fix(agent): branch on a dedicated-summarizer flag instead of comparing providers

Review follow-ups for #532:

- summarizeProvider now reports whether the dedicated summarizer was
  selected and summarizeClosure branches on that flag; the previous
  `chosen == provider` compared Provider interface values, which panics
  when the dynamic type is not comparable. Regression test uses a provider
  with a slice field for both the summarizer and the main provider.
- CompactionModelID's curated-default test covers the official OpenAI
  profile alongside Anthropic and Google.

Co-Authored-By: Claude Fable 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_012JqvAf7zsP1qYFVZayKXHq

README.md

@@ -273,19 +273,6 @@ zero sandbox grants list
 Zero includes local file/search/edit/shell tools, `web_fetch` for public URLs,
 and MCP support for additional tools.
 
-`web_fetch` refuses loopback, private and other special-use addresses: it checks
-the URL before asking permission, resolves the host, and dials the address it
-validated so a name cannot resolve to something else in between.
-
-If `HTTP_PROXY`/`HTTPS_PROXY` is set, `web_fetch` and the provider connectivity
-probe use it, and that last step changes: the proxy is dialed and the target
-hostname is sent to it, so the proxy decides which address the request actually
-reaches. The URL is still checked and resolved locally first, but a proxy that
-answers differently can reach a private service. A forward proxy already sees
-and can rewrite every request through it, so this is the trust you accept by
-configuring one. Leave the variables unset for the checks to be enforced end to
-end.
-
 For local dev servers, use shell commands such as `curl` through `exec_command`
 so the normal sandbox and permission policy applies. Long-running commands stay
 attached to a background terminal session and can be listed or stopped from the
@@ -384,13 +371,9 @@ go run ./cmd/zero-perf-bench
 
 Experimental: `ZERO_OPENAI_TURN_SESSION=1` enables the optimized OpenAI turn
 session (background connection prewarm + request-prefix telemetry) for headless
-`zero exec` runs against official OpenAI profiles. Off by default; `0`, `false`,
-or `off` disable it. A/B-benchmark it by running the same `zero-perf-bench` suite
-with the variable unset and set.
-
-Native ChatGPT Responses sessions are enabled by default. Set
-`ZERO_CHATGPT_TURN_SESSION=0`, `false`, or `off` to restore stateless HTTP/SSE
-transport.
+`zero exec` runs against official OpenAI profiles. Off by default; `0`/`false`
+disable. A/B-benchmark it by running the same `zero-perf-bench` suite with the
+variable unset and set.
 
 ### Code Quality and Security Checks
 

docs/HOW_ZERO_WORKS.md

@@ -627,12 +627,7 @@ Core tool groups include:
   skills, `ask_user`, permission requests.
 - **Write tools**: `write_file`, `edit_file`, `apply_patch`, `update_plan`.
 - **Shell tools**: `exec_command`, `write_stdin`, legacy `bash`.
-- **Network tools**: `web_fetch` and optional web search backend. `web_fetch`
-  validates the URL before the permission prompt, refuses loopback/private/
-  special-use addresses, and dials the address it resolved. With
-  `HTTP_PROXY`/`HTTPS_PROXY` set, the proxy is dialed instead and resolves the
-  target itself, so destination enforcement ends at the proxy; see the note in
-  the README.
+- **Network tools**: `web_fetch` and optional web search backend.
 - **Local-control tools**: config-gated wrappers for browser, terminal, desktop,
   and artifact helpers backed by packages such as `internal/localcontrol` and
   `internal/browser`.

go.mod

@@ -4,7 +4,7 @@ go 1.26.6
 
 require (
 	charm.land/bubbles/v2 v2.1.1
-	charm.land/bubbletea/v2 v2.0.9
+	charm.land/bubbletea/v2 v2.0.8
 	charm.land/lipgloss/v2 v2.0.5
 	github.com/Microsoft/go-winio v0.6.2
 	github.com/alecthomas/chroma/v2 v2.27.0

go.sum

@@ -1,7 +1,7 @@
 charm.land/bubbles/v2 v2.1.1 h1:7r55WzBxpo/R3z98hGmY7KKPd3ET6vsf0Fb9sDHOV60=
 charm.land/bubbles/v2 v2.1.1/go.mod h1:GE6M31gaWZVXzGw73OeuTTgy4lX+OtkH0E5ymnNsHxo=
-charm.land/bubbletea/v2 v2.0.9 h1:DpJCMWKgzQK8SJv4zbKKFHAI10ymWy/evClPFk0k0f8=
-charm.land/bubbletea/v2 v2.0.9/go.mod h1:2SkdgoTXluXJHOUwAoRlRXF/28vklb1rFl6GcgV1/ss=
+charm.land/bubbletea/v2 v2.0.8 h1:SxTJMhCAI3lbPmy4SgX5LWZ24AdINr4I6UEqzZvYJuY=
+charm.land/bubbletea/v2 v2.0.8/go.mod h1:2SkdgoTXluXJHOUwAoRlRXF/28vklb1rFl6GcgV1/ss=
 charm.land/lipgloss/v2 v2.0.5 h1:kbNxgeeUOYv5J0YdpxFjfvf3dFvqH8Aci4zB6xqFtrY=
 charm.land/lipgloss/v2 v2.0.5/go.mod h1:9oqhxt4yxIMe6q5A4kHr44DremZk7J9UNh74GlWa5nc=
 github.com/Microsoft/go-winio v0.6.2 h1:F2VQgta7ecxGYO8k3ZZz3RS8fVIXVxONVUPlNERoyfY=
@@ -64,6 +64,8 @@ github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e h1:JVG44RsyaB9T2KIHavM
 github.com/xo/terminfo v0.0.0-20220910002029-abceb7e1c41e/go.mod h1:RbqR21r5mrJuqunuUZ/Dhy/avygyECGrLceyNeo4LiM=
 golang.org/x/exp v0.0.0-20260611194520-c48552f49976 h1:X8Hz2ImujgbmetVuW+w2YkyZChE3cBpZi2P158rTG9M=
 golang.org/x/exp v0.0.0-20260611194520-c48552f49976/go.mod h1:vnf4pv9iKZXY58sQE1L86zmNWJ4159e1RkcWiLCkeEY=
+golang.org/x/image v0.44.0 h1:+tDekMZED9+LrtB3G5xzRggpVh9CARjZqROla3R3R+I=
+golang.org/x/image v0.44.0/go.mod h1:V8K3KE9KKKE+pLpQDOeN18w9oacNSvy1tDOirTu4xtY=
 golang.org/x/image v0.45.0 h1:FMb1nTbH5H9vF55SriQHgFw5GnNL9Jg6L25BwXKzhB0=
 golang.org/x/image v0.45.0/go.mod h1:n62x/7RqlwXDvGsSU4u6IUTUf6KghUZ9Bt7cG/T9Fx4=
 golang.org/x/sync v0.22.0 h1:SZjpbeLmrCk4xhRSZFNZW5gFUeCeFgjekvI/+gfScek=

internal/acp/permission.go

@@ -142,15 +142,13 @@ func actionOffered(optionID string, offered []PermissionOption) bool {
 // session/request_permission request from a ZERO permission request.
 func permissionToolCall(req agent.PermissionRequest) ToolCallUpdate {
 	args := marshalArgs(req.Args)
-	upd := ToolCallUpdate{
+	return ToolCallUpdate{
 		ToolCallID: req.ToolCallID,
 		Title:      toolTitle(req.ToolName, string(args)),
 		Kind:       toolKindFor(req.ToolName),
 		Status:     ToolStatusPending,
 		RawInput:   rawInputBytes(args),
 	}
-	attachBrowserToolDetails(&upd, req.ToolName)
-	return upd
 }
 
 func marshalArgs(args map[string]any) []byte {

internal/acp/permission_test.go

@@ -82,17 +82,3 @@ func TestPermissionToolCall(t *testing.T) {
 		t.Error("expected rawInput from args")
 	}
 }
-
-func TestPermissionToolCallKeepsTheBrowserDescriptor(t *testing.T) {
-	call := permissionToolCall(agent.PermissionRequest{
-		ToolCallID: "browser-1",
-		ToolName:   "browser_connect",
-		Args:       map[string]any{"target": "127.0.0.1:9222"},
-	})
-	if got := browserDescriptor(t, call); got != (BrowserToolDetails{Version: 1, Command: "connect"}) {
-		t.Fatalf("browser descriptor = %#v", got)
-	}
-	if call.Title != "browser connect" {
-		t.Fatalf("title = %q", call.Title)
-	}
-}

internal/acp/translate.go

@@ -2,9 +2,7 @@ package acp
 
 import (
 	"encoding/json"
-	"net/url"
 	"strings"
-	"unicode"
 	"unicode/utf8"
 
 	"github.com/Gitlawb/zero/internal/agent"
@@ -46,125 +44,12 @@ func toolKindFor(name string) string {
 
 // toolTitle builds a concise human title, e.g. "read_file src/main.go".
 func toolTitle(name, rawArgs string) string {
-	if browser, ok := browserToolDetails(name); ok {
-		return browserToolTitle(browser.Command, rawArgs)
-	}
 	if hint := primaryArgHint(rawArgs); hint != "" {
 		return name + " " + hint
 	}
 	return name
 }
 
-// browserToolDetails identifies ZERO's local browser helpers without treating
-// similarly named MCP tools as browser automation. The descriptor intentionally
-// contains no request data: ACP tool input is already protocol-visible, but a
-// durable UI must not need to retain text, local CDP targets, or full URLs just
-// to recognise the browser operation.
-func browserToolDetails(name string) (*BrowserToolDetails, bool) {
-	const prefix = "browser_"
-	command, ok := strings.CutPrefix(name, prefix)
-	if !ok {
-		return nil, false
-	}
-	switch command {
-	case "install", "launch", "connect", "open", "snapshot", "click", "type", "press", "action":
-		return &BrowserToolDetails{Version: 1, Command: command}, true
-	default:
-		return nil, false
-	}
-}
-
-const zeroBrowserMetaKey = "github.com/Gitlawb/zero/browser"
-
-// attachBrowserToolDetails stores ZERO's browser descriptor in ACP's reserved
-// extension channel. Keeping this in one helper prevents start, result, and
-// permission payloads from drifting onto different wire shapes.
-func attachBrowserToolDetails(update *ToolCallUpdate, name string) {
-	browser, ok := browserToolDetails(name)
-	if !ok {
-		return
-	}
-	raw, err := json.Marshal(browser)
-	if err != nil {
-		return
-	}
-	update.Meta = map[string]json.RawMessage{zeroBrowserMetaKey: raw}
-}
-
-// browserToolTitle avoids putting browser_type text, an attached DevTools
-// endpoint, or a URL query/fragment in a tool-card title. Those values can
-// carry credentials or session data; the UI only needs the operation and, for
-// navigation, a human-recognisable origin.
-func browserToolTitle(command, rawArgs string) string {
-	switch command {
-	case "action":
-		action, ok := exactJSONStringArg(rawArgs, "command")
-		if !ok {
-			return "browser action"
-		}
-		if action, ok := tools.NormalizedBrowserActionCommand(action); ok {
-			return "browser action " + action
-		}
-		return "browser action"
-	case "open":
-		rawURL, ok := exactJSONStringArg(rawArgs, "url")
-		if !ok {
-			return "browser open"
-		}
-		normalized, err := tools.NormalizeBrowserOpenURL(rawURL)
-		if err != nil {
-			return "browser open"
-		}
-		u, err := url.Parse(normalized)
-		if err != nil || u.Scheme == "" || u.Host == "" {
-			return "browser open"
-		}
-		origin := u.Scheme + "://" + u.Host
-		if !browserTitleTextSafe(origin) {
-			return "browser open"
-		}
-		return "browser open " + truncateHint(origin)
-	default:
-		return "browser " + command
-	}
-}
-
-// browserTitleTextSafe validates text after URL parsing has decoded escaped
-// UTF-8 in the host. Valid UTF-8 alone is not presentation-safe: control,
-// format/bidi, and line/paragraph separator runes can reorder or split the
-// permission label shown to a user. The execution URL remains unchanged.
-func browserTitleTextSafe(text string) bool {
-	if !utf8.ValidString(text) {
-		return false
-	}
-	for _, r := range text {
-		if unicode.IsControl(r) || unicode.Is(unicode.Cf, r) || unicode.Is(unicode.Zl, r) || unicode.Is(unicode.Zp, r) {
-			return false
-		}
-	}
-	return true
-}
-
-// exactJSONStringArg mirrors ZERO's map-based tool argument decoding: only the
-// exact JSON key is considered, and a non-string value is invalid. In
-// particular, an incidental "URL" key must not change a permission title when
-// browser_open will only read "url".
-func exactJSONStringArg(rawArgs, key string) (string, bool) {
-	var args map[string]json.RawMessage
-	if json.Unmarshal([]byte(rawArgs), &args) != nil {
-		return "", false
-	}
-	raw, ok := args[key]
-	if !ok {
-		return "", false
-	}
-	var value string
-	if json.Unmarshal(raw, &value) != nil {
-		return "", false
-	}
-	return value, true
-}
-
 // primaryArgHint extracts the most relevant argument (path/pattern/command) from
 // raw JSON arguments. Best-effort; returns "" when it can't parse.
 func primaryArgHint(rawArgs string) string {
@@ -204,7 +89,7 @@ func rawInput(args string) json.RawMessage {
 // toolCallStart maps an advertised ZERO tool call to the initial ACP "tool_call"
 // update (status in_progress — ZERO executes immediately after advertising).
 func toolCallStart(call agent.ToolCall) ToolCallUpdate {
-	upd := ToolCallUpdate{
+	return ToolCallUpdate{
 		SessionUpdate: UpdateToolCall,
 		ToolCallID:    call.ID,
 		Title:         toolTitle(call.Name, call.Arguments),
@@ -212,8 +97,6 @@ func toolCallStart(call agent.ToolCall) ToolCallUpdate {
 		Status:        ToolStatusInProgress,
 		RawInput:      rawInput(call.Arguments),
 	}
-	attachBrowserToolDetails(&upd, call.Name)
-	return upd
 }
 
 // toolCallResult maps a finished ZERO tool result to a "tool_call_update".
@@ -233,7 +116,6 @@ func toolCallResult(result agent.ToolResult) ToolCallUpdate {
 	if locs := toolResultLocations(result); len(locs) > 0 {
 		upd.Locations = locs
 	}
-	attachBrowserToolDetails(&upd, result.Name)
 	return upd
 }
 

internal/acp/translate_test.go

@@ -1,29 +1,14 @@
 package acp
 
 import (
-	"encoding/json"
 	"strings"
 	"testing"
-	"unicode"
 	"unicode/utf8"
 
 	"github.com/Gitlawb/zero/internal/agent"
 	"github.com/Gitlawb/zero/internal/tools"
 )
 
-func browserDescriptor(t *testing.T, update ToolCallUpdate) BrowserToolDetails {
-	t.Helper()
-	raw, ok := update.Meta[zeroBrowserMetaKey]
-	if !ok {
-		t.Fatalf("browser metadata = %#v, want %q", update.Meta, zeroBrowserMetaKey)
-	}
-	var details BrowserToolDetails
-	if err := json.Unmarshal(raw, &details); err != nil {
-		t.Fatalf("decode browser metadata: %v", err)
-	}
-	return details
-}
-
 func TestAgentMessageAndThoughtChunks(t *testing.T) {
 	m := agentMessageChunk("hello")
 	if m.SessionUpdate != UpdateAgentMessageChunk || m.Content.Type != "text" || m.Content.Text != "hello" {
@@ -71,217 +56,6 @@ func TestToolTitleAndHint(t *testing.T) {
 	}
 }
 
-func TestBrowserToolUpdatesAreStructuredAndPresentationSafe(t *testing.T) {
-	start := toolCallStart(agent.ToolCall{
-		ID:        "browser-1",
-		Name:      "browser_open",
-		Arguments: `{"url":"https://example.com/settings?token=not-for-a-title#account"}`,
-	})
-	if got := browserDescriptor(t, start); got != (BrowserToolDetails{Version: 1, Command: "open"}) {
-		t.Fatalf("browser descriptor = %#v, want open", got)
-	}
-	if start.Title != "browser open https://example.com" {
-		t.Fatalf("browser title = %q", start.Title)
-	}
-	if strings.Contains(start.Title, "token=") || strings.Contains(start.Title, "#account") {
-		t.Fatalf("browser title leaked URL-sensitive data: %q", start.Title)
-	}
-	encoded, err := json.Marshal(start)
-	if err != nil {
-		t.Fatal(err)
-	}
-	var wire struct {
-		Meta map[string]json.RawMessage `json:"_meta"`
-	}
-	if err := json.Unmarshal(encoded, &wire); err != nil {
-		t.Fatal(err)
-	}
-	if _, ok := wire.Meta[zeroBrowserMetaKey]; !ok {
-		t.Fatalf("browser wire metadata = %#v", wire.Meta)
-	}
-
-	typed := toolCallStart(agent.ToolCall{
-		ID:        "browser-2",
-		Name:      "browser_type",
-		Arguments: `{"ref":"email","text":"[email protected]"}`,
-	})
-	if got := browserDescriptor(t, typed); got.Command != "type" {
-		t.Fatalf("browser type descriptor = %#v", got)
-	}
-	if typed.Title != "browser type" || strings.Contains(typed.Title, "[email protected]") {
-		t.Fatalf("browser type title = %q", typed.Title)
-	}
-
-	action := toolCallStart(agent.ToolCall{
-		ID:        "browser-3",
-		Name:      "browser_action",
-		Arguments: `{"command":"keyboard_insert_text","args":["[email protected]"]}`,
-	})
-	if action.Title != "browser action keyboard_insert_text" {
-		t.Fatalf("browser action title = %q", action.Title)
-	}
-
-	result := toolCallResult(agent.ToolResult{
-		ToolCallID: "browser-2",
-		Name:       "browser_type",
-		Status:     tools.StatusOK,
-	})
-	if got := browserDescriptor(t, result); got.Command != "type" {
-		t.Fatalf("browser result descriptor = %#v", got)
-	}
-}
-
-func TestBrowserDescriptorSurvivesProtocolShapedRoundTrip(t *testing.T) {
-	updates := []ToolCallUpdate{
-		toolCallStart(agent.ToolCall{
-			ID:        "start",
-			Name:      "browser_open",
-			Arguments: `{"url":"https://user:[email protected]/private?token=secret#fragment"}`,
-		}),
-		toolCallResult(agent.ToolResult{
-			ToolCallID: "result",
-			Name:       "browser_type",
-			Status:     tools.StatusOK,
-		}),
-		permissionToolCall(agent.PermissionRequest{
-			ToolCallID: "permission",
-			ToolName:   "browser_connect",
-			Args:       map[string]any{"target": "127.0.0.1:9222"},
-		}),
-	}
-
-	type protocolToolCallUpdate struct {
-		SessionUpdate string                     `json:"sessionUpdate,omitempty"`
-		ToolCallID    string                     `json:"toolCallId"`
-		Title         string                     `json:"title,omitempty"`
-		Kind          string                     `json:"kind,omitempty"`
-		Status        string                     `json:"status,omitempty"`
-		RawInput      json.RawMessage            `json:"rawInput,omitempty"`
-		Content       []ToolCallContent          `json:"content,omitempty"`
-		Locations     []ToolCallLocation         `json:"locations,omitempty"`
-		Meta          map[string]json.RawMessage `json:"_meta,omitempty"`
-	}
-
-	for _, update := range updates {
-		encoded, err := json.Marshal(update)
-		if err != nil {
-			t.Fatal(err)
-		}
-		var root map[string]json.RawMessage
-		if err := json.Unmarshal(encoded, &root); err != nil {
-			t.Fatal(err)
-		}
-		if _, ok := root["browser"]; ok {
-			t.Fatalf("browser descriptor escaped ACP _meta: %s", encoded)
-		}
-
-		var protocol protocolToolCallUpdate
-		if err := json.Unmarshal(encoded, &protocol); err != nil {
-			t.Fatal(err)
-		}
-		forwarded, err := json.Marshal(protocol)
-		if err != nil {
-			t.Fatal(err)
-		}
-		var roundTripped ToolCallUpdate
-		if err := json.Unmarshal(forwarded, &roundTripped); err != nil {
-			t.Fatal(err)
-		}
-		details := browserDescriptor(t, roundTripped)
-		if details.Version != 1 || details.Command == "" {
-			t.Fatalf("round-tripped browser descriptor = %#v", details)
-		}
-		descriptorJSON := string(roundTripped.Meta[zeroBrowserMetaKey])
-		for _, secret := range []string{"password", "private", "token", "fragment", "127.0.0.1", "9222"} {
-			if strings.Contains(descriptorJSON, secret) {
-				t.Fatalf("browser descriptor leaked %q: %s", secret, descriptorJSON)
-			}
-		}
-	}
-}
-
-func TestBrowserPermissionTitlesMirrorSafeToolArguments(t *testing.T) {
-	if got := browserToolTitle("open", `{"url":"evil.example.test/pay?token=hidden#fragment"}`); got != "browser open https://evil.example.test" {
-		t.Fatalf("bare-host title = %q", got)
-	}
-	if got := browserToolTitle("open", `{"URL":"https://different.example.test"}`); got != "browser open" {
-		t.Fatalf("case-variant URL title = %q", got)
-	}
-	if got := browserToolTitle("open", `{"URL":"https://different.example.test","url":"https://actual.example.test/path"}`); got != "browser open https://actual.example.test" {
-		t.Fatalf("exact URL key title = %q", got)
-	}
-	if got := browserToolTitle("action", `{"command":"not an action"}`); got != "browser action" {
-		t.Fatalf("unknown browser action title = %q", got)
-	}
-
-	longHost := "https://" + strings.Repeat("a", 200) + ".example.test/path?token=hidden"
-	title := browserToolTitle("open", `{"url":"`+longHost+`"}`)
-	if !utf8.ValidString(title) || utf8.RuneCountInString(title) > len("browser open ")+61 || strings.Contains(title, "token=") {
-		t.Fatalf("bounded browser origin title = %q", title)
-	}
-}
-
-func TestBrowserOpenTitlesRejectDecodedUnicodePresentationControls(t *testing.T) {
-	for _, rawURL := range []string{
-		"https://safe.example%E2%80%AEevil.test/path",
-		"https://safe.example%E2%81%A6evil.test/path",
-		"https://safe.example%C2%85evil.test/path",
-		"https://safe.example%E2%80%A8evil.test/path",
-		"https://safe.example%E2%80%A9evil.test/path",
-	} {
-		t.Run(rawURL, func(t *testing.T) {
-			normalized, err := tools.NormalizeBrowserOpenURL(rawURL)
-			if err != nil {
-				t.Fatalf("execution URL rejected: %v", err)
-			}
-			if normalized != rawURL {
-				t.Fatalf("execution URL = %q, want unchanged %q", normalized, rawURL)
-			}
-
-			args, err := json.Marshal(map[string]any{"url": rawURL})
-			if err != nil {
-				t.Fatal(err)
-			}
-			updates := []ToolCallUpdate{
-				toolCallStart(agent.ToolCall{ID: "start", Name: "browser_open", Arguments: string(args)}),
-				permissionToolCall(agent.PermissionRequest{ToolCallID: "permission", ToolName: "browser_open", Args: map[string]any{"url": rawURL}}),
-			}
-			for _, update := range updates {
-				encoded, err := json.Marshal(update)
-				if err != nil {
-					t.Fatal(err)
-				}
-				var decoded ToolCallUpdate
-				if err := json.Unmarshal(encoded, &decoded); err != nil {
-					t.Fatal(err)
-				}
-				if decoded.Title != "browser open" {
-					t.Fatalf("unsafe browser title survived wire round trip: %q", decoded.Title)
-				}
-				for _, r := range decoded.Title {
-					if unicode.IsControl(r) || unicode.Is(unicode.Cf, r) || unicode.Is(unicode.Zl, r) || unicode.Is(unicode.Zp, r) {
-						t.Fatalf("browser title contains unsafe presentation rune %U: %q", r, decoded.Title)
-					}
-				}
-			}
-		})
-	}
-}
-
-func TestBrowserDescriptorDoesNotClaimSimilarlyNamedMCPTools(t *testing.T) {
-	start := toolCallStart(agent.ToolCall{ID: "mcp-1", Name: "browser_plugin_open", Arguments: `{}`})
-	if len(start.Meta) != 0 {
-		t.Fatalf("MCP-like tool received built-in browser metadata: %#v", start.Meta)
-	}
-	encoded, err := json.Marshal(start)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if strings.Contains(string(encoded), `"browser"`) {
-		t.Fatalf("non-browser tool encoded browser field: %s", encoded)
-	}
-}
-
 func TestToolCallStart(t *testing.T) {
 	upd := toolCallStart(agent.ToolCall{ID: "tc1", Name: "read_file", Arguments: `{"path":"a.go"}`})
 	if upd.SessionUpdate != UpdateToolCall {

internal/acp/types.go

@@ -210,21 +210,6 @@ type ToolCallUpdate struct {
 	RawInput      json.RawMessage    `json:"rawInput,omitempty"`
 	Content       []ToolCallContent  `json:"content,omitempty"`
 	Locations     []ToolCallLocation `json:"locations,omitempty"`
-	// Meta is ACP's extension channel. ZERO-owned values must remain beneath a
-	// namespaced key so protocol-shaped clients can preserve them while decoding
-	// and re-encoding a tool call.
-	Meta map[string]json.RawMessage `json:"_meta,omitempty"`
-}
-
-// BrowserToolDetails identifies the browser helper operation behind a tool
-// call. Version is the schema version for this optional ZERO extension;
-// Command is one of install, launch, connect, open, snapshot, click, type,
-// press, or action. Future fields must remain display-safe and must not
-// include browser profile data, cookies, typed text, URL paths/queries, or
-// DevTools endpoints.
-type BrowserToolDetails struct {
-	Version int    `json:"version"`
-	Command string `json:"command"`
 }
 
 // ToolCallContent is a tool call's rendered output. ZERO emits "content" (a

internal/agent/compaction.go

@@ -146,17 +146,11 @@ func estimateToolDefTokens(tools []zeroruntime.ToolDefinition) int {
 	for _, tool := range tools {
 		total += ApproxTextTokens(tool.Name)
 		total += ApproxTextTokens(tool.Description)
-		total += ApproxTextTokens(string(tool.Type))
 		if len(tool.Parameters) > 0 {
 			if encoded, err := json.Marshal(tool.Parameters); err == nil {
 				total += ApproxTextTokens(string(encoded))
 			}
 		}
-		if tool.Format != nil {
-			total += ApproxTextTokens(tool.Format.Type)
-			total += ApproxTextTokens(tool.Format.Syntax)
-			total += ApproxTextTokens(tool.Format.Definition)
-		}
 		total += 4 // per-tool overhead
 	}
 	return total

internal/agent/compaction_projection.go

@@ -126,11 +126,8 @@ func capCompactionBrief(brief string) (string, bool) {
 
 func compactionToolCallLine(call zeroruntime.ToolCall) string {
 	detail := ""
-	if call.Freeform && call.Name == "apply_patch" {
-		detail = strings.Join(patchPaths(call.Arguments), ", ")
-	}
 	var arguments map[string]any
-	if detail == "" && json.Unmarshal([]byte(strings.TrimSpace(call.Arguments)), &arguments) == nil {
+	if json.Unmarshal([]byte(strings.TrimSpace(call.Arguments)), &arguments) == nil {
 		for _, key := range []string{"file_path", "path", "url", "query", "pattern", "prompt", "description", "question"} {
 			if value, ok := arguments[key].(string); ok && strings.TrimSpace(value) != "" {
 				detail = value

internal/agent/compaction_projection_test.go

@@ -73,7 +73,6 @@ func TestProjectCompactionInputRetainsAskUserExchangeAndSemanticArguments(t *tes
 		{Role: zeroruntime.MessageRoleTool, ToolCallID: "ask", Content: "Which database should remain?: Postgres only; do not touch MySQL."},
 		{Role: zeroruntime.MessageRoleAssistant, ToolCalls: []zeroruntime.ToolCall{
 			{ID: "patch", Name: "apply_patch", Arguments: `{"patch":"*** Begin Patch\n*** Update File: internal/db.go\n*** End Patch"}`},
-			{ID: "raw-patch", Name: "apply_patch", Freeform: true, Arguments: "*** Begin Patch\n*** Update File: internal/api.go\n*** Add File: internal/config.go\n*** End Patch\n"},
 			{ID: "fetch", Name: "web_fetch", Arguments: `{"url":"https://example.com/spec"}`},
 			{ID: "task", Name: "task", Arguments: `{"prompt":"Inspect the Windows implementation"}`},
 		}},
@@ -81,7 +80,7 @@ func TestProjectCompactionInputRetainsAskUserExchangeAndSemanticArguments(t *tes
 	}
 
 	content := projectCompactionInput(messages).messages[0].Content
-	for _, want := range []string{"Which database should remain?", "Postgres only; do not touch MySQL", "internal/db.go", "internal/api.go", "internal/config.go", "https://example.com/spec", "Inspect the Windows implementation"} {
+	for _, want := range []string{"Which database should remain?", "Postgres only; do not touch MySQL", "internal/db.go", "https://example.com/spec", "Inspect the Windows implementation"} {
 		if !strings.Contains(content, want) {
 			t.Fatalf("projection missing %q: %q", want, content)
 		}

internal/agent/compaction_test.go

@@ -275,27 +275,6 @@ func TestEstimateToolDefTokensCountsDefinitions(t *testing.T) {
 	if estimateToolDefTokens(one) <= 0 {
 		t.Fatal("a tool definition (name + description + schema) should estimate > 0 tokens")
 	}
-	typed := append([]zeroruntime.ToolDefinition(nil), one...)
-	typed[0].Type = zeroruntime.ToolDefinitionFreeform
-	if estimateToolDefTokens(typed) <= estimateToolDefTokens(one) {
-		t.Fatal("a non-empty tool type must increase the estimated request cost")
-	}
-	for _, test := range []struct {
-		name   string
-		format zeroruntime.ToolDefinitionFormat
-	}{
-		{name: "type", format: zeroruntime.ToolDefinitionFormat{Type: "grammar"}},
-		{name: "syntax", format: zeroruntime.ToolDefinitionFormat{Syntax: "lark"}},
-		{name: "definition", format: zeroruntime.ToolDefinitionFormat{Definition: "start: WORD"}},
-	} {
-		t.Run("format "+test.name, func(t *testing.T) {
-			formatted := append([]zeroruntime.ToolDefinition(nil), one...)
-			formatted[0].Format = &test.format
-			if estimateToolDefTokens(formatted) <= estimateToolDefTokens(one) {
-				t.Fatalf("a non-empty format %s must increase the estimated request cost", test.name)
-			}
-		})
-	}
 	two := append(append([]zeroruntime.ToolDefinition{}, one...), zeroruntime.ToolDefinition{
 		Name:        "write_file",
 		Description: "Write contents to a file in the workspace.",

internal/agent/context_planner.go

@@ -102,10 +102,6 @@ func copyToolDefinitions(toolDefs []zeroruntime.ToolDefinition) []zeroruntime.To
 	for index, definition := range toolDefs {
 		copied[index] = definition
 		copied[index].Parameters = copySchemaMap(definition.Parameters)
-		if definition.Format != nil {
-			format := *definition.Format
-			copied[index].Format = &format
-		}
 	}
 	return copied
 }

internal/agent/context_planner_test.go

@@ -15,7 +15,6 @@ func TestContextPlannerPreservesProviderRequest(t *testing.T) {
 	}
 	toolDefs := []zeroruntime.ToolDefinition{{
 		Name: "read_file", Description: "Read a file",
-		Format: &zeroruntime.ToolDefinitionFormat{Type: "grammar", Syntax: "lark", Definition: "start: PATH"},
 		Parameters: map[string]any{
 			"type":       "object",
 			"required":   []string{"path"},
@@ -54,12 +53,10 @@ func TestContextPlannerPreservesProviderRequest(t *testing.T) {
 	toolDefs[0].Parameters["required"].([]string)[0] = "other"
 	toolDefs[0].Parameters["properties"].(map[string]any)["path"].(map[string]any)["type"] = "integer"
 	toolDefs[0].Parameters["anyOf"].([]any)[0].(map[string]any)["type"] = "array"
-	toolDefs[0].Format.Definition = "changed"
 	if plan.Request.Messages[1].Content != "inspect this" || plan.Request.Messages[1].Images[0].Data[0] != 1 {
 		t.Fatalf("planned messages alias caller state: %#v", plan.Request.Messages[1])
 	}
 	if plan.Request.Tools[0].Name != "read_file" ||
-		plan.Request.Tools[0].Format == nil || plan.Request.Tools[0].Format.Definition != "start: PATH" ||
 		plan.Request.Tools[0].Parameters["required"].([]string)[0] != "path" ||
 		plan.Request.Tools[0].Parameters["properties"].(map[string]any)["path"].(map[string]any)["type"] != "string" ||
 		plan.Request.Tools[0].Parameters["anyOf"].([]any)[0].(map[string]any)["type"] != "object" {

