server: built-in IDE tools for agents.
+    pub mcp: crate::commands::mcp::McpService,
     /// Credential prompts of `ssh` / `git` child processes (`None` if it failed to start).
     pub askpass: Option<ide_ssh::askpass::AskpassServer>,
     /// Remote development connections, by window label.
@@ -101,6 +103,7 @@ impl AppState {
             sink: global_sink,
             plugins: crate::commands::plugin::create_host(&app, &data_dir, &host)?,
             web: ide_web::WebServer::new(),
+            mcp: Default::default(),
             remote_dev: crate::remote_dev::Connections::default(),
             host,
             startup: Startup {

src/bindings.ts

@@ -8,6 +8,17 @@ import { invoke as __TAURI_INVOKE, Channel } from "@tauri-apps/api/core";
 /** Commands */
 export const commands = {
 	appInfo: () => __TAURI_INVOKE<AppInfo>("app_info"),
+	mcpUiReady: (ready: boolean) => typedError<null, IdeError>(__TAURI_INVOKE("mcp_ui_ready", { ready })),
+	mcpRespond: (id: number, allow: boolean, error: string | null) => typedError<null, IdeError>(__TAURI_INVOKE("mcp_respond", { id, allow, error })),
+	mcpServerStatus: () => typedError<McpServerStatus, IdeError>(__TAURI_INVOKE("mcp_server_status")),
+	mcpSetOpenEditors: (paths: IpcPath[]) => typedError<null, IdeError>(__TAURI_INVOKE("mcp_set_open_editors", { paths })),
+	mcpSetFocusedEditor: (editor: {
+	path: IpcPath,
+	/**  Zero-based lines and UTF-16 columns, end exclusive. */
+	selection: Range,
+	selectedText: string,
+} | null, focused: boolean) => typedError<null, IdeError>(__TAURI_INVOKE("mcp_set_focused_editor", { editor, focused })),
+	mcpReportProblems: (reset: boolean, files: FileProblems[]) => typedError<null, IdeError>(__TAURI_INVOKE("mcp_report_problems", { reset, files })),
 	/**  Devices `adb` knows about, online ones first. */
 	androidDevices: () => typedError<AndroidDevice[], IdeError>(__TAURI_INVOKE("android_devices")),
 	/**
@@ -3956,6 +3967,11 @@ export type FileProbe = {
 	tooLarge: boolean,
 };
 
+export type FileProblems = {
+	path: IpcPath,
+	items: Diagnostic[],
+};
+
 /**  A path written in a document: an HTML URL attribute, a CSS `url()` / `@import`. */
 export type FileReference = {
 	range: Range,
@@ -4024,6 +4040,13 @@ export type FilesChanged = {
 	removed: string[],
 };
 
+export type FocusedEditor = {
+	path: IpcPath,
+	/**  Zero-based lines and UTF-16 columns, end exclusive. */
+	selection: Range,
+	selectedText: string,
+};
+
 export type FoldKind = "region" | "comment" | "imports";
 
 export type FoldRange = {
@@ -4531,7 +4554,7 @@ export type IdeError = {
 	data?: ErrorData | null,
 };
 
-export type IdeEvent = 
+export type IdeEvent = { type: "mcpRequest"; id: number; request: McpUiRequest } | { type: "mcpRequestClosed"; id: number } | 
 /**  Project window membership or selection changed. */
 { type: "windowGroupsChanged" } | 
 /**  A window entered or left full screen, itself or as a member of a full-screen window group. */
@@ -5596,6 +5619,30 @@ export type MavenSettings = {
 	threads?: string,
 };
 
+/**  Tools › MCP Server: agents use the IDE's built-in tools. */
+export type McpServerSettings = {
+	/**  Serve the tools on 127.0.0.1 while the IDE runs. */
+	enabled?: boolean,
+};
+
+/**  What Settings › Tools › MCP Server shows. */
+export type McpServerStatus = {
+	running: boolean,
+	/**  Why it isn't running though turned on. */
+	error: string | null,
+	port: number | null,
+	/**  The window's local project, which the URL and command below are for. */
+	project: IpcPath | null,
+	/**  `http://127.0.0.1:<port>/mcp?project=<root>`. */
+	url: string | null,
+	/**  Bearer token of `url` (changes with every run). */
+	token: string | null,
+	/**  The stdio bridge: this executable and its arguments. */
+	stdioCommand: string[],
+};
+
+export type McpUiRequest = { type: "confirm"; client: string; tool: string; subject: string; project: string; detail: string | null } | { type: "openFile"; path: IpcPath; line: number | null; column: number | null };
+
 export type MemoryCategory = 
 /**  The backend and its WebView processes. */
 "app" | "languageServer" | 
@@ -7373,6 +7420,8 @@ export type Settings_Deserialize = {
 	cmake?: CMakeSettings_Deserialize,
 	/**  Tools › Agents › Chat. */
 	agents?: AgentSettings,
+	/**  Tools › MCP Server (global only). */
+	mcpServer?: McpServerSettings,
 	/**  Plugin settings (`[contributes.settings]`): plugin id → its values by key. */
 	plugins?: { [key in string]: { [key in string]: unknown } },
 };
@@ -7433,6 +7482,8 @@ export type Settings_Serialize = {
 	cmake: CMakeSettings_Serialize,
 	/**  Tools › Agents › Chat. */
 	agents: AgentSettings,
+	/**  Tools › MCP Server (global only). */
+	mcpServer: McpServerSettings,
 	/**  Plugin settings (`[contributes.settings]`): plugin id → its values by key. */
 	plugins: { [key in string]: { [key in string]: unknown } },
 };