internal/agent/freeform_tool_test.go

@@ -1,378 +0,0 @@
-package agent
-
-import (
-	"context"
-	"os"
-	"path/filepath"
-	"runtime"
-	"strings"
-	"testing"
-
-	"github.com/Gitlawb/zero/internal/sandbox"
-	"github.com/Gitlawb/zero/internal/tools"
-	"github.com/Gitlawb/zero/internal/zeroruntime"
-)
-
-type customApplyPatchTool struct {
-	calls int
-}
-
-type fixedPathScope struct {
-	roots []string
-}
-
-func (scope fixedPathScope) Roots() []string {
-	return append([]string(nil), scope.roots...)
-}
-
-func newFixedPathScope(t *testing.T, roots ...string) fixedPathScope {
-	t.Helper()
-	resolved := make([]string, 0, len(roots))
-	for _, root := range roots {
-		absolute, err := filepath.Abs(root)
-		if err != nil {
-			t.Fatalf("Abs(%q): %v", root, err)
-		}
-		if physical, err := filepath.EvalSymlinks(absolute); err == nil {
-			absolute = physical
-		}
-		resolved = append(resolved, absolute)
-	}
-	return fixedPathScope{roots: resolved}
-}
-
-func (*customApplyPatchTool) Name() string        { return "apply_patch" }
-func (*customApplyPatchTool) Description() string { return "custom JSON tool" }
-func (*customApplyPatchTool) Parameters() tools.Schema {
-	return tools.Schema{Type: "object", Properties: map[string]tools.PropertySchema{"value": {Type: "string"}}}
-}
-func (*customApplyPatchTool) Safety() tools.Safety {
-	return tools.Safety{Permission: tools.PermissionAllow, SideEffect: tools.SideEffectRead}
-}
-func (tool *customApplyPatchTool) Run(context.Context, map[string]any) tools.Result {
-	tool.calls++
-	return tools.Result{Status: tools.StatusOK}
-}
-
-func TestFreeformApplyPatchUsesExistingToolExecutionPath(t *testing.T) {
-	root := t.TempDir()
-	registry := tools.NewRegistry()
-	registry.Register(tools.NewScopedApplyPatchTool(root, nil))
-	patch := "*** Begin Patch\n*** Add File: hello.txt\n+hello\n*** End Patch\n"
-
-	result, err := executeToolCall(context.Background(), registry, zeroruntime.ToolCall{
-		ID:        "call-1",
-		Name:      "apply_patch",
-		Arguments: patch,
-		Freeform:  true,
-	}, PermissionModeUnsafe, Options{Cwd: root, FileTracker: tools.NewFileTracker()})
-	if err != nil {
-		t.Fatalf("executeToolCall: %v", err)
-	}
-	if result.Status != tools.StatusOK {
-		t.Fatalf("freeform apply_patch status = %s: %s", result.Status, result.Output)
-	}
-	content, err := os.ReadFile(filepath.Join(root, "hello.txt"))
-	if err != nil {
-		t.Fatalf("read patched file: %v", err)
-	}
-	if string(content) != "hello\n" {
-		t.Fatalf("patched content = %q, want hello newline", content)
-	}
-}
-
-func TestFreeformApplyPatchSupportsGrantedExtraRoot(t *testing.T) {
-	root := t.TempDir()
-	extra := t.TempDir()
-	scope, err := sandbox.NewScope(root, []string{extra})
-	if err != nil {
-		t.Fatalf("NewScope: %v", err)
-	}
-	registry := tools.NewRegistry()
-	registry.Register(tools.NewScopedApplyPatchTool(root, scope))
-	target := filepath.Join(extra, "hello.txt")
-	patch := "*** Begin Patch\n*** Add File: " + target + "\n+hello\n*** End Patch\n"
-
-	result, err := executeToolCall(context.Background(), registry, zeroruntime.ToolCall{
-		ID: "call-1", Name: "apply_patch", Arguments: patch, Freeform: true,
-	}, PermissionModeUnsafe, Options{Cwd: root, FileTracker: tools.NewFileTracker()})
-	if err != nil {
-		t.Fatalf("executeToolCall: %v", err)
-	}
-	if result.Status != tools.StatusOK {
-		t.Fatalf("freeform extra-root apply_patch status = %s: %s", result.Status, result.Output)
-	}
-	content, err := os.ReadFile(target)
-	if err != nil {
-		t.Fatalf("read extra-root patched file: %v", err)
-	}
-	if string(content) != "hello\n" {
-		t.Fatalf("patched content = %q, want hello newline", content)
-	}
-}
-
-func TestFreeformApplyPatchRejectsMixedWorkspaceAndExtraRoots(t *testing.T) {
-	for _, extraHasMatchingPath := range []bool{false, true} {
-		name := "extra target missing"
-		if extraHasMatchingPath {
-			name = "extra target exists"
-		}
-		t.Run(name, func(t *testing.T) {
-			workspace := t.TempDir()
-			extra := t.TempDir()
-			if err := os.MkdirAll(filepath.Join(workspace, "src"), 0o755); err != nil {
-				t.Fatal(err)
-			}
-			workspaceTarget := filepath.Join(workspace, "src", "a.go")
-			if err := os.WriteFile(workspaceTarget, []byte("old\n"), 0o644); err != nil {
-				t.Fatal(err)
-			}
-			extraTarget := filepath.Join(extra, "src", "a.go")
-			if extraHasMatchingPath {
-				if err := os.MkdirAll(filepath.Dir(extraTarget), 0o755); err != nil {
-					t.Fatal(err)
-				}
-				if err := os.WriteFile(extraTarget, []byte("old\n"), 0o644); err != nil {
-					t.Fatal(err)
-				}
-			}
-			scope, err := sandbox.NewScope(workspace, []string{extra})
-			if err != nil {
-				t.Fatal(err)
-			}
-			registry := tools.NewRegistry()
-			registry.Register(tools.NewScopedApplyPatchTool(workspace, scope))
-			extraCreated := filepath.Join(extra, "b.go")
-			patch := strings.Join([]string{
-				"*** Begin Patch",
-				"*** Update File: src/a.go",
-				"@@",
-				"-old",
-				"+new",
-				"*** Add File: " + extraCreated,
-				"+extra",
-				"*** End Patch",
-			}, "\n")
-
-			result, err := executeToolCall(context.Background(), registry, zeroruntime.ToolCall{
-				ID: "call-1", Name: "apply_patch", Arguments: patch, Freeform: true,
-			}, PermissionModeUnsafe, Options{Cwd: workspace, FileTracker: tools.NewFileTracker()})
-			if err != nil {
-				t.Fatalf("executeToolCall: %v", err)
-			}
-			if result.Status != tools.StatusError || !strings.Contains(result.Output, "mixes workspace-relative paths with an extra write root") {
-				t.Fatalf("mixed-root patch result = %s: %s", result.Status, result.Output)
-			}
-			if content, err := os.ReadFile(workspaceTarget); err != nil || string(content) != "old\n" {
-				t.Fatalf("workspace target changed: content=%q err=%v", content, err)
-			}
-			if extraHasMatchingPath {
-				if content, err := os.ReadFile(extraTarget); err != nil || string(content) != "old\n" {
-					t.Fatalf("extra-root target changed: content=%q err=%v", content, err)
-				}
-			}
-			if _, err := os.Stat(extraCreated); !os.IsNotExist(err) {
-				t.Fatalf("mixed-root patch created extra file: %v", err)
-			}
-		})
-	}
-}
-
-func TestFreeformApplyPatchAcceptsOneSemanticRoot(t *testing.T) {
-	for _, test := range []struct {
-		name         string
-		useExtraRoot bool
-	}{
-		{name: "workspace"},
-		{name: "extra root", useExtraRoot: true},
-	} {
-		t.Run(test.name, func(t *testing.T) {
-			workspace := t.TempDir()
-			extra := t.TempDir()
-			scope, err := sandbox.NewScope(workspace, []string{extra})
-			if err != nil {
-				t.Fatal(err)
-			}
-			root := workspace
-			if test.useExtraRoot {
-				root = extra
-			}
-			if err := os.MkdirAll(filepath.Join(root, "src"), 0o755); err != nil {
-				t.Fatal(err)
-			}
-			target := filepath.Join(root, "src", "a.go")
-			if err := os.WriteFile(target, []byte("old\n"), 0o644); err != nil {
-				t.Fatal(err)
-			}
-			updatePath := target
-			if !test.useExtraRoot {
-				updatePath = filepath.Join("src", "a.go")
-			}
-			created := filepath.Join(root, "b.go")
-			patch := strings.Join([]string{
-				"*** Begin Patch",
-				"*** Update File: " + updatePath,
-				"@@",
-				"-old",
-				"+new",
-				"*** Add File: " + created,
-				"+created",
-				"*** End Patch",
-			}, "\n")
-			registry := tools.NewRegistry()
-			registry.Register(tools.NewScopedApplyPatchTool(workspace, scope))
-			result, err := executeToolCall(context.Background(), registry, zeroruntime.ToolCall{
-				ID: "call-1", Name: "apply_patch", Arguments: patch, Freeform: true,
-			}, PermissionModeUnsafe, Options{Cwd: workspace, FileTracker: tools.NewFileTracker()})
-			if err != nil {
-				t.Fatalf("executeToolCall: %v", err)
-			}
-			if result.Status != tools.StatusOK {
-				t.Fatalf("single-root patch status = %s: %s", result.Status, result.Output)
-			}
-			if content, err := os.ReadFile(target); err != nil || string(content) != "new\n" {
-				t.Fatalf("updated content=%q err=%v", content, err)
-			}
-			if content, err := os.ReadFile(created); err != nil || string(content) != "created\n" {
-				t.Fatalf("created content=%q err=%v", content, err)
-			}
-		})
-	}
-}
-
-func TestFreeformApplyPatchRejectsAbsolutePathOutsideGrantedRoots(t *testing.T) {
-	root := t.TempDir()
-	granted := t.TempDir()
-	outside := t.TempDir()
-	scope := newFixedPathScope(t, root, granted)
-	registry := tools.NewRegistry()
-	registry.Register(tools.NewScopedApplyPatchTool(root, scope))
-	target := filepath.Join(outside, "blocked.txt")
-	patch := "*** Begin Patch\n*** Add File: " + target + "\n+blocked\n*** End Patch\n"
-
-	result, err := executeToolCall(context.Background(), registry, zeroruntime.ToolCall{
-		ID: "call-1", Name: "apply_patch", Arguments: patch, Freeform: true,
-	}, PermissionModeUnsafe, Options{Cwd: root})
-	if err != nil {
-		t.Fatalf("executeToolCall: %v", err)
-	}
-	if result.Status != tools.StatusError {
-		t.Fatalf("ungranted absolute patch status = %s, want error: %s", result.Status, result.Output)
-	}
-	if _, err := os.Stat(target); !os.IsNotExist(err) {
-		t.Fatalf("ungranted absolute patch created target: %v", err)
-	}
-}
-
-func TestPreparedFreeformPatchRejectsIntermediateSymlinkSwap(t *testing.T) {
-	if runtime.GOOS == "windows" {
-		t.Skip("creating directory symlinks requires privileges on Windows")
-	}
-	root := t.TempDir()
-	extra := t.TempDir()
-	outside := t.TempDir()
-	intermediate := filepath.Join(extra, "nested")
-	if err := os.Mkdir(intermediate, 0o755); err != nil {
-		t.Fatalf("Mkdir: %v", err)
-	}
-	scope := newFixedPathScope(t, root, extra)
-	tool := tools.NewScopedApplyPatchTool(root, scope)
-	target := filepath.Join(intermediate, "blocked.txt")
-	patch := "*** Begin Patch\n*** Add File: " + target + "\n+blocked\n*** End Patch\n"
-	args, err := tools.PrepareFreeformApplyPatchArguments(tool, patch)
-	if err != nil {
-		t.Fatalf("PrepareFreeformApplyPatchArguments: %v", err)
-	}
-
-	if err := os.Remove(intermediate); err != nil {
-		t.Fatalf("Remove intermediate: %v", err)
-	}
-	if err := os.Symlink(outside, intermediate); err != nil {
-		t.Fatalf("Symlink: %v", err)
-	}
-	result := tool.Run(context.Background(), args)
-	if result.Status != tools.StatusError {
-		t.Fatalf("symlink-swapped patch status = %s, want error: %s", result.Status, result.Output)
-	}
-	if _, err := os.Stat(filepath.Join(outside, "blocked.txt")); !os.IsNotExist(err) {
-		t.Fatalf("symlink-swapped patch wrote outside root: %v", err)
-	}
-}
-
-func TestUnknownFreeformToolFailsClosed(t *testing.T) {
-	result, err := executeToolCall(context.Background(), tools.NewRegistry(), zeroruntime.ToolCall{
-		ID: "call-1", Name: "unknown", Arguments: "raw", Freeform: true,
-	}, PermissionModeUnsafe, Options{})
-	if err != nil {
-		t.Fatalf("executeToolCall: %v", err)
-	}
-	if result.Status != tools.StatusError {
-		t.Fatalf("unknown freeform status = %s, want error", result.Status)
-	}
-}
-
-func TestCustomApplyPatchCannotUseFreeformContract(t *testing.T) {
-	custom := &customApplyPatchTool{}
-	registry := tools.NewRegistry()
-	registry.Register(custom)
-
-	result, err := executeToolCall(context.Background(), registry, zeroruntime.ToolCall{
-		ID: "call-1", Name: "apply_patch", Arguments: "raw patch", Freeform: true,
-	}, PermissionModeUnsafe, Options{})
-	if err != nil {
-		t.Fatalf("executeToolCall: %v", err)
-	}
-	if result.Status != tools.StatusError || !strings.Contains(result.Output, "Unsupported freeform tool call") {
-		t.Fatalf("custom freeform apply_patch result = %#v, want unsupported error", result)
-	}
-	if custom.calls != 0 {
-		t.Fatalf("custom apply_patch executed %d times", custom.calls)
-	}
-}
-
-func TestDeniedFreeformApplyPatchDoesNotWrite(t *testing.T) {
-	root := t.TempDir()
-	registry := tools.NewRegistry()
-	registry.Register(tools.NewScopedApplyPatchTool(root, nil))
-	patch := "*** Begin Patch\n*** Add File: denied.txt\n+must not exist\n*** End Patch\n"
-
-	result, err := executeToolCall(context.Background(), registry, zeroruntime.ToolCall{
-		ID:        "call-1",
-		Name:      "apply_patch",
-		Arguments: patch,
-		Freeform:  true,
-	}, PermissionModeAsk, Options{
-		Cwd: root,
-		OnPermissionRequest: func(context.Context, PermissionRequest) (PermissionDecision, error) {
-			return PermissionDecision{Action: PermissionDecisionDeny, Reason: "test denial"}, nil
-		},
-	})
-	if err != nil {
-		t.Fatalf("executeToolCall: %v", err)
-	}
-	if result.Status != tools.StatusError {
-		t.Fatalf("denied freeform status = %s, want error", result.Status)
-	}
-	if _, err := os.Stat(filepath.Join(root, "denied.txt")); !os.IsNotExist(err) {
-		t.Fatalf("denied freeform patch changed the workspace: %v", err)
-	}
-}
-
-func TestHistorySafeToolCallsPreservesRawFreeformArguments(t *testing.T) {
-	raw := "*** Begin Patch\n*** Update File: internal/main.go\n@@\n-old\n+new\n*** End Patch\n"
-	safe := historySafeToolCalls([]ToolCall{{
-		ID: "call-1", ProviderCallID: "provider-1", Name: "apply_patch", Arguments: raw, Freeform: true,
-	}})
-	if len(safe) != 1 || safe[0].Arguments != raw || safe[0].ProviderCallID != "provider-1" || !safe[0].Freeform {
-		t.Fatalf("freeform history changed raw call: %#v", safe)
-	}
-}
-
-func TestAbortedToolResultPreservesProviderCallID(t *testing.T) {
-	messages := appendAbortedToolResults(nil, []ToolCall{{
-		ID: "call-1", ProviderCallID: "provider-1", Name: "read_file",
-	}})
-	if len(messages) != 1 || messages[0].ToolCallID != "call-1" || messages[0].ToolCallProviderID != "provider-1" || !messages[0].IsError {
-		t.Fatalf("aborted tool result lost provider identity: %#v", messages)
-	}
-}

internal/agent/guardrails.go

@@ -33,11 +33,11 @@ const (
 	// knows before spending more tool turns.
 	toolOnlyProgressReminderAt = 6
 
-	// planReminderTurn and planReminderToolThreshold keep bounded implementation
-	// work plan-free while still nudging a genuinely sustained run that has not
-	// established any structured progress. Both thresholds must be met.
-	planReminderTurn          = 7
-	planReminderToolThreshold = 7
+	// planReminderTurn is the turn (1-based) by the end of which a multi-step
+	// task should have called update_plan; if it hasn't, a one-time reminder is
+	// injected. Set to 3 (not 2) so short, legitimate two-step tasks finish
+	// without a spurious planning nag.
+	planReminderTurn = 3
 
 	// planToolName is the planning tool the loop watches for by name.
 	planToolName = "update_plan"
@@ -591,12 +591,13 @@ func (state *guardState) planReminder(turn int) string {
 		return planStaleReminder(state.toolCallsSincePlanUpdate)
 	}
 
-	// NOT-CALLED reminder: once both the turn and tool-call thresholds are met,
-	// sustained work should have called update_plan. One-shot for the whole run.
+	// NOT-CALLED reminder: by the end of planReminderTurn the model should have
+	// called update_plan if it's doing a multi-step task (>=1 other tool call).
+	// One-shot for the whole run.
 	if !state.notCalledReminderSent &&
 		!state.planEverCalled &&
 		turn >= planReminderTurn &&
-		state.totalToolCalls >= planReminderToolThreshold {
+		state.totalToolCalls >= 1 {
 		state.notCalledReminderSent = true
 		return planNotCalledReminder()
 	}

internal/agent/guardrails_test.go

@@ -257,16 +257,19 @@ func TestRunDoesNotCountDroppedToolCallTurnsAsEmpty(t *testing.T) {
 }
 
 func TestRunInjectsPlanNotCalledReminderForMultiStepTask(t *testing.T) {
-	const expectedThreshold = 7
-	if planReminderToolThreshold != expectedThreshold {
-		t.Fatalf("plan reminder tool threshold = %d, want %d", planReminderToolThreshold, expectedThreshold)
-	}
 	root := t.TempDir()
 	writeAgentTestFile(t, root+"/notes.txt", "alpha")
 	registry := tools.NewRegistry()
 	registry.Register(tools.NewScopedReadFileTool(root, nil))
 
-	provider := &mockProvider{turns: append(repeatedReadTurns(expectedThreshold), textTurn("done"))}
+	provider := &mockProvider{
+		turns: [][]zeroruntime.StreamEvent{
+			toolTurn("call-1", "read_file", `{"path":"notes.txt"}`), // turn 1: other tool call
+			toolTurn("call-2", "read_file", `{"path":"notes.txt"}`), // turn 2: still no update_plan
+			toolTurn("call-3", "read_file", `{"path":"notes.txt"}`), // turn 3: reminder fires here
+			textTurn("done"),
+		},
+	}
 
 	result, err := Run(context.Background(), "go", provider, Options{
 		Registry: registry,
@@ -284,44 +287,6 @@ func TestRunInjectsPlanNotCalledReminderForMultiStepTask(t *testing.T) {
 	}
 }
 
-func TestRunDoesNotInjectPlanReminderForBoundedToolSequence(t *testing.T) {
-	const expectedThreshold = 7
-	root := t.TempDir()
-	writeAgentTestFile(t, root+"/notes.txt", "alpha")
-	registry := tools.NewRegistry()
-	registry.Register(tools.NewScopedReadFileTool(root, nil))
-
-	provider := &mockProvider{turns: append(repeatedReadTurns(expectedThreshold-1), textTurn("done"))}
-	result, err := Run(context.Background(), "go", provider, Options{Registry: registry, MaxTurns: 12})
-	if err != nil {
-		t.Fatal(err)
-	}
-	if result.FinalAnswer != "done" {
-		t.Fatalf("expected final answer, got %q", result.FinalAnswer)
-	}
-	if count := countUserMessagesContaining(result.Messages, planNotCalledReminderMarker); count != 0 {
-		t.Fatalf("bounded tool sequence must not draw a plan reminder, got %d", count)
-	}
-}
-
-func TestPlanReminderWaitsForTurnThresholdAfterEnoughToolCalls(t *testing.T) {
-	state := guardState{totalToolCalls: 7}
-	if got := state.planReminder(6); got != "" {
-		t.Fatalf("planReminder(6) = %q, want no reminder before turn threshold", got)
-	}
-	if state.notCalledReminderSent {
-		t.Fatal("early turn marked the not-called reminder as sent")
-	}
-}
-
-func repeatedReadTurns(count int) [][]zeroruntime.StreamEvent {
-	turns := make([][]zeroruntime.StreamEvent, 0, count)
-	for range count {
-		turns = append(turns, toolTurn("call", "read_file", `{"path":"notes.txt"}`))
-	}
-	return turns
-}
-
 func TestRunDoesNotInjectPlanReminderForTrivialTask(t *testing.T) {
 	root := t.TempDir()
 	writeAgentTestFile(t, root+"/notes.txt", "alpha")

internal/agent/loop.go

@@ -141,7 +141,6 @@ func Run(ctx context.Context, prompt string, provider Provider, options Options)
 			}
 			options.Trace.Counter(trace.CounterInputTokens, int64(usage.InputTokens))
 			options.Trace.Counter(trace.CounterCachedInputTokens, int64(usage.CachedInputTokens))
-			options.Trace.Counter(trace.CounterCacheWriteTokens, int64(usage.CacheWriteTokens))
 			options.Trace.Counter(trace.CounterOutputTokens, int64(usage.OutputTokens))
 		}
 	}
@@ -698,12 +697,11 @@ func Run(ctx context.Context, prompt string, provider Provider, options Options)
 				turnRequestedModel = toolResult.RequestedModel
 			}
 			messages = append(messages, zeroruntime.Message{
-				Role:               zeroruntime.MessageRoleTool,
-				Content:            toolResult.ModelOutput(),
-				ToolCallID:         toolResult.ToolCallID,
-				ToolCallProviderID: call.ProviderCallID,
-				IsError:            toolResult.Status == tools.StatusError,
-				ChangedFiles:       append([]string(nil), toolResult.ChangedFiles...),
+				Role:         zeroruntime.MessageRoleTool,
+				Content:      toolResult.ModelOutput(),
+				ToolCallID:   toolResult.ToolCallID,
+				IsError:      toolResult.Status == tools.StatusError,
+				ChangedFiles: append([]string(nil), toolResult.ChangedFiles...),
 			})
 			// Images ride a following USER message rather than the tool result
 			// above. Every provider drops images on a tool-role message —
@@ -1047,9 +1045,6 @@ func historySafeToolCalls(calls []ToolCall) []ToolCall {
 	safe := make([]ToolCall, len(calls))
 	for i, call := range calls {
 		safe[i] = call
-		if call.Freeform {
-			continue
-		}
 		args := strings.TrimSpace(call.Arguments)
 		switch {
 		case args == "":
@@ -1133,28 +1128,8 @@ func decodeToolArguments(arguments string, v any) error {
 }
 
 func executeToolCall(ctx context.Context, registry *tools.Registry, call ToolCall, permissionMode PermissionMode, options Options) (ToolResult, error) {
-	tool, toolFound := registry.Get(call.Name)
 	args := map[string]any{}
-	if call.Freeform {
-		if !toolFound || !tools.IsBuiltInApplyPatch(tool) {
-			return ToolResult{
-				ToolCallID: call.ID,
-				Name:       call.Name,
-				Status:     tools.StatusError,
-				Output:     "Error: Unsupported freeform tool call for " + call.Name + ".",
-			}, nil
-		}
-		prepared, err := tools.PrepareFreeformApplyPatchArguments(tool, call.Arguments)
-		if err != nil {
-			return ToolResult{
-				ToolCallID: call.ID,
-				Name:       call.Name,
-				Status:     tools.StatusError,
-				Output:     "Error: Invalid freeform apply_patch input: " + err.Error(),
-			}, nil
-		}
-		args = prepared
-	} else if call.Arguments != "" {
+	if call.Arguments != "" {
 		if err := decodeToolArguments(call.Arguments, &args); err != nil {
 			return ToolResult{
 				ToolCallID: call.ID,
@@ -1182,6 +1157,7 @@ func executeToolCall(ctx context.Context, registry *tools.Registry, call ToolCal
 			DenialReason: DenialFiltered,
 		}, nil
 	}
+	tool, toolFound := registry.Get(call.Name)
 	if (permissionMode == PermissionModeSpecDraft || permissionMode == PermissionModePlan) && toolFound && !ToolAdvertised(tool, permissionMode) {
 		modeName := string(permissionMode)
 		return ToolResult{
@@ -3244,15 +3220,11 @@ func cachedRuntimeToolDefinition(defCache map[string]zeroruntime.ToolDefinition,
 // runtimeToolDefinition renders a tool's advertised definition (name, description,
 // JSON-schema parameters) as sent to the provider.
 func runtimeToolDefinition(tool tools.Tool) zeroruntime.ToolDefinition {
-	definition := zeroruntime.ToolDefinition{
+	return zeroruntime.ToolDefinition{
 		Name:        tool.Name(),
 		Description: tool.Description(),
 		Parameters:  schemaToRuntimeMap(tool.Parameters()),
 	}
-	if tools.IsBuiltInApplyPatch(tool) {
-		definition.Type = zeroruntime.ToolDefinitionFreeform
-	}
-	return definition
 }
 
 func ToolVisible(tool tools.Tool, permissionMode PermissionMode, enabledTools []string, disabledTools []string) bool {
@@ -3407,11 +3379,10 @@ func loadedToolsFromResult(meta map[string]string) []string {
 func appendAbortedToolResults(messages []Message, remaining []ToolCall) []Message {
 	for _, call := range remaining {
 		messages = append(messages, zeroruntime.Message{
-			Role:               zeroruntime.MessageRoleTool,
-			Content:            abortedToolResultNotice,
-			ToolCallID:         call.ID,
-			ToolCallProviderID: call.ProviderCallID,
-			IsError:            true,
+			Role:       zeroruntime.MessageRoleTool,
+			Content:    abortedToolResultNotice,
+			ToolCallID: call.ID,
+			IsError:    true,
 		})
 	}
 	return messages

internal/agent/loop_test.go

@@ -4096,7 +4096,7 @@ func TestRunDoesNotFlagCleanToolOutput(t *testing.T) {
 // caller's callback AND stamps token counters, and the run completes.
 func TestRunTracingWrapperStampsUsage(t *testing.T) {
 	provider := &mockProvider{turns: [][]zeroruntime.StreamEvent{{
-		{Type: zeroruntime.StreamEventUsage, Usage: zeroruntime.Usage{PromptTokens: 100, CachedInputTokens: 20, CacheWriteTokens: 10, CompletionTokens: 40}},
+		{Type: zeroruntime.StreamEventUsage, Usage: zeroruntime.Usage{InputTokens: 100, CachedInputTokens: 20, OutputTokens: 40}},
 		{Type: zeroruntime.StreamEventText, Content: "done"},
 		{Type: zeroruntime.StreamEventDone},
 	}}}
@@ -4135,9 +4135,6 @@ func TestRunTracingWrapperStampsUsage(t *testing.T) {
 	if got := tr.Counter(trace.CounterCachedInputTokens); got != 20 {
 		t.Fatalf("cached input token counter = %d, want 20", got)
 	}
-	if got := tr.Counter(trace.CounterCacheWriteTokens); got != 10 {
-		t.Fatalf("cache-write token counter = %d, want 10", got)
-	}
 	if got := tr.Counter(trace.CounterOutputTokens); got != 40 {
 		t.Fatalf("output token counter = %d, want 40", got)
 	}

internal/agent/partition_cache_test.go

@@ -31,19 +31,6 @@ func (t countingSchemaTool) Run(_ context.Context, _ map[string]any) tools.Resul
 	return tools.Result{Status: tools.StatusOK}
 }
 
-func TestRuntimeToolDefinitionMarksOnlyBuiltInApplyPatchFreeform(t *testing.T) {
-	builtIn := runtimeToolDefinition(tools.NewScopedApplyPatchTool(t.TempDir(), nil))
-	if builtIn.Type != zeroruntime.ToolDefinitionFreeform {
-		t.Fatalf("built-in apply_patch type = %q, want freeform", builtIn.Type)
-	}
-
-	calls := 0
-	custom := runtimeToolDefinition(countingSchemaTool{name: "apply_patch", calls: &calls})
-	if custom.Type != "" {
-		t.Fatalf("custom apply_patch type = %q, want legacy function shape", custom.Type)
-	}
-}
-
 // The cache renders a tool's schema once and reuses it across calls, and its
 // output is identical to the uncached path.
 func TestPartitionToolsCacheRendersOnceAndMatchesUncached(t *testing.T) {

internal/agent/prompt_fingerprint.go

@@ -58,18 +58,12 @@ func toolSubstrings(exposed []zeroruntime.ToolDefinition) (toolsSubstr, schemaSu
 	for _, def := range exposed {
 		writeLengthPrefixed(&toolsSB, def.Name)
 		writeLengthPrefixed(&toolsSB, def.Description)
-		writeLengthPrefixed(&toolsSB, string(def.Type))
 		// Parameters is rendered to a canonical JSON string per tool. The
 		// schema-render cache in internal/agent (used by partitionToolsCached)
 		// guarantees the same render is byte-identical across turns for the
 		// same tool, so this substring is a stable hash input.
 		writeLengthPrefixed(&schemaSB, def.Name)
 		writeLengthPrefixed(&schemaSB, canonicalSchemaString(def.Parameters))
-		if def.Format != nil {
-			writeLengthPrefixed(&schemaSB, def.Format.Type)
-			writeLengthPrefixed(&schemaSB, def.Format.Syntax)
-			writeLengthPrefixed(&schemaSB, def.Format.Definition)
-		}
 	}
 	return toolsSB.String(), schemaSB.String()
 }

internal/agent/prompt_fingerprint_test.go

@@ -73,38 +73,6 @@ func TestComputePrefixFingerprintSchemaChangeChangesSchemaHash(t *testing.T) {
 	}
 }
 
-func TestComputePrefixFingerprintIncludesToolTypeAndFormat(t *testing.T) {
-	opts := Options{Cwd: t.TempDir(), SystemPrompt: "core"}
-	base := zeroruntime.ToolDefinition{Name: "apply_patch", Description: "Patch files"}
-	baseFingerprint := ComputePrefixFingerprint(opts, []zeroruntime.ToolDefinition{base})
-
-	typed := base
-	typed.Type = zeroruntime.ToolDefinitionFreeform
-	if got := ComputePrefixFingerprint(opts, []zeroruntime.ToolDefinition{typed}); got.ToolsHash == baseFingerprint.ToolsHash {
-		t.Fatal("ToolsHash must change when tool Type changes")
-	}
-
-	formatCases := []struct {
-		name   string
-		format zeroruntime.ToolDefinitionFormat
-	}{
-		{name: "type", format: zeroruntime.ToolDefinitionFormat{Type: "grammar"}},
-		{name: "syntax", format: zeroruntime.ToolDefinitionFormat{Syntax: "lark"}},
-		{name: "definition", format: zeroruntime.ToolDefinitionFormat{Definition: "start: PATCH"}},
-		{name: "empty", format: zeroruntime.ToolDefinitionFormat{}},
-	}
-	for _, test := range formatCases {
-		t.Run(test.name, func(t *testing.T) {
-			withFormat := base
-			withFormat.Format = &test.format
-			got := ComputePrefixFingerprint(opts, []zeroruntime.ToolDefinition{withFormat})
-			if got.SchemaHash == baseFingerprint.SchemaHash {
-				t.Fatalf("SchemaHash must change for %s format input", test.name)
-			}
-		})
-	}
-}
-
 // TestComputePrefixFingerprintSystemPromptChangeChangesBaseHash asserts the
 // most common drift path: a system-prompt edit (e.g. an agent.md update, a
 // model addendum change) must move the base-instructions hash, which moves

internal/agent/system_prompt.md

@@ -30,10 +30,13 @@ work.
    read-before-edit discipline: inspect the target file and nearby callers,
    tests, or config before you modify behavior. Never edit a file you have not
    read.
-2. **Plan.** Use update_plan for multi-component, sequencing-uncertain, or long
-   work. Skip it for bounded changes in one component. Update only when the
-   overall phase changes, keep at most one item in_progress, and never create a
-   plan after the work is complete.
+2. **Plan.** Use update_plan for implementation or investigation that has at
+   least three meaningful dependent steps, then keep it current at milestones.
+   Mark completed work and the next in-progress step together when practical;
+   do not spend separate turns updating it after every file or command. Keep at
+   most one item in_progress. Skip plans for simple lookups, explanations, code
+   navigation, and other short tasks. Never create a plan after the work is
+   already complete merely to describe what you did.
 3. **Implement.** Make focused changes that match the surrounding code's style,
    naming, and conventions. Prefer the smallest change that fully solves the
    problem. Avoid broad refactors, unrelated rewrites, dependency churn, and
@@ -52,9 +55,9 @@ work.
   edit_file, apply_patch, write_file - over shelling out to
   cat/sed/awk/python for file operations.
   They are safer, reviewable, and produce clean diffs.
-- Use read_minified_file only to explore large or unfamiliar source. Use
-  read_file for small or likely edit targets and exact text, comments, or line
-  numbers. Do not read both unless a new need for exact content appears.
+- Prefer read_minified_file when initially exploring source code; it preserves
+  code while removing comments and redundant whitespace. Use read_file when
+  exact text, comments, or line numbers are needed.
 - Keep edits focused and reviewable. A single patch may update several related
   files when they form one coherent change; do not hide unrelated edits in a
   bulk shell or script rewrite.
@@ -73,24 +76,21 @@ work.
 - Solve the problem as posed, not a more general version of it. Add no
   speculative abstraction, configurability, or handling for cases that cannot
   occur, and nothing the user did not ask for. A small diff can still be
-  over-built; if a 200-line solution could be 50, rewrite it. Once the required
-  behavior passes validation, stop instead of adding optional cleanup.
+  over-built; if a 200-line solution could be 50, rewrite it.
 - Preserve behavior you were not asked to change. Do not delete or rewrite code
   you did not author unless the task requires it; if you must, say so.
 
 ## Testing gate (mandatory)
 
-- After code changes, run the project's documented appropriate validators.
-  Scope iteration checks, combine compatible commands when diagnostics stay
-  useful, and run the final set once after the last edit. Rerun only after a
-  change or failure.
-- If unsure which entry points apply, inspect the Makefile, manifests, or CI;
-  do not invent a parallel flow.
+- After any change to code, verify after edits by running the project's
+  validators before you summarize or commit: tests, type-checks, linters, and/or
+  the build, as appropriate. Scope them to the change while iterating; reserve
+  full-suite runs for milestones.
+- If you are unsure which validators apply, search the repo (Makefile, package
+  manifests, CI config) to find them.
 - Never claim a task is done, and never commit, while validators are failing. If
   they fail, fix the cause and rerun; do not paper over it. If you could not run
   a validator, say so explicitly rather than implying success.
-- A successful native patch confirms the edit. Reread only when the next change
-  needs exact content or the result was ambiguous.
 
 ## Tool use
 
@@ -148,7 +148,6 @@ work.
 - Default to concise, skimmable output. Lead with the answer or the result.
 - Use GitHub-flavored Markdown: headings to structure longer replies, fenced
   code blocks for code, and `inline code` for file paths, commands, symbols, and
-  short snippets. Reference code with file paths and include line numbers when
-  already known; do not look them up solely for the final summary.
+  short snippets. Reference code as `file:line` so it is clickable.
 - Report outcomes faithfully: if tests failed, show it; if a step was skipped,
   say so; when something is done and verified, state it plainly without hedging.

internal/agent/system_prompt_models.go

@@ -60,11 +60,12 @@ const openAIPromptAddendum = `<model_guidance>
   longer answers, fenced code blocks for code, and ` + "`inline code`" + ` for paths,
   commands, and symbols.
 - Strongly prefer the native file tools (read_file, list_directory, grep, glob,
-  edit_file, apply_patch, write_file) over shelling out to cat/sed/awk/python for
-  file work. Use them directly; never run apply_patch through exec_command.
-  read_file, edit_file and write_file take one file per call, while one coherent
-  apply_patch may span several files. Keep independent native calls in the same
-  turn, and do not batch file writes into a script.
+  edit_file, apply_patch, write_file) over shelling out to cat/sed/awk/python
+  for file work. read_file, edit_file and write_file take one file per call;
+  a single apply_patch may span several files when they form one coherent
+  change. Do not batch file writes into a script. Independent tool calls
+  (several reads, several edit_file calls to different files) belong in the
+  same turn.
 - Persist until the task is fully handled this turn: gather context, implement,
   run the validators, and report — do not stop at a partial result.
 </model_guidance>`

internal/agent/system_prompt_models_test.go

@@ -29,9 +29,6 @@ func TestBuildSystemPromptAppendsModelAddendum(t *testing.T) {
 	if got := buildSystemPrompt(Options{Model: "gpt-5"}); !strings.Contains(got, openAIPromptAddendum) {
 		t.Fatalf("expected the OpenAI addendum in the gpt-5 prompt")
 	}
-	if got := strings.Join(strings.Fields(strings.ToLower(buildSystemPrompt(Options{Model: "gpt-5"}))), " "); !strings.Contains(got, "never run apply_patch through exec_command") {
-		t.Fatalf("OpenAI prompt must route edits through the native patch tool:\n%s", got)
-	}
 	// Claude is aligned with the core prompt and gets no family addendum now that
 	// comment discipline is universal; it must not pick up another family's block.
 	claude := buildSystemPrompt(Options{Model: "claude-opus-4-6"})

internal/agent/system_prompt_test.go

@@ -29,10 +29,7 @@ func TestMain(m *testing.M) {
 }
 
 func TestCoreSystemPromptIncludesCodingQualityRules(t *testing.T) {
-	prompt := strings.Join(strings.Fields(strings.ToLower(buildSystemPrompt(Options{}))), " ")
-	if strings.Contains(prompt, "clickable file paths") {
-		t.Fatalf("system prompt must not claim inline-code file paths are clickable: %s", prompt)
-	}
+	prompt := strings.ToLower(buildSystemPrompt(Options{}))
 
 	for _, want := range []string{
 		"read-before-edit",
@@ -47,13 +44,6 @@ func TestCoreSystemPromptIncludesCodingQualityRules(t *testing.T) {
 		"do not recognize",
 		"scaled to the work",
 		"comment density",
-		"skip it for bounded changes in one component",
-		"do not read both unless a new need for exact content appears",
-		"combine compatible commands when diagnostics stay useful",
-		"do not invent a parallel flow",
-		"a successful native patch confirms the edit",
-		"once the required behavior passes validation, stop",
-		"do not look them up solely for the final summary",
 	} {
 		if !strings.Contains(prompt, want) {
 			t.Fatalf("expected core system prompt to include %q, got:\n%s", want, buildSystemPrompt(Options{}))

internal/cli/app.go

@@ -839,20 +839,18 @@ func runInteractiveTUIWithSetup(stderr io.Writer, deps appDeps, permissionMode a
 		mcpTokenStore = nil
 		err = nil
 	}
-	criticalMCPConfig, optionalMCPConfig := splitMCPStartupConfig(mcpConfig)
 	mcpRuntime := mcpToolRuntime(noopMCPRuntime{})
-	if len(criticalMCPConfig.Servers) > 0 {
-		runtime, registerErr := deps.registerMCPTools(context.Background(), registry, criticalMCPConfig, mcp.RegisterOptions{
+	if len(mcpConfig.Servers) > 0 {
+		mcpRuntime, err = deps.registerMCPTools(context.Background(), registry, mcpConfig, mcp.RegisterOptions{
 			PermissionStore: mcpPermissionStore,
 			Autonomy:        mcp.AutonomyLow,
 			Execution:       executionRunner,
 			WorkspaceRoot:   workspaceRoot,
 		})
-		if registerErr != nil {
-			closeMCPRuntime(stderr, runtime)
-			return writeAppError(stderr, redaction.ErrorMessage(registerErr, redaction.Options{}), 1)
-		}
-		mcpRuntime = runtime
+	}
+	if err != nil {
+		closeMCPRuntime(stderr, mcpRuntime)
+		return writeAppError(stderr, err.Error(), 1)
 	}
 	defer closeMCPRuntime(stderr, mcpRuntime)
 	// A server that could not be reached or validated is skipped, not fatal (one
@@ -911,35 +909,11 @@ func runInteractiveTUIWithSetup(stderr io.Writer, deps appDeps, permissionMode a
 	}
 	// Activate deferred MCP-tool loading for the interactive run only when the
 	// VISIBLE deferred-eligible count meets the resolved threshold, matching exec.
-	// This first pass covers every prompt-critical tool. Optional built-in MCP
-	// defaults re-run the same gate after publishing their atomic batch, so a
-	// later catalog generation cannot miss its loader. The interactive surface
-	// applies no operator tool filters, so enabled/disabled are nil — matching the
-	// AgentOptions below.
+	// The registry is complete (core + specialist + MCP + plugins) here, so the
+	// count is accurate; below threshold this is a no-op and the surface is
+	// unchanged. The interactive surface applies no operator tool filters, so
+	// enabled/disabled are nil — matching the AgentOptions below.
 	registerToolSearchIfEligible(registry, resolved.Tools.DeferThreshold, permissionMode, nil, nil)
-	var optionalMCPRuntime *optionalMCPStartup
-	var awaitToolReadiness func(context.Context)
-	if len(optionalMCPConfig.Servers) > 0 {
-		optionalMCPRuntime = startOptionalMCP(
-			context.Background(),
-			registry,
-			optionalMCPConfig,
-			mcp.RegisterOptions{
-				PermissionStore: mcpPermissionStore,
-				Autonomy:        mcp.AutonomyLow,
-				Execution:       executionRunner,
-				WorkspaceRoot:   workspaceRoot,
-			},
-			deps.registerMCPTools,
-			func() {
-				registerToolSearchIfEligible(registry, resolved.Tools.DeferThreshold, permissionMode, nil, nil)
-			},
-		)
-		defer closeMCPRuntime(stderr, optionalMCPRuntime)
-		awaitToolReadiness = func(ctx context.Context) {
-			optionalMCPRuntime.Await(ctx, optionalMCPPromptGrace)
-		}
-	}
 	lastKnownMCPConfig := mcpConfig
 	fileTracker := tools.NewFileTracker()
 	var scratchBaseline scratchFileBaseline
@@ -977,17 +951,8 @@ func runInteractiveTUIWithSetup(stderr io.Writer, deps appDeps, permissionMode a
 		CompactionModel:      resolved.Preferences.CompactionModel,
 		Provider:             provider,
 		NewProvider:          deps.newProvider,
-		NewTurnSessionProvider: func(profile config.ProviderProfile, provider zeroruntime.Provider) zeroruntime.TurnSessionProvider {
-			if provider == nil {
-				return nil
-			}
-			if optimized, ok := providers.OptimizedTurnSessions(profile, provider, providers.Options{}); ok {
-				return optimized
-			}
-			return providers.DefaultTurnSessions(profile, provider, providers.Options{})
-		},
-		ProbeProviderHealth: deps.probeProviderHealth,
-		UserAgent:           userAgent(),
+		ProbeProviderHealth:  deps.probeProviderHealth,
+		UserAgent:            userAgent(),
 		PrepareRunCompletionWarning: func() {
 			scratchBaseline = scratchFileSnapshot(workspaceRoot)
 		},
@@ -995,7 +960,6 @@ func runInteractiveTUIWithSetup(stderr io.Writer, deps appDeps, permissionMode a
 			return scratchFileWarning(workspaceRoot, scratchBaseline)
 		},
 		Registry:           registry,
-		AwaitToolReadiness: awaitToolReadiness,
 		SessionStore:       sessionStore,
 		PeerService:        peerService,
 		SandboxStore:       sandboxStore,

internal/cli/app_test.go

@@ -17,7 +17,6 @@ import (
 	"github.com/Gitlawb/zero/internal/agent"
 	"github.com/Gitlawb/zero/internal/config"
 	"github.com/Gitlawb/zero/internal/mcp"
-	"github.com/Gitlawb/zero/internal/redaction"
 	"github.com/Gitlawb/zero/internal/tools"
 	"github.com/Gitlawb/zero/internal/tui"
 	"github.com/Gitlawb/zero/internal/update"
@@ -487,74 +486,6 @@ func TestRunNoArgsLaunchesTUIWithMCPState(t *testing.T) {
 	}
 }
 
-func TestRunNoArgsPaintsBeforeOptionalDefaultMCPIsReady(t *testing.T) {
-	var stdout bytes.Buffer
-	var stderr bytes.Buffer
-	cwd := t.TempDir()
-	userConfigPath := filepath.Join(t.TempDir(), "zero", "config.json")
-	permissionStore, err := mcp.NewPermissionStore(mcp.StoreOptions{FilePath: filepath.Join(t.TempDir(), "mcp-permissions.json")})
-	if err != nil {
-		t.Fatalf("NewPermissionStore() error = %v", err)
-	}
-	tokenStore, err := mcp.NewTokenStore(mcp.TokenStoreOptions{FilePath: filepath.Join(t.TempDir(), "mcp-oauth.json")})
-	if err != nil {
-		t.Fatalf("NewTokenStore() error = %v", err)
-	}
-	started := make(chan struct{})
-	release := make(chan struct{})
-	configResult := make(chan error, 1)
-
-	exitCode := runWithDeps([]string{}, &stdout, &stderr, appDeps{
-		getwd:          func() (string, error) { return cwd, nil },
-		userConfigPath: func() (string, error) { return userConfigPath, nil },
-		resolveConfig: func(string, config.Overrides) (config.ResolvedConfig, error) {
-			return config.ResolvedConfig{MaxTurns: 8}, nil
-		},
-		resolveMCPConfig: func(string, bool) (config.MCPConfig, error) {
-			return config.MCPConfig{Servers: config.DefaultMCPServers()}, nil
-		},
-		newMCPStore:      func() (*mcp.PermissionStore, error) { return permissionStore, nil },
-		newMCPTokenStore: func() (*mcp.TokenStore, error) { return tokenStore, nil },
-		registerMCPTools: func(_ context.Context, registry *tools.Registry, cfg config.MCPConfig, _ mcp.RegisterOptions) (mcpToolRuntime, error) {
-			var configErr error
-			if _, ok := cfg.Servers["exa"]; !ok || len(cfg.Servers) != 1 {
-				configErr = fmt.Errorf("optional MCP config = %#v, want only exa", cfg.Servers)
-			}
-			configResult <- configErr
-			close(started)
-			<-release
-			registry.Register(cliFakeMCPRegistryTool{})
-			return noopMCPRuntime{}, nil
-		},
-		runTUI: func(ctx context.Context, options tui.Options) int {
-			select {
-			case <-started:
-			case <-time.After(time.Second):
-				t.Fatal("optional MCP initialization did not start")
-			}
-			if options.AwaitToolReadiness == nil {
-				t.Fatal("TUI did not receive optional tool readiness barrier")
-			}
-			if _, ok := options.Registry.Get("mcp_docs_lookup"); ok {
-				t.Fatal("optional MCP tool was published before registration completed")
-			}
-			close(release)
-			options.AwaitToolReadiness(ctx)
-			if _, ok := options.Registry.Get("mcp_docs_lookup"); !ok {
-				t.Fatal("optional MCP tool was not visible after readiness completed")
-			}
-			return 0
-		},
-	})
-
-	if exitCode != 0 {
-		t.Fatalf("exitCode = %d stderr=%s", exitCode, stderr.String())
-	}
-	if configErr := <-configResult; configErr != nil {
-		t.Fatal(configErr)
-	}
-}
-
 func TestTUIMCPCommandUsesLastGoodConfigOnRefreshError(t *testing.T) {
 	var stdout bytes.Buffer
 	var stderr bytes.Buffer
@@ -634,7 +565,6 @@ func TestRunNoArgsClosesPartialMCPRuntimeWhenRegistrationFails(t *testing.T) {
 		t.Fatalf("NewTokenStore() error = %v", err)
 	}
 	runtimeClosed := false
-	secret := "sk-proj-" + strings.Repeat("a", 23) + "0"
 
 	exitCode := runWithDeps([]string{}, &stdout, &stderr, appDeps{
 		getwd: func() (string, error) {
@@ -661,7 +591,7 @@ func TestRunNoArgsClosesPartialMCPRuntimeWhenRegistrationFails(t *testing.T) {
 			return closeFunc(func() error {
 				runtimeClosed = true
 				return nil
-			}), fmt.Errorf("register mcp tools failed: %s", secret)
+			}), errors.New("register mcp tools failed")
 		},
 		runTUI: func(ctx context.Context, options tui.Options) int {
 			t.Fatal("TUI should not launch after MCP registration fails")
@@ -675,12 +605,6 @@ func TestRunNoArgsClosesPartialMCPRuntimeWhenRegistrationFails(t *testing.T) {
 	if !strings.Contains(stderr.String(), "register mcp tools failed") {
 		t.Fatalf("stderr missing registration error: %s", stderr.String())
 	}
-	if strings.Contains(stderr.String(), secret) {
-		t.Fatalf("stderr leaked MCP registration secret: %s", stderr.String())
-	}
-	if !strings.Contains(stderr.String(), redaction.RedactedSecret) {
-		t.Fatalf("stderr missing redaction marker: %s", stderr.String())
-	}
 	if !runtimeClosed {
 		t.Fatal("partial MCP runtime was not closed after registration error")
 	}

internal/cli/exec.go

@@ -943,9 +943,6 @@ func registerToolSearchIfEligible(registry *tools.Registry, deferThreshold int,
 	if deferThreshold <= 0 {
 		return
 	}
-	if _, registered := registry.Get(tools.ToolSearchToolName); registered {
-		return
-	}
 	if deferredEligibleCount(registry, permissionMode, enabledTools, disabledTools) < deferThreshold {
 		return
 	}

internal/cli/exec_writer.go

@@ -267,29 +267,23 @@ func streamJSONPermissionEventType(event agent.PermissionEvent) streamjson.Event
 func (writer *execEventWriter) usage(usage agent.Usage) {
 	if writer.format == execOutputJSON {
 		writer.writeJSON(map[string]any{
-			"type":                "usage",
-			"prompt_tokens":       usage.PromptTokens,
-			"completion_tokens":   usage.CompletionTokens,
-			"cached_input_tokens": usage.CachedInputTokens,
-			"cache_write_tokens":  usage.CacheWriteTokens,
-			"total_tokens":        usage.TotalTokens(),
+			"type":              "usage",
+			"prompt_tokens":     usage.PromptTokens,
+			"completion_tokens": usage.CompletionTokens,
+			"total_tokens":      usage.TotalTokens(),
 		})
 		return
 	}
 	if writer.format == execOutputStreamJSON {
 		promptTokens := usage.EffectiveInputTokens()
 		completionTokens := usage.EffectiveOutputTokens()
-		cachedInputTokens := usage.CachedInputTokens
-		cacheWriteTokens := usage.CacheWriteTokens
 		totalTokens := usage.TotalTokens()
 		writer.writeStreamJSON(streamjson.Event{
-			Type:              streamjson.EventUsage,
-			RunID:             writer.runID,
-			PromptTokens:      &promptTokens,
-			CompletionTokens:  &completionTokens,
-			CachedInputTokens: &cachedInputTokens,
-			CacheWriteTokens:  &cacheWriteTokens,
-			TotalTokens:       &totalTokens,
+			Type:             streamjson.EventUsage,
+			RunID:            writer.runID,
+			PromptTokens:     &promptTokens,
+			CompletionTokens: &completionTokens,
+			TotalTokens:      &totalTokens,
 		})
 	}
 }

internal/cli/exec_writer_test.go

@@ -52,39 +52,3 @@ func TestExecWriterPropagatesToolResultTruncation(t *testing.T) {
 		})
 	}
 }
-
-func TestExecWriterPropagatesCacheUsage(t *testing.T) {
-	for _, format := range []execOutputFormat{execOutputJSON, execOutputStreamJSON} {
-		t.Run(string(format), func(t *testing.T) {
-			var stdout bytes.Buffer
-			writer := execEventWriter{
-				stdout:       &stdout,
-				format:       format,
-				runID:        "run_usage",
-				streamedText: &strings.Builder{},
-			}
-			writer.usage(agent.Usage{
-				InputTokens:       100,
-				OutputTokens:      20,
-				PromptTokens:      100,
-				CompletionTokens:  20,
-				CachedInputTokens: 60,
-				CacheWriteTokens:  10,
-			})
-			if writer.err != nil {
-				t.Fatalf("usage: %v", writer.err)
-			}
-			var payload map[string]any
-			if err := json.Unmarshal(bytes.TrimSpace(stdout.Bytes()), &payload); err != nil {
-				t.Fatalf("decode output %q: %v", stdout.String(), err)
-			}
-			cachedKey, writeKey := "cached_input_tokens", "cache_write_tokens"
-			if format == execOutputStreamJSON {
-				cachedKey, writeKey = "cachedInputTokens", "cacheWriteTokens"
-			}
-			if payload[cachedKey] != float64(60) || payload[writeKey] != float64(10) {
-				t.Fatalf("cache usage missing from payload: %#v", payload)
-			}
-		})
-	}
-}

internal/cli/mcp_startup.go

@@ -1,147 +0,0 @@
-package cli
-
-import (
-	"context"
-	"sync"
-	"time"
-
-	"github.com/Gitlawb/zero/internal/config"
-	"github.com/Gitlawb/zero/internal/mcp"
-	"github.com/Gitlawb/zero/internal/tools"
-)
-
-const (
-	optionalMCPPromptGrace = time.Second
-	optionalMCPCloseGrace  = 250 * time.Millisecond
-)
-
-// splitMCPStartupConfig keeps explicitly configured servers on the
-// prompt-critical path. Only unchanged built-in defaults may initialize after
-// first paint; their failure was already intentionally silent.
-func splitMCPStartupConfig(cfg config.MCPConfig) (critical config.MCPConfig, optional config.MCPConfig) {
-	critical.Servers = map[string]config.MCPServerConfig{}
-	optional.Servers = map[string]config.MCPServerConfig{}
-	for name, server := range cfg.Servers {
-		if server.Disabled {
-			continue
-		}
-		if config.IsUnconfiguredDefault(name, server) {
-			optional.Servers[name] = server
-			continue
-		}
-		critical.Servers[name] = server
-	}
-	return critical, optional
-}
-
-type optionalMCPStartup struct {
-	cancel context.CancelFunc
-	done   chan struct{}
-
-	mu      sync.Mutex
-	runtime mcpToolRuntime
-
-	closeOnce        sync.Once
-	runtimeCloseOnce sync.Once
-	closeErr         error
-}
-
-func startOptionalMCP(
-	parent context.Context,
-	registry *tools.Registry,
-	cfg config.MCPConfig,
-	options mcp.RegisterOptions,
-	register func(context.Context, *tools.Registry, config.MCPConfig, mcp.RegisterOptions) (mcpToolRuntime, error),
-	onReady func(),
-) *optionalMCPStartup {
-	ctx, cancel := context.WithCancel(parent)
-	startup := &optionalMCPStartup{cancel: cancel, done: make(chan struct{})}
-	go func() {
-		runtime, err := register(ctx, registry, cfg, options)
-		if err == nil && onReady != nil {
-			onReady()
-		}
-		startup.mu.Lock()
-		startup.runtime = runtime
-		startup.mu.Unlock()
-		close(startup.done)
-	}()
-	return startup
-}
-
-// Await gives optional tools one bounded opportunity to join the next turn's
-// immutable registry snapshot. A timeout leaves this turn on the existing core
-// tool set; a later turn observes the completed generation.
-func (startup *optionalMCPStartup) Await(ctx context.Context, timeout time.Duration) bool {
-	if startup == nil {
-		return true
-	}
-	select {
-	case <-startup.done:
-		return true
-	default:
-	}
-	if timeout <= 0 {
-		select {
-		case <-startup.done:
-			return true
-		case <-ctx.Done():
-			return false
-		}
-	}
-	timer := time.NewTimer(timeout)
-	defer timer.Stop()
-	select {
-	case <-startup.done:
-		return true
-	case <-timer.C:
-		return false
-	case <-ctx.Done():
-		return false
-	}
-}
-
-func (startup *optionalMCPStartup) Close() error {
-	if startup == nil {
-		return nil
-	}
-	startup.closeOnce.Do(func() {
-		startup.cancel()
-		reaped := make(chan struct{})
-		go func() {
-			defer close(reaped)
-			<-startup.done
-			startup.closeRuntime()
-		}()
-		timer := time.NewTimer(optionalMCPCloseGrace)
-		defer timer.Stop()
-		select {
-		case <-reaped:
-		case <-timer.C:
-		}
-	})
-	startup.mu.Lock()
-	defer startup.mu.Unlock()
-	return startup.closeErr
-}
-
-func (startup *optionalMCPStartup) closeRuntime() {
-	startup.runtimeCloseOnce.Do(func() {
-		startup.mu.Lock()
-		runtime := startup.runtime
-		startup.mu.Unlock()
-		if runtime == nil {
-			return
-		}
-		err := runtime.Close()
-		startup.mu.Lock()
-		if err != nil && startup.closeErr == nil {
-			startup.closeErr = err
-		}
-		startup.mu.Unlock()
-	})
-}
-
-func (startup *optionalMCPStartup) Skipped() []mcp.SkippedServer {
-	return nil
-}

internal/cli/mcp_startup_test.go

@@ -1,187 +0,0 @@
-package cli
-
-import (
-	"context"
-	"errors"
-	"testing"
-	"time"
-
-	"github.com/Gitlawb/zero/internal/config"
-	"github.com/Gitlawb/zero/internal/mcp"
-	"github.com/Gitlawb/zero/internal/tools"
-)
-
-type closeTrackingMCPRuntime struct {
-	closed chan struct{}
-	err    error
-}
-
-func (runtime *closeTrackingMCPRuntime) Close() error {
-	close(runtime.closed)
-	return runtime.err
-}
-
-func (*closeTrackingMCPRuntime) Skipped() []mcp.SkippedServer { return nil }
-
-func TestSplitMCPStartupConfigDefersOnlyUnconfiguredDefaults(t *testing.T) {
-	defaults := config.DefaultMCPServers()
-	cfg := config.MCPConfig{Servers: map[string]config.MCPServerConfig{
-		"exa":      defaults["exa"],
-		"docs":     {Type: "http", URL: "https://docs.example.test/mcp"},
-		"disabled": {Type: "http", URL: "https://disabled.example.test/mcp", Disabled: true},
-	}}
-
-	critical, optional := splitMCPStartupConfig(cfg)
-	if _, ok := critical.Servers["docs"]; !ok || len(critical.Servers) != 1 {
-		t.Fatalf("critical servers = %#v, want only docs", critical.Servers)
-	}
-	if _, ok := optional.Servers["exa"]; !ok || len(optional.Servers) != 1 {
-		t.Fatalf("optional servers = %#v, want only exa", optional.Servers)
-	}
-}
-
-func TestOptionalMCPAwaitTimesOutThenObservesPublishedTools(t *testing.T) {
-	registry := tools.NewRegistry()
-	release := make(chan struct{})
-	started := make(chan struct{})
-	startup := startOptionalMCP(
-		context.Background(),
-		registry,
-		config.MCPConfig{Servers: config.DefaultMCPServers()},
-		mcp.RegisterOptions{},
-		func(ctx context.Context, registry *tools.Registry, _ config.MCPConfig, _ mcp.RegisterOptions) (mcpToolRuntime, error) {
-			close(started)
-			select {
-			case <-release:
-				registry.RegisterBatch([]tools.Tool{tools.NewScopedReadFileTool(t.TempDir(), nil)})
-				return noopMCPRuntime{}, nil
-			case <-ctx.Done():
-				return noopMCPRuntime{}, ctx.Err()
-			}
-		},
-		nil,
-	)
-	defer func() { _ = startup.Close() }()
-	<-started
-
-	if startup.Await(t.Context(), time.Millisecond) {
-		t.Fatal("optional startup unexpectedly completed before release")
-	}
-	if got := len(registry.All()); got != 0 {
-		t.Fatalf("registry published tools before readiness: %d", got)
-	}
-	close(release)
-	if !startup.Await(t.Context(), time.Second) {
-		t.Fatal("optional startup did not complete after release")
-	}
-	if _, ok := registry.Get("read_file"); !ok {
-		t.Fatal("completed optional startup did not publish its tool batch")
-	}
-}
-
-func TestOptionalMCPFailedRegistrationSkipsReadinessCallback(t *testing.T) {
-	readyCalls := 0
-	startup := startOptionalMCP(
-		context.Background(),
-		tools.NewRegistry(),
-		config.MCPConfig{Servers: config.DefaultMCPServers()},
-		mcp.RegisterOptions{},
-		func(context.Context, *tools.Registry, config.MCPConfig, mcp.RegisterOptions) (mcpToolRuntime, error) {
-			return noopMCPRuntime{}, errors.New("connect failed")
-		},
-		func() { readyCalls++ },
-	)
-	defer func() { _ = startup.Close() }()
-
-	if !startup.Await(t.Context(), time.Second) {
-		t.Fatal("failed optional startup did not settle")
-	}
-	if readyCalls != 0 {
-		t.Fatalf("readiness callback ran after failed registration: %d", readyCalls)
-	}
-}
-
-func TestOptionalMCPCloseCancelsBlockedStartup(t *testing.T) {
-	started := make(chan struct{})
-	startup := startOptionalMCP(
-		context.Background(),
-		tools.NewRegistry(),
-		config.MCPConfig{Servers: config.DefaultMCPServers()},
-		mcp.RegisterOptions{},
-		func(ctx context.Context, _ *tools.Registry, _ config.MCPConfig, _ mcp.RegisterOptions) (mcpToolRuntime, error) {
-			close(started)
-			<-ctx.Done()
-			return noopMCPRuntime{}, nil
-		},
-		nil,
-	)
-	<-started
-	if err := startup.Close(); err != nil {
-		t.Fatalf("Close() error = %v", err)
-	}
-}
-
-func TestOptionalMCPCloseReturnsRuntimeErrorWithinGrace(t *testing.T) {
-	closeErr := errors.New("close failed")
-	runtime := &closeTrackingMCPRuntime{closed: make(chan struct{}), err: closeErr}
-	startup := startOptionalMCP(
-		context.Background(),
-		tools.NewRegistry(),
-		config.MCPConfig{Servers: config.DefaultMCPServers()},
-		mcp.RegisterOptions{},
-		func(context.Context, *tools.Registry, config.MCPConfig, mcp.RegisterOptions) (mcpToolRuntime, error) {
-			return runtime, nil
-		},
-		nil,
-	)
-	if !startup.Await(t.Context(), time.Second) {
-		t.Fatal("optional startup did not settle")
-	}
-	if err := startup.Close(); !errors.Is(err, closeErr) {
-		t.Fatalf("Close() error = %v, want %v", err, closeErr)
-	}
-}
-
-func TestOptionalMCPCloseBoundsRegistrationThatIgnoresCancellation(t *testing.T) {
-	started := make(chan struct{})
-	release := make(chan struct{})
-	released := false
-	defer func() {
-		if !released {
-			close(release)
-		}
-	}()
-	runtime := &closeTrackingMCPRuntime{closed: make(chan struct{})}
-	startup := startOptionalMCP(
-		context.Background(),
-		tools.NewRegistry(),
-		config.MCPConfig{Servers: config.DefaultMCPServers()},
-		mcp.RegisterOptions{},
-		func(context.Context, *tools.Registry, config.MCPConfig, mcp.RegisterOptions) (mcpToolRuntime, error) {
-			close(started)
-			<-release
-			return runtime, nil
-		},
-		nil,
-	)
-	<-started
-
-	closeResult := make(chan error, 1)
-	go func() { closeResult <- startup.Close() }()
-	select {
-	case err := <-closeResult:
-		if err != nil {
-			t.Fatalf("Close() error = %v", err)
-		}
-	case <-time.After(time.Second):
-		t.Fatal("Close blocked on registration after cancellation")
-	}
-
-	close(release)
-	released = true
-	select {
-	case <-runtime.closed:
-	case <-time.After(time.Second):
-		t.Fatal("late optional MCP runtime was not closed")
-	}
-}

internal/cron/lock.go

@@ -5,23 +5,31 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"sync/atomic"
 	"time"
 
 	"github.com/Gitlawb/zero/internal/lockutil"
 )
 
 // Cross-process lock tuning. The lock is held only for a single metadata
-// read-modify-write (milliseconds), never across a job's exec, so the timeout
-// is generous relative to any real hold.
+// read-modify-write (milliseconds), never across a job's exec, so the timeout is
+// generous and the stale threshold sits far above any real hold.
 const (
 	cronLockTimeout    = 10 * time.Second
+	cronLockStaleAfter = 60 * time.Second
 	cronLockRetryDelay = 20 * time.Millisecond
 )
 
-// lockJob takes a cross-process advisory lock for one job on a stable sibling
-// "<id>.lock" file next to the job directory. It serializes the read-modify-write
-// of a job's metadata across concurrent schedulers and commands. The kernel
-// releases the lock when a holder exits; the file is never renamed or removed.
+var cronLockSeq atomic.Uint64
+
+// lockJob takes a cross-process exclusive lock for one job by O_EXCL-creating a
+// sibling "<id>.lock" file next to the job directory (so Remove's RemoveAll of
+// the job dir never deletes a live lock). It serializes the read-modify-write of
+// a job's metadata across concurrent schedulers and commands. The lock file is
+// removed on release; a stale lock from a crashed holder (older than
+// cronLockStaleAfter) is reclaimed. Wall-clock time.Now is used deliberately
+// (not the injectable Store.now) so lock timing never depends on a frozen test
+// clock and the stale check compares against real file mtimes.
 func (s *Store) lockJob(id string) (func(), error) {
 	if !validID(id) {
 		return nil, fmt.Errorf("invalid cron job id %q", id)
@@ -30,15 +38,64 @@ func (s *Store) lockJob(id string) (func(), error) {
 	if err := os.MkdirAll(filepath.Dir(lockPath), 0o700); err != nil {
 		return nil, err
 	}
+	token := fmt.Sprintf("%d-%d-%d", os.Getpid(), time.Now().UnixNano(), cronLockSeq.Add(1))
 	deadline := time.Now().Add(cronLockTimeout)
 	for {
-		lock, err := lockutil.TryAcquireFileLock(lockPath)
+		f, err := os.OpenFile(lockPath, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0o600)
 		if err == nil {
-			return func() { _ = lock.Release() }, nil
+			// A partial write would leave a lock file without our token, so the
+			// releaser could never delete it — stranding the lock. Fail closed.
+			if _, werr := f.WriteString(token); werr != nil {
+				_ = f.Close()
+				_ = lockutil.RemoveLockFile(lockPath)
+				return nil, fmt.Errorf("cron: write job lock: %w", werr)
+			}
+			if cerr := f.Close(); cerr != nil {
+				_ = lockutil.RemoveLockFile(lockPath)
+				return nil, fmt.Errorf("cron: close job lock: %w", cerr)
+			}
+			var released bool
+			return func() {
+				if released {
+					return
+				}
+				released = true
+				if data, rerr := os.ReadFile(lockPath); rerr == nil && string(data) == token {
+					_ = lockutil.RemoveLockFile(lockPath)
+				}
+			}, nil
 		}
-		if !errors.Is(err, lockutil.ErrLockHeld) {
+		// On Windows a concurrent holder's os.Remove leaves the lock file in a
+		// "delete pending" state, so an O_EXCL create races it with
+		// ERROR_ACCESS_DENIED (os.ErrPermission) rather than ErrExist. Treat that
+		// as contention and retry, exactly like ErrExist — otherwise the lock
+		// spuriously fails under concurrency on Windows.
+		if !errors.Is(err, os.ErrExist) && !errors.Is(err, os.ErrPermission) {
 			return nil, fmt.Errorf("cron: acquire job lock: %w", err)
 		}
+		// Reclaim a stale lock left by a crashed holder — atomically (H3). A blind
+		// Remove lets two racers both "reclaim" and recreate, so both hold the lock;
+		// reclaimStaleLock renames the file aside (only one rename of a given file
+		// wins) and restores it if it turns out fresh, so a live lock is never deleted
+		// out from under its holder.
+		if info, statErr := os.Stat(lockPath); statErr == nil && time.Since(info.ModTime()) > cronLockStaleAfter {
+			cleared, rerr := lockutil.ReclaimStaleLock(lockPath, token, func(reclaimedPath string) bool {
+				info, err := os.Stat(reclaimedPath)
+				return err == nil && time.Since(info.ModTime()) <= cronLockStaleAfter
+			})
+			if rerr != nil {
+				// Reclaim hit a hard failure: the rename aside failed outright, or a
+				// live holder's lock could not be put back (the lock path may be
+				// missing, so re-acquiring would break mutual exclusion). Fail closed
+				// instead of spinning to the deadline.
+				return nil, fmt.Errorf("cron: reclaim stale job lock: %w", rerr)
+			}
+			if cleared {
+				continue // cleared a genuinely stale lock; retry the O_EXCL create now
+			}
+			// Lost the reclaim race (or it was actually fresh) — fall through to the
+			// bounded wait instead of hot-spinning on a reclaim that never wins (L13).
+		}
 		if !time.Now().Before(deadline) {
 			return nil, fmt.Errorf("cron: timed out acquiring job lock for %q", id)
 		}

internal/cron/mutate_test.go

@@ -64,7 +64,7 @@ func TestMutateRemovedJobReturnsNotFound(t *testing.T) {
 	if !errors.Is(err, ErrJobNotFound) {
 		t.Fatalf("Mutate on removed job = %v, want ErrJobNotFound", err)
 	}
-	// The stable advisory-lock file does not resurrect the removed job dir.
+	// And the lock file left no litter / did not resurrect the job dir.
 	if _, gerr := store.Get(job.ID); !errors.Is(gerr, ErrJobNotFound) {
 		t.Fatalf("job should remain removed, Get = %v", gerr)
 	}

internal/daemon/lock.go

@@ -3,60 +3,107 @@ package daemon
 import (
 	"errors"
 	"fmt"
+	"io/fs"
 	"os"
 	"strconv"
 	"strings"
+	"sync/atomic"
 
 	"github.com/Gitlawb/zero/internal/lockutil"
 )
 
-// Single-instance lock. The stable PID file carries a kernel advisory lock for
-// the daemon's full lifetime. Process exit releases the lock automatically, so
-// stale metadata needs no rename/remove recovery protocol.
+// Single-instance lock. Mirrors reference-daemon-code-agent-js/supervisor.js's
+// lock file: a PID file created with O_EXCL. A second start fails; a STALE lock
+// left by a dead daemon (the recorded PID is no longer alive) is reclaimed so the
+// daemon recovers from an unclean shutdown without manual cleanup.
 
 // ErrAlreadyRunning is returned when a live daemon already holds the lock.
 var ErrAlreadyRunning = errors.New("daemon: another instance is already running")
 
 // fileLock is an acquired single-instance lock.
 type fileLock struct {
-	lock *lockutil.FileLock
+	path string
 }
 
 // processAlive reports whether pid is a live process. Implemented per-platform
 // (lock_posix.go / lock_windows.go). It is a package var so tests can stub it.
 var processAlive = osProcessAlive
 
-// acquireLock takes the single-instance advisory lock at path. isAlive is used
-// only to enrich a contention error with the current holder's PID; the kernel
-// lock, not PID metadata, is authoritative.
+// acquireLock takes the single-instance lock at path, reclaiming a stale lock
+// whose recorded PID is dead. isAlive overrides the liveness check (tests pass a
+// stub); nil uses the real processAlive.
 func acquireLock(path string, isAlive func(pid int) bool) (*fileLock, error) {
 	if isAlive == nil {
 		isAlive = processAlive
 	}
-	lock, err := lockutil.TryAcquireFileLock(path)
-	if err != nil {
-		if !errors.Is(err, lockutil.ErrLockHeld) {
+	// At most two passes: create, or detect-stale-then-retry once.
+	for attempt := 0; attempt < 2; attempt++ {
+		f, err := os.OpenFile(path, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0o600)
+		if err == nil {
+			// A failed PID write would leave a malformed lock file that another
+			// process reads as stale (unparsable PID) and wrongly reclaims, breaking
+			// the single-instance guarantee — so on write failure, remove it and fail.
+			if _, werr := fmt.Fprintf(f, "%d\n", os.Getpid()); werr != nil {
+				_ = f.Close()
+				_ = lockutil.RemoveLockFile(path)
+				return nil, werr
+			}
+			if cerr := f.Close(); cerr != nil {
+				_ = lockutil.RemoveLockFile(path)
+				return nil, cerr
+			}
+			return &fileLock{path: path}, nil
+		}
+		if !errors.Is(err, fs.ErrExist) && !errors.Is(err, os.ErrPermission) {
 			return nil, err
 		}
 		pid, perr := readPidFile(path)
 		if perr == nil && pid > 0 && isAlive(pid) {
 			return nil, fmt.Errorf("%w (pid %d)", ErrAlreadyRunning, pid)
 		}
-		return nil, ErrAlreadyRunning
+		// Stale lock (dead PID or unreadable) — reclaim it atomically, then retry the
+		// O_EXCL create. A blind Remove here races: two daemons starting at once could
+		// both read the stale PID, both Remove, and then one Removes the OTHER's
+		// freshly-created lock — leaving both "holding" the single-instance lock.
+		// reclaimStaleLock renames the file aside so only one racer wins the rename,
+		// and restores it if a live holder reacquired in the gap (D6).
+		if _, rerr := reclaimStaleLock(path, isAlive); rerr != nil {
+			// Reclaim hit a hard failure: the rename aside failed outright, or a
+			// live holder's lock could not be put back (the lock path may be
+			// missing, so re-acquiring would break the single-instance guarantee).
+			// Fail closed instead of spinning to the deadline.
+			return nil, fmt.Errorf("daemon: reclaim stale lock: %w", rerr)
+		}
 	}
-	if err := lock.WriteMetadata([]byte(fmt.Sprintf("%d\n", os.Getpid()))); err != nil {
-		return nil, errors.Join(err, lock.Release())
-	}
-	return &fileLock{lock: lock}, nil
+	return nil, ErrAlreadyRunning
 }
 
-// release drops the kernel lock and closes its handle. The stable PID file is
-// deliberately retained so contenders always address the same inode.
+// daemonLockSeq makes each reclaim attempt's sidelined filename unique per process.
+var daemonLockSeq atomic.Uint64
+
+// reclaimStaleLock atomically reclaims a single-instance lock whose recorded
+// PID is dead, via lockutil.ReclaimStaleLock: the lock file is renamed aside
+// (only one racer can win the rename) and stolen only if the moved file's PID
+// is still dead; a holder that reacquired the lock in the gap between the
+// stale check and the rename carries a LIVE pid and is restored rather than
+// stolen. Returns true only when a genuinely stale lock was removed. A
+// non-nil error means the caller must fail closed instead of re-acquiring
+// (see lockutil.ReclaimStaleLock).
+func reclaimStaleLock(path string, isAlive func(pid int) bool) (bool, error) {
+	suffix := fmt.Sprintf("%d-%d", os.Getpid(), daemonLockSeq.Add(1))
+	return lockutil.ReclaimStaleLock(path, suffix, func(reclaimedPath string) bool {
+		pid, err := readPidFile(reclaimedPath)
+		return err == nil && pid > 0 && isAlive(pid)
+	})
+}
+
+// release removes the lock file. Safe to call once. An already-missing lock
+// file is not an error (lockutil.RemoveLockFile swallows it on every platform).
 func (l *fileLock) release() error {
-	if l == nil || l.lock == nil {
+	if l == nil || l.path == "" {
 		return nil
 	}
-	return l.lock.Release()
+	return lockutil.RemoveLockFile(l.path)
 }
 
 // readPidFile reads and parses the PID recorded in a lock file.
@@ -65,20 +112,5 @@ func readPidFile(path string) (int, error) {
 	if err != nil {
 		return 0, err
 	}
-	metadata := strings.TrimSpace(string(data))
-	if pid, err := strconv.Atoi(metadata); err == nil {
-		return pid, nil
-	}
-	pidText, sequenceText, ok := strings.Cut(metadata, "-")
-	if !ok || pidText == "" || sequenceText == "" || strings.Contains(sequenceText, "-") {
-		return 0, fmt.Errorf("daemon: parse lock PID metadata %q", metadata)
-	}
-	if _, err := strconv.ParseUint(sequenceText, 10, 64); err != nil {
-		return 0, fmt.Errorf("daemon: parse lock holder sequence: %w", err)
-	}
-	pid, err := strconv.Atoi(pidText)
-	if err != nil {
-		return 0, fmt.Errorf("daemon: parse lock PID: %w", err)
-	}
-	return pid, nil
+	return strconv.Atoi(strings.TrimSpace(string(data)))
 }

internal/daemon/lock_test.go

@@ -32,48 +32,27 @@ func TestLockSingleInstance(t *testing.T) {
 	_ = l2.release()
 }
 
-// A PID liveness probe is diagnostic only. Even if it reports the recorded PID
-// dead, a contended kernel lock proves that the holder is active and must win.
-// The old rename-aside protocol trusted this stale observation and admitted a
-// second daemon while the first one was still inside its critical section.
-func TestLockDoesNotOverrideKernelHolderWithStalePIDProbe(t *testing.T) {
+func TestLockStaleRecovery(t *testing.T) {
 	path := filepath.Join(t.TempDir(), "daemon.lock")
-	first, err := acquireLock(path, func(int) bool { return true })
-	if err != nil {
-		t.Fatalf("first acquireLock: %v", err)
-	}
-	defer first.release()
-
-	second, err := acquireLock(path, func(int) bool { return false })
-	if second != nil {
-		_ = second.release()
-	}
-	if !errors.Is(err, ErrAlreadyRunning) {
-		t.Fatalf("contended acquire with stale PID probe = %v, want ErrAlreadyRunning", err)
-	}
-}
-
-func TestLockIgnoresStaleMetadataWhenKernelLockIsFree(t *testing.T) {
-	path := filepath.Join(t.TempDir(), "daemon.lock")
-	// A crashed daemon may leave PID metadata behind, but its kernel lock is
-	// released automatically, so the next daemon can acquire without moving it.
+	// Simulate a stale lock from a crashed daemon: a PID file whose process is
+	// dead.
 	if err := os.WriteFile(path, []byte("4242\n"), 0o600); err != nil {
 		t.Fatalf("write stale lock: %v", err)
 	}
 	dead := func(int) bool { return false }
 	l, err := acquireLock(path, dead)
 	if err != nil {
-		t.Fatalf("acquire over stale metadata: %v", err)
+		t.Fatalf("stale-lock recovery failed: %v", err)
 	}
 	// The lock now records OUR pid, not the stale one.
 	data, _ := os.ReadFile(path)
 	if strings.TrimSpace(string(data)) != strconv.Itoa(os.Getpid()) {
-		t.Fatalf("lock pid = %q, want %d", strings.TrimSpace(string(data)), os.Getpid())
+		t.Fatalf("reclaimed lock pid = %q, want %d", strings.TrimSpace(string(data)), os.Getpid())
 	}
 	_ = l.release()
 }
 
-func TestLockReleaseKeepsStableFile(t *testing.T) {
+func TestLockReleaseRemovesFile(t *testing.T) {
 	path := filepath.Join(t.TempDir(), "daemon.lock")
 	l, err := acquireLock(path, func(int) bool { return true })
 	if err != nil {
@@ -82,37 +61,46 @@ func TestLockReleaseKeepsStableFile(t *testing.T) {
 	if err := l.release(); err != nil {
 		t.Fatalf("release: %v", err)
 	}
-	if _, err := os.Stat(path); err != nil {
-		t.Fatalf("release removed stable lock file: %v", err)
+	if _, err := os.Stat(path); !errors.Is(err, os.ErrNotExist) {
+		t.Fatalf("lock file still present after release: %v", err)
 	}
 }
 
-func TestReadPidFileMetadataFormats(t *testing.T) {
+func TestReclaimStaleLockRemovesDeadHolder(t *testing.T) {
 	path := filepath.Join(t.TempDir(), "daemon.lock")
-	for _, test := range []struct {
-		name     string
-		metadata string
-		wantPID  int
-		wantErr  bool
-	}{
-		{name: "legacy PID", metadata: "4242\n", wantPID: 4242},
-		{name: "PID and holder sequence", metadata: "4242-7\n", wantPID: 4242},
-		{name: "missing sequence", metadata: "4242-", wantErr: true},
-		{name: "non-numeric sequence", metadata: "4242-next", wantErr: true},
-		{name: "extra component", metadata: "4242-7-8", wantErr: true},
-	} {
-		t.Run(test.name, func(t *testing.T) {
-			if err := os.WriteFile(path, []byte(test.metadata), 0o600); err != nil {
-				t.Fatal(err)
-			}
-			got, err := readPidFile(path)
-			if (err != nil) != test.wantErr {
-				t.Fatalf("readPidFile() error = %v, wantErr %v", err, test.wantErr)
-			}
-			if !test.wantErr && got != test.wantPID {
-				t.Fatalf("readPidFile() = %d, want %d", got, test.wantPID)
-			}
-		})
+	if err := os.WriteFile(path, []byte("4242\n"), 0o600); err != nil {
+		t.Fatalf("write stale lock: %v", err)
+	}
+	if ok, err := reclaimStaleLock(path, func(int) bool { return false }); err != nil || !ok {
+		t.Fatalf("reclaimStaleLock must report a genuinely stale (dead-PID) lock reclaimed (ok=%v err=%v)", ok, err)
+	}
+	if _, err := os.Stat(path); !errors.Is(err, os.ErrNotExist) {
+		t.Fatalf("a reclaimed stale lock must be removed, stat = %v", err)
+	}
+}
+
+func TestReclaimStaleLockRestoresLiveHolder(t *testing.T) {
+	// If a holder reacquires the lock in the gap between the stale check and the
+	// rename, the moved file carries a LIVE pid; reclaim must restore it untouched
+	// rather than steal it — otherwise two daemons both "hold" the lock (D6).
+	path := filepath.Join(t.TempDir(), "daemon.lock")
+	if err := os.WriteFile(path, []byte("4242\n"), 0o600); err != nil {
+		t.Fatalf("write lock: %v", err)
+	}
+	if ok, err := reclaimStaleLock(path, func(int) bool { return true }); err != nil || ok {
+		t.Fatalf("reclaimStaleLock must NOT report a live-PID lock reclaimed (ok=%v err=%v)", ok, err)
+	}
+	data, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatalf("live lock must be restored in place, read = %v", err)
+	}
+	if strings.TrimSpace(string(data)) != "4242" {
+		t.Fatalf("restored lock content = %q, want %q (unchanged)", strings.TrimSpace(string(data)), "4242")
+	}
+	// No sidelined ".stale" leftovers.
+	matches, _ := filepath.Glob(path + ".stale.*")
+	if len(matches) != 0 {
+		t.Fatalf("reclaim left sidelined files: %v", matches)
 	}
 }
 

internal/daemon/server_test.go

@@ -124,16 +124,12 @@ func TestServerEndToEnd(t *testing.T) {
 	case <-time.After(3 * time.Second):
 		t.Fatal("Serve did not return after shutdown")
 	}
-	// Runtime endpoints are removed on exit. The advisory lock file remains as
-	// a stable inode, but the kernel lock on it has been released.
-	for _, p := range []string{paths.Socket, paths.Status} {
+	// Socket, status, and lock files are removed on exit.
+	for _, p := range []string{paths.Socket, paths.Status, paths.Lock} {
 		if _, err := os.Stat(p); !errors.Is(err, os.ErrNotExist) {
 			t.Fatalf("file %s not cleaned up after shutdown: %v", p, err)
 		}
 	}
-	if _, err := os.Stat(paths.Lock); err != nil {
-		t.Fatalf("stable lock file missing after shutdown: %v", err)
-	}
 }
 
 func TestServerSecondInstanceFails(t *testing.T) {

internal/execution/process_unix_test.go

@@ -3,93 +3,13 @@
 package execution
 
 import (
-	"errors"
-	"os"
 	"os/exec"
 	"strconv"
-	"strings"
 	"syscall"
 	"testing"
 	"time"
 )
 
-// requireProcessState refuses to let a broken ps pipeline masquerade as passing
-// coverage. Every test in this file proves something about zombie detection,
-// and every one of those proofs is read out of ps — so if ps cannot report
-// state, the tests verify nothing whatever they do next.
-//
-// The old code answered that with t.Skip, which is indistinguishable from
-// success in CI output. This probes BOTH ps pipelines against this test
-// process, which is by definition alive and not a zombie, so a working ps must
-// report a live state for it. Failing that:
-//
-//   - In CI (or with ZERO_REQUIRE_PS=1) it is a hard failure. ps is present on
-//     every image used today, so its absence means the pipeline regressed and
-//     that has to surface immediately rather than as skipped-green.
-//   - Elsewhere it stays a skip, so a contributor on an exotic box is not
-//     blocked by an environment the project does not claim to support.
-//
-// This only covers "ps cannot report state at all". Once it passes, a later
-// failure to observe an EXPECTED state is a real defect, and the tests below
-// treat it as one.
-func requireProcessState(t *testing.T) {
-	t.Helper()
-	self := os.Getpid()
-	var reasons []string
-	// The production path: ps -A -o pid=,pgid=,stat=, parsed by
-	// processTableStateMatches. This is what signalTargetRunning consults.
-	if running, ok := processIsRunning(self); !ok || !running {
-		reasons = append(reasons, "the process table read used by signalTargetRunning reported no live state for this test process")
-	}
-	// This file's independent oracle: ps -o stat= -p <pid>. It is deliberately
-	// NOT the production parser, so a regression in that parser cannot hide by
-	// breaking the test's own precondition check in the same way.
-	if zombie, ok := processIsZombie(self); !ok || zombie {
-		reasons = append(reasons, "the per-PID state read used by this test file reported no live state for this test process")
-	}
-	if len(reasons) == 0 {
-		return
-	}
-	reason := "cannot read process state, so ps-based zombie detection is unverifiable here: " + strings.Join(reasons, "; ")
-	if requireWorkingPS() {
-		t.Fatal(reason + " — failing rather than skipping because CI (or ZERO_REQUIRE_PS) is set, where ps is expected to work")
-	}
-	t.Skip(reason)
-}
-
-// requireWorkingPS reports whether an unusable ps must fail the run instead of
-// skipping it. ZERO_REQUIRE_PS lets a developer opt into the strict behavior
-// locally to reproduce what CI does.
-func requireWorkingPS() bool {
-	if strings.TrimSpace(os.Getenv("ZERO_REQUIRE_PS")) != "" {
-		return true
-	}
-	return strings.TrimSpace(os.Getenv("CI")) != ""
-}
-
-// awaitZombie blocks until pid is an unreaped zombie. The caller must not have
-// waited on the child, so the zombie is a stable state rather than a race: it
-// persists until something reaps it. Failing to reach it therefore means the
-// child never exited or ps stopped reporting its state, and both are defects
-// rather than reasons to skip.
-func awaitZombie(t *testing.T, pid int) {
-	t.Helper()
-	deadline := time.Now().Add(5 * time.Second)
-	for {
-		zombie, ok := processIsZombie(pid)
-		if ok && zombie {
-			return
-		}
-		if time.Now().After(deadline) {
-			if !ok {
-				t.Fatalf("pid %d left the process table without being reaped; this test never waited on it, so its zombie row must persist", pid)
-			}
-			t.Fatalf("pid %d did not reach the zombie state within 5s", pid)
-		}
-		time.Sleep(10 * time.Millisecond)
-	}
-}
-
 // TestTerminateProcessTreeTreatsZombieGroupAsExited is the regression test for
 // counting unreaped processes as alive: kill(2) with signal 0 succeeds for a
 // zombie, so a group whose only remaining member is waiting to be reaped used to
@@ -97,8 +17,6 @@ func awaitZombie(t *testing.T, pid int) {
 // as "did not exit after SIGKILL" — a spurious cleanup failure whose timing
 // depended on when the reaper ran.
 func TestTerminateProcessTreeTreatsZombieGroupAsExited(t *testing.T) {
-	requireProcessState(t)
-
 	cmd := exec.Command("sh", "-c", "exit 0")
 	ConfigureProcessGroup(cmd)
 	if err := cmd.Start(); err != nil {
@@ -109,59 +27,23 @@ func TestTerminateProcessTreeTreatsZombieGroupAsExited(t *testing.T) {
 	// is exactly the state a terminated tree passes through.
 	t.Cleanup(func() { _ = cmd.Wait() })
 