src/features/code-insight/index.ts

@@ -16,6 +16,7 @@ import { HierarchyTabs, HierarchyView } from "./HierarchyView";
 import { resetHierarchy, showHierarchy } from "./hierarchy";
 import { installServerEvents } from "./servers";
 import { ServerStatus } from "./ServerStatus";
+import { reportProblems } from "./problemsReport";
 import { installWorkspaceEditUndo } from "./workspaceUndo";
 
 const EDITOR_WHEN = "textEditorActive && (editorFocus || popupOpen || !toolWindowFocus)";
@@ -43,6 +44,7 @@ export function activate(): () => void {
   const disposers = [
     unsubProject,
     installProblemsEvents(),
+    reportProblems(),
     installProblemDecorations(),
     installServerEvents(),
     installWorkspaceEditUndo(),

src/features/code-insight/problemsReport.test.ts

@@ -0,0 +1,67 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import type { Diagnostic, FileProblems } from "@/bindings";
+
+const reports = vi.hoisted(() => [] as [boolean, FileProblems[]][]);
+vi.mock("@/platform/ipc", async (importOriginal) => ({
+  ...(await importOriginal<typeof import("@/platform/ipc")>()),
+  call: (promise: Promise<unknown>) => promise,
+  commands: {
+    mcpReportProblems: async (reset: boolean, files: FileProblems[]) => {
+      reports.push([reset, files]);
+    },
+  },
+}));
+
+vi.mock("@/platform/project", () => ({
+  useProject: { getState: () => ({ project: { root: "/p" } }), subscribe: () => () => {} },
+}));
+
+const { applyDiagnosticsEvent, clearProblems } = await import("./problemsStore");
+const { reportProblems } = await import("./problemsReport");
+
+const d = (line: number): Diagnostic => ({
+  range: { start: { line, col: 0 }, end: { line, col: 1 } },
+  severity: "error",
+  message: `line ${line}`,
+  source: null,
+  code: null,
+});
+
+const summary = () => reports.map(([reset, files]) => [reset, files.map((f) => [f.path, f.items.length])]);
+
+describe("reportProblems", () => {
+  let stop: () => void;
+  beforeEach(() => {
+    vi.useFakeTimers();
+    clearProblems();
+    reports.length = 0;
+    applyDiagnosticsEvent("/p/a.rs", "ra", [d(1), d(2)]);
+    stop = reportProblems();
+  });
+  afterEach(() => {
+    stop();
+    vi.useRealTimers();
+  });
+
+  it("sends everything first, then only the files that changed once diagnostics settle", async () => {
+    await vi.advanceTimersByTimeAsync(1000);
+    applyDiagnosticsEvent("/p/b.rs", "ra", [d(0)]);
+    applyDiagnosticsEvent("/p/a.rs", "ra", []);
+    await vi.advanceTimersByTimeAsync(500);
+    expect(reports).toHaveLength(1);
+    await vi.advanceTimersByTimeAsync(500);
+    applyDiagnosticsEvent("/p/b.rs", "clippy", [d(3)]);
+    await vi.advanceTimersByTimeAsync(1000);
+    expect(summary()).toEqual([
+      [true, [["/p/a.rs", 2]]],
+      [
+        false,
+        [
+          ["/p/b.rs", 1],
+          ["/p/a.rs", 0],
+        ],
+      ],
+      [false, [["/p/b.rs", 2]]],
+    ]);
+  });
+});

src/features/code-insight/problemsReport.ts

@@ -0,0 +1,51 @@
+/** Reports changed files from the Problems view to the built-in MCP host. */
+import { commands, call, type FileProblems } from "@/platform/ipc";
+import { useProject } from "@/platform/project";
+import { isRemoteWindow } from "@/platform/remote";
+import { useProblems, type ProblemsMap } from "./problemsStore";
+
+const REPORT_MS = 1000;
+
+export function reportProblems(): () => void {
+  let disposed = false;
+  let reported: ProblemsMap = new Map();
+  let reset = true;
+  let timer: ReturnType<typeof setTimeout> | null = null;
+  const flush = () => {
+    timer = null;
+    if (isRemoteWindow() || !useProject.getState().project) return;
+    const map = useProblems.getState().map;
+    const files: FileProblems[] = [];
+    for (const [path, sources] of map)
+      if (reset || reported.get(path) !== sources) files.push({ path, items: [...sources.values()].flat() });
+    if (!reset) for (const path of reported.keys()) if (!map.has(path)) files.push({ path, items: [] });
+    if (!files.length && !reset) return;
+    const wasReset = reset;
+    reported = map;
+    reset = false;
+    void call(commands.mcpReportProblems(wasReset, files)).catch(() => {
+      reset = true;
+      if (!disposed) schedule();
+    });
+  };
+  const schedule = () => {
+    if (!timer) timer = setTimeout(flush, REPORT_MS);
+  };
+  schedule();
+  const off = useProblems.subscribe((s, prev) => {
+    if (s.map !== prev.map) schedule();
+  });
+  const offProject = useProject.subscribe((s, prev) => {
+    if (s.project?.root !== prev.project?.root) {
+      reset = true;
+      reported = new Map();
+      schedule();
+    }
+  });
+  return () => {
+    disposed = true;
+    offProject();
+    off();
+    if (timer) clearTimeout(timer);
+  };
+}