-	awaitZombie(t, pid)
-
-	// Whether a zombie-only group can be signalled is a KERNEL difference, not a
-	// ps one. On Linux the zombie still occupies the process table and
-	// kill(-pid, 0) succeeds, so signalTargetRunning goes on to consult ps —
-	// which is the branch this test was written for. Darwin returns EPERM for
-	// the same call, so signalTargetRunning short-circuits on the kill and never
-	// reaches the ps check.
-	//
-	// The OUTCOME is identical and is asserted on every platform below. Only the
-	// branch that produces it differs, so record that instead of skipping the
-	// whole test (which would drop Darwin's coverage of the outcome) or failing
-	// it (which would report a supported platform as broken). Any errno other
-	// than EPERM means the group is not in the state this test needs.
-	psPathReachable := true
-	if err := syscall.Kill(-pid, syscall.Signal(0)); err != nil {
-		if !errors.Is(err, syscall.EPERM) {
-			t.Fatalf("zombie group %d is unsignalable with an unexpected error (%v); the zombie case is not present, so nothing below would be meaningful", pid, err)
+	deadline := time.Now().Add(5 * time.Second)
+	for {
+		if zombie, ok := processIsZombie(pid); ok && zombie {
+			break
 		}
-		psPathReachable = false
-		t.Logf("kernel refuses to signal zombie-only group %d (EPERM); signalTargetRunning answers from kill(2) rather than ps here, so the ps-based zombie check is asserted directly on platforms that allow the signal", pid)
+		if time.Now().After(deadline) {
+			t.Skip("child did not reach the zombie state; ps output is unavailable in this environment")
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
+	if syscall.Kill(-pid, syscall.Signal(0)) != nil {
+		t.Skip("the zombie group is no longer signalable; cannot exercise the case")
 	}
 
-	// Where the signal IS permitted, pin the ps-based check itself. This is the
-	// regression #774 was about, and asserting only signalTargetRunning would
-	// let a ps-side regression hide behind the kill result.
-	if psPathReachable {
-		running, ok := processGroupHasRunningMember(pid)
-		if !ok {
-			t.Fatalf("process group %d has no rows while its zombie is unreaped; ps stopped reporting the group rather than the group being gone", pid)
-		}
-		if running {
-			t.Fatal("the ps-based group check must not report a zombie-only group as running")
-		}
-	}
-
-	// Valid on every platform: whichever branch answers, a zombie-only group is
-	// not running. On a kernel that refuses the signal this is the whole of the
-	// coverage, and it is more than the previous skip provided.
 	if signalTargetRunning(-pid) {
 		t.Fatal("a group holding only a zombie must not count as running")
 	}
-
-	if !psPathReachable {
-		// terminateTarget's own kill(2) would hit the same EPERM and be returned
-		// as a cleanup error, so this assertion cannot be made where the kernel
-		// refuses the signal. That may be a real gap in TerminateProcessTree on
-		// such a platform rather than a test limitation — a zombie-only tree is
-		// already exited and should terminate cleanly — but confirming and
-		// changing that is a production fix, not this test's business.
-		t.Log("skipping the TerminateProcessTree assertion: its kill(2) would hit the same EPERM as the probe above")
-		return
-	}
 	if err := TerminateProcessTree(pid, 50*time.Millisecond, 10*time.Millisecond); err != nil {
 		t.Fatalf("TerminateProcessTree on an already-exited tree: %v", err)
 	}
@@ -171,8 +53,6 @@ func TestTerminateProcessTreeTreatsZombieGroupAsExited(t *testing.T) {
 // a live member must still be seen as running and then actually stopped, so the
 // zombie tolerance above cannot degrade into ignoring real processes.
 func TestTerminateProcessTreeStopsRunningGroup(t *testing.T) {
-	requireProcessState(t)
-
 	cmd := exec.Command("sh", "-c", "sleep 30")
 	ConfigureProcessGroup(cmd)
 	if err := cmd.Start(); err != nil {
@@ -187,15 +67,7 @@ func TestTerminateProcessTreeStopsRunningGroup(t *testing.T) {
 	if err := TerminateProcessTree(pid, time.Second, 10*time.Millisecond); err != nil {
 		t.Fatalf("TerminateProcessTree: %v", err)
 	}
-	// ok reports whether ANY row for this group was found. This test never waits
-	// on the child, so its zombie row must still be there — an unknown state
-	// means ps stopped answering, not that the group is gone. Treating that as a
-	// pass is what let this assertion succeed without checking anything.
-	running, ok := processGroupHasRunningMember(pid)
-	if !ok {
-		t.Fatalf("process group %d has no rows after termination; the unreaped child's zombie row must persist, so the group's state is undeterminable rather than clean", pid)
-	}
-	if running {
+	if running, ok := processGroupHasRunningMember(pid); ok && running {
 		t.Fatal("the group still has a running member after termination")
 	}
 }
@@ -210,8 +82,6 @@ func TestTerminateProcessTreeStopsRunningGroup(t *testing.T) {
 // "unknown" resulted every time, and signalTargetRunning conservatively (and
 // incorrectly) treated a zombie individual-PID target as still running.
 func TestSignalTargetRunningTreatsZombieIndividualPIDAsExited(t *testing.T) {
-	requireProcessState(t)
-
 	cmd := exec.Command("sh", "-c", "exit 0")
 	// Deliberately do NOT call ConfigureProcessGroup: the child inherits this
 	// test process's group, so it is not its own leader and processSignalTarget
@@ -222,38 +92,40 @@ func TestSignalTargetRunningTreatsZombieIndividualPIDAsExited(t *testing.T) {
 	pid := cmd.Process.Pid
 	t.Cleanup(func() { _ = cmd.Wait() })
 
-	awaitZombie(t, pid)
+	deadline := time.Now().Add(5 * time.Second)
+	for {
+		if zombie, ok := processIsZombie(pid); ok && zombie {
+			break
+		}
+		if time.Now().After(deadline) {
+			t.Skip("child did not reach the zombie state; ps output is unavailable in this environment")
+		}
+		time.Sleep(10 * time.Millisecond)
+	}
 
 	target, err := processSignalTarget(pid)
 	if err != nil {
 		t.Fatalf("processSignalTarget: %v", err)
 	}
-	// The child inherited this process's group, so its PGID is this process's
-	// PID and can never equal its own PID. A negative target here would mean
-	// processSignalTarget misread the group, which is the very thing the
-	// individual-PID fallback exists to handle.
 	if target != pid {
-		t.Fatalf("processSignalTarget(%d) = %d, want the individual PID: the child inherited this process's group, so it is not its own leader", pid, target)
+		t.Skip("child unexpectedly became its own group leader; cannot exercise the individual-PID fallback")
 	}
 	if signalTargetRunning(target) {
 		t.Fatal("a zombie individual-PID target must not count as running")
 	}
 }
 
-// processIsZombie reports a process's zombie state via ps. It is deliberately a
-// separate, per-PID ps invocation rather than a reuse of the production
-// process-table parser: these tests assert what that parser concludes, so
-// borrowing it to establish their own preconditions would let one regression
-// silence both sides at once.
-//
-// ok is false when no state could be read, which after requireProcessState has
-// passed means the process left the table rather than that ps is broken.
+// processIsZombie reports a process's zombie state via ps. ok is false when the
+// state could not be read.
 func processIsZombie(pid int) (zombie bool, ok bool) {
 	output, err := exec.Command("ps", "-o", "stat=", "-p", strconv.Itoa(pid)).Output()
 	if err != nil {
 		return false, false
 	}
-	state := strings.TrimLeft(string(output), " \n\t")
+	state := string(output)
+	for len(state) > 0 && (state[0] == ' ' || state[0] == '\n' || state[0] == '\t') {
+		state = state[1:]
+	}
 	if state == "" {
 		return false, false
 	}

internal/hooks/lock.go

@@ -5,39 +5,93 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"sync/atomic"
 	"time"
 
 	"github.com/Gitlawb/zero/internal/lockutil"
 )
 
 // Cross-process lock tuning for the audit log. The lock is held only across a
-// single read-then-append (milliseconds), so the timeout is generous relative
-// to any real hold.
+// single read-then-append (milliseconds), so the timeout is generous and the
+// stale threshold sits far above any real hold.
 const (
 	auditLockTimeout    = 10 * time.Second
+	auditLockStaleAfter = 60 * time.Second
 	auditLockRetryDelay = 20 * time.Millisecond
 )
 
-// lockAudit takes a cross-process advisory lock on the audit log through a
-// stable sibling "<auditPath>.lock" file. It makes
+var auditLockSeq atomic.Uint64
+
+// lockAudit takes a cross-process exclusive lock on the audit log by
+// O_EXCL-creating a sibling "<auditPath>.lock" file (removed on release). It makes
 // the lastSequence()+append in append() atomic across processes; the audit log is
 // a shared global file, so without it two processes can read the same last
-// sequence and write duplicate numbers. Kernel lock lifetime provides crash
-// recovery without moving or deleting the lock path.
+// sequence and write duplicate numbers. A stale lock from a crashed holder (older
+// than auditLockStaleAfter) is reclaimed. Wall-clock time is used deliberately so
+// lock timing never depends on the store's injectable clock and the stale check
+// compares against real file mtimes. This mirrors internal/cron/lock.go and
+// internal/oauth/lock.go. Uses internal/lockutil for lock restore and reclaim.
 func (store *AuditStore) lockAudit() (func(), error) {
 	lockPath := store.auditPath + ".lock"
 	if err := os.MkdirAll(filepath.Dir(lockPath), 0o700); err != nil {
 		return nil, err
 	}
+	token := fmt.Sprintf("%d-%d-%d", os.Getpid(), time.Now().UnixNano(), auditLockSeq.Add(1))
 	deadline := time.Now().Add(auditLockTimeout)
 	for {
-		lock, err := lockutil.TryAcquireFileLock(lockPath)
+		f, err := os.OpenFile(lockPath, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0o600)
 		if err == nil {
-			return func() { _ = lock.Release() }, nil
+			// A partial write would leave a lock file without our token, so the
+			// releaser could never delete it — stranding the lock. Fail closed.
+			if _, werr := f.WriteString(token); werr != nil {
+				_ = f.Close()
+				_ = lockutil.RemoveLockFile(lockPath)
+				return nil, fmt.Errorf("hooks: write audit lock: %w", werr)
+			}
+			if cerr := f.Close(); cerr != nil {
+				_ = lockutil.RemoveLockFile(lockPath)
+				return nil, fmt.Errorf("hooks: close audit lock: %w", cerr)
+			}
+			var released bool
+			return func() {
+				if released {
+					return
+				}
+				released = true
+				if data, rerr := os.ReadFile(lockPath); rerr == nil && string(data) == token {
+					_ = lockutil.RemoveLockFile(lockPath)
+				}
+			}, nil
 		}
-		if !errors.Is(err, lockutil.ErrLockHeld) {
+		// On Windows a concurrent holder's os.Remove leaves the lock file in a
+		// "delete pending" state, so an O_EXCL create races it with
+		// ERROR_ACCESS_DENIED (os.ErrPermission) rather than ErrExist. Treat both
+		// as contention and retry.
+		if !errors.Is(err, os.ErrExist) && !errors.Is(err, os.ErrPermission) {
 			return nil, fmt.Errorf("hooks: acquire audit lock: %w", err)
 		}
+		// Reclaim a stale lock left by a crashed holder — atomically (H3). A blind
+		// Remove lets two racers both reclaim + recreate and so both hold the lock;
+		// reclaimStaleLock renames the file aside (only one rename wins) and restores
+		// it if it turns out fresh, so a live lock is never deleted out from under it.
+		if info, statErr := os.Stat(lockPath); statErr == nil && time.Since(info.ModTime()) > auditLockStaleAfter {
+			cleared, rerr := lockutil.ReclaimStaleLock(lockPath, token, func(reclaimedPath string) bool {
+				info, err := os.Stat(reclaimedPath)
+				return err == nil && time.Since(info.ModTime()) <= auditLockStaleAfter
+			})
+			if rerr != nil {
+				// Reclaim hit a hard failure: the rename aside failed outright, or a
+				// live holder's lock could not be put back (the lock path may be
+				// missing, so re-acquiring would break mutual exclusion). Fail closed
+				// instead of spinning to the deadline.
+				return nil, fmt.Errorf("hooks: reclaim stale audit lock: %w", rerr)
+			}
+			if cleared {
+				continue
+			}
+			// Lost the reclaim race (or it was actually fresh) — fall through to the
+			// bounded wait rather than hot-spinning on a reclaim that never wins.
+		}
 		if !time.Now().Before(deadline) {
 			return nil, fmt.Errorf("hooks: timed out acquiring audit lock")
 		}

internal/lockutil/lockutil.go

@@ -1,127 +1,64 @@
-// Package lockutil provides cross-process advisory file locks used by cron,
-// daemon, hooks, oauth, and swarm. Locks are held by the kernel for the lifetime
-// of an open file handle, so process exit releases them without a stale-file
-// reclaim protocol. The lock file itself is stable: holders never rename or
-// remove it while another process may still have its inode locked.
+// Package lockutil provides the platform-specific file primitives behind the
+// O_EXCL lock files in cron, daemon, hooks, oauth, and swarm: a no-overwrite
+// restore for locks that were sidelined during a stale-reclaim attempt, and a
+// lock file remover with one cross-platform contract (missing files are a
+// no-op; Windows retries transient sharing violations).
 package lockutil
 
 import (
-	"errors"
-	"fmt"
+	"io"
 	"os"
-	"path/filepath"
-	"strings"
-	"sync"
-	"sync/atomic"
 )
 
-var (
-	// ErrLockHeld reports that another process or goroutine currently holds the
-	// advisory lock. Callers may wait and retry until their own deadline.
-	ErrLockHeld = errors.New("lockutil: lock is held")
-	// ErrLockReleased reports an attempt to update metadata after Release.
-	ErrLockReleased = errors.New("lockutil: lock is released")
-)
-
-var holderSequence atomic.Uint64
-
-// FileLock is an exclusive advisory lock held through an open file handle.
-// Release is idempotent. The lock path remains on disk after release; deleting
-// or replacing it would let different processes lock different inodes.
-type FileLock struct {
-	mu         sync.Mutex
-	file       *os.File
-	state      platformLockState
-	released   bool
-	releaseErr error
-}
-
-// TryAcquireFileLock attempts to take an exclusive advisory lock without
-// waiting. A contended lock returns ErrLockHeld. The kernel releases a lock if
-// its process exits, so an old unlocked file never needs stale reclamation.
-func TryAcquireFileLock(path string) (*FileLock, error) {
-	return TryAcquireFileLockAt(filepath.Dir(path), path)
-}
-
-// TryAcquireFileLockAt attempts to lock path while confining every component
-// below root to a handle-relative traversal. root is the caller's trusted
-// boundary and may itself be reached through a legitimate link; links and
-// reparse points below it are rejected before metadata can be written.
-func TryAcquireFileLockAt(root, path string) (*FileLock, error) {
-	if root == "" {
-		return nil, errors.New("lockutil: lock root is empty")
-	}
-	relative, err := filepath.Rel(root, path)
+// restoreByCopy restores reclaimed to path without overwriting an existing
+// path, as a fallback for when the platform's primary no-replace primitive
+// (hard link on POSIX, MoveFileEx on Windows) fails for a reason other than
+// the destination existing. It stages a full copy under a private name next
+// to reclaimed and publishes it to path with publish (the same no-replace
+// primitive the caller's platform uses for the primary restore), so path
+// never appears in a partially-copied state: a crash between staging and
+// publish leaves path exactly as it was (missing or, if a competing holder
+// created it, untouched), never a truncated file that a PID/content-based
+// liveness check could mistake for dead. Leaving path missing here would let
+// the next O_EXCL create succeed while the sidelined holder is still live,
+// breaking mutual exclusion. publish keeps the no-overwrite guarantee: a new
+// holder that appeared in the meantime wins and this returns os.ErrExist. The
+// copy resets the lock's mtime to now, which only makes the restored lock
+// look fresher; that is safe, since it is being handed back to a live holder.
+func restoreByCopy(reclaimed, path string, publish func(from, to string) error) error {
+	staged := reclaimed + ".copy"
+	src, err := os.Open(reclaimed)
 	if err != nil {
-		return nil, fmt.Errorf("lockutil: resolve lock path relative to root: %w", err)
+		return err
 	}
-	relative = filepath.Clean(relative)
-	if relative == "." || relative == ".." || filepath.IsAbs(relative) || strings.HasPrefix(relative, ".."+string(filepath.Separator)) {
-		return nil, fmt.Errorf("lockutil: lock path %q escapes root %q", path, root)
-	}
-
-	file, err := openLockFileAt(root, relative, path)
+	dst, err := os.OpenFile(staged, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0o600)
 	if err != nil {
-		return nil, fmt.Errorf("lockutil: open lock file: %w", err)
+		_ = src.Close()
+		return err
 	}
-	state, contended, err := tryLockFile(file)
+	_, err = io.Copy(dst, src)
+	// Close the source before removing anything below: Go opens files without
+	// FILE_SHARE_DELETE on Windows, so deleting reclaimed or staged while src
+	// is open would fail with a sharing violation.
+	_ = src.Close()
 	if err != nil {
-		_ = file.Close()
-		return nil, fmt.Errorf("lockutil: acquire advisory lock: %w", err)
+		_ = dst.Close()
+		_ = os.Remove(staged)
+		return err
 	}
-	if contended {
-		_ = file.Close()
-		return nil, ErrLockHeld
+	if err := dst.Close(); err != nil {
+		_ = os.Remove(staged)
+		return err
 	}
-
-	lock := &FileLock{file: file, state: state}
-	metadata := []byte(fmt.Sprintf("%d-%d\n", os.Getpid(), holderSequence.Add(1)))
-	if err := lock.WriteMetadata(metadata); err != nil {
-		return nil, errors.Join(err, lock.Release())
-	}
-	return lock, nil
-}
-
-// WriteMetadata replaces the diagnostic contents of the lock file while the
-// caller holds it. Metadata does not establish ownership; the kernel lock does.
-func (lock *FileLock) WriteMetadata(data []byte) error {
-	if lock == nil {
-		return ErrLockReleased
-	}
-	lock.mu.Lock()
-	defer lock.mu.Unlock()
-	if lock.released || lock.file == nil {
-		return ErrLockReleased
-	}
-	if err := lock.file.Truncate(0); err != nil {
-		return fmt.Errorf("lockutil: truncate lock metadata: %w", err)
-	}
-	if _, err := lock.file.Seek(0, 0); err != nil {
-		return fmt.Errorf("lockutil: seek lock metadata: %w", err)
-	}
-	if _, err := lock.file.Write(data); err != nil {
-		return fmt.Errorf("lockutil: write lock metadata: %w", err)
+	if err := publish(staged, path); err != nil {
+		_ = os.Remove(staged)
+		return err
 	}
+	// publish may leave staged behind (a hard-link publish keeps both names),
+	// so remove it explicitly; a move-based publish already made this a no-op.
+	_ = os.Remove(staged)
+	// The lock is back at path, so the restore has succeeded; failing to clean
+	// up the sidelined name must not be reported as a failed restore.
+	_ = RemoveLockFile(reclaimed)
 	return nil
 }
-
-// Release unlocks and closes the held file handle. It deliberately leaves the
-// stable lock file in place. Repeated calls return the first release result.
-func (lock *FileLock) Release() error {
-	if lock == nil {
-		return nil
-	}
-	lock.mu.Lock()
-	defer lock.mu.Unlock()
-	if lock.released {
-		return lock.releaseErr
-	}
-	lock.released = true
-	unlockErr := unlockFile(lock.file, &lock.state)
-	closeErr := lock.file.Close()
-	lock.file = nil
-	if err := errors.Join(unlockErr, closeErr); err != nil {
-		lock.releaseErr = fmt.Errorf("lockutil: release advisory lock: %w", err)
-	}
-	return lock.releaseErr
-}

internal/lockutil/lockutil_other.go

@@ -4,92 +4,43 @@ package lockutil
 
 import (
 	"errors"
-	"fmt"
+	"io/fs"
 	"os"
-	"path/filepath"
-	"strings"
-
-	"golang.org/x/sys/unix"
 )
 
-type platformLockState struct{}
-
-func openLockFileAt(root, relative, displayPath string) (_ *os.File, resultErr error) {
-	parentFD, err := unix.Open(root, unix.O_RDONLY|unix.O_DIRECTORY|unix.O_CLOEXEC, 0)
-	if err != nil {
-		return nil, fmt.Errorf("open lock root: %w", err)
-	}
-	defer func() {
-		if parentFD >= 0 {
-			resultErr = errors.Join(resultErr, unix.Close(parentFD))
-		}
-	}()
-
-	components := strings.Split(filepath.Clean(relative), string(filepath.Separator))
-	for _, component := range components[:len(components)-1] {
-		nextFD, openErr := unix.Openat(parentFD, component, unix.O_RDONLY|unix.O_DIRECTORY|unix.O_CLOEXEC|unix.O_NOFOLLOW, 0)
-		if openErr != nil {
-			return nil, fmt.Errorf("open lock path component %q: %w", component, openErr)
-		}
-		if closeErr := unix.Close(parentFD); closeErr != nil {
-			_ = unix.Close(nextFD)
-			parentFD = -1
-			return nil, fmt.Errorf("close lock path component: %w", closeErr)
-		}
-		parentFD = nextFD
-	}
-
-	name := components[len(components)-1]
-	fd := -1
-	// Darwin can transiently return ENOENT when many callers race to create the
-	// same O_NOFOLLOW entry. The bound parent handle cannot be redirected, so a
-	// bounded retry preserves first-use contention without weakening no-follow.
-	for attempt := 0; attempt < 10; attempt++ {
-		fd, err = unix.Openat(parentFD, name, unix.O_CREAT|unix.O_RDWR|unix.O_CLOEXEC|unix.O_NOFOLLOW, 0o600)
-		if !errors.Is(err, unix.ENOENT) {
-			break
-		}
-	}
-	if err != nil {
-		return nil, err
-	}
-	file := os.NewFile(uintptr(fd), displayPath)
-	if file == nil {
-		_ = unix.Close(fd)
-		return nil, errors.New("convert lock handle to file")
-	}
-	var stat unix.Stat_t
-	if err := unix.Fstat(fd, &stat); err != nil {
-		return nil, errors.Join(fmt.Errorf("inspect lock file: %w", err), file.Close())
-	}
-	if stat.Mode&unix.S_IFMT != unix.S_IFREG {
-		return nil, errors.Join(errors.New("refusing non-regular lock file"), file.Close())
-	}
-	if stat.Nlink != 1 {
-		return nil, errors.Join(errors.New("refusing multiply-linked lock file"), file.Close())
-	}
-	if err := unix.Close(parentFD); err != nil {
-		parentFD = -1
-		return nil, errors.Join(fmt.Errorf("close lock parent: %w", err), file.Close())
-	}
-	parentFD = -1
-	return file, nil
-}
-
-func tryLockFile(file *os.File) (platformLockState, bool, error) {
-	err := unix.Flock(int(file.Fd()), unix.LOCK_EX|unix.LOCK_NB)
+// RestoreLockFile restores a sidelined lock file on non-Windows platforms. It
+// uses os.Link so a competing lock created at path in the meantime wins: the
+// link fails with os.ErrExist instead of overwriting it. If the link fails for
+// any other reason (hardlink-incapable filesystems such as FAT or some
+// FUSE/network mounts, ENOSPC, EPERM), it falls back to an O_EXCL copy rather
+// than leaving path missing and the live holder's lock stranded in reclaimed.
+// Once the lock is back at path the restore has succeeded, so a failed cleanup
+// of the sidelined name is not reported as an error; the leftover file is
+// invisible to the lock protocol.
+func RestoreLockFile(reclaimed, path string) error {
+	err := os.Link(reclaimed, path)
 	if err == nil {
-		return platformLockState{}, false, nil
-	}
-	if errors.Is(err, unix.EWOULDBLOCK) || errors.Is(err, unix.EAGAIN) {
-		return platformLockState{}, true, nil
-	}
-	return platformLockState{}, false, err
-}
-
-func unlockFile(file *os.File, _ *platformLockState) error {
-	if file == nil {
+		_ = RemoveLockFile(reclaimed)
 		return nil
 	}
-	return unix.Flock(int(file.Fd()), unix.LOCK_UN)
+	if errors.Is(err, os.ErrExist) {
+		return err
+	}
+	return restoreByCopy(reclaimed, path, os.Link)
+}
+
+// isReclaimContended reports whether a failed rename-aside of a suspected
+// stale lock means it was lost to a racer rather than a hard failure. POSIX
+// rename has no contention errno (a lost race surfaces only as ENOENT, which
+// ReclaimStaleLock already treats as benign), so nothing extra is benign here.
+func isReclaimContended(error) bool { return false }
+
+// RemoveLockFile removes a lock file on non-Windows platforms. Removing an
+// already-missing file reports nil, matching the Windows implementation, so
+// callers see one cross-platform contract.
+func RemoveLockFile(path string) error {
+	if err := os.Remove(path); err != nil && !errors.Is(err, fs.ErrNotExist) {
+		return err
+	}
+	return nil
 }

internal/lockutil/lockutil_test.go

@@ -1,220 +1,116 @@
 package lockutil
 
 import (
-	"bufio"
 	"errors"
-	"fmt"
-	"io"
 	"os"
-	"os/exec"
 	"path/filepath"
-	"runtime"
-	"strings"
-	"sync"
 	"testing"
 )
 
-func TestFileLockSerializesAndKeepsStablePath(t *testing.T) {
+func TestRestoreLockFile(t *testing.T) {
+	tempDir := t.TempDir()
+	path := filepath.Join(tempDir, "lock")
+	reclaimed := filepath.Join(tempDir, "lock.stale.token")
+
+	// 1. Successful restore when target does not exist
+	if err := os.WriteFile(reclaimed, []byte("token"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := RestoreLockFile(reclaimed, path); err != nil {
+		t.Fatalf("RestoreLockFile failed: %v", err)
+	}
+	if data, err := os.ReadFile(path); err != nil || string(data) != "token" {
+		t.Fatalf("restored lock content = %q, err %v; want %q intact", data, err, "token")
+	}
+	if _, err := os.Stat(reclaimed); !os.IsNotExist(err) {
+		t.Fatalf("expected sidelined lock to be cleaned up/removed: %v", err)
+	}
+
+	// 2. Fail when target already exists (prevent overwrite)
+	if err := os.WriteFile(reclaimed, []byte("token"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(path, []byte("competing"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+
+	err := RestoreLockFile(reclaimed, path)
+	if err == nil {
+		t.Fatal("expected RestoreLockFile to fail when target exists")
+	}
+	if !errors.Is(err, os.ErrExist) {
+		t.Fatalf("expected os.ErrExist, got: %v", err)
+	}
+
+	// The sidelined lock must still exist on failure, and the competing lock
+	// must be untouched.
+	if _, err := os.Stat(reclaimed); err != nil {
+		t.Fatalf("expected sidelined lock to still exist: %v", err)
+	}
+	if data, _ := os.ReadFile(path); string(data) != "competing" {
+		t.Fatalf("competing lock was clobbered: %q", data)
+	}
+}
+
+func TestRestoreByCopy(t *testing.T) {
+	tempDir := t.TempDir()
+	path := filepath.Join(tempDir, "lock")
+	reclaimed := filepath.Join(tempDir, "lock.stale.token")
+
+	// 1. Restores content and cleans up the sidelined file when the target is
+	// free (the fallback taken when the platform's no-replace primitive fails
+	// for a reason other than the destination existing).
+	if err := os.WriteFile(reclaimed, []byte("token"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := restoreByCopy(reclaimed, path, os.Link); err != nil {
+		t.Fatalf("restoreByCopy failed: %v", err)
+	}
+	if data, err := os.ReadFile(path); err != nil || string(data) != "token" {
+		t.Fatalf("restored lock content = %q, err %v; want %q intact", data, err, "token")
+	}
+	if _, err := os.Stat(reclaimed); !errors.Is(err, os.ErrNotExist) {
+		t.Fatalf("expected sidelined lock to be cleaned up after copy: %v", err)
+	}
+	if _, err := os.Stat(reclaimed + ".copy"); !errors.Is(err, os.ErrNotExist) {
+		t.Fatalf("expected staged copy to be cleaned up: %v", err)
+	}
+
+	// 2. Keeps the no-overwrite guarantee: a competing lock at the target wins
+	// and the sidelined lock survives for the caller's ErrExist cleanup.
+	if err := os.WriteFile(reclaimed, []byte("token"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(path, []byte("competing"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := restoreByCopy(reclaimed, path, os.Link); !errors.Is(err, os.ErrExist) {
+		t.Fatalf("expected os.ErrExist when target exists, got: %v", err)
+	}
+	if data, _ := os.ReadFile(path); string(data) != "competing" {
+		t.Fatalf("competing lock was clobbered: %q", data)
+	}
+	if _, err := os.Stat(reclaimed); err != nil {
+		t.Fatalf("expected sidelined lock to still exist: %v", err)
+	}
+	if _, err := os.Stat(reclaimed + ".copy"); !errors.Is(err, os.ErrNotExist) {
+		t.Fatalf("expected staged copy to be cleaned up after a failed publish: %v", err)
+	}
+}
+
+func TestRemoveLockFile(t *testing.T) {
 	path := filepath.Join(t.TempDir(), "lock")
-	first, err := TryAcquireFileLock(path)
-	if err != nil {
-		t.Fatalf("first acquire: %v", err)
+	if err := os.WriteFile(path, []byte("token"), 0o600); err != nil {
+		t.Fatal(err)
 	}
-	firstInfo, err := os.Stat(path)
-	if err != nil {
-		t.Fatalf("stat first lock path: %v", err)
+	if err := RemoveLockFile(path); err != nil {
+		t.Fatalf("RemoveLockFile failed: %v", err)
 	}
-	if _, err := TryAcquireFileLock(path); !errors.Is(err, ErrLockHeld) {
-		t.Fatalf("contended acquire = %v, want ErrLockHeld", err)
+	if _, err := os.Stat(path); !errors.Is(err, os.ErrNotExist) {
+		t.Fatalf("expected lock file to be removed: %v", err)
 	}
-	if err := first.Release(); err != nil {
-		t.Fatalf("release first: %v", err)
-	}
-	releasedInfo, err := os.Stat(path)
-	if err != nil {
-		t.Fatalf("release removed stable lock path: %v", err)
-	}
-	if !os.SameFile(firstInfo, releasedInfo) {
-		t.Fatal("release replaced the stable lock file")
-	}
-
-	second, err := TryAcquireFileLock(path)
-	if err != nil {
-		t.Fatalf("acquire after release: %v", err)
-	}
-	secondInfo, err := os.Stat(path)
-	if err != nil {
-		t.Fatalf("stat second lock path: %v", err)
-	}
-	if !os.SameFile(firstInfo, secondInfo) {
-		t.Fatal("reacquire used a different lock file")
-	}
-	if err := second.Release(); err != nil {
-		t.Fatalf("release second: %v", err)
-	}
-	if err := second.Release(); err != nil {
-		t.Fatalf("idempotent release: %v", err)
+	// Removing an already-missing lock file is a no-op on every platform.
+	if err := RemoveLockFile(path); err != nil {
+		t.Fatalf("RemoveLockFile on a missing file = %v, want nil", err)
 	}
 }
-
-func TestFileLockMetadata(t *testing.T) {
-	path := filepath.Join(t.TempDir(), "lock")
-	lock, err := TryAcquireFileLock(path)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if err := lock.WriteMetadata([]byte("holder\n")); err != nil {
-		t.Fatalf("write metadata: %v", err)
-	}
-	data, err := os.ReadFile(path)
-	if err != nil || string(data) != "holder\n" {
-		t.Fatalf("metadata = %q, err %v", data, err)
-	}
-	if err := lock.Release(); err != nil {
-		t.Fatal(err)
-	}
-	if err := lock.WriteMetadata(nil); !errors.Is(err, ErrLockReleased) {
-		t.Fatalf("write after release = %v, want ErrLockReleased", err)
-	}
-}
-
-func TestFileLockConcurrentFirstAcquisition(t *testing.T) {
-	path := filepath.Join(t.TempDir(), "lock")
-	const contenders = 200
-	start := make(chan struct{})
-	results := make(chan error, contenders)
-	locks := make(chan *FileLock, contenders)
-	var ready sync.WaitGroup
-	ready.Add(contenders)
-	for range contenders {
-		go func() {
-			ready.Done()
-			<-start
-			lock, err := TryAcquireFileLock(path)
-			if lock != nil {
-				locks <- lock
-			}
-			results <- err
-		}()
-	}
-	ready.Wait()
-	close(start)
-	acquired := 0
-	for range contenders {
-		err := <-results
-		switch {
-		case err == nil:
-			acquired++
-		case !errors.Is(err, ErrLockHeld):
-			t.Errorf("concurrent first acquire: %v", err)
-		}
-	}
-	close(locks)
-	for lock := range locks {
-		if err := lock.Release(); err != nil {
-			t.Error(err)
-		}
-	}
-	if acquired != 1 {
-		t.Fatalf("concurrent first acquire: got %d holders, want 1", acquired)
-	}
-}
-
-func TestFileLockRefusesMultiplyLinkedEntry(t *testing.T) {
-	dir := t.TempDir()
-	target := filepath.Join(dir, "target")
-	lockPath := filepath.Join(dir, "lock")
-	const sentinel = "do not overwrite"
-	if err := os.WriteFile(target, []byte(sentinel), 0o600); err != nil {
-		t.Fatal(err)
-	}
-	if err := os.Link(target, lockPath); err != nil {
-		t.Fatalf("create redirected hard link: %v", err)
-	}
-	if lock, err := TryAcquireFileLock(lockPath); err == nil {
-		_ = lock.Release()
-		t.Fatal("TryAcquireFileLock accepted a multiply-linked entry")
-	}
-	data, err := os.ReadFile(target)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if string(data) != sentinel {
-		t.Fatalf("redirected target was modified: %q", data)
-	}
-}
-
-func TestFileLockAtRejectsEscapingPath(t *testing.T) {
-	base := t.TempDir()
-	outside := filepath.Join(filepath.Dir(base), "outside.lock")
-	if lock, err := TryAcquireFileLockAt(base, outside); err == nil {
-		_ = lock.Release()
-		t.Fatal("TryAcquireFileLockAt accepted a path outside its root")
-	}
-	if _, err := os.Stat(outside); !errors.Is(err, os.ErrNotExist) {
-		t.Fatalf("escaping path was created: %v", err)
-	}
-}
-
-// TestFileLockReleasedByProcessExit proves crash recovery is provided by the
-// kernel lock lifetime. The child exits without calling Release; the next
-// process can then lock the same persistent file without moving or deleting it.
-func TestFileLockReleasedByProcessExit(t *testing.T) {
-	path := filepath.Join(t.TempDir(), "lock")
-	cmd := exec.Command(os.Args[0], "-test.run=^TestFileLockHelperProcess$")
-	cmd.Env = append(os.Environ(), "ZERO_LOCKUTIL_HELPER=1", "ZERO_LOCKUTIL_PATH="+path)
-	stdout, err := cmd.StdoutPipe()
-	if err != nil {
-		t.Fatal(err)
-	}
-	stdin, err := cmd.StdinPipe()
-	if err != nil {
-		t.Fatal(err)
-	}
-	cmd.Stderr = os.Stderr
-	if err := cmd.Start(); err != nil {
-		t.Fatal(err)
-	}
-
-	ready, err := bufio.NewReader(stdout).ReadString('\n')
-	if err != nil || strings.TrimSpace(ready) != "ready" {
-		_ = cmd.Process.Kill()
-		_ = cmd.Wait()
-		t.Fatalf("helper readiness = %q, err %v", ready, err)
-	}
-	if _, err := TryAcquireFileLock(path); !errors.Is(err, ErrLockHeld) {
-		_ = cmd.Process.Kill()
-		_ = cmd.Wait()
-		t.Fatalf("acquire while helper holds lock = %v, want ErrLockHeld", err)
-	}
-	if err := stdin.Close(); err != nil {
-		t.Fatal(err)
-	}
-	if err := cmd.Wait(); err != nil {
-		t.Fatalf("helper exit: %v", err)
-	}
-
-	lock, err := TryAcquireFileLock(path)
-	if err != nil {
-		t.Fatalf("acquire after helper exit: %v", err)
-	}
-	if err := lock.Release(); err != nil {
-		t.Fatal(err)
-	}
-}
-
-func TestFileLockHelperProcess(t *testing.T) {
-	if os.Getenv("ZERO_LOCKUTIL_HELPER") != "1" {
-		return
-	}
-	lock, err := TryAcquireFileLock(os.Getenv("ZERO_LOCKUTIL_PATH"))
-	if err != nil {
-		fmt.Fprintln(os.Stderr, err)
-		os.Exit(2)
-	}
-	if _, err := fmt.Fprintln(os.Stdout, "ready"); err != nil {
-		os.Exit(3)
-	}
-	_, _ = io.Copy(io.Discard, os.Stdin)
-	runtime.KeepAlive(lock) // deliberately exit without Release
-}

internal/lockutil/lockutil_windows.go

@@ -4,202 +4,77 @@ package lockutil
 
 import (
 	"errors"
-	"fmt"
 	"os"
-	"path/filepath"
-	"strings"
-	"unsafe"
+	"syscall"
+	"time"
 
 	"golang.org/x/sys/windows"
 )
 
-type platformLockState struct {
-	overlapped windows.Overlapped
+// RestoreLockFile restores a sidelined lock file on Windows. It moves the file
+// with a no-replace MoveFileEx so a competing lock created at path in the
+// meantime wins: the move fails with os.ErrExist instead of overwriting it. If
+// the move fails for any other reason (ERROR_SHARING_VIOLATION or
+// ERROR_ACCESS_DENIED under concurrent access to the file), it falls back to
+// an O_EXCL copy rather than leaving path missing and the live holder's lock
+// stranded in reclaimed.
+func RestoreLockFile(reclaimed, path string) error {
+	err := moveFileNoReplace(reclaimed, path)
+	if err == nil || errors.Is(err, os.ErrExist) {
+		return err
+	}
+	return restoreByCopy(reclaimed, path, moveFileNoReplace)
 }
 
-const lockByteOffsetHigh = 1
-
-func openLockFileAt(root, relative, displayPath string) (_ *os.File, resultErr error) {
-	rootPtr, err := windows.UTF16PtrFromString(root)
+// moveFileNoReplace renames from to to, failing if to already exists. It calls
+// MoveFileExW directly via golang.org/x/sys/windows (the standard library's
+// syscall package does not export MoveFileEx on this platform) with no flags,
+// so an existing destination fails with ERROR_ALREADY_EXISTS, which satisfies
+// errors.Is(err, os.ErrExist) (pinned by
+// TestMoveFileNoReplaceMapsAlreadyExistsToErrExist), instead of overwriting it
+// the way os.Rename does on Windows (it passes MOVEFILE_REPLACE_EXISTING to
+// match POSIX rename semantics cross-platform).
+func moveFileNoReplace(from, to string) error {
+	fromPtr, err := windows.UTF16PtrFromString(from)
 	if err != nil {
-		return nil, err
+		return err
 	}
-	parent, err := windows.CreateFile(
-		rootPtr,
-		windows.FILE_READ_ATTRIBUTES|windows.FILE_TRAVERSE|windows.SYNCHRONIZE,
-		windows.FILE_SHARE_READ|windows.FILE_SHARE_WRITE|windows.FILE_SHARE_DELETE,
-		nil,
-		windows.OPEN_EXISTING,
-		windows.FILE_FLAG_BACKUP_SEMANTICS,
-		0,
-	)
+	toPtr, err := windows.UTF16PtrFromString(to)
 	if err != nil {
-		return nil, fmt.Errorf("open lock root: %w", err)
+		return err
 	}
-	defer func() {
-		if parent != 0 {
-			resultErr = errors.Join(resultErr, windows.CloseHandle(parent))
-		}
-	}()
-
-	components := strings.Split(filepath.Clean(relative), string(filepath.Separator))
-	for _, component := range components[:len(components)-1] {
-		next, openErr := openLockDirectoryAt(parent, component)
-		if openErr != nil {
-			return nil, fmt.Errorf("open lock path component %q: %w", component, openErr)
-		}
-		if closeErr := windows.CloseHandle(parent); closeErr != nil {
-			_ = windows.CloseHandle(next)
-			parent = 0
-			return nil, fmt.Errorf("close lock path component: %w", closeErr)
-		}
-		parent = next
-	}
-
-	handle, err := openLockFileHandleAt(parent, components[len(components)-1])
-	if err != nil {
-		return nil, err
-	}
-	file := os.NewFile(uintptr(handle), displayPath)
-	if file == nil {
-		_ = windows.CloseHandle(handle)
-		return nil, errors.New("convert lock handle to file")
-	}
-	if err := windows.CloseHandle(parent); err != nil {
-		parent = 0
-		return nil, errors.Join(fmt.Errorf("close lock parent: %w", err), file.Close())
-	}
-	parent = 0
-	return file, nil
+	return windows.MoveFileEx(fromPtr, toPtr, 0)
 }
 