src/features/index.ts

@@ -4,6 +4,7 @@
  * a disposer. The editor provides the editor service; app must install its launch
  * barrier before welcome can restore a remembered project.
  */
+import { activate as mcp } from "./mcp";
 import { activate as projectTrust } from "./project-trust";
 import { activate as editor } from "@/editor/core";
 import { activate as editorLsp } from "@/editor/lsp";
@@ -59,6 +60,7 @@ const features: Array<[string, Activate]> = [
   ["project-trust", projectTrust],
   ["editor", editor],
   ["editor-lsp", editorLsp],
+  ["mcp", mcp],
   ["app", app],
   ["welcome", welcome],
   ["project-tree", projectTree],

src/features/mcp/ConfirmDialog.module.css

@@ -0,0 +1,16 @@
+.content {
+  display: flex;
+  flex-direction: column;
+  gap: var(--space-3);
+  overflow-wrap: anywhere;
+}
+
+.detail {
+  margin: 0;
+  max-height: 240px;
+  overflow: auto;
+  white-space: pre-wrap;
+  font-family: var(--font-mono);
+  font-size: var(--fs-small);
+  color: var(--fg-secondary);
+}

src/features/mcp/ConfirmDialog.tsx

@@ -0,0 +1,33 @@
+import { useTx } from "@/platform/i18n";
+import { Dialog } from "@/ui";
+import { answerConfirm, useMcpConfirms } from "./requests";
+import styles from "./ConfirmDialog.module.css";
+
+export function McpConfirmHost() {
+  const request = useMcpConfirms((s) => s.queue[0]);
+  const waiting = useMcpConfirms((s) => s.queue.length - 1);
+  const t = useTx();
+  if (!request) return null;
+  const deny = () => answerConfirm(request, false);
+  return (
+    <Dialog
+      open
+      icon="warning"
+      title={t`${request.client} wants to run ${request.subject}`}
+      onClose={deny}
+      width={480}
+      footerStart={waiting > 0 ? <span>{t`${waiting} more waiting`}</span> : undefined}
+      buttons={[
+        { label: "Allow", role: "extra", onClick: () => answerConfirm(request, true) },
+        { label: "Deny", role: "default", autoFocus: true, onClick: deny },
+      ]}
+    >
+      <div className={styles.content}>
+        <div>{t`Project: ${request.project}`}</div>
+        <div>{t`Tool: ${request.tool}`}</div>
+        {request.detail && <pre className={styles.detail}>{request.detail}</pre>}
+        {request.error && <div role="alert">{t`Could not send the answer: ${request.error}`}</div>}
+      </div>
+    </Dialog>
+  );
+}

src/features/mcp/index.ts

@@ -0,0 +1,104 @@
+/** Window snapshots used by the built-in MCP tools. */
+import { activeEditor, onEditorEvent, openEditorPaths, useEditorRegistry } from "@/editor/api";
+import { commands, call, onIdeEvent, ideEventsReady } from "@/platform/ipc";
+import { useProject } from "@/platform/project";
+import { isRemoteWindow } from "@/platform/remote";
+
+import { registerOverlay } from "@/workbench/contributions";
+import { McpConfirmHost } from "./ConfirmDialog";
+import { denyAll, dropConfirm, handleMcpRequest } from "./requests";
+
+export function activate(): () => void {
+  const offOverlay = registerOverlay({ id: "mcp.confirm", component: McpConfirmHost });
+  const offRequests = onIdeEvent("mcpRequest", (e) => void handleMcpRequest(e.id, e.request));
+  const offClosed = onIdeEvent("mcpRequestClosed", (e) => dropConfirm(e.id));
+  const ready = () => {
+    if (!isRemoteWindow() && useProject.getState().project)
+      void ideEventsReady()
+        .then(() => call(commands.mcpUiReady(true)))
+        .catch(() => {});
+  };
+  const unload = () => {
+    denyAll();
+    if (!isRemoteWindow()) void call(commands.mcpUiReady(false)).catch(() => {});
+  };
+  ready();
+  window.addEventListener("beforeunload", unload);
+  let lastPaths: string | undefined;
+  let lastEditor: string | undefined;
+  let disposed = false;
+  let timer: ReturnType<typeof setTimeout> | null = null;
+  const report = () => {
+    timer = null;
+    if (isRemoteWindow() || !useProject.getState().project) return;
+    const paths = openEditorPaths();
+    const editor = activeEditor();
+    const focused = document.hasFocus();
+    const selection = editor?.view.state.selection.main;
+    const doc = editor?.view.state.doc;
+    const start = doc && selection ? doc.lineAt(selection.from) : null;
+    const end = doc && selection ? doc.lineAt(selection.to) : null;
+    const current =
+      editor && selection && start && end
+        ? {
+            path: editor.ctx.path,
+            selection: {
+              start: { line: start.number - 1, col: selection.from - start.from },
+              end: { line: end.number - 1, col: selection.to - end.from },
+            },
+            selectedText: doc!
+              .sliceString(selection.from, Math.min(selection.to, selection.from + 65536))
+              .replace(/[\uD800-\uDBFF]$/, ""),
+          }
+        : null;
+    const root = useProject.getState().project?.root;
+    const pathKey = JSON.stringify([root, paths]);
+    const editorKey = JSON.stringify([root, current, focused]);
+    if (pathKey !== lastPaths) {
+      lastPaths = pathKey;
+      void call(commands.mcpSetOpenEditors(paths)).catch(() => {
+        lastPaths = undefined;
+        if (!disposed) schedule();
+      });
+    }
+    if (editorKey !== lastEditor) {
+      lastEditor = editorKey;
+      void call(commands.mcpSetFocusedEditor(current, focused)).catch(() => {
+        lastEditor = undefined;
+        if (!disposed) schedule();
+      });
+    }
+  };
+  const schedule = () => {
+    if (timer) clearTimeout(timer);
+    timer = setTimeout(report, 300);
+  };
+  schedule();
+  const offRegistry = useEditorRegistry.subscribe(schedule);
+  const offEvents = onEditorEvent(schedule);
+  const offProject = useProject.subscribe((s, prev) => {
+    if (s.project?.root !== prev.project?.root) {
+      denyAll();
+      ready();
+      lastPaths = undefined;
+      lastEditor = undefined;
+      schedule();
+    }
+  });
+  window.addEventListener("focus", schedule);
+  window.addEventListener("blur", schedule);
+  return () => {
+    disposed = true;
+    unload();
+    offOverlay();
+    offRequests();
+    offClosed();
+    window.removeEventListener("beforeunload", unload);
+    offRegistry();
+    offEvents();
+    offProject();
+    window.removeEventListener("focus", schedule);
+    window.removeEventListener("blur", schedule);
+    if (timer) clearTimeout(timer);
+  };
+}

src/features/mcp/reporters.test.ts

@@ -0,0 +1,119 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+const state = vi.hoisted(() => ({
+  paths: ["/p/a.txt"],
+  remote: false,
+  root: "/p",
+  registryChanged: () => {},
+  editorChanged: () => {},
+  projectChanged: () => {},
+  reportOpen: vi.fn(async () => undefined),
+  reportFocused: vi.fn(async () => undefined),
+}));
+vi.mock("@/editor/api", () => ({
+  openEditorPaths: () => state.paths,
+  activeEditor: () => ({
+    ctx: { path: "/p/a.txt" },
+    view: {
+      state: {
+        selection: { main: { from: 3, to: 5 } },
+        doc: {
+          lineAt: () => ({ number: 1, from: 0 }),
+          sliceString: () => "hi",
+        },
+      },
+    },
+  }),
+  useEditorRegistry: {
+    subscribe: (fn: () => void) => {
+      state.registryChanged = fn;
+      return () => {};
+    },
+  },
+  onEditorEvent: (fn: () => void) => {
+    state.editorChanged = fn;
+    return () => {};
+  },
+}));
+vi.mock("@/platform/project", () => ({
+  useProject: {
+    getState: () => ({ project: { root: state.root } }),
+    subscribe: (fn: (s: unknown, prev: unknown) => void) => {
+      state.projectChanged = () => fn({ project: { root: state.root } }, { project: null });
+      return () => {};
+    },
+  },
+}));
+vi.mock("@/platform/remote", () => ({ isRemoteWindow: () => state.remote }));
+vi.mock("@/platform/ipc", () => ({
+  call: (promise: Promise<unknown>) => promise,
+  onIdeEvent: () => () => {},
+  ideEventsReady: async () => {},
+  commands: {
+    mcpUiReady: vi.fn(async () => {}),
+    mcpSetOpenEditors: state.reportOpen,
+    mcpSetFocusedEditor: state.reportFocused,
+  },
+}));
+vi.mock("@/workbench/contributions", () => ({ registerOverlay: () => () => {}, editorService: vi.fn() }));
+vi.mock("./ConfirmDialog", () => ({ McpConfirmHost: () => null }));
+const { activate } = await import("./index");
+
+describe("MCP editor reports", () => {
+  let stop: () => void;
+  beforeEach(() => {
+    vi.useFakeTimers();
+    vi.clearAllMocks();
+    state.paths = ["/p/a.txt"];
+    state.remote = false;
+    state.root = "/p";
+    vi.spyOn(document, "hasFocus").mockReturnValue(true);
+    stop = activate();
+  });
+  afterEach(() => {
+    stop();
+    vi.restoreAllMocks();
+    vi.useRealTimers();
+  });
+  it("debounces editor tabs and sends only changes", async () => {
+    await vi.advanceTimersByTimeAsync(200);
+    state.paths = ["/p/a.txt", "/p/b.txt"];
+    state.registryChanged();
+    await vi.advanceTimersByTimeAsync(299);
+    expect(state.reportOpen).not.toHaveBeenCalled();
+    await vi.advanceTimersByTimeAsync(1);
+    expect(state.reportOpen).toHaveBeenCalledWith(["/p/a.txt", "/p/b.txt"]);
+    expect(state.reportFocused).toHaveBeenCalledWith(
+      {
+        path: "/p/a.txt",
+        selection: {
+          start: { line: 0, col: 3 },
+          end: { line: 0, col: 5 },
+        },
+        selectedText: "hi",
+      },
+      true,
+    );
+    state.editorChanged();
+    await vi.advanceTimersByTimeAsync(300);
+    expect(state.reportOpen).toHaveBeenCalledTimes(1);
+    expect(state.reportFocused).toHaveBeenCalledTimes(1);
+  });
+  it("reports again after reopening the same project", async () => {
+    await vi.advanceTimersByTimeAsync(300);
+    state.projectChanged();
+    await vi.advanceTimersByTimeAsync(300);
+    expect(state.reportOpen).toHaveBeenCalledTimes(2);
+    expect(state.reportFocused).toHaveBeenCalledTimes(2);
+  });
+  it("does not report remote windows or after disposal", async () => {
+    state.remote = true;
+    await vi.advanceTimersByTimeAsync(300);
+    expect(state.reportOpen).not.toHaveBeenCalled();
+    state.remote = false;
+    state.registryChanged();
+    stop();
+    await vi.advanceTimersByTimeAsync(300);
+    expect(state.reportOpen).not.toHaveBeenCalled();
+  });
+});