-func openLockDirectoryAt(parent windows.Handle, name string) (windows.Handle, error) {
-	handle, err := openLockPathAt(
-		parent,
-		name,
-		windows.FILE_READ_ATTRIBUTES|windows.FILE_TRAVERSE|windows.SYNCHRONIZE,
-		windows.FILE_OPEN,
-		windows.FILE_ATTRIBUTE_DIRECTORY,
-		windows.FILE_DIRECTORY_FILE|windows.FILE_SYNCHRONOUS_IO_NONALERT|windows.FILE_OPEN_REPARSE_POINT,
-	)
-	if err != nil {
-		return 0, err
-	}
-	if err := validateWindowsLockHandle(handle, true); err != nil {
-		return 0, errors.Join(err, windows.CloseHandle(handle))
-	}
-	return handle, nil
+// isReclaimContended reports whether a failed rename-aside of a suspected
+// stale lock means the file was concurrently open or pending deletion (which
+// surfaces as ERROR_SHARING_VIOLATION or ERROR_ACCESS_DENIED on Windows)
+// rather than a hard failure, so ReclaimStaleLock reports a lost race instead
+// of an error. Neither errno satisfies errors.Is(err, os.ErrExist), and
+// ERROR_SHARING_VIOLATION does not satisfy errors.Is(err, os.ErrPermission)
+// either, so the classification compares raw errnos like RemoveLockFile below.
+func isReclaimContended(err error) bool {
+	var errno syscall.Errno
+	return errors.As(err, &errno) && (errno == windows.ERROR_SHARING_VIOLATION || errno == windows.ERROR_ACCESS_DENIED)
 }
 
-func openLockFileHandleAt(parent windows.Handle, name string) (windows.Handle, error) {
-	for attempt := 0; attempt < 10; attempt++ {
-		handle, err := openLockPathAt(
-			parent,
-			name,
-			windows.GENERIC_READ|windows.GENERIC_WRITE|windows.SYNCHRONIZE,
-			windows.FILE_OPEN,
-			windows.FILE_ATTRIBUTE_NORMAL,
-			windows.FILE_NON_DIRECTORY_FILE|windows.FILE_SYNCHRONOUS_IO_NONALERT|windows.FILE_OPEN_REPARSE_POINT,
-		)
-		if err == nil {
-			if err := validateWindowsLockHandle(handle, false); err != nil {
-				return 0, errors.Join(err, windows.CloseHandle(handle))
-			}
-			return handle, nil
+// RemoveLockFile removes a lock file on Windows, retrying on the sharing
+// violation or access denied errors that are common under heavy concurrent
+// contention. Removing an already-missing file reports nil, matching the
+// non-Windows implementation, so callers see one cross-platform contract.
+func RemoveLockFile(path string) error {
+	var err error
+	for i := 0; i < 15; i++ {
+		err = os.Remove(path)
+		if err == nil || os.IsNotExist(err) {
+			return nil
 		}
-		if !windowsLockPathMissing(err) {
-			return 0, err
-		}
-
-		handle, err = openLockPathAt(
-			parent,
-			name,
-			windows.GENERIC_READ|windows.GENERIC_WRITE|windows.SYNCHRONIZE,
-			windows.FILE_CREATE,
-			windows.FILE_ATTRIBUTE_NORMAL,
-			windows.FILE_NON_DIRECTORY_FILE|windows.FILE_SYNCHRONOUS_IO_NONALERT|windows.FILE_OPEN_REPARSE_POINT,
-		)
-		if err == windows.STATUS_OBJECT_NAME_COLLISION || errors.Is(err, windows.ERROR_ALREADY_EXISTS) {
+		var errno syscall.Errno
+		if errors.As(err, &errno) && (errno == windows.ERROR_SHARING_VIOLATION || errno == windows.ERROR_ACCESS_DENIED) {
+			time.Sleep(5 * time.Millisecond)
 			continue
 		}
-		if err != nil {
-			return 0, err
-		}
-		if err := validateWindowsLockHandle(handle, false); err != nil {
-			return 0, errors.Join(err, windows.CloseHandle(handle))
-		}
-		return handle, nil
+		return err
 	}
-	return 0, errors.New("lock file creation did not stabilize")
-}
-
-func windowsLockPathMissing(err error) bool {
-	return err == windows.STATUS_NO_SUCH_FILE ||
-		err == windows.STATUS_OBJECT_NAME_NOT_FOUND ||
-		err == windows.STATUS_OBJECT_PATH_NOT_FOUND ||
-		errors.Is(err, windows.ERROR_FILE_NOT_FOUND) ||
-		errors.Is(err, windows.ERROR_PATH_NOT_FOUND)
-}
-
-func openLockPathAt(parent windows.Handle, name string, access, disposition, attributes, options uint32) (windows.Handle, error) {
-	objectName, err := windows.NewNTUnicodeString(name)
-	if err != nil {
-		return 0, err
-	}
-	objectAttributes := &windows.OBJECT_ATTRIBUTES{
-		Length:        uint32(unsafe.Sizeof(windows.OBJECT_ATTRIBUTES{})),
-		RootDirectory: parent,
-		ObjectName:    objectName,
-		Attributes:    windows.OBJ_CASE_INSENSITIVE | windows.OBJ_DONT_REPARSE,
-	}
-	var handle windows.Handle
-	err = windows.NtCreateFile(
-		&handle,
-		access,
-		objectAttributes,
-		&windows.IO_STATUS_BLOCK{},
-		nil,
-		attributes,
-		windows.FILE_SHARE_READ|windows.FILE_SHARE_WRITE|windows.FILE_SHARE_DELETE,
-		disposition,
-		options,
-		0,
-		0,
-	)
-	return handle, err
-}
-
-func validateWindowsLockHandle(handle windows.Handle, wantDirectory bool) error {
-	var info windows.ByHandleFileInformation
-	if err := windows.GetFileInformationByHandle(handle, &info); err != nil {
-		return fmt.Errorf("inspect lock path handle: %w", err)
-	}
-	isDirectory := info.FileAttributes&windows.FILE_ATTRIBUTE_DIRECTORY != 0
-	if info.FileAttributes&windows.FILE_ATTRIBUTE_REPARSE_POINT != 0 || isDirectory != wantDirectory {
-		return errors.New("refusing non-file or reparse-point lock path")
-	}
-	if !wantDirectory && info.NumberOfLinks != 1 {
-		return errors.New("refusing multiply-linked lock file")
-	}
-	return nil
-}
-
-func tryLockFile(file *os.File) (platformLockState, bool, error) {
-	state := platformLockState{overlapped: windows.Overlapped{OffsetHigh: lockByteOffsetHigh}}
-	flags := uint32(windows.LOCKFILE_EXCLUSIVE_LOCK | windows.LOCKFILE_FAIL_IMMEDIATELY)
-	err := windows.LockFileEx(windows.Handle(file.Fd()), flags, 0, 1, 0, &state.overlapped)
-	if err == nil {
-		return state, false, nil
-	}
-	if errors.Is(err, windows.ERROR_LOCK_VIOLATION) || errors.Is(err, windows.ERROR_SHARING_VIOLATION) {
-		return platformLockState{}, true, nil
-	}
-	return platformLockState{}, false, err
-}
-
-func unlockFile(file *os.File, state *platformLockState) error {
-	if file == nil {
-		return nil
-	}
-	return windows.UnlockFileEx(windows.Handle(file.Fd()), 0, 1, 0, &state.overlapped)
+	return err
 }

internal/lockutil/lockutil_windows_test.go

@@ -0,0 +1,83 @@
+//go:build windows
+
+package lockutil
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"golang.org/x/sys/windows"
+)
+
+// TestMoveFileNoReplaceMapsAlreadyExistsToErrExist pins the errno coupling
+// every caller keys its cleanup on: with no flags, MoveFileEx fails with
+// ERROR_ALREADY_EXISTS when the destination exists, and that errno must
+// satisfy errors.Is(err, os.ErrExist).
+func TestMoveFileNoReplaceMapsAlreadyExistsToErrExist(t *testing.T) {
+	dir := t.TempDir()
+	from := filepath.Join(dir, "from")
+	to := filepath.Join(dir, "to")
+	if err := os.WriteFile(from, []byte("sidelined"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(to, []byte("competing"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	err := moveFileNoReplace(from, to)
+	if !errors.Is(err, windows.ERROR_ALREADY_EXISTS) {
+		t.Fatalf("MoveFileEx with an existing destination = %v, want ERROR_ALREADY_EXISTS", err)
+	}
+	if !errors.Is(err, os.ErrExist) {
+		t.Fatalf("ERROR_ALREADY_EXISTS must satisfy errors.Is(err, os.ErrExist), got: %v", err)
+	}
+	if data, _ := os.ReadFile(to); string(data) != "competing" {
+		t.Fatalf("destination was overwritten: %q", data)
+	}
+}
+
+// TestRemoveLockFileRetriesSharingViolation holds the file open briefly (Go
+// opens files without FILE_SHARE_DELETE on Windows, so a concurrent DeleteFile
+// fails with ERROR_SHARING_VIOLATION while the handle is open); RemoveLockFile
+// must ride its retry loop (15 x 5ms) past the window and succeed once the
+// handle closes.
+func TestRemoveLockFileRetriesSharingViolation(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "lock")
+	if err := os.WriteFile(path, []byte("token"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	f, err := os.Open(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	go func() {
+		time.Sleep(10 * time.Millisecond)
+		_ = f.Close()
+	}()
+	if err := RemoveLockFile(path); err != nil {
+		t.Fatalf("RemoveLockFile should succeed once the contending handle closes: %v", err)
+	}
+	if _, err := os.Stat(path); !errors.Is(err, os.ErrNotExist) {
+		t.Fatalf("expected lock file to be removed: %v", err)
+	}
+}
+
+// TestRemoveLockFileSharingViolationExhausts verifies the retry loop is
+// bounded: with the contending handle held for the whole call, RemoveLockFile
+// surfaces the sharing violation instead of retrying forever.
+func TestRemoveLockFileSharingViolationExhausts(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "lock")
+	if err := os.WriteFile(path, []byte("token"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	f, err := os.Open(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	if err := RemoveLockFile(path); !errors.Is(err, windows.ERROR_SHARING_VIOLATION) {
+		t.Fatalf("RemoveLockFile with a held handle = %v, want ERROR_SHARING_VIOLATION", err)
+	}
+}

internal/lockutil/reclaim.go

@@ -0,0 +1,82 @@
+package lockutil
+
+import (
+	"errors"
+	"os"
+)
+
+// restoreLockFile is swappable so tests can force the fail-closed path of
+// ReclaimStaleLock, which requires both the fast restore and its no-replace
+// fallback (with its own copy fallback) to fail; that cannot be provoked
+// portably on a healthy filesystem.
+var restoreLockFile = restoreLiveLock
+
+// restoreLiveLock puts a lock that turned out to be live back at path after
+// ReclaimStaleLock moved it aside to inspect it. It first tries a fast,
+// replacing rename straight from reclaimed to path: a single syscall, which
+// keeps the window during which path does not exist (and so is open to a
+// fourth process's unrelated O_EXCL create landing on it) as short as
+// possible. RestoreLockFile's no-replace restore (with its slower copy
+// fallback on some failures) is a correctness-preserving fallback for when
+// the fast path itself fails (e.g. a cross-device sidelined name): it is a
+// much longer version of the identical race, but still detects rather than
+// silently clobbers a competing lock, which the fast path's replacing rename
+// cannot do. Neither path makes the race impossible, only unlikely; see
+// ReclaimStaleLock's doc comment.
+func restoreLiveLock(reclaimed, path string) error {
+	if err := os.Rename(reclaimed, path); err == nil {
+		return nil
+	}
+	return RestoreLockFile(reclaimed, path)
+}
+
+// ReclaimStaleLock atomically reclaims a suspected-stale lock file. It renames
+// lockPath aside to "<lockPath>.stale.<suffix>" (only one racer can win the
+// rename of a given file, so two racers can never both reclaim the same lock),
+// then consults isLive on the moved file; if the lock turns out to be live (a
+// holder reacquired it in the gap between the caller's stale check and the
+// rename) it is restored rather than stolen. The suffix must be unique per
+// acquirer attempt. Returns true only when a genuinely stale lock was removed,
+// so the caller knows it is safe to retry its exclusive create immediately; on
+// a lost race it returns false. A non-nil error means either the rename aside
+// failed for a reason that is not contention (so retrying cannot help and the
+// caller should fail fast instead of spinning to its deadline), or a live
+// holder's lock could not be restored (both restoreLiveLock's fast path and
+// its no-replace fallback failed), so lockPath may be missing; callers must
+// fail closed instead of re-acquiring. The sidelined file is removed on every
+// restore failure: once the restore has failed it has no protocol function
+// (release only consults the lock path), so keeping it would only leak files.
+//
+// The live-restore path has an inherent, unclosed race: between the rename
+// aside above and restoreLiveLock putting the lock back, lockPath does not
+// exist, so an unrelated caller's O_EXCL create can legitimately succeed
+// there. restoreLiveLock's fast path then silently overwrites that new
+// claimant's lock file, which does not corrupt release (it is
+// ownership-aware, so the new claimant's later release safely no-ops against
+// content it no longer owns) but does mean the new claimant can still run
+// its critical section concurrently with the original live holder. Making
+// this race actually impossible would need an OS-level advisory lock (flock
+// / LockFileEx) held for a holder's whole critical section, checked
+// non-destructively instead of by moving the file; restoreLiveLock only
+// shrinks the window to roughly one syscall, it does not close it.
+func ReclaimStaleLock(lockPath, suffix string, isLive func(reclaimedPath string) bool) (bool, error) {
+	reclaimed := lockPath + ".stale." + suffix
+	if err := os.Rename(lockPath, reclaimed); err != nil {
+		if errors.Is(err, os.ErrNotExist) || isReclaimContended(err) {
+			return false, nil // another racer already moved/removed it, or it vanished
+		}
+		return false, err
+	}
+	if isLive(reclaimed) {
+		// Put the live lock back instead of stealing it, and let the caller wait.
+		if rerr := restoreLockFile(reclaimed, lockPath); rerr != nil {
+			_ = RemoveLockFile(reclaimed)
+			if !errors.Is(rerr, os.ErrExist) {
+				return false, rerr
+			}
+		}
+		return false, nil
+	}
+	_ = RemoveLockFile(reclaimed)
+	return true, nil
+}

internal/lockutil/reclaim_other_test.go

@@ -0,0 +1,31 @@
+//go:build !windows
+
+package lockutil
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// TestReclaimStaleLockPropagatesRenameFailure pins the fail-fast contract of
+// the rename aside: a failure that is not a lost race must reach the caller.
+// Mapping it to the benign lost-race result would leave acquirers spinning
+// until their deadline and reporting a timeout instead of the real cause. A
+// directory squatting on the sidelined name makes os.Rename fail with EISDIR,
+// which matches neither os.ErrNotExist nor a contention errno.
+func TestReclaimStaleLockPropagatesRenameFailure(t *testing.T) {
+	lockPath := filepath.Join(t.TempDir(), "lock")
+	if err := os.WriteFile(lockPath, []byte("stale-holder"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Mkdir(lockPath+".stale.tok", 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if ok, err := ReclaimStaleLock(lockPath, "tok", func(string) bool { return false }); err == nil || ok {
+		t.Fatalf("a hard rename failure must surface an error (ok=%v err=%v)", ok, err)
+	}
+	if _, err := os.Stat(lockPath); err != nil {
+		t.Fatalf("the lock file must be left in place on a failed rename: %v", err)
+	}
+}

internal/lockutil/reclaim_test.go

@@ -0,0 +1,112 @@
+package lockutil
+
+import (
+	"errors"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestReclaimStaleLock(t *testing.T) {
+	lockPath := filepath.Join(t.TempDir(), "lock")
+	dead := func(string) bool { return false }
+	live := func(string) bool { return true }
+
+	// A lock the predicate reports dead is reclaimed and removed.
+	if err := os.WriteFile(lockPath, []byte("crashed-holder"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if ok, err := ReclaimStaleLock(lockPath, "tok-a", dead); err != nil || !ok {
+		t.Fatalf("a dead lock should be reclaimed (ok=%v err=%v)", ok, err)
+	}
+	if _, err := os.Stat(lockPath); !errors.Is(err, os.ErrNotExist) {
+		t.Fatalf("reclaimed dead lock should be gone, stat err=%v", err)
+	}
+
+	// A LIVE lock (a holder reacquired in the gap) must be RESTORED intact.
+	if err := os.WriteFile(lockPath, []byte("live-holder"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if ok, err := ReclaimStaleLock(lockPath, "tok-b", live); err != nil || ok {
+		t.Fatalf("a live lock must not be reclaimed (ok=%v err=%v)", ok, err)
+	}
+	if data, err := os.ReadFile(lockPath); err != nil || string(data) != "live-holder" {
+		t.Fatalf("live lock must be left intact, got %q err %v", data, err)
+	}
+
+	// A missing lock reports no reclaim (nothing to steal).
+	_ = os.Remove(lockPath)
+	if ok, err := ReclaimStaleLock(lockPath, "tok-c", live); err != nil || ok {
+		t.Fatalf("a missing lock should not report a reclaim (ok=%v err=%v)", ok, err)
+	}
+}
+
+// restoreLiveLock's fast path is a single replacing rename, chosen to
+// minimize (not eliminate) the window during which lockPath is absent and
+// open to an unrelated O_EXCL create; see ReclaimStaleLock's doc comment for
+// why that residual race exists. This test pins the resulting behavior: the
+// fast path overwrites a competing file at path rather than detecting it,
+// unlike RestoreLockFile's own no-replace contract.
+func TestRestoreLiveLockFastPathOverwritesCompetingFile(t *testing.T) {
+	dir := t.TempDir()
+	reclaimed := filepath.Join(dir, "lock.stale.tok")
+	path := filepath.Join(dir, "lock")
+
+	if err := os.WriteFile(reclaimed, []byte("original-holder"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(path, []byte("new-claimant"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := restoreLiveLock(reclaimed, path); err != nil {
+		t.Fatalf("restoreLiveLock failed: %v", err)
+	}
+	data, err := os.ReadFile(path)
+	if err != nil || string(data) != "original-holder" {
+		t.Fatalf("path = %q, err %v; want the original holder's content restored", data, err)
+	}
+	if _, err := os.Stat(reclaimed); !errors.Is(err, os.ErrNotExist) {
+		t.Fatalf("expected reclaimed to be consumed by the rename: %v", err)
+	}
+}
+
+func TestReclaimStaleLockFailsClosedOnRestoreError(t *testing.T) {
+	// When both the no-replace restore and its copy fallback fail (only
+	// provokable via the seam; a healthy filesystem cannot produce it), the
+	// caller must receive an error so it fails closed instead of re-acquiring a
+	// missing lock path, and the sidelined file must not leak.
+	restoreLockFile = func(reclaimed, path string) error { return errors.New("restore failed") }
+	defer func() { restoreLockFile = restoreLiveLock }()
+
+	lockPath := filepath.Join(t.TempDir(), "lock")
+	if err := os.WriteFile(lockPath, []byte("live-holder"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	ok, err := ReclaimStaleLock(lockPath, "tok", func(string) bool { return true })
+	if err == nil || ok {
+		t.Fatalf("a failed restore must surface an error (ok=%v err=%v)", ok, err)
+	}
+	if matches, _ := filepath.Glob(lockPath + ".stale.*"); len(matches) != 0 {
+		t.Fatalf("a failed restore must not leak sidelined files: %v", matches)
+	}
+}
+
+func TestReclaimStaleLockDropsSidelinedWhenNewHolderWins(t *testing.T) {
+	// An os.ErrExist restore failure means a new holder recreated the lock
+	// path; that is not an error for the caller, and the sidelined file is
+	// dropped rather than leaked.
+	restoreLockFile = func(reclaimed, path string) error { return os.ErrExist }
+	defer func() { restoreLockFile = restoreLiveLock }()
+
+	lockPath := filepath.Join(t.TempDir(), "lock")
+	if err := os.WriteFile(lockPath, []byte("live-holder"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	ok, err := ReclaimStaleLock(lockPath, "tok", func(string) bool { return true })
+	if err != nil || ok {
+		t.Fatalf("losing to a new holder is not an error (ok=%v err=%v)", ok, err)
+	}
+	if matches, _ := filepath.Glob(lockPath + ".stale.*"); len(matches) != 0 {
+		t.Fatalf("the sidelined file must be dropped when a new holder wins: %v", matches)
+	}
+}

internal/lockutil/reclaim_windows_test.go

@@ -0,0 +1,50 @@
+//go:build windows
+
+package lockutil
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+// TestReclaimStaleLockTreatsSharingViolationAsLostRace pins the errno
+// classification the Windows acquire loops depend on: a rename aside that
+// fails because the lock file is concurrently open (Go opens files without
+// FILE_SHARE_DELETE, so the rename fails with ERROR_SHARING_VIOLATION or
+// ERROR_ACCESS_DENIED) is contention, not a hard failure, and must report a
+// benign lost race so the caller keeps waiting.
+func TestReclaimStaleLockTreatsSharingViolationAsLostRace(t *testing.T) {
+	lockPath := filepath.Join(t.TempDir(), "lock")
+	if err := os.WriteFile(lockPath, []byte("held"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	f, err := os.Open(lockPath)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	if ok, rerr := ReclaimStaleLock(lockPath, "tok", func(string) bool { return true }); rerr != nil || ok {
+		t.Fatalf("a sharing-violation rename must report a benign lost race (ok=%v err=%v)", ok, rerr)
+	}
+	if _, err := os.Stat(lockPath); err != nil {
+		t.Fatalf("the lock file must be left in place: %v", err)
+	}
+}
+
+// TestReclaimStaleLockPropagatesRenameFailure pins the fail-fast contract of
+// the rename aside on Windows: a failure that is not contention must reach
+// the caller instead of masquerading as a lost race. A quote is an invalid
+// filename character, so the sidelined name fails with ERROR_INVALID_NAME.
+func TestReclaimStaleLockPropagatesRenameFailure(t *testing.T) {
+	lockPath := filepath.Join(t.TempDir(), "lock")
+	if err := os.WriteFile(lockPath, []byte("stale-holder"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if ok, err := ReclaimStaleLock(lockPath, `bad"name`, func(string) bool { return false }); err == nil || ok {
+		t.Fatalf("a hard rename failure must surface an error (ok=%v err=%v)", ok, err)
+	}
+	if _, err := os.Stat(lockPath); err != nil {
+		t.Fatalf("the lock file must be left in place on a failed rename: %v", err)
+	}
+}

internal/mcp/oauth.go

@@ -63,9 +63,8 @@ func tokenToStored(t oauth.Token) StoredToken {
 }
 
 // OAuthConfig describes how to authenticate to a remote MCP server using OAuth.
-// Endpoints may be discovered through RFC 9728 protected-resource metadata and
-// RFC 8414 authorization-server metadata; explicit values override or fill in
-// anything discovery cannot provide.
+// Endpoints may be discovered from the server's metadata document; explicit
+// values here override or fill in anything discovery cannot provide.
 type OAuthConfig struct {
 	ClientID              string
 	ClientSecret          string
@@ -86,11 +85,6 @@ type authServerMetadata struct {
 	TokenEndpoint         string   `json:"token_endpoint"`
 	RegistrationEndpoint  string   `json:"registration_endpoint"`
 	ScopesSupported       []string `json:"scopes_supported"`
-
-	protectedResourceURL         string
-	protectAuthorizationEndpoint bool
-	protectTokenEndpoint         bool
-	protectRegistrationEndpoint  bool
 }
 
 // pkceParams holds a PKCE verifier/challenge pair.
@@ -126,7 +120,7 @@ type authorizationFlow struct {
 // discoverAuthorizationServer fetches the RFC 8414 authorization server metadata
 // at the well-known path under baseURL, via the shared engine.
 func discoverAuthorizationServer(ctx context.Context, client *http.Client, baseURL string) (authServerMetadata, error) {
-	meta, err := oauth.DiscoverAuthorizationServer(ctx, withoutDiscoveryRedirects(client), baseURL)
+	meta, err := oauth.DiscoverAuthorizationServer(ctx, client, baseURL)
 	if err != nil {
 		return authServerMetadata{}, err
 	}
@@ -139,9 +133,10 @@ func discoverAuthorizationServer(ctx context.Context, client *http.Client, baseU
 	}, nil
 }
 
-// validateResolvedEndpoints applies the shared https/loopback scheme rule to
-// every non-empty endpoint in the resolved metadata. Protected-resource
-// discovery adds its stricter provenance-aware network rule below.
+// validateResolvedEndpoints applies the shared https/loopback endpoint rule to
+// every non-empty endpoint in the resolved metadata — configured or discovered
+// alike — so discovery metadata can never downgrade an MCP login to an insecure
+// or attacker-controlled authorization, token, or registration endpoint.
 func validateResolvedEndpoints(metadata authServerMetadata) error {
 	for _, ep := range []struct{ kind, url string }{
 		{"authorization", metadata.AuthorizationEndpoint},
@@ -158,43 +153,9 @@ func validateResolvedEndpoints(metadata authServerMetadata) error {
 	return nil
 }
 
-func validateProtectedDiscoveredEndpoints(ctx context.Context, metadata authServerMetadata) error {
-	if metadata.protectedResourceURL == "" {
-		return nil
-	}
-	policy, err := newOAuthDiscoveryNetworkPolicy(metadata.protectedResourceURL)
-	if err != nil {
-		return err
-	}
-	for _, endpoint := range []struct {
-		kind      string
-		url       string
-		protected bool
-	}{
-		{kind: "authorization", url: metadata.AuthorizationEndpoint, protected: metadata.protectAuthorizationEndpoint},
-		{kind: "token", url: metadata.TokenEndpoint, protected: metadata.protectTokenEndpoint},
-		{kind: "registration", url: metadata.RegistrationEndpoint, protected: metadata.protectRegistrationEndpoint},
-	} {
-		if !endpoint.protected || strings.TrimSpace(endpoint.url) == "" {
-			continue
-		}
-		parsed, parseErr := url.Parse(endpoint.url)
-		if parseErr != nil || parsed.Hostname() == "" {
-			return fmt.Errorf("mcp oauth: %s endpoint: %w", endpoint.kind, errUnsafeOAuthDiscoveryTarget)
-		}
-		if err := policy.validateLiteralHost(parsed.Hostname()); err != nil {
-			return fmt.Errorf("mcp oauth: %s endpoint: %w", endpoint.kind, err)
-		}
-		if _, err := policy.resolve(ctx, parsed.Hostname()); err != nil {
-			return fmt.Errorf("mcp oauth: %s endpoint: %w", endpoint.kind, err)
-		}
-	}
-	return nil
-}
-
-// resolveAuthorizationServer follows protected-resource metadata when the MCP
-// endpoint advertises it, falls back to direct authorization-server discovery
-// for legacy providers, then applies explicit config overrides.
+// resolveAuthorizationServer discovers metadata and applies explicit config
+// overrides. Configured endpoints take precedence over discovered ones, and act
+// as a fallback when discovery fails or omits a value.
 func resolveAuthorizationServer(ctx context.Context, client *http.Client, baseURL string, cfg OAuthConfig) (authServerMetadata, error) {
 	// When the config supplies both the authorization and token endpoints
 	// directly, skip network discovery entirely: there is nothing to discover,
@@ -213,40 +174,17 @@ func resolveAuthorizationServer(ctx context.Context, client *http.Client, baseUR
 		return metadata, nil
 	}
 
-	discoveryClient := withoutDiscoveryRedirects(client)
 	discoveryBase := strings.TrimSpace(cfg.IssuerURL)
-	protectedResourceDiscovery := false
 	if discoveryBase == "" {
-		issuer, found, protectedErr := discoverProtectedResourceAuthorizationServer(ctx, discoveryClient, baseURL)
-		if protectedErr != nil {
-			return authServerMetadata{}, protectedErr
-		}
-		if found {
-			discoveryBase = issuer
-			protectedResourceDiscovery = true
-			discoveryClient, protectedErr = newAdvertisedOAuthDiscoveryClient(discoveryClient, baseURL)
-			if protectedErr != nil {
-				return authServerMetadata{}, protectedErr
-			}
-		} else {
-			discoveryBase = baseURL
-		}
+		discoveryBase = baseURL
 	}
 
-	metadata, err := discoverAuthorizationServer(ctx, discoveryClient, discoveryBase)
+	metadata, err := discoverAuthorizationServer(ctx, client, discoveryBase)
 	if err != nil {
 		// Discovery failures are non-fatal when the config supplies the endpoints
 		// directly; otherwise surface the discovery error.
 		metadata = authServerMetadata{}
 	}
-	if protectedResourceDiscovery {
-		if strings.TrimSpace(metadata.Issuer) == "" {
-			return authServerMetadata{}, errors.New("mcp oauth: authorization server metadata is missing its required issuer")
-		}
-		if metadata.Issuer != discoveryBase {
-			return authServerMetadata{}, errors.New("mcp oauth: authorization server metadata issuer does not match protected resource metadata")
-		}
-	}
 
 	if endpoint := strings.TrimSpace(cfg.AuthorizationEndpoint); endpoint != "" {
 		metadata.AuthorizationEndpoint = endpoint
@@ -257,12 +195,6 @@ func resolveAuthorizationServer(ctx context.Context, client *http.Client, baseUR
 	if endpoint := strings.TrimSpace(cfg.RegistrationEndpoint); endpoint != "" {
 		metadata.RegistrationEndpoint = endpoint
 	}
-	if protectedResourceDiscovery {
-		metadata.protectedResourceURL = strings.TrimSpace(baseURL)
-		metadata.protectAuthorizationEndpoint = strings.TrimSpace(cfg.AuthorizationEndpoint) == ""
-		metadata.protectTokenEndpoint = strings.TrimSpace(cfg.TokenEndpoint) == ""
-		metadata.protectRegistrationEndpoint = strings.TrimSpace(cfg.RegistrationEndpoint) == ""
-	}
 
 	if strings.TrimSpace(metadata.AuthorizationEndpoint) == "" {
 		return authServerMetadata{}, errors.New("no authorization endpoint discovered or configured")
@@ -273,9 +205,6 @@ func resolveAuthorizationServer(ctx context.Context, client *http.Client, baseUR
 	if err := validateResolvedEndpoints(metadata); err != nil {
 		return authServerMetadata{}, err
 	}
-	if err := validateProtectedDiscoveredEndpoints(ctx, metadata); err != nil {
-		return authServerMetadata{}, err
-	}
 	return metadata, nil
 }
 
@@ -434,25 +363,10 @@ func Login(ctx context.Context, options LoginOptions) (StoredToken, error) {
 	}
 	defer listener.Close()
 	redirectURI := fmt.Sprintf("http://%s/callback", listener.Addr().String())
-	protectedEndpointClient := httpClient
-	if metadata.protectRegistrationEndpoint || metadata.protectTokenEndpoint {
-		protectedEndpointClient, err = newAdvertisedOAuthDiscoveryClient(httpClient, metadata.protectedResourceURL)
-		if err != nil {
-			return StoredToken{}, err
-		}
-	}
-	tokenClient := httpClient
-	if metadata.protectTokenEndpoint {
-		tokenClient = protectedEndpointClient
-	}
 
 	if strings.TrimSpace(cfg.ClientID) == "" {
 		if registration := strings.TrimSpace(metadata.RegistrationEndpoint); registration != "" {
-			registrationClient := httpClient
-			if metadata.protectRegistrationEndpoint {
-				registrationClient = protectedEndpointClient
-			}
-			clientID, clientSecret, regErr := registerClient(loginCtx, registrationClient, registration, redirectURI, cfg.Scopes)
+			clientID, clientSecret, regErr := registerClient(loginCtx, httpClient, registration, redirectURI, cfg.Scopes)
 			if regErr != nil {
 				return StoredToken{}, regErr
 			}
@@ -476,7 +390,7 @@ func Login(ctx context.Context, options LoginOptions) (StoredToken, error) {
 	}
 
 	flow := &authorizationFlow{
-		httpClient: tokenClient,
+		httpClient: httpClient,
 		metadata:   metadata,
 		config:     cfg,
 		pkce:       pkce,

internal/mcp/oauth_discovery_network.go

@@ -1,290 +0,0 @@
-package mcp
-
-import (
-	"context"
-	"crypto/tls"
-	"errors"
-	"fmt"
-	"net"
-	"net/http"
-	"net/netip"
-	"net/url"
-	"strings"
-)
-
-var errUnsafeOAuthDiscoveryTarget = errors.New("mcp oauth: refused non-public server-advertised discovery target")
-
-var nonPublicOAuthDiscoveryPrefixes = []netip.Prefix{
-	netip.MustParsePrefix("0.0.0.0/8"),
-	netip.MustParsePrefix("10.0.0.0/8"),
-	netip.MustParsePrefix("100.64.0.0/10"),
-	netip.MustParsePrefix("127.0.0.0/8"),
-	netip.MustParsePrefix("169.254.0.0/16"),
-	netip.MustParsePrefix("172.16.0.0/12"),
-	netip.MustParsePrefix("192.0.0.0/24"),
-	netip.MustParsePrefix("192.0.2.0/24"),
-	netip.MustParsePrefix("192.88.99.0/24"),
-	netip.MustParsePrefix("192.168.0.0/16"),
-	netip.MustParsePrefix("198.18.0.0/15"),
-	netip.MustParsePrefix("198.51.100.0/24"),
-	netip.MustParsePrefix("203.0.113.0/24"),
-	netip.MustParsePrefix("224.0.0.0/4"),
-	netip.MustParsePrefix("240.0.0.0/4"),
-	netip.MustParsePrefix("::/128"),
-	netip.MustParsePrefix("::1/128"),
-	netip.MustParsePrefix("100::/64"),
-	netip.MustParsePrefix("2001:2::/48"),
-	netip.MustParsePrefix("2001:db8::/32"),
-	netip.MustParsePrefix("fc00::/7"),
-	netip.MustParsePrefix("fe80::/10"),
-	netip.MustParsePrefix("ff00::/8"),
-}
-
-type oauthDiscoveryNetworkPolicy struct {
-	allowLoopback bool
-	lookupNetIP   func(context.Context, string, string) ([]netip.Addr, error)
-}
-
-type advertisedOAuthDiscoveryTransport struct {
-	base   http.RoundTripper
-	policy oauthDiscoveryNetworkPolicy
-}
-
-// newAdvertisedOAuthDiscoveryClient binds server-advertised discovery to the
-// public network. Loopback targets remain available only when the operator
-// explicitly configured a loopback MCP resource.
-func newAdvertisedOAuthDiscoveryClient(client *http.Client, resourceURL string) (*http.Client, error) {
-	policy, err := newOAuthDiscoveryNetworkPolicy(resourceURL)
-	if err != nil {
-		return nil, err
-	}
-	copied := withoutDiscoveryRedirects(client)
-	transport := copied.Transport
-	if transport == nil {
-		transport = http.DefaultTransport
-	}
-	copied.Transport = advertisedOAuthDiscoveryTransport{base: transport, policy: policy}
-	return copied, nil
-}
-
-func newOAuthDiscoveryNetworkPolicy(resourceURL string) (oauthDiscoveryNetworkPolicy, error) {
-	parsed, err := url.Parse(strings.TrimSpace(resourceURL))
-	if err != nil || parsed.Hostname() == "" {
-		return oauthDiscoveryNetworkPolicy{}, errors.New("mcp oauth: invalid MCP resource URL for discovery policy")
-	}
-	return oauthDiscoveryNetworkPolicy{allowLoopback: isExplicitOAuthLoopbackHost(parsed.Hostname())}, nil
-}
-
-func validateAdvertisedOAuthDiscoveryURL(resourceURL string, targetURL string) error {
-	policy, err := newOAuthDiscoveryNetworkPolicy(resourceURL)
-	if err != nil {
-		return err
-	}
-	parsed, err := url.Parse(targetURL)
-	if err != nil || parsed.Hostname() == "" {
-		return errUnsafeOAuthDiscoveryTarget
-	}
-	return policy.validateLiteralHost(parsed.Hostname())
-}
-
-func (transport advertisedOAuthDiscoveryTransport) RoundTrip(request *http.Request) (*http.Response, error) {
-	if request == nil || request.URL == nil {
-		return nil, errors.New("mcp oauth: discovery request has no URL")
-	}
-	if err := transport.policy.validateLiteralHost(request.URL.Hostname()); err != nil {
-		return nil, err
-	}
-
-	baseTransport, ok := transport.base.(*http.Transport)
-	if !ok {
-		return nil, errors.New("mcp oauth: cannot enforce discovery network policy with a custom HTTP transport")
-	}
-	addresses, err := transport.policy.resolve(request.Context(), request.URL.Hostname())
-	if err != nil {
-		return nil, err
-	}
-	var lastErr error
-	for index, address := range addresses {
-		attempt := request
-		if index > 0 && request.Body != nil {
-			if request.GetBody == nil {
-				break
-			}
-			body, bodyErr := request.GetBody()
-			if bodyErr != nil {
-				return nil, bodyErr
-			}
-			attempt = request.Clone(request.Context())
-			attempt.Body = body
-		}
-		response, roundTripErr := roundTripPinnedOAuthDiscovery(attempt, baseTransport, address)
-		if roundTripErr == nil {
-			return response, nil
-		}
-		lastErr = roundTripErr
-	}
-	if lastErr == nil {
-		lastErr = errUnsafeOAuthDiscoveryTarget
-	}
-	return nil, lastErr
-}
-
-func roundTripPinnedOAuthDiscovery(request *http.Request, base *http.Transport, address netip.Addr) (*http.Response, error) {
-	pinnedRequest := request.Clone(request.Context())
-	pinnedURL := *request.URL
-	originalHost := request.URL.Hostname()
-	port := request.URL.Port()
-	if port == "" {
-		switch strings.ToLower(request.URL.Scheme) {
-		case "http":
-			port = "80"
-		case "https":
-			port = "443"
-		default:
-			return nil, errUnsafeOAuthDiscoveryTarget
-		}
-	}
-	pinnedURL.Host = net.JoinHostPort(address.String(), port)
-	pinnedRequest.URL = &pinnedURL
-	if pinnedRequest.Host == "" {
-		pinnedRequest.Host = request.URL.Host
-	}
-
-	pinnedTransport := base.Clone()
-	pinnedTransport.DisableKeepAlives = true
-	var proxyURL *url.URL
-	if base.Proxy != nil {
-		var err error
-		proxyURL, err = base.Proxy(request)
-		if err != nil {
-			return nil, fmt.Errorf("mcp oauth: resolve discovery proxy: %w", err)
-		}
-		if proxyURL == nil {
-			pinnedTransport.Proxy = nil
-		} else {
-			pinnedTransport.Proxy = http.ProxyURL(proxyURL)
-		}
-	}
-	if pinnedTransport.TLSClientConfig == nil {
-		pinnedTransport.TLSClientConfig = &tls.Config{ServerName: originalHost} //nolint:gosec // standard verification remains enabled
-	} else {
-		pinnedTransport.TLSClientConfig = pinnedTransport.TLSClientConfig.Clone()
-		pinnedTransport.TLSClientConfig.ServerName = originalHost
-	}
-	// A custom TLS dialer must not resolve the advertised hostname again after
-	// the policy has pinned it. For an HTTPS proxy, however, that proxy remains
-	// the TLS first hop and the transport sends CONNECT to the pinned target.
-	dialContext := pinnedTransport.DialContext
-	if dialContext == nil {
-		dialContext = (&net.Dialer{}).DialContext
-	}
-	pinnedAddress := net.JoinHostPort(address.String(), port)
-	targetTLSConfig := pinnedTransport.TLSClientConfig
-	pinnedTransport.DialTLSContext = func(ctx context.Context, network string, address string) (net.Conn, error) {
-		if proxyURL != nil && strings.EqualFold(proxyURL.Scheme, "https") {
-			proxyTLSConfig := targetTLSConfig.Clone()
-			proxyTLSConfig.ServerName = proxyURL.Hostname()
-			return dialOAuthDiscoveryTLS(ctx, dialContext, network, address, proxyTLSConfig)
-		}
-		return dialOAuthDiscoveryTLS(ctx, dialContext, network, pinnedAddress, targetTLSConfig)
-	}
-	return pinnedTransport.RoundTrip(pinnedRequest)
-}
-
-func dialOAuthDiscoveryTLS(ctx context.Context, dialContext func(context.Context, string, string) (net.Conn, error), network string, address string, config *tls.Config) (net.Conn, error) {
-	connection, err := dialContext(ctx, network, address)
-	if err != nil {
-		return nil, err
-	}
-	tlsConnection := tls.Client(connection, config)
-	if err := tlsConnection.HandshakeContext(ctx); err != nil {
-		connection.Close()
-		return nil, err
-	}
-	return tlsConnection, nil
-}
-
-func (policy oauthDiscoveryNetworkPolicy) resolve(ctx context.Context, host string) ([]netip.Addr, error) {
-	if address, err := netip.ParseAddr(strings.Trim(host, "[]")); err == nil {
-		address = address.Unmap()
-		if err := policy.validateAddress(address); err != nil {
-			return nil, err
-		}
-		return []netip.Addr{address}, nil
-	}
-
-	lookupNetIP := policy.lookupNetIP
-	if lookupNetIP == nil {
-		lookupNetIP = net.DefaultResolver.LookupNetIP
-	}
-	addresses, err := lookupNetIP(ctx, "ip", host)
-	if err != nil {
-		return nil, errors.New("mcp oauth: resolve server-advertised discovery target failed")
-	}
-	if len(addresses) == 0 {
-		return nil, errors.New("mcp oauth: server-advertised discovery target resolved to no addresses")
-	}
-	explicitLoopback := isExplicitOAuthLoopbackHost(host)
-	resolved := make([]netip.Addr, 0, len(addresses))
-	for _, address := range addresses {
-		address = address.Unmap()
-		if explicitLoopback && !address.IsLoopback() {
-			return nil, errUnsafeOAuthDiscoveryTarget
-		}
-		if err := policy.validateAddress(address); err != nil {
-			return nil, err
-		}
-		resolved = append(resolved, address)
-	}
-	return resolved, nil
-}
-
-func (policy oauthDiscoveryNetworkPolicy) validateLiteralHost(host string) error {
-	normalized := strings.ToLower(strings.TrimSuffix(strings.Trim(host, "[]"), "."))
-	if normalized == "" {
-		return errUnsafeOAuthDiscoveryTarget
-	}
-	if isCloudMetadataHostname(normalized) {
-		return errUnsafeOAuthDiscoveryTarget
-	}
-	if isExplicitOAuthLoopbackHost(normalized) && !policy.allowLoopback {
-		return errUnsafeOAuthDiscoveryTarget
-	}
-	if address, err := netip.ParseAddr(normalized); err == nil {
-		return policy.validateAddress(address.Unmap())
-	}
-	return nil
-}
-
-func (policy oauthDiscoveryNetworkPolicy) validateAddress(address netip.Addr) error {
-	if policy.allowLoopback && address.IsLoopback() {
-		return nil
-	}
-	if !address.IsValid() || !address.IsGlobalUnicast() || address.IsPrivate() {
-		return errUnsafeOAuthDiscoveryTarget
-	}
-	for _, prefix := range nonPublicOAuthDiscoveryPrefixes {
-		if prefix.Contains(address) {
-			return errUnsafeOAuthDiscoveryTarget
-		}
-	}
-	return nil
-}
-
-func isExplicitOAuthLoopbackHost(host string) bool {
-	normalized := strings.ToLower(strings.TrimSuffix(strings.Trim(host, "[]"), "."))
-	if normalized == "localhost" || strings.HasSuffix(normalized, ".localhost") {
-		return true
-	}
-	address, err := netip.ParseAddr(normalized)
-	return err == nil && address.Unmap().IsLoopback()
-}
-
-func isCloudMetadataHostname(host string) bool {
-	switch strings.ToLower(strings.TrimSuffix(host, ".")) {
-	case "metadata", "metadata.google.internal", "metadata.azure.internal":
-		return true
-	default:
-		return false
-	}
-}

internal/mcp/oauth_discovery_network_test.go

@@ -1,180 +0,0 @@
-package mcp
-
-import (
-	"bufio"
-	"context"
-	"errors"
-	"io"
-	"net"
-	"net/http"
-	"net/netip"
-	"net/url"
-	"strings"
-	"sync/atomic"
-	"testing"
-)
-
-func TestOAuthDiscoveryNetworkPolicyRejectsNonPublicAddresses(t *testing.T) {
-	policy := oauthDiscoveryNetworkPolicy{}
-	for _, value := range []string{
-		"127.0.0.1",
-		"10.0.0.1",
-		"169.254.169.254",
-		"192.0.2.10",
-		"224.0.0.1",
-		"::1",
-		"fc00::1",
-		"fe80::1",
-		"2001:db8::1",
-	} {
-		t.Run(value, func(t *testing.T) {
-			if err := policy.validateAddress(netip.MustParseAddr(value)); err == nil {
-				t.Fatalf("address %s should be rejected", value)
-			}
-		})
-	}
-	for _, value := range []string{"8.8.8.8", "2606:4700:4700::1111"} {
-		if err := policy.validateAddress(netip.MustParseAddr(value)); err != nil {
-			t.Fatalf("public address %s rejected: %v", value, err)
-		}
-	}
-	loopbackPolicy := oauthDiscoveryNetworkPolicy{allowLoopback: true}
-	if err := loopbackPolicy.validateAddress(netip.MustParseAddr("127.0.0.1")); err != nil {
-		t.Fatalf("explicit loopback resource should allow loopback discovery: %v", err)
-	}
-	if err := loopbackPolicy.validateAddress(netip.MustParseAddr("10.0.0.1")); err == nil {
-		t.Fatal("loopback development must not permit arbitrary private targets")
-	}
-}
-
-func TestProtectedDiscoveryRejectsNonPublicOAuthEndpoints(t *testing.T) {
-	for _, endpoint := range []struct {
-		name     string
-		metadata authServerMetadata
-	}{
-		{
-			name: "authorization",
-			metadata: authServerMetadata{
-				AuthorizationEndpoint:        "http://127.0.0.1/authorize",
-				protectAuthorizationEndpoint: true,
-			},
-		},
-		{
-			name: "token",
-			metadata: authServerMetadata{
-				TokenEndpoint:        "https://10.0.0.1/token",
-				protectTokenEndpoint: true,
-			},
-		},
-		{
-			name: "registration",
-			metadata: authServerMetadata{
-				RegistrationEndpoint:        "https://169.254.169.254/register",
-				protectRegistrationEndpoint: true,
-			},
-		},
-	} {
-		t.Run(endpoint.name, func(t *testing.T) {
-			endpoint.metadata.protectedResourceURL = "https://mcp.example/mcp"
-			if err := validateProtectedDiscoveredEndpoints(context.Background(), endpoint.metadata); err == nil {
-				t.Fatalf("protected %s endpoint should be rejected", endpoint.name)
-			}
-		})
-	}
-}
-
-func TestAdvertisedOAuthDiscoveryRejectsHostnameResolvingPrivateAtUseTime(t *testing.T) {
-	var dialed atomic.Bool
-	policy := oauthDiscoveryNetworkPolicy{
-		lookupNetIP: func(context.Context, string, string) ([]netip.Addr, error) {
-			return []netip.Addr{netip.MustParseAddr("10.0.0.12")}, nil
-		},
-	}
-	client := &http.Client{Transport: advertisedOAuthDiscoveryTransport{
-		base: &http.Transport{DialContext: func(context.Context, string, string) (net.Conn, error) {
-			dialed.Store(true)
-			return nil, io.EOF
-		}},
-		policy: policy,
-	}}
-
-	_, err := client.Get("https://auth.example/.well-known/oauth-authorization-server")
-	if err == nil || !strings.Contains(err.Error(), errUnsafeOAuthDiscoveryTarget.Error()) {
-		t.Fatalf("error = %v, want private-resolution rejection", err)
-	}
-	if dialed.Load() {
-		t.Fatal("private resolved address reached the dialer")
-	}
-}
-
-func TestAdvertisedOAuthDiscoveryPinsResolvedAddress(t *testing.T) {
-	const publicAddress = "93.184.216.34"
-	var dialedAddress string
-	policy := oauthDiscoveryNetworkPolicy{
-		lookupNetIP: func(context.Context, string, string) ([]netip.Addr, error) {
-			return []netip.Addr{netip.MustParseAddr(publicAddress)}, nil
-		},
-	}
-	baseTransport := &http.Transport{DialContext: func(_ context.Context, _, address string) (net.Conn, error) {
-		dialedAddress = address
-		clientConn, serverConn := net.Pipe()
-		go func() {
-			defer serverConn.Close()
-			reader := bufio.NewReader(serverConn)
-			for {
-				line, err := reader.ReadString('\n')
-				if err != nil || line == "\r\n" {
-					break
-				}
-			}
-			_, _ = io.WriteString(serverConn, "HTTP/1.1 200 OK\r\nContent-Length: 2\r\nConnection: close\r\n\r\n{}")
-		}()
-		return clientConn, nil
-	}}
-	client := &http.Client{Transport: advertisedOAuthDiscoveryTransport{base: baseTransport, policy: policy}}
-
-	response, err := client.Get("http://auth.example/metadata")
-	if err != nil {
-		t.Fatalf("GET pinned discovery target: %v", err)
-	}
-	response.Body.Close()
-	if dialedAddress != net.JoinHostPort(publicAddress, "80") {
-		t.Fatalf("dialed %q, want resolved address", dialedAddress)
-	}
-}
-
-func TestPinnedOAuthDiscoveryPreservesHTTPSProxyFirstHop(t *testing.T) {
-	for _, test := range []struct {
-		name     string
-		proxy    string
-		firstHop string
-	}{
-		{name: "HTTP", proxy: "http://proxy.example:8080", firstHop: "proxy.example:8080"},
-		{name: "HTTPS", proxy: "https://proxy.example:8443", firstHop: "proxy.example:8443"},
-		{name: "SOCKS", proxy: "socks5://proxy.example:1080", firstHop: "proxy.example:1080"},
-	} {
-		t.Run(test.name, func(t *testing.T) {
-			proxyURL, err := url.Parse(test.proxy)
-			if err != nil {
-				t.Fatalf("parse proxy URL: %v", err)
-			}
-			var dialedAddress string
-			baseTransport := &http.Transport{
-				Proxy: http.ProxyURL(proxyURL),
-				DialContext: func(_ context.Context, _, address string) (net.Conn, error) {
-					dialedAddress = address
-					return nil, errors.New("stop after observing first hop")
-				},
-			}
-			request, err := http.NewRequestWithContext(context.Background(), http.MethodGet, "https://auth.example/metadata", nil)
-			if err != nil {
-				t.Fatalf("create request: %v", err)
-			}
-
-			_, _ = roundTripPinnedOAuthDiscovery(request, baseTransport, netip.MustParseAddr("93.184.216.34"))
-			if dialedAddress != test.firstHop {
-				t.Fatalf("dialed %q, want %s proxy first hop", dialedAddress, test.name)
-			}
-		})
-	}
-}

internal/mcp/oauth_protected_resource.go

@@ -1,233 +0,0 @@
-package mcp
-
-import (
-	"context"
-	"encoding/json"
-	"errors"
-	"fmt"
-	"io"
-	"net/http"
-	"net/url"
-	"strings"
-
-	"github.com/Gitlawb/zero/internal/oauth"
-)
-
-const protectedResourceMetadataLimit = 1 << 20
-
-type protectedResourceMetadata struct {
-	Resource             string   `json:"resource"`
-	AuthorizationServers []string `json:"authorization_servers"`
-}
-
-// withoutDiscoveryRedirects returns a shallow client copy that exposes 3xx
-// responses to the caller. Every discovered URL is validated before use, so a
-// redirect must never replace that validated target with an unchecked one.
-func withoutDiscoveryRedirects(client *http.Client) *http.Client {
-	if client == nil {
-		client = http.DefaultClient
-	}
-	copied := *client
-	// Discovery requests are deliberately unauthenticated. A caller-supplied
-	// jar must not turn a plain metadata GET into a credential-bearing request.
-	copied.Jar = nil
-	copied.CheckRedirect = func(*http.Request, []*http.Request) error {
-		return http.ErrUseLastResponse
-	}
-	return &copied
-}
-
-// discoverProtectedResourceAuthorizationServer follows the RFC 9728 URL
-// advertised by a protected MCP resource. found is false when the endpoint does
-// not advertise protected-resource metadata, allowing legacy direct discovery.
-func discoverProtectedResourceAuthorizationServer(ctx context.Context, client *http.Client, resourceURL string) (issuer string, found bool, err error) {
-	resourceURL = strings.TrimSpace(resourceURL)
-	client = withoutDiscoveryRedirects(client)
-	metadataURL, found, err := probeProtectedResourceMetadataURL(ctx, client, resourceURL)
-	if err != nil || !found {
-		return "", found, err
-	}
-	if err := validateResourceMetadataOrigin(resourceURL, metadataURL); err != nil {
-		return "", true, err
-	}
-	client, err = newAdvertisedOAuthDiscoveryClient(client, resourceURL)
-	if err != nil {
-		return "", true, err
-	}
-	metadata, err := fetchProtectedResourceMetadata(ctx, client, metadataURL)
-	if err != nil {
-		return "", true, err
-	}
-	if metadata.Resource != resourceURL {
-		return "", true, errors.New("mcp oauth: protected resource metadata resource does not match the MCP server URL")
-	}
-	if len(metadata.AuthorizationServers) == 0 {
-		return "", true, errors.New("mcp oauth: protected resource metadata has no authorization_servers")
-	}
-	issuer = metadata.AuthorizationServers[0]
-	if strings.TrimSpace(issuer) == "" {
-		return "", true, errors.New("mcp oauth: protected resource metadata has an empty authorization server")
-	}
-	if issuer != strings.TrimSpace(issuer) {
-		return "", true, errors.New("mcp oauth: protected resource authorization server must not contain surrounding whitespace")
-	}
-	if err := oauth.ValidateEndpointURL(issuer); err != nil {
-		return "", true, fmt.Errorf("mcp oauth: protected resource authorization server: %w", err)
-	}
-	if err := validateAdvertisedOAuthDiscoveryURL(resourceURL, issuer); err != nil {
-		return "", true, err
-	}
-	return issuer, true, nil
-}
-
-func validateResourceMetadataOrigin(resourceURL string, metadataURL string) error {
-	resource, resourceErr := url.Parse(resourceURL)
-	metadata, metadataErr := url.Parse(metadataURL)
-	if resourceErr != nil || metadataErr != nil || !sameMCPOrigin(resource, metadata) {
-		return errors.New("mcp oauth: protected resource metadata URL must be same-origin with the MCP server URL")
-	}
-	return nil
-}
-
-func probeProtectedResourceMetadataURL(ctx context.Context, client *http.Client, resourceURL string) (string, bool, error) {
-	if client == nil {
-		client = http.DefaultClient
-	}
-	request, err := http.NewRequestWithContext(ctx, http.MethodGet, strings.TrimSpace(resourceURL), nil)
-	if err != nil {
-		return "", false, errors.New("mcp oauth: invalid MCP resource URL")
-	}
-	request.Header.Set("Accept", "application/json, text/event-stream")
-	request.Header.Set("MCP-Protocol-Version", defaultProtocolVersion)
-	response, err := client.Do(request)
-	if err != nil {
-		// A resource that cannot be probed may still support the legacy direct
-		// authorization-server discovery flow.
-		return "", false, nil
-	}
-	defer response.Body.Close()
-	if response.StatusCode != http.StatusUnauthorized {
-		return "", false, nil
-	}
-	metadataURL, found, err := parseResourceMetadataURL(response.Header.Values("WWW-Authenticate"))
-	if err != nil {
-		return "", false, fmt.Errorf("mcp oauth: invalid WWW-Authenticate resource_metadata parameter: %w", err)
-	}
-	if !found {
-		return "", false, nil
-	}
-	if err := oauth.ValidateEndpointURL(metadataURL); err != nil {
-		return "", false, fmt.Errorf("mcp oauth: protected resource metadata URL: %w", err)
-	}
-	return metadataURL, true, nil
-}
-
-func fetchProtectedResourceMetadata(ctx context.Context, client *http.Client, metadataURL string) (protectedResourceMetadata, error) {
-	if client == nil {
-		client = http.DefaultClient
-	}
-	request, err := http.NewRequestWithContext(ctx, http.MethodGet, metadataURL, nil)
-	if err != nil {
-		return protectedResourceMetadata{}, errors.New("mcp oauth: invalid protected resource metadata URL")
-	}
-	request.Header.Set("Accept", "application/json")
-	response, err := client.Do(request)
-	if err != nil {
-		return protectedResourceMetadata{}, errors.New("mcp oauth: fetch protected resource metadata failed")
-	}
-	defer response.Body.Close()
-	if response.StatusCode < http.StatusOK || response.StatusCode >= http.StatusMultipleChoices {
-		return protectedResourceMetadata{}, fmt.Errorf("mcp oauth: protected resource metadata returned HTTP %d", response.StatusCode)
-	}
-	var metadata protectedResourceMetadata
-	if err := json.NewDecoder(io.LimitReader(response.Body, protectedResourceMetadataLimit)).Decode(&metadata); err != nil {
-		return protectedResourceMetadata{}, errors.New("mcp oauth: decode protected resource metadata failed")
-	}
-	return metadata, nil
-}
-
-func parseResourceMetadataURL(headerValues []string) (string, bool, error) {
-	var selected string
-	for _, headerValue := range headerValues {
-		for index := 0; index < len(headerValue); {
-			if headerValue[index] == '"' {
-				_, next, err := readAuthQuotedString(headerValue, index)
-				if err != nil {
-					// Malformed parameters for another authentication scheme do
-					// not suppress a valid challenge in a separate header value.
-					break
-				}
-				index = next
-				continue
-			}
-			if !isAuthTokenByte(headerValue[index]) {
-				index++
-				continue
-			}
-			start := index
-			for index < len(headerValue) && isAuthTokenByte(headerValue[index]) {
-				index++
-			}
-			name := headerValue[start:index]
-			for index < len(headerValue) && (headerValue[index] == ' ' || headerValue[index] == '\t') {
-				index++
-			}
-			if index >= len(headerValue) || headerValue[index] != '=' {
-				continue
-			}
-			index++
-			for index < len(headerValue) && (headerValue[index] == ' ' || headerValue[index] == '\t') {
-				index++
-			}
-			if !strings.EqualFold(name, "resource_metadata") {
-				continue
-			}
-			if index >= len(headerValue) || headerValue[index] != '"' {
-				return "", false, errors.New("resource_metadata must be a quoted URL")
-			}
-			value, next, err := readAuthQuotedString(headerValue, index)
-			if err != nil {
-				return "", false, err
-			}
-			value = strings.TrimSpace(value)
-			if value == "" {
-				return "", false, errors.New("resource_metadata URL is empty")
-			}
-			if selected != "" && selected != value {
-				return "", false, errors.New("conflicting resource_metadata URLs")
-			}
-			selected = value
-			index = next
-		}
-	}
-	return selected, selected != "", nil
-}
-
-func readAuthQuotedString(value string, quote int) (string, int, error) {
-	var decoded strings.Builder
-	for index := quote + 1; index < len(value); index++ {
-		switch value[index] {
-		case '"':
-			return decoded.String(), index + 1, nil
-		case '\\':
-			index++
-			if index >= len(value) {
-				return "", 0, errors.New("unterminated quoted resource_metadata URL")
-			}
-			decoded.WriteByte(value[index])
-		default:
-			if value[index] < 0x20 || value[index] == 0x7f {
-				return "", 0, errors.New("resource_metadata URL contains a control character")
-			}
-			decoded.WriteByte(value[index])
-		}
-	}
-	return "", 0, errors.New("unterminated quoted resource_metadata URL")
-}
-
-func isAuthTokenByte(value byte) bool {
-	if value >= 'a' && value <= 'z' || value >= 'A' && value <= 'Z' || value >= '0' && value <= '9' {
-		return true
-	}
-	return strings.ContainsRune("!#$%&'*+-.^_`|~", rune(value))
-}

internal/mcp/oauth_protected_resource_test.go

@@ -1,742 +0,0 @@
-package mcp
-
-import (
-	"context"
-	"encoding/json"
-	"errors"
-	"fmt"
-	"io"
-	"net"
-	"net/http"
-	"net/http/cookiejar"
-	"net/http/httptest"
-	"net/url"
-	"strings"
-	"sync/atomic"
-	"testing"
-	"time"
-)
-
-func TestParseResourceMetadataURL(t *testing.T) {
-	got, found, err := parseResourceMetadataURL([]string{
-		`Basic realm="resource_metadata=not-a-parameter"`,
-		`Bearer realm="OAuth", scope="read", Resource_Metadata="https://mcp.example/resource-metadata"`,
-	})
-	if err != nil || !found {
-		t.Fatalf("parseResourceMetadataURL() found=%v err=%v", found, err)
-	}
-	if got != "https://mcp.example/resource-metadata" {
-		t.Fatalf("resource metadata URL = %q", got)
-	}
-
-	got, found, err = parseResourceMetadataURL([]string{
-		`Basic realm="unterminated`,
-		`Bearer resource_metadata="https://mcp.example/fallback-metadata"`,
-	})
-	if err != nil || !found || got != "https://mcp.example/fallback-metadata" {
-		t.Fatalf("unrelated malformed challenge blocked discovery: got=%q found=%v err=%v", got, found, err)
-	}
-
-	for name, headers := range map[string][]string{
-		"unquoted":     {`Bearer resource_metadata=https://mcp.example/metadata`},
-		"unterminated": {`Bearer resource_metadata="https://mcp.example/metadata`},
-		"conflicting": {
-			`Bearer resource_metadata="https://mcp.example/one"`,
-			`DPoP resource_metadata="https://mcp.example/two"`,
-		},
-	} {
-		t.Run(name, func(t *testing.T) {
-			if _, _, err := parseResourceMetadataURL(headers); err == nil {
-				t.Fatal("expected malformed resource_metadata rejection")
-			}
-		})
-	}
-}
-
-func TestProtectedResourceDiscoveryRejectsInvalidMetadata(t *testing.T) {
-	for _, test := range []struct {
-		name      string
-		challenge func(base string) string
-		metadata  func(base string) string
-		wantError string
-	}{
-		{
-			name:      "malformed challenge",
-			challenge: func(string) string { return `Bearer resource_metadata="unterminated` },
-			wantError: "WWW-Authenticate",
-		},
-		{
-			name:      "insecure metadata URL",
-			challenge: func(string) string { return `Bearer resource_metadata="http://metadata.example/resource"` },
-			wantError: "metadata URL",
-		},
-		{
-			name:      "invalid JSON",
-			challenge: func(base string) string { return `Bearer resource_metadata="` + base + `/metadata"` },
-			metadata:  func(string) string { return `{` },
-			wantError: "decode protected resource metadata",
-		},
-		{
-			name:      "resource mismatch",
-			challenge: func(base string) string { return `Bearer resource_metadata="` + base + `/metadata"` },
-			metadata: func(base string) string {
-				return `{"resource":"` + base + `/other","authorization_servers":["https://auth.example"]}`
-			},
-			wantError: "does not match",
-		},
-		{
-			name:      "resource leading whitespace mismatch",
-			challenge: func(base string) string { return `Bearer resource_metadata="` + base + `/metadata"` },
-			metadata: func(base string) string {
-				return `{"resource":" ` + base + `/mcp","authorization_servers":["https://auth.example"]}`
-			},
-			wantError: "does not match",
-		},
-		{
-			name:      "resource trailing whitespace mismatch",
-			challenge: func(base string) string { return `Bearer resource_metadata="` + base + `/metadata"` },
-			metadata: func(base string) string {
-				return `{"resource":"` + base + `/mcp ","authorization_servers":["https://auth.example"]}`
-			},
-			wantError: "does not match",
-		},
-		{
-			name:      "authorization servers missing",
-			challenge: func(base string) string { return `Bearer resource_metadata="` + base + `/metadata"` },
-			metadata: func(base string) string {
-				return `{"resource":"` + base + `/mcp"}`
-			},
-			wantError: "authorization_servers",
-		},
-		{
-			name:      "insecure authorization server",
-			challenge: func(base string) string { return `Bearer resource_metadata="` + base + `/metadata"` },
-			metadata: func(base string) string {
-				return `{"resource":"` + base + `/mcp","authorization_servers":["http://auth.example"]}`
-			},
-			wantError: "authorization server",
-		},
-	} {
-		t.Run(test.name, func(t *testing.T) {
-			server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-				base := "http://" + r.Host
-				switch r.URL.Path {
-				case "/mcp":
-					w.Header().Set("WWW-Authenticate", test.challenge(base))
-					w.WriteHeader(http.StatusUnauthorized)
-				case "/metadata":
-					if test.metadata == nil {
-						http.NotFound(w, r)
-						return
-					}
-					_, _ = w.Write([]byte(test.metadata(base)))
-				default:
-					http.NotFound(w, r)
-				}
-			}))
-			defer server.Close()
-
-			_, _, err := discoverProtectedResourceAuthorizationServer(context.Background(), server.Client(), server.URL+"/mcp")
-			if err == nil || !strings.Contains(err.Error(), test.wantError) {
-				t.Fatalf("error = %v, want %q", err, test.wantError)
-			}
-		})
-	}
-}
-
-func TestProtectedResourceProbeSendsNoCredentials(t *testing.T) {
-	var authorization, cookie string
-	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		authorization = r.Header.Get("Authorization")
-		cookie = r.Header.Get("Cookie")
-		w.WriteHeader(http.StatusNotFound)
-	}))
-	defer server.Close()
-	jar, err := cookiejar.New(nil)
-	if err != nil {
-		t.Fatalf("create cookie jar: %v", err)
-	}
-	serverURL, err := url.Parse(server.URL)
-	if err != nil {
-		t.Fatalf("parse server URL: %v", err)
-	}
-	jar.SetCookies(serverURL, []*http.Cookie{{Name: "session", Value: "secret"}})
-	client := server.Client()
-	client.Jar = jar
-
-	_, found, err := discoverProtectedResourceAuthorizationServer(context.Background(), client, server.URL+"/mcp")
-	if err != nil || found {
-		t.Fatalf("discovery found=%v err=%v", found, err)
-	}
-	if authorization != "" || cookie != "" {
-		t.Fatalf("probe sent credentials: authorization=%q cookie=%q", authorization, cookie)
-	}
-}
-
-func TestDirectAuthorizationServerDiscoverySendsNoCookies(t *testing.T) {
-	var cookie string
-	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		cookie = r.Header.Get("Cookie")
-		base := "http://" + r.Host
-		_ = json.NewEncoder(w).Encode(map[string]any{
-			"issuer":                 base,
-			"authorization_endpoint": base + "/authorize",
-			"token_endpoint":         base + "/token",
-		})
-	}))
-	defer server.Close()
-	jar, err := cookiejar.New(nil)
-	if err != nil {
-		t.Fatalf("create cookie jar: %v", err)
-	}
-	serverURL, err := url.Parse(server.URL)
-	if err != nil {
-		t.Fatalf("parse server URL: %v", err)
-	}
-	jar.SetCookies(serverURL, []*http.Cookie{{Name: "session", Value: "secret"}})
-	client := server.Client()
-	client.Jar = jar
-
-	if _, err := resolveAuthorizationServer(context.Background(), client, server.URL, OAuthConfig{}); err != nil {
-		t.Fatalf("resolveAuthorizationServer() error = %v", err)
-	}
-	if cookie != "" {
-		t.Fatalf("direct discovery sent cookie %q", cookie)
-	}
-}
-
-func TestProtectedResourceDiscoveryRejectsAdvertisedLoopbackMetadata(t *testing.T) {
-	var metadataHits atomic.Int64
-	client := &http.Client{Transport: roundTripperFunc(func(request *http.Request) (*http.Response, error) {
-		response := &http.Response{
-			StatusCode: http.StatusOK,
-			Header:     make(http.Header),
-			Body:       io.NopCloser(strings.NewReader("")),
-			Request:    request,
-		}
-		switch request.URL.String() {
-		case "https://mcp.example/mcp":
-			response.StatusCode = http.StatusUnauthorized
-			response.Header.Set("WWW-Authenticate", `Bearer resource_metadata="http://127.0.0.1/metadata"`)
-		case "http://127.0.0.1/metadata":
-			metadataHits.Add(1)
-			response.Body = io.NopCloser(strings.NewReader(`{"resource":"https://mcp.example/mcp","authorization_servers":["https://auth.example"]}`))
-		default:
-			response.StatusCode = http.StatusNotFound
-		}
-		return response, nil
-	})}
-
-	_, _, err := discoverProtectedResourceAuthorizationServer(context.Background(), client, "https://mcp.example/mcp")
-	if err == nil {
-		t.Fatal("advertised loopback metadata URL should be rejected")
-	}
-	if metadataHits.Load() != 0 {
-		t.Fatalf("loopback metadata target was fetched %d time(s)", metadataHits.Load())
-	}
-}
-
-func TestProtectedResourceDiscoveryRejectsAdvertisedLoopbackIssuer(t *testing.T) {
-	var issuerHits atomic.Int64
-	client := &http.Client{Transport: roundTripperFunc(func(request *http.Request) (*http.Response, error) {
-		response := &http.Response{
-			StatusCode: http.StatusOK,
-			Header:     make(http.Header),
-			Body:       io.NopCloser(strings.NewReader("")),
-			Request:    request,
-		}
-		switch request.URL.String() {
-		case "https://mcp.example/mcp":
-			response.StatusCode = http.StatusUnauthorized
-			response.Header.Set("WWW-Authenticate", `Bearer resource_metadata="https://mcp.example/metadata"`)
-		case "https://mcp.example/metadata":
-			response.Body = io.NopCloser(strings.NewReader(`{"resource":"https://mcp.example/mcp","authorization_servers":["http://127.0.0.1"]}`))
-		case "http://127.0.0.1/.well-known/oauth-authorization-server":
-			issuerHits.Add(1)
-			response.Body = io.NopCloser(strings.NewReader(`{"issuer":"http://127.0.0.1","authorization_endpoint":"http://127.0.0.1/authorize","token_endpoint":"http://127.0.0.1/token"}`))
-		default:
-			response.StatusCode = http.StatusNotFound
-		}
-		return response, nil
-	})}
-
-	_, err := resolveAuthorizationServer(context.Background(), client, "https://mcp.example/mcp", OAuthConfig{})
-	if err == nil {
-		t.Fatal("advertised loopback issuer should be rejected")
-	}
-	if issuerHits.Load() != 0 {
-		t.Fatalf("loopback issuer target was fetched %d time(s)", issuerHits.Load())
-	}
-}
-
-func TestProtectedResourceDiscoveryRejectsAdvertisedPrivateTargets(t *testing.T) {
-	for _, target := range []string{
-		"http://10.0.0.8/metadata",
-		"https://169.254.169.254/metadata",
-		"https://metadata.google.internal/metadata",
-	} {
-		t.Run(target, func(t *testing.T) {
-			if err := validateAdvertisedOAuthDiscoveryURL("https://mcp.example/mcp", target); err == nil {
-				t.Fatalf("advertised target %q should be rejected", target)
-			}
-		})
-	}
-}
-
-func TestProtectedDiscoveryPathsSendNoCookies(t *testing.T) {
-	var probeCookie, resourceCookie, issuerCookie string
-	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		base := "http://" + r.Host
-		switch r.URL.Path {
-		case "/mcp":
-			probeCookie = r.Header.Get("Cookie")
-			w.Header().Set("WWW-Authenticate", `Bearer resource_metadata="`+base+`/metadata"`)
-			w.WriteHeader(http.StatusUnauthorized)
-		case "/metadata":
-			resourceCookie = r.Header.Get("Cookie")
-			_ = json.NewEncoder(w).Encode(map[string]any{
-				"resource":              base + "/mcp",
-				"authorization_servers": []string{base},
-			})
-		case "/.well-known/oauth-authorization-server":
-			issuerCookie = r.Header.Get("Cookie")
-			_ = json.NewEncoder(w).Encode(map[string]any{
-				"issuer":                 base,
-				"authorization_endpoint": base + "/authorize",
-				"token_endpoint":         base + "/token",
-			})
-		default:
-			http.NotFound(w, r)
-		}
-	}))
-	defer server.Close()
-	jar, err := cookiejar.New(nil)
-	if err != nil {
-		t.Fatalf("create cookie jar: %v", err)
-	}
-	serverURL, err := url.Parse(server.URL)
-	if err != nil {
-		t.Fatalf("parse server URL: %v", err)
-	}
-	jar.SetCookies(serverURL, []*http.Cookie{{Name: "session", Value: "secret"}})
-	client := server.Client()
-	client.Jar = jar
-
-	if _, err := resolveAuthorizationServer(context.Background(), client, server.URL+"/mcp", OAuthConfig{}); err != nil {
-		t.Fatalf("resolveAuthorizationServer() error = %v", err)
-	}
-	if probeCookie != "" || resourceCookie != "" || issuerCookie != "" {
-		t.Fatalf("discovery sent cookies: probe=%q resource=%q issuer=%q", probeCookie, resourceCookie, issuerCookie)
-	}
-}
-
-func TestProtectedDiscoveryPreservesExplicitEndpointOverride(t *testing.T) {
-	fixture := newPublicProtectedOAuthFixture(t, "", "https://93.184.216.35/token", "", "")
-	explicitToken := "http://127.0.0.1:19432/token"
-	metadata, err := resolveAuthorizationServer(context.Background(), fixture.client, fixture.resourceURL, OAuthConfig{TokenEndpoint: explicitToken})
-	if err != nil {
-		t.Fatalf("resolve with explicit endpoint override: %v", err)
-	}
-	if metadata.TokenEndpoint != explicitToken || metadata.protectTokenEndpoint {
-		t.Fatalf("explicit token override lost provenance: endpoint=%q protected=%v", metadata.TokenEndpoint, metadata.protectTokenEndpoint)
-	}
-}
-
-func TestProtectedDiscoveryRejectsLoopbackRegistrationEndpointBeforeUse(t *testing.T) {
-	var registrationHits atomic.Int64
-	registration := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
-		registrationHits.Add(1)
-		_ = json.NewEncoder(w).Encode(map[string]any{"client_id": "registered-client"})
-	}))
-	defer registration.Close()
-	fixture := newPublicProtectedOAuthFixture(t, registration.URL+"/register", "https://93.184.216.35/token", "", "")
-
-	_, err := Login(context.Background(), LoginOptions{
-		ServerName: "registration-ssrf",
-		ServerURL:  fixture.resourceURL,
-		HTTPClient: fixture.client,
-		OpenBrowser: func(string) error {
-			return errors.New("authorization browser should not open")
-		},
-		Timeout: 5 * time.Second,
-	})
-	if err == nil {
-		t.Fatal("protected discovery should reject a loopback registration endpoint")
-	}
-	if registrationHits.Load() != 0 {
-		t.Fatalf("loopback registration endpoint received %d request(s)", registrationHits.Load())
-	}
-}
-
-func TestProtectedDiscoveryRejectsLoopbackTokenEndpointBeforeUse(t *testing.T) {
-	var tokenHits atomic.Int64
-	tokenServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
-		tokenHits.Add(1)
-		_ = json.NewEncoder(w).Encode(map[string]any{
-			"access_token": "unexpected",
-			"token_type":   "Bearer",
-		})
-	}))
-	defer tokenServer.Close()
-	fixture := newPublicProtectedOAuthFixture(t, "", tokenServer.URL+"/token", "", "")
-
-	_, err := Login(context.Background(), LoginOptions{
-		ServerName: "token-ssrf",
-		ServerURL:  fixture.resourceURL,
-		Config:     OAuthConfig{ClientID: "configured-client"},
-		HTTPClient: fixture.client,
-		OpenBrowser: func(authURL string) error {
-			parsed, parseErr := url.Parse(authURL)
-			if parseErr != nil {
-				return parseErr
-			}
-			callbackURL := parsed.Query().Get("redirect_uri") + "?code=code&state=" + url.QueryEscape(parsed.Query().Get("state"))
-			go func() {
-				for attempt := 0; attempt < 20; attempt++ {
-					response, requestErr := http.Get(callbackURL)
-					if requestErr == nil {
-						response.Body.Close()
-						return
-					}
-					time.Sleep(25 * time.Millisecond)
-				}
-			}()
-			return nil
-		},
-		Timeout: 5 * time.Second,
-	})
-	if err == nil {
-		t.Fatal("protected discovery should reject a loopback token endpoint")
-	}
-	if tokenHits.Load() != 0 {
-		t.Fatalf("loopback token endpoint received %d request(s)", tokenHits.Load())
-	}
-}
-
-func TestProtectedDiscoveryRegistrationRefusesPublicToPrivateRedirect(t *testing.T) {
-	var victimHits atomic.Int64
-	victim := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
-		victimHits.Add(1)
-		_ = json.NewEncoder(w).Encode(map[string]any{"client_id": "redirected-client"})
-	}))
-	defer victim.Close()
-	fixture := newPublicProtectedOAuthFixture(t, "", "https://93.184.216.35/token", victim.URL+"/register", "")
-
-	_, err := Login(context.Background(), LoginOptions{
-		ServerName: "registration-redirect",
-		ServerURL:  fixture.resourceURL,
-		HTTPClient: fixture.client,
-		OpenBrowser: func(string) error {
-			return errors.New("authorization browser should not open")
-		},
-		Timeout: 5 * time.Second,
-	})
-	if err == nil {
-		t.Fatal("protected registration redirect should be refused")
-	}
-	if victimHits.Load() != 0 {
-		t.Fatalf("registration redirect reached private victim %d time(s)", victimHits.Load())
-	}
-}
-
-func TestProtectedDiscoveryTokenRefusesPublicToPrivateRedirect(t *testing.T) {
-	var victimHits atomic.Int64
-	victim := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
-		victimHits.Add(1)
-		_ = json.NewEncoder(w).Encode(map[string]any{"access_token": "redirected-token", "token_type": "Bearer"})
-	}))
-	defer victim.Close()
-	fixture := newPublicProtectedOAuthFixture(t, "", "", "", victim.URL+"/token")
-
-	_, err := Login(context.Background(), LoginOptions{
-		ServerName: "token-redirect",
-		ServerURL:  fixture.resourceURL,
-		Config:     OAuthConfig{ClientID: "configured-client"},
-		HTTPClient: fixture.client,
-		OpenBrowser: func(authURL string) error {
-			parsed, parseErr := url.Parse(authURL)
-			if parseErr != nil {
-				return parseErr
-			}
-			callbackURL := parsed.Query().Get("redirect_uri") + "?code=code&state=" + url.QueryEscape(parsed.Query().Get("state"))
-			go func() {
-				for attempt := 0; attempt < 20; attempt++ {
-					response, requestErr := http.Get(callbackURL)
-					if requestErr == nil {
-						response.Body.Close()
-						return
-					}
-					time.Sleep(25 * time.Millisecond)
-				}
-			}()
-			return nil
-		},
-		Timeout: 5 * time.Second,
-	})
-	if err == nil {
-		t.Fatal("protected token redirect should be refused")
-	}
-	if victimHits.Load() != 0 {
-		t.Fatalf("token redirect reached private victim %d time(s)", victimHits.Load())
-	}
-}
-
-type publicProtectedOAuthFixture struct {
-	client      *http.Client
-	resourceURL string
-}
-
-func newPublicProtectedOAuthFixture(t *testing.T, registrationEndpoint string, tokenEndpoint string, registrationRedirect string, tokenRedirect string) publicProtectedOAuthFixture {
-	t.Helper()
-	var resourceOrigin, issuerOrigin string
-	gateway := httptest.NewTLSServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		resourceHost := strings.TrimPrefix(resourceOrigin, "https://")
-		issuerHost := strings.TrimPrefix(issuerOrigin, "https://")
-		switch {
-		case r.Host == resourceHost && r.URL.Path == "/mcp":
-			w.Header().Set("WWW-Authenticate", `Bearer resource_metadata="`+resourceOrigin+`/metadata"`)
-			w.WriteHeader(http.StatusUnauthorized)
-		case r.Host == resourceHost && r.URL.Path == "/metadata":
-			_ = json.NewEncoder(w).Encode(map[string]any{
-				"resource":              resourceOrigin + "/mcp",
-				"authorization_servers": []string{issuerOrigin},
-			})
-		case r.Host == issuerHost && r.URL.Path == "/.well-known/oauth-authorization-server":
-			metadataRegistration := registrationEndpoint
-			metadataToken := tokenEndpoint
-			if registrationRedirect != "" {
-				metadataRegistration = issuerOrigin + "/register"
-			}
-			if tokenRedirect != "" {
-				metadataToken = issuerOrigin + "/token"
-			}
-			_ = json.NewEncoder(w).Encode(map[string]any{
-				"issuer":                 issuerOrigin,
-				"authorization_endpoint": issuerOrigin + "/authorize",
-				"token_endpoint":         metadataToken,
-				"registration_endpoint":  metadataRegistration,
-			})
-		case r.Host == issuerHost && r.URL.Path == "/register" && registrationRedirect != "":
-			http.Redirect(w, r, registrationRedirect, http.StatusTemporaryRedirect)
-		case r.Host == issuerHost && r.URL.Path == "/token" && tokenRedirect != "":
-			http.Redirect(w, r, tokenRedirect, http.StatusTemporaryRedirect)
-		default:
-			http.NotFound(w, r)
-		}
-	}))
-	t.Cleanup(gateway.Close)
-	port := gateway.Listener.Addr().(*net.TCPAddr).Port
-	resourceOrigin = fmt.Sprintf("https://93.184.216.34:%d", port)
-	issuerOrigin = fmt.Sprintf("https://93.184.216.35:%d", port)
-
-	transport := gateway.Client().Transport.(*http.Transport).Clone()
-	transport.TLSClientConfig = transport.TLSClientConfig.Clone()
-	transport.TLSClientConfig.InsecureSkipVerify = true //nolint:gosec // hermetic public-address routing fixture
-	dialer := &net.Dialer{}
-	gatewayAddress := gateway.Listener.Addr().String()
-	transport.DialContext = func(ctx context.Context, network string, address string) (net.Conn, error) {
-		host, _, err := net.SplitHostPort(address)
-		if err == nil && (host == "93.184.216.34" || host == "93.184.216.35") {
-			return dialer.DialContext(ctx, network, gatewayAddress)
-		}
-		return dialer.DialContext(ctx, network, address)
-	}
-	return publicProtectedOAuthFixture{
-		client:      &http.Client{Transport: transport},
-		resourceURL: resourceOrigin + "/mcp",
-	}
-}
-
-func TestProtectedResourceProbeDoesNotFollowRedirects(t *testing.T) {
-	var redirectedHits atomic.Int64
-	redirected := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
-		redirectedHits.Add(1)
-		w.WriteHeader(http.StatusUnauthorized)
-	}))
-	defer redirected.Close()
-	source := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		http.Redirect(w, r, redirected.URL+"/mcp", http.StatusFound)
-	}))
-	defer source.Close()
-
-	_, found, err := discoverProtectedResourceAuthorizationServer(context.Background(), source.Client(), source.URL+"/mcp")
-	if err != nil || found {
-		t.Fatalf("redirected probe found=%v err=%v", found, err)
-	}
-	if redirectedHits.Load() != 0 {
-		t.Fatalf("probe followed redirect %d time(s)", redirectedHits.Load())
-	}
-}
-
-func TestProtectedResourceMetadataDoesNotFollowRedirects(t *testing.T) {
-	var redirectedHits atomic.Int64
-	redirected := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
-		redirectedHits.Add(1)
-		_ = json.NewEncoder(w).Encode(map[string]any{
-			"resource":              "https://attacker.example/mcp",
-			"authorization_servers": []string{"https://attacker.example"},
-		})
-	}))
-	defer redirected.Close()
-	source := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		base := "http://" + r.Host
-		switch r.URL.Path {
-		case "/mcp":
-			w.Header().Set("WWW-Authenticate", `Bearer resource_metadata="`+base+`/metadata"`)
-			w.WriteHeader(http.StatusUnauthorized)
-		case "/metadata":
-			http.Redirect(w, r, redirected.URL+"/metadata", http.StatusFound)
-		}
-	}))
-	defer source.Close()
-
-	_, _, err := discoverProtectedResourceAuthorizationServer(context.Background(), source.Client(), source.URL+"/mcp")
-	if err == nil || !strings.Contains(err.Error(), "HTTP 302") {
-		t.Fatalf("error = %v, want redirect refusal", err)
-	}
-	if redirectedHits.Load() != 0 {
-		t.Fatalf("metadata fetch followed redirect %d time(s)", redirectedHits.Load())
-	}
-}
-
-func TestResolveAuthorizationServerRejectsProtectedIssuerMismatch(t *testing.T) {
-	authorizationServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		base := "http://" + r.Host
-		_ = json.NewEncoder(w).Encode(map[string]any{
-			"issuer":                 "https://unexpected.example",
-			"authorization_endpoint": base + "/authorize",
-			"token_endpoint":         base + "/token",
-		})
-	}))
-	defer authorizationServer.Close()
-	resourceServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		base := "http://" + r.Host
-		switch r.URL.Path {
-		case "/mcp":
-			w.Header().Set("WWW-Authenticate", `Bearer resource_metadata="`+base+`/metadata"`)
-			w.WriteHeader(http.StatusUnauthorized)
-		case "/metadata":
-			_ = json.NewEncoder(w).Encode(map[string]any{
-				"resource":              base + "/mcp",
-				"authorization_servers": []string{authorizationServer.URL},
-			})
-		}
-	}))
-	defer resourceServer.Close()
-
-	_, err := resolveAuthorizationServer(context.Background(), resourceServer.Client(), resourceServer.URL+"/mcp", OAuthConfig{})
-	if err == nil || !strings.Contains(err.Error(), "issuer does not match") {
-		t.Fatalf("error = %v, want issuer mismatch", err)
-	}
-}
-
-func TestResolveAuthorizationServerRejectsMissingProtectedIssuer(t *testing.T) {
-	authorizationServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		base := "http://" + r.Host
-		_ = json.NewEncoder(w).Encode(map[string]any{
-			"authorization_endpoint": base + "/authorize",
-			"token_endpoint":         base + "/token",
-		})
-	}))
-	defer authorizationServer.Close()
-	resourceServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		base := "http://" + r.Host
-		switch r.URL.Path {
-		case "/mcp":
-			w.Header().Set("WWW-Authenticate", `Bearer resource_metadata="`+base+`/metadata"`)
-			w.WriteHeader(http.StatusUnauthorized)
-		case "/metadata":
-			_ = json.NewEncoder(w).Encode(map[string]any{
-				"resource":              base + "/mcp",
-				"authorization_servers": []string{authorizationServer.URL},
-			})
-		}
-	}))
-	defer resourceServer.Close()
-
-	_, err := resolveAuthorizationServer(context.Background(), resourceServer.Client(), resourceServer.URL+"/mcp", OAuthConfig{})
-	if err == nil || !strings.Contains(err.Error(), "issuer") {
-		t.Fatalf("error = %v, want missing issuer rejection", err)
-	}
-}
-
-func TestResolveAuthorizationServerRejectsWhitespaceAlteredProtectedIssuer(t *testing.T) {
-	for _, alter := range []struct {
-		name  string
-		apply func(string) string
-	}{
-		{name: "leading", apply: func(value string) string { return " " + value }},
-		{name: "trailing", apply: func(value string) string { return value + " " }},
-	} {
-		t.Run(alter.name, func(t *testing.T) {
-			authorizationServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-				base := "http://" + r.Host
-				_ = json.NewEncoder(w).Encode(map[string]any{
-					"issuer":                 alter.apply(base),
-					"authorization_endpoint": base + "/authorize",
-					"token_endpoint":         base + "/token",
-				})
-			}))
-			defer authorizationServer.Close()
-			resourceServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-				base := "http://" + r.Host
-				switch r.URL.Path {
-				case "/mcp":
-					w.Header().Set("WWW-Authenticate", `Bearer resource_metadata="`+base+`/metadata"`)
-					w.WriteHeader(http.StatusUnauthorized)
-				case "/metadata":
-					_ = json.NewEncoder(w).Encode(map[string]any{
-						"resource":              base + "/mcp",
-						"authorization_servers": []string{authorizationServer.URL},
-					})
-				}
-			}))
-			defer resourceServer.Close()
-
-			_, err := resolveAuthorizationServer(context.Background(), resourceServer.Client(), resourceServer.URL+"/mcp", OAuthConfig{})
-			if err == nil || !strings.Contains(err.Error(), "issuer does not match") {
-				t.Fatalf("error = %v, want whitespace issuer mismatch", err)
-			}
-		})
-	}
-}
-
-func TestAuthorizationServerMetadataDoesNotFollowRedirects(t *testing.T) {
-	var redirectedHits atomic.Int64
-	redirected := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		redirectedHits.Add(1)
-		base := "http://" + r.Host
-		_ = json.NewEncoder(w).Encode(map[string]any{
-			"issuer":                 base,
-			"authorization_endpoint": base + "/authorize",
-			"token_endpoint":         base + "/token",
-		})
-	}))
-	defer redirected.Close()
-	authorizationServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		http.Redirect(w, r, redirected.URL+"/.well-known/oauth-authorization-server", http.StatusFound)
-	}))
-	defer authorizationServer.Close()
-	resourceServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		base := "http://" + r.Host
-		switch r.URL.Path {
-		case "/mcp":
-			w.Header().Set("WWW-Authenticate", `Bearer resource_metadata="`+base+`/metadata"`)
-			w.WriteHeader(http.StatusUnauthorized)
-		case "/metadata":
-			_ = json.NewEncoder(w).Encode(map[string]any{
-				"resource":              base + "/mcp",
-				"authorization_servers": []string{authorizationServer.URL},
-			})
-		}
-	}))
-	defer resourceServer.Close()
-
-	_, err := resolveAuthorizationServer(context.Background(), resourceServer.Client(), resourceServer.URL+"/mcp", OAuthConfig{})
-	if err == nil {
-		t.Fatal("authorization metadata redirect should fail")
-	}
-	if redirectedHits.Load() != 0 {
-		t.Fatalf("authorization metadata fetch followed redirect %d time(s)", redirectedHits.Load())
-	}
-}