src/features/mcp/requests.test.tsx

@@ -0,0 +1,78 @@
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { act, cleanup, fireEvent, render, screen, waitFor } from "@testing-library/react";
+
+const mocks = vi.hoisted(() => ({ respond: vi.fn(async () => ({ status: "ok", data: null })), open: vi.fn() }));
+vi.mock("@/platform/ipc", async (original) => ({
+  ...(await original<object>()),
+  commands: { mcpRespond: mocks.respond },
+}));
+vi.mock("@/workbench/contributions", () => ({ editorService: () => ({ openFile: mocks.open }) }));
+import { McpConfirmHost } from "./ConfirmDialog";
+import { answerConfirm, denyAll, dropConfirm, handleMcpRequest, useMcpConfirms } from "./requests";
+
+const confirm = {
+  type: "confirm",
+  client: "test client",
+  tool: "execute_run_configuration",
+  subject: "Tests",
+  project: "/project",
+  detail: "npm test",
+} as const;
+beforeEach(() => {
+  vi.clearAllMocks();
+  useMcpConfirms.setState({ queue: [] });
+});
+afterEach(() => {
+  cleanup();
+  denyAll();
+});
+
+describe("MCP confirmations", () => {
+  it("queues requests, allows one, and denies the next on Escape", async () => {
+    await handleMcpRequest(1, confirm);
+    await handleMcpRequest(2, { ...confirm, subject: "Build" });
+    render(<McpConfirmHost />);
+    expect(screen.getByText("npm test")).toBeTruthy();
+    expect(screen.getByText("test client wants to run Tests")).toBeTruthy();
+    fireEvent.click(screen.getByRole("button", { name: "Allow" }));
+    await waitFor(() => expect(mocks.respond).toHaveBeenCalledWith(1, true, null));
+    expect(screen.getByText("test client wants to run Build")).toBeTruthy();
+    fireEvent.keyDown(document, { key: "Escape" });
+    await waitFor(() => expect(mocks.respond).toHaveBeenCalledWith(2, false, null));
+    expect(useMcpConfirms.getState().queue).toEqual([]);
+  });
+  it("denies by default on Enter and denies everything on unload", async () => {
+    await handleMcpRequest(3, confirm);
+    render(<McpConfirmHost />);
+    fireEvent.keyDown(document, { key: "Enter" });
+    await waitFor(() => expect(mocks.respond).toHaveBeenCalledWith(3, false, null));
+    await act(async () => {
+      await handleMcpRequest(4, confirm);
+      await handleMcpRequest(5, confirm);
+      denyAll();
+    });
+    expect(mocks.respond).toHaveBeenCalledWith(4, false, null);
+    expect(mocks.respond).toHaveBeenCalledWith(5, false, null);
+  });
+  it("drops expired requests, including failed answers that arrive later", async () => {
+    await handleMcpRequest(6, confirm);
+    const request = useMcpConfirms.getState().queue[0]!;
+    let reject!: (e: Error) => void;
+    const sending = new Promise<void>((_, no) => {
+      reject = no;
+    });
+    answerConfirm(request, true, () => sending);
+    dropConfirm(6);
+    reject(new Error("expired"));
+    await Promise.resolve();
+    expect(useMcpConfirms.getState().queue).toEqual([]);
+  });
+  it("opens a file with zero-based UTF-16 coordinates and reports errors", async () => {
+    await handleMcpRequest(7, { type: "openFile", path: "/project/a.ts", line: 2, column: 4 });
+    expect(mocks.open).toHaveBeenCalledWith("/project/a.ts", { selection: { line: 1, col: 3 }, focus: true });
+    expect(mocks.respond).toHaveBeenCalledWith(7, true, null);
+    mocks.open.mockRejectedValueOnce(new Error("cannot open"));
+    await handleMcpRequest(8, { type: "openFile", path: "/project/b.ts", line: null, column: null });
+    expect(mocks.respond).toHaveBeenCalledWith(8, false, "Error: cannot open");
+  });
+});

src/features/mcp/requests.ts

@@ -0,0 +1,55 @@
+/** Window requests from the built-in MCP server, answered through window-scoped IPC. */
+import { create } from "zustand";
+import { call, commands, type McpUiRequest } from "@/platform/ipc";
+import { editorService } from "@/workbench/contributions";
+
+type Confirm = Extract<McpUiRequest, { type: "confirm" }> & { id: number; error?: string };
+export const useMcpConfirms = create<{ queue: Confirm[] }>(() => ({ queue: [] }));
+export type Respond = (id: number, allow: boolean, error?: string) => Promise<void>;
+const respond: Respond = async (id, allow, error) => {
+  await call(commands.mcpRespond(id, allow, error ?? null));
+};
+const sending = new Set<number>();
+export function dropConfirm(id: number) {
+  sending.delete(id);
+  useMcpConfirms.setState((s) => ({ queue: s.queue.filter((c) => c.id !== id) }));
+}
+export function answerConfirm(c: Confirm, allow: boolean, send: Respond = respond) {
+  dropConfirm(c.id);
+  sending.add(c.id);
+  void send(c.id, allow).then(
+    () => sending.delete(c.id),
+    (error: unknown) => {
+      if (!sending.delete(c.id)) return;
+      useMcpConfirms.setState((s) => ({ queue: [{ ...c, error: String(error) }, ...s.queue] }));
+    },
+  );
+}
+export function denyAll(send: Respond = respond) {
+  const queue = useMcpConfirms.getState().queue;
+  useMcpConfirms.setState({ queue: [] });
+  sending.clear();
+  for (const c of queue) void send(c.id, false).catch(() => {});
+}
+export async function handleMcpRequest(
+  id: number,
+  request: McpUiRequest,
+  send: Respond = respond,
+  editor = editorService,
+) {
+  if (request.type === "confirm") {
+    useMcpConfirms.setState((s) =>
+      s.queue.some((c) => c.id === id) ? s : { queue: [...s.queue, { ...request, id }] },
+    );
+    return;
+  }
+  try {
+    await editor().openFile(request.path, {
+      selection: request.line != null ? { line: request.line - 1, col: (request.column ?? 1) - 1 } : undefined,
+      focus: true,
+    });
+    await send(id, true);
+  } catch (error) {
+    await send(id, false, String(error)).catch(() => {});
+  }
+}

src/features/settings/__tests__/mcpServer.test.ts

@@ -0,0 +1,41 @@
+import { describe, expect, it } from "vitest";
+import type { McpServerStatus } from "@/bindings";
+import { DEFAULT_SETTINGS, validateSettings } from "../model/schema";
+import { httpConfig, stdioConfig, MCP_SERVER_PAGE } from "../pages/mcpServer";
+
+const status: McpServerStatus = {
+  running: true,
+  error: null,
+  port: 1234,
+  project: "/p",
+  url: "http://127.0.0.1:1234/mcp?project=/p",
+  token: "secret",
+  stdioCommand: ["/Applications/OpenIDEA.app/Contents/MacOS/openidea", "--mcp-stdio", "--project", "/p"],
+};
+
+describe("MCP server settings", () => {
+  it("defaults to off and only offers global scope", () => {
+    expect(DEFAULT_SETTINGS.mcpServer.enabled).toBe(false);
+    expect(validateSettings({}).mcpServer.enabled).toBe(false);
+    expect(validateSettings({ mcpServer: { enabled: true } }).mcpServer.enabled).toBe(true);
+    expect(MCP_SERVER_PAGE.projectScope).not.toBe(true);
+  });
+  it("copies a reusable stdio configuration without the token", () => {
+    const config = stdioConfig(status)!;
+    expect(JSON.parse(config).mcpServers.openidea).toEqual({
+      type: "stdio",
+      command: status.stdioCommand[0],
+      args: status.stdioCommand.slice(1),
+    });
+    expect(config).not.toContain("secret");
+    expect(stdioConfig({ ...status, stdioCommand: [] })).toBeNull();
+  });
+  it("copies the current HTTP endpoint and bearer header", () => {
+    expect(JSON.parse(httpConfig(status)!).mcpServers.openidea).toEqual({
+      type: "http",
+      url: status.url,
+      headers: { Authorization: "Bearer secret" },
+    });
+    expect(httpConfig({ ...status, url: null, token: null })).toBeNull();
+  });
+});

src/features/settings/model/schema.ts

@@ -96,6 +96,8 @@ export interface ValidSettings extends WorkflowSettings {
   languageServers: Record<string, LanguageServerEntry>;
   /** Tools › Agents › Chat: the meters in an agent task's header. */
   agents: Required<AgentSettings>;
+  /** Tools › MCP Server (global). */
+  mcpServer: { enabled: boolean };
 }
 
 /** One `languageServers.<name>` entry; every field optional, like in settings.toml. */
@@ -164,6 +166,7 @@ export const DEFAULT_SETTINGS: ValidSettings = {
   tools: {},
   languageServers: {},
   agents: { showContextUsage: true, showWorkTime: true, showUsageLimits: true, showCost: false },
+  mcpServer: { enabled: false },
   ...DEFAULT_WORKFLOW,
 };
 