internal/mcp/oauth_test.go

@@ -10,7 +10,6 @@ import (
 	"net/http/httptest"
 	"net/url"
 	"strings"
-	"sync/atomic"
 	"testing"
 	"time"
 
@@ -146,130 +145,6 @@ func TestResolveEndpointsConfigOverridesDiscovery(t *testing.T) {
 	}
 }
 
-func TestResolveAuthorizationServerUsesProtectedResourceMetadata(t *testing.T) {
-	var authorizationMetadataHits atomic.Int64
-	authorizationServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if r.URL.Path != "/.well-known/oauth-authorization-server" {
-			http.NotFound(w, r)
-			return
-		}
-		authorizationMetadataHits.Add(1)
-		base := "http://" + r.Host
-		_ = json.NewEncoder(w).Encode(map[string]any{
-			"issuer":                 base,
-			"authorization_endpoint": base + "/authorize",
-			"token_endpoint":         base + "/token",
-			"registration_endpoint":  base + "/register",
-		})
-	}))
-	defer authorizationServer.Close()
-
-	var resourceProbeHits, resourceMetadataHits atomic.Int64
-	resourceServer := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		switch r.URL.Path {
-		case "/mcp":
-			resourceProbeHits.Add(1)
-			metadataURL := "http://" + r.Host + "/resource-metadata"
-			w.Header().Set("WWW-Authenticate", `Bearer realm="OAuth", resource_metadata="`+metadataURL+`"`)
-			w.WriteHeader(http.StatusUnauthorized)
-		case "/resource-metadata":
-			resourceMetadataHits.Add(1)
-			_ = json.NewEncoder(w).Encode(map[string]any{
-				"resource":              "http://" + r.Host + "/mcp",
-				"authorization_servers": []string{authorizationServer.URL},
-			})
-		default:
-			http.NotFound(w, r)
-		}
-	}))
-	defer resourceServer.Close()
-
-	metadata, err := resolveAuthorizationServer(context.Background(), resourceServer.Client(), resourceServer.URL+"/mcp", OAuthConfig{})
-	if err != nil {
-		t.Fatalf("resolveAuthorizationServer() error = %v", err)
-	}
-	if metadata.Issuer != authorizationServer.URL {
-		t.Fatalf("issuer = %q, want %q", metadata.Issuer, authorizationServer.URL)
-	}
-	if metadata.AuthorizationEndpoint != authorizationServer.URL+"/authorize" || metadata.TokenEndpoint != authorizationServer.URL+"/token" {
-		t.Fatalf("resolved metadata = %#v", metadata)
-	}
-	if resourceProbeHits.Load() != 1 || resourceMetadataHits.Load() != 1 || authorizationMetadataHits.Load() != 1 {
-		t.Fatalf("discovery hits = probe:%d resource:%d authorization:%d", resourceProbeHits.Load(), resourceMetadataHits.Load(), authorizationMetadataHits.Load())
-	}
-}
-
-func TestResolveAuthorizationServerFallsBackToDirectDiscovery(t *testing.T) {
-	var resourceProbeHits, directDiscoveryHits atomic.Int64
-	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		switch r.URL.Path {
-		case "/mcp":
-			resourceProbeHits.Add(1)
-			w.Header().Set("Content-Type", "text/event-stream")
-			w.WriteHeader(http.StatusOK)
-			if flusher, ok := w.(http.Flusher); ok {
-				flusher.Flush()
-			}
-			<-r.Context().Done()
-		case "/.well-known/oauth-authorization-server/mcp":
-			directDiscoveryHits.Add(1)
-			base := "http://" + r.Host
-			_ = json.NewEncoder(w).Encode(map[string]any{
-				"issuer":                 base + "/mcp",
-				"authorization_endpoint": base + "/authorize",
-				"token_endpoint":         base + "/token",
-			})
-		default:
-			http.NotFound(w, r)
-		}
-	}))
-	defer server.Close()
-
-	metadata, err := resolveAuthorizationServer(context.Background(), server.Client(), server.URL+"/mcp", OAuthConfig{})
-	if err != nil {
-		t.Fatalf("resolveAuthorizationServer() error = %v", err)
-	}
-	if metadata.AuthorizationEndpoint != server.URL+"/authorize" || metadata.TokenEndpoint != server.URL+"/token" {
-		t.Fatalf("resolved metadata = %#v", metadata)
-	}
-	if resourceProbeHits.Load() != 1 || directDiscoveryHits.Load() != 1 {
-		t.Fatalf("discovery hits = probe:%d direct:%d", resourceProbeHits.Load(), directDiscoveryHits.Load())
-	}
-}
-
-func TestResolveAuthorizationServerIssuerOverrideSkipsResourceProbe(t *testing.T) {
-	var resourceProbeHits, issuerDiscoveryHits atomic.Int64
-	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		base := "http://" + r.Host
-		switch r.URL.Path {
-		case "/mcp":
-			resourceProbeHits.Add(1)
-			w.WriteHeader(http.StatusUnauthorized)
-		case "/.well-known/oauth-authorization-server/issuer":
-			issuerDiscoveryHits.Add(1)
-			_ = json.NewEncoder(w).Encode(map[string]any{
-				"issuer":                 base + "/issuer",
-				"authorization_endpoint": base + "/authorize",
-				"token_endpoint":         base + "/token",
-			})
-		default:
-			http.NotFound(w, r)
-		}
-	}))
-	defer server.Close()
-
-	metadata, err := resolveAuthorizationServer(context.Background(), server.Client(), server.URL+"/mcp", OAuthConfig{IssuerURL: server.URL + "/issuer"})
-	if err != nil {
-		t.Fatalf("resolveAuthorizationServer() error = %v", err)
-	}
-	if metadata.AuthorizationEndpoint != server.URL+"/authorize" || metadata.TokenEndpoint != server.URL+"/token" {
-		t.Fatalf("resolved metadata = %#v", metadata)
-	}
-	if resourceProbeHits.Load() != 0 || issuerDiscoveryHits.Load() != 1 {
-		t.Fatalf("discovery hits = resource:%d issuer:%d", resourceProbeHits.Load(), issuerDiscoveryHits.Load())
-	}
-}
-
 func TestPKCEChallengeIsS256OfVerifier(t *testing.T) {
 	pkce, err := newPKCE()
 	if err != nil {
@@ -573,98 +448,3 @@ func TestFullFlowStoresTokens(t *testing.T) {
 		t.Fatalf("login token = %#v", result)
 	}
 }
-
-func TestFullFlowUsesProtectedResourceDiscovery(t *testing.T) {
-	var resourceProbeHits, resourceMetadataHits, authorizationMetadataHits, tokenHits atomic.Int64
-	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		base := "http://" + r.Host
-		switch r.URL.Path {
-		case "/mcp":
-			resourceProbeHits.Add(1)
-			if r.Header.Get("Authorization") != "" || r.Header.Get("Cookie") != "" {
-				t.Error("resource probe sent credentials")
-			}
-			w.Header().Set("WWW-Authenticate", `Bearer resource_metadata="`+base+`/resource-metadata"`)
-			w.WriteHeader(http.StatusUnauthorized)
-		case "/resource-metadata":
-			resourceMetadataHits.Add(1)
-			_ = json.NewEncoder(w).Encode(map[string]any{
-				"resource":              base + "/mcp",
-				"authorization_servers": []string{base},
-			})
-		case "/.well-known/oauth-authorization-server":
-			authorizationMetadataHits.Add(1)
-			_ = json.NewEncoder(w).Encode(map[string]any{
-				"issuer":                 base,
-				"authorization_endpoint": base + "/authorize",
-				"token_endpoint":         base + "/token",
-			})
-		case "/token":
-			tokenHits.Add(1)
-			if err := r.ParseForm(); err != nil {
-				t.Errorf("parse token form: %v", err)
-			}
-			if r.Form.Get("code") != "authorization-code-secret" || r.Form.Get("code_verifier") == "" {
-				t.Error("token exchange omitted the authorization code or PKCE verifier")
-			}
-			_ = json.NewEncoder(w).Encode(map[string]any{
-				"access_token":  "access-token-secret",
-				"refresh_token": "refresh-token-secret",
-				"token_type":    "Bearer",
-				"expires_in":    3600,
-			})
-		default:
-			http.NotFound(w, r)
-		}
-	}))
-	defer server.Close()
-
-	opener := func(authURL string) error {
-		parsed, err := url.Parse(authURL)
-		if err != nil {
-			return err
-		}
-		if parsed.Path != "/authorize" || parsed.Query().Get("code_challenge_method") != "S256" || parsed.Query().Get("code_challenge") == "" {
-			return errors.New("authorization request omitted the discovered endpoint or PKCE challenge")
-		}
-		if parsed.Query().Get("code") != "" || parsed.Query().Get("code_verifier") != "" {
-			return errors.New("authorization request exposed an authorization code or PKCE verifier")
-		}
-		state := parsed.Query().Get("state")
-		redirect := parsed.Query().Get("redirect_uri")
-		go func() {
-			callbackURL := redirect + "?code=authorization-code-secret&state=" + url.QueryEscape(state)
-			for attempt := 0; attempt < 20; attempt++ {
-				response, requestErr := http.Get(callbackURL)
-				if requestErr == nil {
-					response.Body.Close()
-					return
-				}
-				time.Sleep(50 * time.Millisecond)
-			}
-		}()
-		return nil
-	}
-
-	token, err := Login(context.Background(), LoginOptions{
-		ServerName: "notion-style",
-		ServerURL:  server.URL + "/mcp",
-		Config: OAuthConfig{
-			ClientID: "client-123",
-			Scopes:   []string{"read"},
-		},
-		HTTPClient:  server.Client(),
-		OpenBrowser: opener,
-		Timeout:     5 * time.Second,
-		Now:         time.Now,
-	})
-	if err != nil {
-		t.Fatalf("Login() error = %v", err)
-	}
-	if token.AccessToken != "access-token-secret" || token.RefreshToken != "refresh-token-secret" {
-		t.Fatal("login did not return the issued tokens")
-	}
-	if resourceProbeHits.Load() != 1 || resourceMetadataHits.Load() != 1 || authorizationMetadataHits.Load() != 1 || tokenHits.Load() != 1 {
-		t.Fatalf("flow hits = probe:%d resource:%d authorization:%d token:%d", resourceProbeHits.Load(), resourceMetadataHits.Load(), authorizationMetadataHits.Load(), tokenHits.Load())
-	}
-}

internal/mcp/registry.go

@@ -176,11 +176,9 @@ func RegisterTools(ctx context.Context, registry *tools.Registry, cfg config.MCP
 			staged = append(staged, tool)
 		}
 	}
-	registered := make([]tools.Tool, 0, len(staged))
-	for index := range staged {
-		registered = append(registered, staged[index])
+	for _, tool := range staged {
+		registry.Register(tool)
 	}
-	registry.RegisterBatch(registered)
 	return runtime, nil
 }
 

internal/mcp/registry_test.go

@@ -70,62 +70,6 @@ func TestRegisterToolsAddsPromptGatedMCPTools(t *testing.T) {
 	}
 }
 
-func TestRegisterToolsPublishesServerToolsInOneGeneration(t *testing.T) {
-	registry := tools.NewRegistry()
-	before := registry.Snapshot().Generation
-	client := &fakeToolClient{listed: []RemoteTool{
-		{Name: "lookup", Description: "Lookup documentation"},
-		{Name: "search", Description: "Search documentation"},
-	}}
-	runtime, err := RegisterTools(context.Background(), registry, config.MCPConfig{Servers: map[string]config.MCPServerConfig{
-		"docs": {Type: "stdio", Command: "docs-mcp"},
-	}}, RegisterOptions{ClientFactory: func(context.Context, Server) (ToolClient, error) {
-		return client, nil
-	}})
-	if err != nil {
-		t.Fatalf("RegisterTools() error = %v", err)
-	}
-	defer runtime.Close()
-
-	after := registry.Snapshot()
-	if after.Generation != before+1 {
-		t.Fatalf("registry generation = %d, want %d", after.Generation, before+1)
-	}
-	for _, name := range []string{"mcp_docs_lookup", "mcp_docs_search"} {
-		if _, ok := registry.Get(name); !ok {
-			t.Fatalf("expected %s to be published in the batch", name)
-		}
-	}
-}
-
-func TestRegisterToolsPublishesNoneWhenServerToolValidationFails(t *testing.T) {
-	registry := tools.NewRegistry()
-	before := registry.Snapshot().Generation
-	client := &fakeToolClient{listed: []RemoteTool{
-		{Name: "lookup", Description: "Lookup documentation"},
-		{Name: "", Description: "Invalid nameless tool"},
-	}}
-	runtime, err := RegisterTools(context.Background(), registry, config.MCPConfig{Servers: map[string]config.MCPServerConfig{
-		"docs": {Type: "stdio", Command: "docs-mcp"},
-	}}, RegisterOptions{ClientFactory: func(context.Context, Server) (ToolClient, error) {
-		return client, nil
-	}})
-	if err != nil {
-		t.Fatalf("RegisterTools() error = %v", err)
-	}
-	defer runtime.Close()
-
-	if got := registry.Snapshot().Generation; got != before {
-		t.Fatalf("registry generation = %d, want unchanged %d", got, before)
-	}
-	if _, ok := registry.Get("mcp_docs_lookup"); ok {
-		t.Fatal("valid prefix of rejected server batch was published")
-	}
-	if skipped := runtime.Skipped(); len(skipped) != 1 || skipped[0].Name != "docs" || skipped[0].Err == nil {
-		t.Fatalf("Skipped() = %#v, want one validation failure for docs", skipped)
-	}
-}
-
 func TestRegisterToolsMarksPersistentlyApprovedToolsAllow(t *testing.T) {
 	store, err := NewPermissionStore(StoreOptions{
 		FilePath: filepath.Join(t.TempDir(), "permissions.json"),

internal/oauth/lock.go

@@ -5,16 +5,24 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"sync/atomic"
 	"time"
 
 	"github.com/Gitlawb/zero/internal/lockutil"
 )
 
-const fileLockTimeout = 5 * time.Second
+const (
+	fileLockTimeout    = 5 * time.Second
+	fileLockStaleAfter = 30 * time.Second
+)
 
-// acquireFileLock takes a cross-process advisory lock through a stable lock
-// file. It retries with a short backoff until a timeout. Kernel lock lifetime
-// provides crash recovery, so the path is never renamed or removed.
+var lockSeq atomic.Uint64
+
+// acquireFileLock takes a cross-process exclusive lock by creating lockPath with
+// O_EXCL. It retries with a short backoff until a timeout, breaking a lock whose
+// file is older than fileLockStaleAfter (so a crashed holder cannot deadlock the
+// store). Release is ownership-aware: it removes the lock only if it still holds
+// our token, so a stale-broken holder cannot delete a newer holder's lock.
 func acquireFileLock(lockPath string, now func() time.Time) (func(), error) {
 	if now == nil {
 		now = time.Now
@@ -22,15 +30,64 @@ func acquireFileLock(lockPath string, now func() time.Time) (func(), error) {
 	if err := os.MkdirAll(filepath.Dir(lockPath), 0o700); err != nil {
 		return nil, err
 	}
+	token := fmt.Sprintf("%d-%d-%d", os.Getpid(), now().UnixNano(), lockSeq.Add(1))
 	deadline := now().Add(fileLockTimeout)
 	for {
-		lock, err := lockutil.TryAcquireFileLock(lockPath)
+		f, err := os.OpenFile(lockPath, os.O_CREATE|os.O_EXCL|os.O_WRONLY, 0o600)
 		if err == nil {
-			return func() { _ = lock.Release() }, nil
+			// A partial/failed write would leave a lock file without our token, so
+			// the releaser below could never delete it — stranding the lock for
+			// other processes. Fail closed: remove the file and surface the error.
+			if _, werr := f.WriteString(token); werr != nil {
+				_ = f.Close()
+				_ = lockutil.RemoveLockFile(lockPath)
+				return nil, fmt.Errorf("oauth: write token lock: %w", werr)
+			}
+			if cerr := f.Close(); cerr != nil {
+				_ = lockutil.RemoveLockFile(lockPath)
+				return nil, fmt.Errorf("oauth: close token lock: %w", cerr)
+			}
+			var released bool
+			return func() {
+				if released {
+					return
+				}
+				released = true
+				if data, rerr := os.ReadFile(lockPath); rerr == nil && string(data) == token {
+					_ = lockutil.RemoveLockFile(lockPath)
+				}
+			}, nil
 		}
-		if !errors.Is(err, lockutil.ErrLockHeld) {
+		// On Windows a concurrent holder's os.Remove leaves the lock file in a
+		// "delete pending" state, so an O_EXCL create races it with
+		// ERROR_ACCESS_DENIED (os.ErrPermission) rather than ErrExist. Treat that
+		// as contention and retry, exactly like ErrExist — otherwise the lock
+		// spuriously fails under concurrency on Windows.
+		if !errors.Is(err, os.ErrExist) && !errors.Is(err, os.ErrPermission) {
 			return nil, fmt.Errorf("oauth: acquire token lock: %w", err)
 		}
+		// Reclaim a stale lock left by a crashed holder — atomically (H3). A blind
+		// Remove lets two racers both reclaim + recreate and so both hold the lock;
+		// reclaimStaleLock renames the file aside (only one rename wins) and restores
+		// it if it turns out fresh, so a live lock is never deleted out from under it.
+		if info, statErr := os.Stat(lockPath); statErr == nil && time.Since(info.ModTime()) > fileLockStaleAfter {
+			cleared, rerr := lockutil.ReclaimStaleLock(lockPath, token, func(reclaimedPath string) bool {
+				info, err := os.Stat(reclaimedPath)
+				return err == nil && time.Since(info.ModTime()) <= fileLockStaleAfter
+			})
+			if rerr != nil {
+				// Reclaim hit a hard failure: the rename aside failed outright, or a
+				// live holder's lock could not be put back (the lock path may be
+				// missing, so re-acquiring would break mutual exclusion). Fail closed
+				// instead of spinning to the deadline.
+				return nil, fmt.Errorf("oauth: reclaim stale token lock: %w", rerr)
+			}
+			if cleared {
+				continue
+			}
+			// Lost the reclaim race (or it was actually fresh) — fall through to the
+			// bounded wait rather than hot-spinning on a reclaim that never wins.
+		}
 		if now().After(deadline) {
 			return nil, fmt.Errorf("oauth: timed out acquiring token lock %s", filepath.Base(lockPath))
 		}

internal/perfbench/turn_bench.go

@@ -191,7 +191,6 @@ type TurnBenchResult struct {
 type TurnBenchTotals struct {
 	InputTokens       int64 `json:"inputTokens"`
 	CachedInputTokens int64 `json:"cachedInputTokens"`
-	CacheWriteTokens  int64 `json:"cacheWriteTokens"`
 	OutputTokens      int64 `json:"outputTokens"`
 	ModelRequests     int64 `json:"modelRequests"`
 	ToolCalls         int64 `json:"toolCalls"`
@@ -480,7 +479,6 @@ func topLatencySources(perSpan map[string]SpanStats, top int) []LatencySource {
 func aggregateTotals(totals *TurnBenchTotals, tr *trace.TurnTrace) {
 	totals.InputTokens += tr.Counter(trace.CounterInputTokens)
 	totals.CachedInputTokens += tr.Counter(trace.CounterCachedInputTokens)
-	totals.CacheWriteTokens += tr.Counter(trace.CounterCacheWriteTokens)
 	totals.OutputTokens += tr.Counter(trace.CounterOutputTokens)
 	totals.ModelRequests += tr.Counter(trace.CounterModelRequests)
 	totals.ToolCalls += tr.Counter(trace.CounterToolCalls)
@@ -533,9 +531,8 @@ func FormatTurnBenchSummary(result TurnBenchResult) string {
 			lines = append(lines, fmt.Sprintf("  %-18s %10s  %5.1f%%", src.Span, FormatMetric(src.TotalMs, "ms"), src.Share*100))
 		}
 	}
-	lines = append(lines, fmt.Sprintf("totals: in=%d (cache-read %d, cache-write %d, uncached %d) out=%d | requests=%d tools=%d retries=%d reconnects=%d compactions=%d",
-		result.Totals.InputTokens, result.Totals.CachedInputTokens, result.Totals.CacheWriteTokens,
-		uncachedInputTokens(result.Totals), result.Totals.OutputTokens,
+	lines = append(lines, fmt.Sprintf("totals: in=%d (cached %d) out=%d | requests=%d tools=%d retries=%d reconnects=%d compactions=%d",
+		result.Totals.InputTokens, result.Totals.CachedInputTokens, result.Totals.OutputTokens,
 		result.Totals.ModelRequests, result.Totals.ToolCalls, result.Totals.Retries,
 		result.Totals.Reconnects, result.Totals.Compactions))
 	for _, class := range sortedClasses(result.PerClass) {
@@ -548,23 +545,6 @@ func FormatTurnBenchSummary(result TurnBenchResult) string {
 	return strings.Join(lines, "\n")
 }
 
-func uncachedInputTokens(totals TurnBenchTotals) int64 {
-	remaining := totals.InputTokens
-	if remaining <= 0 {
-		return 0
-	}
-	for _, cached := range []int64{totals.CachedInputTokens, totals.CacheWriteTokens} {
-		if cached <= 0 {
-			continue
-		}
-		if cached >= remaining {
-			return 0
-		}
-		remaining -= cached
-	}
-	return remaining
-}
-
 // classTier returns the oracle tier label a class was classified into, so the
 // per-class roll-up states explicitly which oracle (if any) its "passed" count
 // is measured against.

internal/perfbench/turn_bench_test.go

@@ -74,7 +74,6 @@ func TestRunTurnBenchAggregation(t *testing.T) {
 		"t3": cannedTrace(150, 20, 1500),
 		"t4": cannedTrace(300, 10, 1000),
 	}
-	canned["t1"].Counters = append(canned["t1"].Counters, trace.Counter{Name: trace.CounterCacheWriteTokens, Value: 125})
 	cfg := TurnBenchConfig{
 		Model:      "fake-model",
 		Iterations: 1,
@@ -156,9 +155,6 @@ func TestRunTurnBenchAggregation(t *testing.T) {
 	if result.Totals.InputTokens != 5500 {
 		t.Fatalf("inputTokens = %d, want 5500", result.Totals.InputTokens)
 	}
-	if result.Totals.CacheWriteTokens != 125 {
-		t.Fatalf("cacheWriteTokens = %d, want 125", result.Totals.CacheWriteTokens)
-	}
 	if result.Totals.OutputTokens != 2750 {
 		t.Fatalf("outputTokens = %d, want 2750", result.Totals.OutputTokens)
 	}
@@ -338,35 +334,6 @@ func TestFormatTurnBenchSummaryNamesTopSources(t *testing.T) {
 	}
 }
 
-func TestUncachedInputTokensClampsInconsistentTotals(t *testing.T) {
-	tests := []struct {
-		name   string
-		totals TurnBenchTotals
-		want   int64
-	}{
-		{name: "normal", totals: TurnBenchTotals{InputTokens: 100, CachedInputTokens: 30, CacheWriteTokens: 20}, want: 50},
-		{name: "cached exceeds input", totals: TurnBenchTotals{InputTokens: 100, CachedInputTokens: 120}, want: 0},
-		{name: "write exceeds remainder", totals: TurnBenchTotals{InputTokens: 100, CachedInputTokens: 20, CacheWriteTokens: 90}, want: 0},
-		{name: "overflowing inconsistent counters", totals: TurnBenchTotals{CachedInputTokens: 1<<63 - 1, CacheWriteTokens: 1<<63 - 1}, want: 0},
-		{name: "overflowing counters with input", totals: TurnBenchTotals{InputTokens: 100, CachedInputTokens: 1<<63 - 1, CacheWriteTokens: 1<<63 - 1}, want: 0},
-		{name: "negative cache counters ignored", totals: TurnBenchTotals{InputTokens: 100, CachedInputTokens: -20, CacheWriteTokens: -10}, want: 100},
-	}
-	for _, test := range tests {
-		t.Run(test.name, func(t *testing.T) {
-			if got := uncachedInputTokens(test.totals); got != test.want {
-				t.Fatalf("uncachedInputTokens(%+v) = %d, want %d", test.totals, got, test.want)
-			}
-		})
-	}
-	summary := FormatTurnBenchSummary(TurnBenchResult{Totals: TurnBenchTotals{
-		CachedInputTokens: 1<<63 - 1,
-		CacheWriteTokens:  1<<63 - 1,
-	}})
-	if !strings.Contains(summary, "uncached 0") {
-		t.Fatalf("summary did not clamp inconsistent cache totals:\n%s", summary)
-	}
-}
-
 func TestLoadBaselineManifest(t *testing.T) {
 	path := filepath.Join("manifests", "baseline.json")
 	set, err := LoadTaskSet(path)

internal/providerhealth/providerhealth.go

@@ -19,7 +19,6 @@ import (
 	"github.com/Gitlawb/zero/internal/providercatalog"
 	"github.com/Gitlawb/zero/internal/providers"
 	"github.com/Gitlawb/zero/internal/providers/providerio"
-	"github.com/Gitlawb/zero/internal/proxydial"
 	"github.com/Gitlawb/zero/internal/redaction"
 )
 