@@ -283,6 +286,7 @@ export function validateSettings(raw: Settings | unknown): ValidSettings {
       showUsageLimits: bool(agents.showUsageLimits, d.agents.showUsageLimits),
       showCost: bool(agents.showCost, d.agents.showCost),
     },
+    mcpServer: { enabled: bool(obj(root.mcpServer).enabled, d.mcpServer.enabled) },
     ...validateWorkflow(root),
   };
 }

src/features/settings/pages/McpServer.module.css

@@ -0,0 +1,14 @@
+.status {
+  color: var(--fg-subtle);
+}
+.error {
+  color: var(--danger);
+}
+.endpoint {
+  width: 100%;
+}
+.buttons {
+  display: flex;
+  align-items: center;
+  gap: var(--space-2);
+}

src/features/settings/pages/mcpServer.tsx

@@ -0,0 +1,140 @@
+/** Built-in MCP server status and client configurations. */
+import { useEffect, useState } from "react";
+import { commands, call, isTauri, onIdeEvent, type McpServerStatus } from "@/platform/ipc";
+import { useProject } from "@/platform/project";
+import { useTx } from "@/platform/i18n";
+import { Button, Input, T, copyText } from "@/ui";
+import { Row } from "../components/Form";
+import type { PageSpec } from "./spec";
+import styles from "./McpServer.module.css";
+
+/** `mcpServers` entry of an MCP client configuration (Claude Code, Cursor…). */
+export function httpConfig(status: McpServerStatus): string | null {
+  if (!status.url || !status.token) return null;
+  const server = { type: "http", url: status.url, headers: { Authorization: `Bearer ${status.token}` } };
+  return JSON.stringify({ mcpServers: { openidea: server } }, null, 2);
+}
+
+/** The same through the stdio bridge: no token, works for as long as OpenIDEA runs. */
+export function stdioConfig(status: McpServerStatus): string | null {
+  const [command, ...args] = status.stdioCommand;
+  if (!command) return null;
+  return JSON.stringify({ mcpServers: { openidea: { type: "stdio", command, args } } }, null, 2);
+}
+
+function useStatus(): McpServerStatus | null {
+  const root = useProject((s) => s.project?.root);
+  const [status, setStatus] = useState<McpServerStatus | null>(null);
+  useEffect(() => {
+    if (!isTauri()) return;
+    let live = true;
+    const load = () =>
+      void call(commands.mcpServerStatus()).then(
+        (s) => live && setStatus(s),
+        () => undefined,
+      );
+    load();
+    // Turning the server on or off takes effect on Apply.
+    const off = onIdeEvent("settingsChanged", (e) => {
+      if (!e.key || e.key.startsWith("mcpServer")) load();
+    });
+    return () => {
+      live = false;
+      off();
+    };
+  }, [root]);
+  return status;
+}
+
+function McpServerEndpoint() {
+  const tx = useTx();
+  const status = useStatus();
+  const [copied, setCopied] = useState<string | null>(null);
+  useEffect(() => {
+    if (!copied) return;
+    const timer = setTimeout(() => setCopied(null), 2000);
+    return () => clearTimeout(timer);
+  }, [copied]);
+  if (!status) return null;
+  const copy = (which: string, text: string | null) => {
+    if (!text) return;
+    void copyText(text).then(() => setCopied(which));
+  };
+  const { port, error } = status;
+  const state = status.running
+    ? tx`Running on port ${port}`
+    : error
+      ? tx`Failed to start: ${error}`
+      : tx("Not running");
+  const http = httpConfig(status);
+  const stdio = stdioConfig(status);
+  return (
+    <>
+      <Row label="Status">
+        <span className={error ? styles.error : styles.status}>{state}</span>
+      </Row>
+      <Row
+        label="Endpoint"
+        hint={
+          status.project
+            ? "For this window's project. Agents name the project with the X-OpenIDEA-Project header or the ?project= query."
+            : "Open a project to get its endpoint."
+        }
+      >
+        <Input
+          mono
+          readOnly
+          className={styles.endpoint}
+          value={status.url ?? ""}
+          placeholder={status.running ? tx("No project open") : tx("Not running")}
+          aria-label="Endpoint"
+        />
+      </Row>
+      <Row
+        label="Client configuration"
+        stacked
+        hint="The HTTP configuration holds this run's token and stops working when OpenIDEA restarts. The stdio one starts OpenIDEA's executable, which relays to the running IDE."
+      >
+        <div className={styles.buttons}>
+          <Button size="small" disabled={!http} onClick={() => copy("http", http)}>
+            <T>Copy HTTP Config</T>
+          </Button>
+          <Button size="small" disabled={!stdio} onClick={() => copy("stdio", stdio)}>
+            <T>Copy Stdio Config</T>
+          </Button>
+          {copied && (
+            <span className={styles.status} role="status">
+              <T>Copied to the clipboard</T>
+            </span>
+          )}
+        </div>
+      </Row>
+    </>
+  );
+}
+
+export const MCP_SERVER_PAGE: PageSpec = {
+  id: "tools.mcpServer",
+  title: "MCP Server",
+  group: "Tools",
+  order: 604,
+  keywords: ["mcp", "model context protocol", "ai", "agent", "claude", "codex", "tools", "stdio"],
+  sections: [
+    {
+      options: [
+        {
+          kind: "toggle",
+          key: "mcpServer.enabled",
+          label: "Enable MCP server",
+          hint: "Agents can read, edit, and run projects open in OpenIDEA through its built-in tools. Run tools ask for confirmation. The server listens on 127.0.0.1 only and requires a token.",
+        },
+        {
+          kind: "custom",
+          label: "Endpoint",
+          keywords: ["Copy HTTP Config", "Copy Stdio Config", "Client configuration", "Status"],
+          component: McpServerEndpoint,
+        },
+      ],
+    },
+  ],
+};

src/features/settings/pages/tools.tsx

@@ -19,6 +19,7 @@ import { Button, Checkbox, IconButton, Input, Menu, type SelectOption, T } from
 import { NumberInput, Row, SearchLabel, Section, Select } from "../components/Form";
 import { useLabelMatch, useSetting } from "../components/context";
 import { selectPage, setQuery } from "../model/staging";
+import { MCP_SERVER_PAGE } from "./mcpServer";
 import type { PageSpec } from "./spec";
 import { BoundToggle, Grid, Indented, PageLink, TableEditor } from "./workflowControls";
 import styles from "./Workflow.module.css";
@@ -682,4 +683,5 @@ export const TOOLS_PAGES: PageSpec[] = [
       },
     ],
   },
+  MCP_SERVER_PAGE,
 ];

src/platform/locales/text/en.json

@@ -461,5 +461,28 @@
   "Branch '{name}' is checked out in the worktree at {path}.\nDelete the worktree and the branch? Its folder is deleted.": "Branch '{name}' is checked out in the worktree at {path}.\nDelete the worktree and the branch? Its folder is deleted.",
   "Starting…": "Starting…",
   "Maven Goals": "Maven Goals",
-  "Gradle Tasks": "Gradle Tasks"
+  "Gradle Tasks": "Gradle Tasks",
+  "MCP Server": "MCP Server",
+  "Enable MCP server": "Enable MCP server",
+  "Status": "Status",
+  "Running on port {port}": "Running on port {port}",
+  "Failed to start: {error}": "Failed to start: {error}",
+  "Not running": "Not running",
+  "Endpoint": "Endpoint",
+  "For this window's project. Agents name the project with the X-OpenIDEA-Project header or the ?project= query.": "For this window's project. Agents name the project with the X-OpenIDEA-Project header or the ?project= query.",
+  "Open a project to get its endpoint.": "Open a project to get its endpoint.",
+  "No project open": "No project open",
+  "Client configuration": "Client configuration",
+  "The HTTP configuration holds this run's token and stops working when OpenIDEA restarts. The stdio one starts OpenIDEA's executable, which relays to the running IDE.": "The HTTP configuration holds this run's token and stops working when OpenIDEA restarts. The stdio one starts OpenIDEA's executable, which relays to the running IDE.",
+  "Copy HTTP Config": "Copy HTTP Config",
+  "Copy Stdio Config": "Copy Stdio Config",
+  "Copied to the clipboard": "Copied to the clipboard",
+  "{0} wants to run {1}": "{0} wants to run {1}",
+  "{0} more waiting": "{0} more waiting",
+  "Project: {0}": "Project: {0}",
+  "Tool: {0}": "Tool: {0}",
+  "Could not send the answer: {0}": "Could not send the answer: {0}",
+  "Allow": "Allow",
+  "Deny": "Deny",
+  "Agents can read, edit, and run projects open in OpenIDEA through its built-in tools. Run tools ask for confirmation. The server listens on 127.0.0.1 only and requires a token.": "Agents can read, edit, and run projects open in OpenIDEA through its built-in tools. Run tools ask for confirmation. The server listens on 127.0.0.1 only and requires a token."
 }

src/platform/locales/text/zh.json

@@ -6806,5 +6806,26 @@
   "Always declined": "已设为始终拒绝",
   "Branch '{name}' is checked out in the worktree at {path}.\nDelete the worktree and the branch? Its folder is deleted.": "分支 '{name}' 被位于 {path} 的工作树签出。\n删除该工作树和分支？其文件夹将被删除。",
   "Maven Goals": "Maven 目标",
-  "Gradle Tasks": "Gradle 任务"
+  "Gradle Tasks": "Gradle 任务",
+  "MCP Server": "MCP 服务器",
+  "Enable MCP server": "启用 MCP 服务器",
+  "Running on port {port}": "正在端口 {port} 上运行",
+  "Failed to start: {error}": "启动失败：{error}",
+  "Not running": "未运行",
+  "Endpoint": "端点",
+  "For this window's project. Agents name the project with the X-OpenIDEA-Project header or the ?project= query.": "用于此窗口的项目。智能体通过 X-OpenIDEA-Project 请求头或 ?project= 查询参数指定项目。",
+  "Open a project to get its endpoint.": "打开一个项目以获取其端点。",
+  "No project open": "未打开项目",
+  "Client configuration": "客户端配置",
+  "The HTTP configuration holds this run's token and stops working when OpenIDEA restarts. The stdio one starts OpenIDEA's executable, which relays to the running IDE.": "HTTP 配置包含本次运行的令牌，OpenIDEA 重启后即失效。stdio 配置会启动 OpenIDEA 的可执行文件，由它转发到正在运行的 IDE。",
+  "Copy HTTP Config": "复制 HTTP 配置",
+  "Copy Stdio Config": "复制 Stdio 配置",
+  "Copied to the clipboard": "已复制到剪贴板",
+  "{0} wants to run {1}": "{0} 想要运行 {1}",
+  "{0} more waiting": "还有 {0} 项等待中",
+  "Project: {0}": "项目：{0}",
+  "Tool: {0}": "工具：{0}",
+  "Could not send the answer: {0}": "无法发送回复：{0}",
+  "Deny": "拒绝",
+  "Agents can read, edit, and run projects open in OpenIDEA through its built-in tools. Run tools ask for confirmation. The server listens on 127.0.0.1 only and requires a token.": "智能体可通过内置工具读取、编辑和运行 OpenIDEA 中打开的项目。运行工具会请求确认。服务器仅监听 127.0.0.1，并需要令牌。"
 }