@@ -519,15 +518,9 @@ func newConnectivityClient(timeout time.Duration, resolver Resolver, sensitiveHe
 		transport = &http.Transport{}
 	}
 	transport.DialContext = safeDialContext(resolver, allowLoopbackOrPrivate)
-	// WRAPPED, SO THE DIALER LEARNS THE ROUTE THIS TRANSPORT CHOSE. The wrapper
-	// records the proxy selected for each request on that request, and the
-	// dialer reads it back on the dial that request causes; installing the bare
-	// transport instead would leave a proxied dial looking like a loopback
-	// target and fail the probe (#569). The cloned default transport already
-	// reads HTTPS_PROXY and friends; nothing new is enabled.
 	return &http.Client{
 		Timeout:   timeout,
-		Transport: proxydial.Wrap(transport),
+		Transport: transport,
 		CheckRedirect: func(req *http.Request, via []*http.Request) error {
 			if len(via) >= maxConnectivityRedirects {
 				return fmt.Errorf("provider connectivity exceeded %d redirects", maxConnectivityRedirects)
@@ -590,17 +583,6 @@ func sensitiveAuthHeaderNames(profile config.ProviderProfile, kind config.Provid
 func safeDialContext(resolver Resolver, allowLoopbackOrPrivate bool) func(context.Context, string, string) (net.Conn, error) {
 	dialer := &net.Dialer{Timeout: 10 * time.Second, KeepAlive: 30 * time.Second}
 	return func(ctx context.Context, network, address string) (net.Conn, error) {
-		// THE PROXY IS NOT THE TARGET. With HTTPS_PROXY set to a local forward
-		// proxy, the transport dials the proxy first and tunnels the request
-		// through it, and this dialer used to refuse that dial as a loopback
-		// address: "proxyconnect tcp: ... loopback hosts are blocked" for a
-		// request whose real target had already been validated (#569). The
-		// target validation is unchanged; only the dial the transport opens to
-		// the proxy it picked for this very request is let past the guard, and a
-		// direct dial is checked as it always was.
-		if proxydial.IsProxyDial(ctx) {
-			return dialer.DialContext(ctx, network, address)
-		}
 		host, port, err := net.SplitHostPort(address)
 		if err != nil {
 			return nil, err

internal/providerhealth/proxy_dial_test.go

@@ -1,218 +0,0 @@
-package providerhealth
-
-import (
-	"context"
-	"errors"
-	"net"
-	"net/http"
-	"net/netip"
-	"net/url"
-	"strconv"
-	"strings"
-	"testing"
-	"time"
-
-	"github.com/Gitlawb/zero/internal/proxydial"
-)
-
-// connectivityClientWithProxy builds the real connectivity client and swaps in
-// a proxy function, which is how the transport learns its route. The
-// environment is left alone deliberately: http.ProxyFromEnvironment reads it
-// once per process, so an environment-driven test would depend on test order.
-func connectivityClientWithProxy(t *testing.T, resolver Resolver, proxyFor func(*http.Request) (*url.URL, error)) *http.Client {
-	t.Helper()
-	client := newConnectivityClient(3*time.Second, resolver, nil, false)
-	wrapped, ok := client.Transport.(*proxydial.Transport)
-	if !ok {
-		t.Fatalf("transport = %T, want the route-recording wrapper; without it no dial can be recognised as the proxy dial", client.Transport)
-	}
-	wrapped.Proxy = proxyFor
-	return client
-}
-
-// recordingProxy is a listener standing in for a local forward proxy. It
-// records the first line it receives and hangs up.
-func recordingProxy(t *testing.T) (*url.URL, <-chan string) {
-	t.Helper()
-	listener, err := net.Listen("tcp", "127.0.0.1:0")
-	if err != nil {
-		t.Fatal(err)
-	}
-	t.Cleanup(func() { _ = listener.Close() })
-	arrived := make(chan string, 1)
-	go func() {
-		conn, err := listener.Accept()
-		if err != nil {
-			return
-		}
-		defer conn.Close()
-		buffer := make([]byte, 256)
-		n, _ := conn.Read(buffer)
-		arrived <- string(buffer[:n])
-	}()
-	proxyURL, err := url.Parse("http://" + listener.Addr().String())
-	if err != nil {
-		t.Fatal(err)
-	}
-	return proxyURL, arrived
-}
-
-// THE PROXY IS NOT THE TARGET, AND THE GUARD HAS TO KNOW THE DIFFERENCE.
-//
-// With HTTPS_PROXY set to a local forward proxy, the transport dials the proxy
-// first and tunnels the request through it. This dialer refused that dial as a
-// loopback address, so `zero doctor --connectivity` failed with "proxyconnect
-// tcp: ... loopback hosts are blocked" for a target that had already been
-// validated and was public (#569). Driven through the real client, so the route
-// is the transport's own decision.
-func TestConnectivityClientTunnelsThroughTheConfiguredProxy(t *testing.T) {
-	proxyURL, arrived := recordingProxy(t)
-	client := connectivityClientWithProxy(t,
-		staticResolver{err: errors.New("resolver must not be called for a proxied request")},
-		func(*http.Request) (*url.URL, error) { return proxyURL, nil })
-
-	request, err := http.NewRequestWithContext(context.Background(), http.MethodGet, "https://api.example.com/v1/models", nil)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, err = client.Do(request)
-	select {
-	case first := <-arrived:
-		if line := strings.SplitN(first, "\r\n", 2)[0]; line != "CONNECT api.example.com:443 HTTP/1.1" {
-			t.Fatalf("proxy received %q, want a CONNECT for the validated target", line)
-		}
-	case <-time.After(5 * time.Second):
-		t.Fatalf("the proxy never received a connection; request error: %v", err)
-	}
-}
-
-// AND A DIRECT REQUEST STAYS GUARDED, EVEN WHEN ITS ORIGIN IS THE PROXY'S OWN
-// ADDRESS.
-//
-// This is the NO_PROXY shape: the proxy function sends one host direct. An
-// exemption derived from asking that function about a request of our own
-// invention would answer "proxied" for the excluded host too, and this dial,
-// whose address equals the configured proxy endpoint, would skip the resolver
-// and reach whatever the name resolves to at connect time.
-func TestDirectRequestToTheProxyEndpointIsStillGuarded(t *testing.T) {
-	proxyURL, err := url.Parse("http://rebind.example:80")
-	if err != nil {
-		t.Fatal(err)
-	}
-	lookups := 0
-	resolver := countingResolver{
-		onLookup: func() { lookups++ },
-		addr:     netip.MustParseAddr("10.0.0.5"),
-	}
-	client := connectivityClientWithProxy(t, resolver, func(request *http.Request) (*url.URL, error) {
-		if request.URL.Hostname() == "rebind.example" {
-			return nil, nil
-		}
-		return proxyURL, nil
-	})
-
-	request, err := http.NewRequestWithContext(context.Background(), http.MethodGet, "http://rebind.example/data", nil)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, err = client.Do(request)
-
-	if lookups == 0 {
-		t.Fatal("the direct dial skipped the safety resolver because its address matched the configured proxy endpoint")
-	}
-	var safety endpointSafetyError
-	if !errors.As(err, &safety) {
-		t.Fatalf("err = %v, want the private answer to be refused", err)
-	}
-}
-
-// A proxy configured with a Unicode hostname is dialed by its IDNA-encoded
-// name, and it is still the proxy: the request must reach it rather than be
-// refused as an ordinary private address.
-func TestUnicodeProxyHostnameIsStillTheProxy(t *testing.T) {
-	dialed := ""
-	client := connectivityClientWithProxy(t,
-		staticResolver{err: errors.New("resolver must not be called for a proxied request")},
-		func(*http.Request) (*url.URL, error) { return url.Parse("http://büro.example:3067") })
-	wrapped := client.Transport.(*proxydial.Transport)
-	guarded := wrapped.DialContext
-	wrapped.DialContext = func(ctx context.Context, network, address string) (net.Conn, error) {
-		dialed = address
-		return guarded(ctx, network, address)
-	}
-
-	request, err := http.NewRequestWithContext(context.Background(), http.MethodGet, "https://api.example.com/v1/models", nil)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, err = client.Do(request)
-
-	if dialed != "xn--bro-hoa.example:3067" {
-		t.Fatalf("SETUP INVALID: dialed %q, want the IDNA-encoded proxy endpoint", dialed)
-	}
-	var safety endpointSafetyError
-	if errors.As(err, &safety) {
-		t.Fatalf("the configured proxy was refused by the guard: %v", err)
-	}
-}
-
-// Without a proxy the guard is exactly what it was: loopback is refused.
-func TestSafeDialContextStillRefusesLoopbackWithoutAProxy(t *testing.T) {
-	dial := safeDialContext(staticResolver{err: errors.New("resolver must not be called")}, false)
-	conn, err := dial(context.Background(), "tcp", "127.0.0.1:3067")
-	if conn != nil {
-		_ = conn.Close()
-		t.Fatal("loopback was dialed with no proxy configured")
-	}
-	var safety endpointSafetyError
-	if !errors.As(err, &safety) {
-		t.Fatalf("err = %v, want endpointSafetyError", err)
-	}
-}
-
-// A sibling loopback port is not the proxy, and the guard is unchanged for it.
-func TestSafeDialContextRefusesALoopbackPortThatIsNotTheProxy(t *testing.T) {
-	proxyURL, arrived := recordingProxy(t)
-	client := connectivityClientWithProxy(t,
-		staticResolver{err: errors.New("resolver must not be called")},
-		func(request *http.Request) (*url.URL, error) {
-			// Only the https probe is proxied; the http one below is direct and
-			// happens to point at the neighbouring port.
-			if request.URL.Scheme == "https" {
-				return proxyURL, nil
-			}
-			return nil, nil
-		})
-
-	_, port, _ := net.SplitHostPort(proxyURL.Host)
-	number, _ := strconv.Atoi(port)
-	sibling := "http://" + net.JoinHostPort("127.0.0.1", strconv.Itoa(number+1)) + "/"
-	request, err := http.NewRequestWithContext(context.Background(), http.MethodGet, sibling, nil)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, err = client.Do(request)
-	var safety endpointSafetyError
-	if !errors.As(err, &safety) {
-		t.Fatalf("err = %v, want a loopback port beside the proxy to stay blocked", err)
-	}
-	select {
-	case first := <-arrived:
-		t.Fatalf("the proxy received a connection it should not have: %q", first)
-	default:
-	}
-}
-
-// countingResolver answers with one address and reports each lookup, so a test
-// can tell a skipped guard from a guard that ran and allowed the address.
-type countingResolver struct {
-	onLookup func()
-	addr     netip.Addr
-}
-
-func (resolver countingResolver) LookupNetIP(context.Context, string, string) ([]netip.Addr, error) {
-	if resolver.onLookup != nil {
-		resolver.onLookup()
-	}
-	return []netip.Addr{resolver.addr}, nil
-}

internal/providers/openai/codex_responses.go

@@ -62,7 +62,6 @@ const (
 	responsesEventReasoningDelta    = "response.reasoning_summary_text.delta"
 	responsesEventOutputTextDone    = "response.output_text.done"
 	responsesEventFunctionArgsDelta = "response.function_call_arguments.delta"
-	responsesEventCustomInputDelta  = "response.custom_tool_call_input.delta"
 	responsesEventContentPartDone   = "response.content_part.done"
 	responsesEventOutputItemDone    = "response.output_item.done"
 	responsesEventCompleted         = "response.completed"
@@ -71,37 +70,17 @@ const (
 	responsesEventIncomplete        = "response.incomplete"
 )
 
-const applyPatchLarkGrammar = `start: begin_patch hunk+ end_patch
-begin_patch: "*** Begin Patch" LF
-end_patch: "*** End Patch" LF?
-hunk: add_hunk | delete_hunk | update_hunk
-add_hunk: "*** Add File: " filename LF add_line+
-delete_hunk: "*** Delete File: " filename LF
-update_hunk: "*** Update File: " filename LF change_move? change?
-filename: /(.+)/
-add_line: "+" /(.*)/ LF -> line
-change_move: "*** Move to: " filename LF
-change: (change_context | change_line)+ eof_line?
-change_context: ("@@" | "@@ " /(.+)/) LF
-change_line: ("+" | "-" | " ") /(.*)/ LF
-eof_line: "*** End of File" LF
-%import common.LF`
-
 // responsesRequest is the wire shape POSTed to {baseURL}/responses.
 type responsesRequest struct {
-	Type               string              `json:"type,omitempty"`
-	Model              string              `json:"model"`
-	Instructions       string              `json:"instructions"`
-	PreviousResponseID string              `json:"previous_response_id,omitempty"`
-	Input              []inputItem         `json:"input"`
-	Stream             bool                `json:"stream"`
-	Store              bool                `json:"store"`
-	ParallelToolCalls  bool                `json:"parallel_tool_calls"`
-	MaxOutputTokens    int                 `json:"max_output_tokens,omitempty"`
-	Tools              []responsesTool     `json:"tools,omitempty"`
-	Reasoning          *responsesReasoning `json:"reasoning,omitempty"`
-	ServiceTier        string              `json:"service_tier,omitempty"`
-	PromptCacheKey     string              `json:"prompt_cache_key,omitempty"`
+	Model           string              `json:"model"`
+	Instructions    string              `json:"instructions"`
+	Input           []inputItem         `json:"input"`
+	Stream          bool                `json:"stream"`
+	Store           bool                `json:"store"`
+	MaxOutputTokens int                 `json:"max_output_tokens,omitempty"`
+	Tools           []responsesTool     `json:"tools,omitempty"`
+	Reasoning       *responsesReasoning `json:"reasoning,omitempty"`
+	ServiceTier     string              `json:"service_tier,omitempty"`
 }
 
 // responsesReasoning carries the reasoning controls for the Responses API. The
@@ -126,7 +105,6 @@ type inputItem struct {
 	CallID    string `json:"call_id,omitempty"`
 	Name      string `json:"name,omitempty"`
 	Arguments string `json:"arguments,omitempty"`
-	Input     string `json:"input,omitempty"`
 	// function_call_output fields
 	Output any `json:"output,omitempty"`
 }
@@ -140,11 +118,10 @@ type contentItem struct {
 }
 
 type responsesTool struct {
-	Type        string                            `json:"type"`
-	Name        string                            `json:"name"`
-	Description string                            `json:"description,omitempty"`
-	Parameters  map[string]any                    `json:"parameters,omitempty"`
-	Format      *zeroruntime.ToolDefinitionFormat `json:"format,omitempty"`
+	Type        string         `json:"type"`
+	Name        string         `json:"name"`
+	Description string         `json:"description,omitempty"`
+	Parameters  map[string]any `json:"parameters,omitempty"`
 }
 
 // responsesEvent is the decoded form of one Responses SSE data payload.
@@ -155,7 +132,6 @@ type responsesEvent struct {
 	Delta string `json:"delta,omitempty"`
 	// item payloads (response.output_item.added / done)
 	ItemID string `json:"item_id,omitempty"`
-	CallID string `json:"call_id,omitempty"`
 	// OutputIndex is a *int so a real 0 (the first output) is distinguishable from
 	// "absent" — a plain int defaulting to 0 dropped a no-item_id call's args (M1).
 	OutputIndex *int         `json:"output_index,omitempty"`
@@ -174,7 +150,6 @@ type itemPayload struct {
 	CallID    string `json:"call_id,omitempty"`
 	Name      string `json:"name,omitempty"`
 	Arguments string `json:"arguments,omitempty"`
-	Input     string `json:"input,omitempty"`
 	Status    string `json:"status,omitempty"`
 }
 
@@ -198,8 +173,7 @@ type outputDetails struct {
 }
 
 type inputDetails struct {
-	CachedTokens     int `json:"cached_tokens"`
-	CacheWriteTokens int `json:"cache_write_tokens"`
+	CachedTokens int `json:"cached_tokens"`
 }
 
 type errorPayload struct {
@@ -213,10 +187,8 @@ type errorPayload struct {
 // response.output_item.done.
 type toolCallBuilder struct {
 	ID        string
-	CallID    string
 	Name      string
 	Arguments strings.Builder
-	Freeform  bool
 	started   bool
 	ended     bool
 }
@@ -225,57 +197,15 @@ type toolCallBuilder struct {
 // event has been emitted. It is the Responses-API equivalent of the
 // chat-completions toolState in provider.go.
 type responsesState struct {
-	toolCalls  map[string]*toolCallBuilder
-	toolOrder  []string
-	text       strings.Builder
-	responseID string
-	usage      *usagePayload
-	emitted    bool
-	done       bool
+	toolCalls map[string]*toolCallBuilder
+	usage     *usagePayload
+	done      bool
 }
 
 func newResponsesState() *responsesState {
 	return &responsesState{toolCalls: map[string]*toolCallBuilder{}}
 }
 
-func (state *responsesState) outputInputItems() []inputItem {
-	items := make([]inputItem, 0, len(state.toolOrder)+1)
-	if state.text.Len() > 0 {
-		items = append(items, inputItem{
-			Type:    "message",
-			Role:    "assistant",
-			Content: []contentItem{{Type: "output_text", Text: state.text.String()}},
-		})
-	}
-	for _, key := range state.toolOrder {
-		builder := state.toolCalls[key]
-		if builder == nil || builder.ID == "" || builder.Name == "" {
-			continue
-		}
-		callID := builder.CallID
-		if callID == "" {
-			callID = builder.ID
-		}
-		itemType := "function_call"
-		if builder.Freeform {
-			itemType = "custom_tool_call"
-		}
-		item := inputItem{
-			Type:   itemType,
-			ID:     builder.ID,
-			CallID: callID,
-			Name:   builder.Name,
-		}
-		if builder.Freeform {
-			item.Input = builder.Arguments.String()
-		} else {
-			item.Arguments = builder.Arguments.String()
-		}
-		items = append(items, item)
-	}
-	return items
-}
-
 // buildResponsesRequest converts a runtime CompletionRequest into the
 // Responses API wire format. System messages fold into a top-level
 // `instructions` field; everything else (user/assistant turns, tool
@@ -285,14 +215,11 @@ func (p *CodexProvider) buildResponsesRequest(request zeroruntime.CompletionRequ
 		return nil, errors.New("codex provider: model is required")
 	}
 	req := &responsesRequest{
-		Model:             p.inner.model,
-		Stream:            true,
-		ParallelToolCalls: true,
-		MaxOutputTokens:   p.inner.maxTokens,
-		PromptCacheKey:    request.PromptCacheKey,
+		Model:           p.inner.model,
+		Stream:          true,
+		MaxOutputTokens: p.inner.maxTokens,
 	}
 	instructions := []string{}
-	customCallIDs := map[string]string{}
 	for _, msg := range request.Messages {
 		switch msg.Role {
 		case zeroruntime.MessageRoleSystem:
@@ -307,31 +234,13 @@ func (p *CodexProvider) buildResponsesRequest(request zeroruntime.CompletionRequ
 				return nil, err
 			}
 			req.Input = append(req.Input, items...)
-			for _, call := range msg.ToolCalls {
-				if call.Freeform && call.ID != "" {
-					callID := call.ProviderCallID
-					if callID == "" {
-						callID = call.ID
-					}
-					customCallIDs[call.ID] = callID
-				}
-			}
 		case zeroruntime.MessageRoleTool:
 			if msg.ToolCallID == "" {
 				return nil, fmt.Errorf("codex provider: tool message missing tool call id")
 			}
-			outputType := "function_call_output"
-			callID := msg.ToolCallProviderID
-			if callID == "" {
-				callID = msg.ToolCallID
-			}
-			if customID, custom := customCallIDs[msg.ToolCallID]; custom {
-				outputType = "custom_tool_call_output"
-				callID = customID
-			}
 			req.Input = append(req.Input, inputItem{
-				Type:   outputType,
-				CallID: callID,
+				Type:   "function_call_output",
+				CallID: msg.ToolCallID,
 				Output: msg.Content,
 			})
 		default:
@@ -340,25 +249,12 @@ func (p *CodexProvider) buildResponsesRequest(request zeroruntime.CompletionRequ
 	}
 	req.Instructions = strings.Join(instructions, "\n\n")
 	for _, tool := range request.Tools {
-		definition := tool
-		if definition.Name == "apply_patch" && definition.Type == zeroruntime.ToolDefinitionFreeform {
-			definition.Description = "The apply_patch tool edits files from a raw structured patch. Use absolute file paths in patch headers to target a granted extra write root. Do not wrap the patch in JSON."
-			definition.Format = &zeroruntime.ToolDefinitionFormat{Type: "grammar", Syntax: "lark", Definition: applyPatchLarkGrammar}
-		}
-		wireTool := responsesTool{
-			Type:        string(definition.Type),
-			Name:        definition.Name,
-			Description: definition.Description,
-			Parameters:  definition.Parameters,
-			Format:      definition.Format,
-		}
-		if wireTool.Type == "" {
-			wireTool.Type = string(zeroruntime.ToolDefinitionFunction)
-		}
-		if wireTool.Type == string(zeroruntime.ToolDefinitionFreeform) {
-			wireTool.Parameters = nil
-		}
-		req.Tools = append(req.Tools, wireTool)
+		req.Tools = append(req.Tools, responsesTool{
+			Type:        "function",
+			Name:        tool.Name,
+			Description: tool.Description,
+			Parameters:  tool.Parameters,
+		})
 	}
 	// Codex / o-series reasoning models take the effort tier nested under
 	// `reasoning` on the Responses API (the chat-completions `reasoning_effort`
@@ -416,26 +312,13 @@ func (p *CodexProvider) assistantInputItems(msg zeroruntime.Message) ([]inputIte
 		if tc.Name == "" {
 			return nil, errors.New("codex provider: assistant tool call missing name")
 		}
-		callID := tc.ProviderCallID
-		if callID == "" {
-			callID = tc.ID
-		}
-		itemType := "function_call"
-		if tc.Freeform {
-			itemType = "custom_tool_call"
-		}
-		item := inputItem{
-			Type:   itemType,
-			ID:     tc.ID,
-			CallID: callID,
-			Name:   tc.Name,
-		}
-		if tc.Freeform {
-			item.Input = tc.Arguments
-		} else {
-			item.Arguments = tc.Arguments
-		}
-		items = append(items, item)
+		items = append(items, inputItem{
+			Type:      "function_call",
+			ID:        tc.ID,
+			CallID:    tc.ID,
+			Name:      tc.Name,
+			Arguments: tc.Arguments,
+		})
 	}
 	return items, nil
 }
@@ -596,18 +479,6 @@ func (p *CodexProvider) emitResponsesEvent(
 		state.done = true
 		return false
 	}
-	return p.emitParsedResponsesEvent(ctx, &event, state, events)
-}
-
-// emitParsedResponsesEvent converts one already-decoded Responses event into
-// zero or more runtime events. WebSocket sessions use this path to avoid
-// decoding each frame twice; the SSE path retains emitResponsesEvent above.
-func (p *CodexProvider) emitParsedResponsesEvent(
-	ctx context.Context,
-	event *responsesEvent,
-	state *responsesState,
-	events chan<- zeroruntime.StreamEvent,
-) bool {
 	if event.Type == "" {
 		// A payload that parses as JSON but carries no `type` field is a
 		// malformed Responses event — the type is the discriminator that
@@ -629,17 +500,12 @@ func (p *CodexProvider) emitParsedResponsesEvent(
 		// the runtime. response.incomplete is folded into a length finish at
 		// scan-end (state.done stays false so the wrapper emits the
 		// StreamEventDone with FinishReasonLength).
-		if event.Response != nil && event.Response.ID != "" {
-			state.responseID = event.Response.ID
-		}
 		return true
 	case responsesEventOutputItemAdded:
-		p.handleOutputItemAdded(ctx, event, state, events)
+		p.handleOutputItemAdded(ctx, &event, state, events)
 		return true
 	case responsesEventOutputTextDelta:
 		if event.Delta != "" {
-			state.emitted = true
-			state.text.WriteString(event.Delta)
 			providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
 				Type:    zeroruntime.StreamEventText,
 				Content: event.Delta,
@@ -651,7 +517,6 @@ func (p *CodexProvider) emitParsedResponsesEvent(
 		// phase shows progress (and keeps the activity clock fresh) instead of
 		// looking like a hang. Requested via reasoning.summary="auto".
 		if event.Delta != "" {
-			state.emitted = true
 			providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
 				Type:    zeroruntime.StreamEventReasoning,
 				Content: event.Delta,
@@ -659,16 +524,13 @@ func (p *CodexProvider) emitParsedResponsesEvent(
 		}
 		return true
 	case responsesEventFunctionArgsDelta:
-		p.handleToolInputDelta(ctx, event, state, events, false)
-		return true
-	case responsesEventCustomInputDelta:
-		p.handleToolInputDelta(ctx, event, state, events, true)
+		p.handleFunctionArgsDelta(ctx, &event, state, events)
 		return true
 	case responsesEventOutputItemDone:
-		p.handleOutputItemDone(ctx, event, state, events)
+		p.handleOutputItemDone(ctx, &event, state, events)
 		return true
 	case responsesEventCompleted, responsesEventFailed:
-		return p.handleTerminalResponse(ctx, event, state, events)
+		return p.handleTerminalResponse(ctx, &event, state, events)
 	case responsesEventError:
 		message := event.Message
 		if event.Code != "" {
@@ -708,38 +570,22 @@ func (p *CodexProvider) handleOutputItemAdded(
 		return
 	}
 	switch event.Item.Type {
-	case "function_call", "custom_tool_call":
+	case "function_call":
 		key := p.toolCallKey(event)
 		if key == "" {
 			return
 		}
-		builder, exists := state.toolCalls[key]
-		if !exists {
-			builder = &toolCallBuilder{ID: key, Freeform: event.Item.Type == "custom_tool_call"}
-			state.toolCalls[key] = builder
-			state.toolOrder = append(state.toolOrder, key)
-		}
-		if event.Item.CallID != "" {
-			builder.CallID = event.Item.CallID
-		}
-		if event.Item.Name != "" {
-			builder.Name = event.Item.Name
-		}
-		builder.Freeform = builder.Freeform || event.Item.Type == "custom_tool_call"
-		if builder.Freeform && event.Item.Input != "" && builder.Arguments.Len() == 0 {
-			builder.Arguments.WriteString(event.Item.Input)
-		}
-		state.emitted = true
-		if !builder.started {
-			providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
-				Type:               zeroruntime.StreamEventToolCallStart,
-				ToolCallID:         key,
-				ToolCallProviderID: builder.CallID,
-				ToolName:           builder.Name,
-				ToolCallFreeform:   builder.Freeform,
-			})
-			builder.started = true
+		builder := &toolCallBuilder{
+			ID:   key,
+			Name: event.Item.Name,
 		}
+		state.toolCalls[key] = builder
+		providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
+			Type:       zeroruntime.StreamEventToolCallStart,
+			ToolCallID: key,
+			ToolName:   event.Item.Name,
+		})
+		builder.started = true
 	}
 }
 
@@ -747,12 +593,11 @@ func (p *CodexProvider) handleOutputItemAdded(
 // to the in-flight builder and emits StreamEventToolCallDelta. The
 // Codex backend uses either `item_id` or `output_index` to attribute
 // the delta; we honor both.
-func (p *CodexProvider) handleToolInputDelta(
+func (p *CodexProvider) handleFunctionArgsDelta(
 	ctx context.Context,
 	event *responsesEvent,
 	state *responsesState,
 	events chan<- zeroruntime.StreamEvent,
-	freeform bool,
 ) {
 	key := p.toolCallKey(event)
 	if key == "" {
@@ -765,16 +610,10 @@ func (p *CodexProvider) handleToolInputDelta(
 		// an intermediate proxy). Treat the delta as the start of a new
 		// tool call with no known name yet — the eventual
 		// response.output_item.done carries the final name.
-		builder = &toolCallBuilder{ID: key, Freeform: freeform}
+		builder = &toolCallBuilder{ID: key}
 		state.toolCalls[key] = builder
-		state.toolOrder = append(state.toolOrder, key)
-	}
-	builder.Freeform = builder.Freeform || freeform
-	if event.CallID != "" && builder.CallID == "" {
-		builder.CallID = event.CallID
 	}
 	builder.Arguments.WriteString(event.Delta)
-	state.emitted = true
 	providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
 		Type:              zeroruntime.StreamEventToolCallDelta,
 		ToolCallID:        key,
@@ -793,7 +632,7 @@ func (p *CodexProvider) handleOutputItemDone(
 	state *responsesState,
 	events chan<- zeroruntime.StreamEvent,
 ) {
-	if event.Item == nil || (event.Item.Type != "function_call" && event.Item.Type != "custom_tool_call") {
+	if event.Item == nil || event.Item.Type != "function_call" {
 		return
 	}
 	key := p.toolCallKey(event)
@@ -802,31 +641,20 @@ func (p *CodexProvider) handleOutputItemDone(
 	}
 	builder, ok := state.toolCalls[key]
 	if !ok {
-		builder = &toolCallBuilder{ID: key, Freeform: event.Item.Type == "custom_tool_call"}
+		builder = &toolCallBuilder{ID: key}
 		state.toolCalls[key] = builder
-		state.toolOrder = append(state.toolOrder, key)
 	}
 	if event.Item.Name != "" {
 		builder.Name = event.Item.Name
 	}
-	if event.Item.CallID != "" {
-		builder.CallID = event.Item.CallID
-	}
-	builder.Freeform = builder.Freeform || event.Item.Type == "custom_tool_call"
-	finalInput := event.Item.Arguments
-	if builder.Freeform {
-		finalInput = event.Item.Input
-	}
-	if finalInput != "" && builder.Arguments.Len() == 0 {
-		builder.Arguments.WriteString(finalInput)
+	if event.Item.Arguments != "" && builder.Arguments.Len() == 0 {
+		builder.Arguments.WriteString(event.Item.Arguments)
 	}
 	if !builder.started {
 		providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
-			Type:               zeroruntime.StreamEventToolCallStart,
-			ToolCallID:         key,
-			ToolCallProviderID: builder.CallID,
-			ToolName:           builder.Name,
-			ToolCallFreeform:   builder.Freeform,
+			Type:       zeroruntime.StreamEventToolCallStart,
+			ToolCallID: key,
+			ToolName:   builder.Name,
 		})
 		builder.started = true
 	}
@@ -836,7 +664,6 @@ func (p *CodexProvider) handleOutputItemDone(
 		ToolName:   builder.Name,
 	})
 	builder.ended = true
-	state.emitted = true
 }
 
 // handleTerminalResponse emits the final usage + done event for a
@@ -866,7 +693,6 @@ func (p *CodexProvider) handleTerminalResponse(
 		return false
 	}
 	state.usage = event.Response.Usage
-	state.responseID = event.Response.ID
 	if event.Response.Usage != nil {
 		usage := zeroruntime.Usage{
 			InputTokens:  event.Response.Usage.InputTokens,
@@ -874,7 +700,6 @@ func (p *CodexProvider) handleTerminalResponse(
 		}
 		if event.Response.Usage.InputTokensDetails != nil {
 			usage.CachedInputTokens = event.Response.Usage.InputTokensDetails.CachedTokens
-			usage.CacheWriteTokens = event.Response.Usage.InputTokensDetails.CacheWriteTokens
 		}
 		if event.Response.Usage.OutputTokensDetails != nil {
 			usage.ReasoningTokens = event.Response.Usage.OutputTokensDetails.ReasoningTokens
@@ -910,7 +735,7 @@ func (p *CodexProvider) handleTerminalResponse(
 		state.done = true
 		return false
 	}
-	providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{Type: zeroruntime.StreamEventDone, ResponseID: event.Response.ID})
+	providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{Type: zeroruntime.StreamEventDone})
 	state.done = true
 	return false
 }
@@ -929,9 +754,6 @@ func (p *CodexProvider) toolCallKey(event *responsesEvent) string {
 	if event.Item != nil && event.Item.CallID != "" {
 		return event.Item.CallID
 	}
-	if event.CallID != "" {
-		return event.CallID
-	}
 	if event.OutputIndex != nil {
 		// output_index is present (a *int distinguishes a real 0 — the first output
 		// in the response — from "absent"), so key on it even when 0 instead of

internal/providers/openai/codex_session.go

@@ -1,421 +0,0 @@
-package openai
-
-import (
-	"context"
-	"encoding/json"
-	"errors"
-	"fmt"
-	"net/http"
-	"net/url"
-	"reflect"
-	"strings"
-	"sync"
-	"time"
-
-	"github.com/coder/websocket"
-
-	"github.com/Gitlawb/zero/internal/providers/providerio"
-	"github.com/Gitlawb/zero/internal/trace"
-	"github.com/Gitlawb/zero/internal/zeroruntime"
-)
-
-const (
-	responsesWebSocketBetaHeader = "OpenAI-Beta"
-	responsesWebSocketBetaValue  = "responses_websockets=2026-02-06"
-	responsesWebSocketRequest    = "response.create"
-	previousResponseNotFoundCode = "previous_response_not_found"
-	webSocketConnectionLimitCode = "websocket_connection_limit_reached"
-	responsesWebSocketReadLimit  = 16 << 20
-)
-
-var errCodexTurnSessionBusy = errors.New("codex turn session already has an active stream")
-
-// NewCodexTurnSessionProvider enables one Responses WebSocket connection for
-// each agent run. The session falls back to the existing HTTP/SSE provider when
-// the endpoint cannot upgrade or loses its response chain.
-func NewCodexTurnSessionProvider(provider *CodexProvider, caps zeroruntime.ProviderCapabilities) zeroruntime.TurnSessionProvider {
-	return &codexTurnSessionProvider{provider: provider, caps: caps}
-}
-
-type codexTurnSessionProvider struct {
-	provider *CodexProvider
-	caps     zeroruntime.ProviderCapabilities
-}
-
-func (provider *codexTurnSessionProvider) OpenTurnSession(ctx context.Context) (zeroruntime.TurnSession, error) {
-	if provider == nil || provider.provider == nil || provider.provider.inner == nil {
-		return nil, errors.New("codex turn session requires a provider")
-	}
-	sessionCtx, cancel := context.WithCancel(ctx)
-	return &codexTurnSession{
-		ctx:         sessionCtx,
-		cancel:      cancel,
-		provider:    provider.provider,
-		prewarmDone: make(chan struct{}),
-	}, nil
-}
-
-func (provider *codexTurnSessionProvider) Capabilities() zeroruntime.ProviderCapabilities {
-	return provider.caps
-}
-
-type codexTurnSession struct {
-	ctx      context.Context
-	cancel   context.CancelFunc
-	provider *CodexProvider
-
-	mu             sync.Mutex
-	connection     *websocket.Conn
-	webSocketOff   bool
-	lastRequest    *responsesRequest
-	lastResponseID string
-	lastOutput     []inputItem
-	streamActive   bool
-
-	prewarmOnce sync.Once
-	prewarmDone chan struct{}
-	closeOnce   sync.Once
-}
-
-// Prewarm starts the WebSocket handshake without blocking prompt assembly. The
-// first Stream waits for this bounded attempt; failure simply selects HTTP/SSE.
-func (session *codexTurnSession) Prewarm(ctx context.Context) error {
-	session.prewarmOnce.Do(func() {
-		go func() {
-			defer close(session.prewarmDone)
-			prewarmCtx, cancel := context.WithTimeout(session.ctx, prewarmTimeout)
-			defer cancel()
-			recorder := trace.FromContext(ctx)
-			span := recorder.Span(trace.SpanProviderPrewarm)
-			defer span.End()
-			recorder.Counter(trace.CounterPrewarmAttempts, 1)
-			connection, err := session.provider.dialResponsesWebSocket(prewarmCtx)
-			session.mu.Lock()
-			defer session.mu.Unlock()
-			if err != nil {
-				session.webSocketOff = true
-				return
-			}
-			session.connection = connection
-		}()
-	})
-	return nil
-}
-
-func (session *codexTurnSession) Stream(ctx context.Context, request zeroruntime.CompletionRequest) (<-chan zeroruntime.StreamEvent, error) {
-	_ = session.Prewarm(ctx)
-	select {
-	case <-session.prewarmDone:
-	case <-ctx.Done():
-		return nil, ctx.Err()
-	}
-
-	fullRequest, err := session.provider.buildResponsesRequest(request)
-	if err != nil {
-		return nil, err
-	}
-
-	session.mu.Lock()
-	if session.streamActive {
-		session.mu.Unlock()
-		return nil, errCodexTurnSessionBusy
-	}
-	if session.webSocketOff || session.connection == nil {
-		session.mu.Unlock()
-		trace.FromContext(ctx).Counter(trace.CounterResponsesHTTPFallback, 1)
-		return session.provider.StreamCompletion(ctx, request)
-	}
-	session.streamActive = true
-	connection := session.connection
-	wireRequest := *fullRequest
-	wireRequest.Type = responsesWebSocketRequest
-	if delta, ok := responseInputDelta(session.lastRequest, session.lastOutput, fullRequest); ok && session.lastResponseID != "" {
-		wireRequest.PreviousResponseID = session.lastResponseID
-		wireRequest.Input = delta
-		trace.FromContext(ctx).Counter(trace.CounterResponseChainReused, 1)
-	} else if session.lastRequest != nil {
-		trace.FromContext(ctx).Counter(trace.CounterResponseChainReset, 1)
-		session.lastRequest = nil
-		session.lastResponseID = ""
-		session.lastOutput = nil
-	}
-	session.mu.Unlock()
-
-	body, err := json.Marshal(wireRequest)
-	if err != nil {
-		session.releaseStream()
-		return nil, fmt.Errorf("encode codex websocket request: %w", err)
-	}
-	events := make(chan zeroruntime.StreamEvent, 16)
-	go func() {
-		defer close(events)
-		defer session.releaseStream()
-		session.streamWebSocket(ctx, connection, body, fullRequest, request, events)
-	}()
-	return events, nil
-}
-
-func (session *codexTurnSession) releaseStream() {
-	session.mu.Lock()
-	session.streamActive = false
-	session.mu.Unlock()
-}
-
-func (session *codexTurnSession) Compact(context.Context, zeroruntime.CompletionRequest) ([]zeroruntime.Message, error) {
-	return nil, zeroruntime.ErrCompactionUnsupported
-}
-
-func (session *codexTurnSession) Close() error {
-	session.closeOnce.Do(func() {
-		session.cancel()
-		session.prewarmOnce.Do(func() { close(session.prewarmDone) })
-		select {
-		case <-session.prewarmDone:
-		case <-time.After(prewarmTimeout):
-		}
-		session.mu.Lock()
-		connection := session.connection
-		session.connection = nil
-		session.webSocketOff = true
-		session.mu.Unlock()
-		if connection != nil {
-			_ = connection.CloseNow()
-		}
-	})
-	return nil
-}
-
-func responseInputDelta(previous *responsesRequest, output []inputItem, current *responsesRequest) ([]inputItem, bool) {
-	if previous == nil || current == nil || !responsesRequestPropertiesEqual(previous, current) {
-		return nil, false
-	}
-	prefix := make([]inputItem, 0, len(previous.Input)+len(output))
-	prefix = append(prefix, previous.Input...)
-	prefix = append(prefix, output...)
-	if len(current.Input) <= len(prefix) || !reflect.DeepEqual(current.Input[:len(prefix)], prefix) {
-		return nil, false
-	}
-	return append([]inputItem(nil), current.Input[len(prefix):]...), true
-}
-
-func responsesRequestPropertiesEqual(left, right *responsesRequest) bool {
-	return left.Model == right.Model &&
-		left.Instructions == right.Instructions &&
-		left.Stream == right.Stream &&
-		left.Store == right.Store &&
-		left.ParallelToolCalls == right.ParallelToolCalls &&
-		left.MaxOutputTokens == right.MaxOutputTokens &&
-		reflect.DeepEqual(left.Tools, right.Tools) &&
-		reflect.DeepEqual(left.Reasoning, right.Reasoning) &&
-		left.ServiceTier == right.ServiceTier &&
-		left.PromptCacheKey == right.PromptCacheKey
-}
-
-func (session *codexTurnSession) streamWebSocket(
-	ctx context.Context,
-	connection *websocket.Conn,
-	body []byte,
-	fullRequest *responsesRequest,
-	runtimeRequest zeroruntime.CompletionRequest,
-	events chan<- zeroruntime.StreamEvent,
-) {
-	if err := connection.Write(ctx, websocket.MessageText, body); err != nil {
-		session.disableWebSocket(connection)
-		session.forwardHTTP(ctx, runtimeRequest, events)
-		return
-	}
-
-	state := newResponsesState()
-	for {
-		readCtx := ctx
-		cancel := func() {}
-		idleTimeout := session.provider.inner.streamIdleTimeout
-		if idleTimeout > 0 {
-			readCtx, cancel = context.WithTimeout(ctx, idleTimeout)
-		}
-		messageType, data, err := connection.Read(readCtx)
-		readTimedOut := errors.Is(readCtx.Err(), context.DeadlineExceeded) && ctx.Err() == nil
-		cancel()
-		if err != nil {
-			session.disableWebSocket(connection)
-			if ctx.Err() != nil {
-				return
-			}
-			if !state.emitted {
-				session.forwardHTTP(ctx, runtimeRequest, events)
-				return
-			}
-			errorMessage := err.Error()
-			if readTimedOut {
-				errorMessage = providerio.StreamTimeoutMessage(providerio.ErrStreamIdle, idleTimeout)
-			}
-			providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
-				Type:  zeroruntime.StreamEventError,
-				Error: session.provider.redact("provider stream error: " + errorMessage),
-			})
-			return
-		}
-		if messageType != websocket.MessageText {
-			continue
-		}
-
-		var responseEvent responsesEvent
-		decodeErr := json.Unmarshal(data, &responseEvent)
-		if decodeErr == nil {
-			if (responseEvent.Code == previousResponseNotFoundCode || responseEvent.Code == webSocketConnectionLimitCode) &&
-				!state.emitted {
-				session.disableWebSocket(connection)
-				session.forwardHTTP(ctx, runtimeRequest, events)
-				return
-			}
-			if responseEvent.Type == responsesEventIncomplete {
-				session.resetResponseChain(connection)
-				providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
-					Type:         zeroruntime.StreamEventDone,
-					FinishReason: zeroruntime.FinishReasonLength,
-				})
-				return
-			}
-		}
-
-		keepReading := false
-		if decodeErr == nil {
-			keepReading = session.provider.emitParsedResponsesEvent(ctx, &responseEvent, state, events)
-		} else {
-			keepReading = session.provider.emitResponsesEvent(ctx, string(data), state, events)
-		}
-		if keepReading {
-			continue
-		}
-		if responseEvent.Type == responsesEventCompleted && responseEvent.Response != nil &&
-			responseEvent.Response.Error == nil && responseEvent.Response.Status != "failed" && state.responseID != "" {
-			session.mu.Lock()
-			if session.connection == connection && !session.webSocketOff {
-				requestCopy := *fullRequest
-				requestCopy.Input = append([]inputItem(nil), fullRequest.Input...)
-				session.lastRequest = &requestCopy
-				session.lastResponseID = state.responseID
-				session.lastOutput = state.outputInputItems()
-			}
-			session.mu.Unlock()
-		}
-		return
-	}
-}
-
-func (session *codexTurnSession) resetResponseChain(connection *websocket.Conn) {
-	session.mu.Lock()
-	defer session.mu.Unlock()
-	if session.connection != connection {
-		return
-	}
-	session.lastRequest = nil
-	session.lastResponseID = ""
-	session.lastOutput = nil
-}
-
-func (session *codexTurnSession) forwardHTTP(ctx context.Context, request zeroruntime.CompletionRequest, events chan<- zeroruntime.StreamEvent) {
-	trace.FromContext(ctx).Counter(trace.CounterResponsesHTTPFallback, 1)
-	stream, err := session.provider.StreamCompletion(ctx, request)
-	if err != nil {
-		providerio.SendEvent(ctx, events, zeroruntime.StreamEvent{
-			Type:  zeroruntime.StreamEventError,
-			Error: session.provider.redact(err.Error()),
-		})
-		return
-	}
-	for event := range stream {
-		providerio.SendEvent(ctx, events, event)
-	}
-}
-
-func (session *codexTurnSession) disableWebSocket(connection *websocket.Conn) {
-	session.mu.Lock()
-	if session.connection == connection {
-		session.connection = nil
-		session.webSocketOff = true
-		session.lastRequest = nil
-		session.lastResponseID = ""
-		session.lastOutput = nil
-	}
-	session.mu.Unlock()
-	_ = connection.CloseNow()
-}
-
-func (provider *CodexProvider) dialResponsesWebSocket(ctx context.Context) (*websocket.Conn, error) {
-	endpoint, err := responsesWebSocketURL(provider.inner.endpoint)
-	if err != nil {
-		return nil, err
-	}
-	for authTry := 0; authTry < 2; authTry++ {
-		headers, err := provider.responsesWebSocketHeaders(ctx, authTry == 1)
-		if err != nil {
-			return nil, err
-		}
-		connection, response, err := websocket.Dial(ctx, endpoint, &websocket.DialOptions{
-			HTTPClient:      provider.inner.httpClient,
-			HTTPHeader:      headers,
-			CompressionMode: websocket.CompressionNoContextTakeover,
-		})
-		if err == nil {
-			connection.SetReadLimit(responsesWebSocketReadLimit)
-			return connection, nil
-		}
-		if response == nil || response.StatusCode != http.StatusUnauthorized || provider.inner.oauthResolver == nil || authTry == 1 {
-			return nil, err
-		}
-	}
-	return nil, errors.New("codex websocket authentication failed")
-}
-
-func (provider *CodexProvider) responsesWebSocketHeaders(ctx context.Context, forceRefresh bool) (http.Header, error) {
-	request, err := http.NewRequestWithContext(ctx, http.MethodGet, provider.inner.endpoint, nil)
-	if err != nil {
-		return nil, err
-	}
-	base := providerio.AuthHeaders{
-		APIKey:            provider.inner.apiKey,
-		DefaultAuthHeader: "Authorization",
-		DefaultAuthScheme: "Bearer",
-		AuthHeader:        provider.inner.authHeader,
-		AuthScheme:        provider.inner.authScheme,
-		AuthHeaderValue:   provider.inner.authHeaderValue,
-		CustomHeaders:     provider.inner.customHeaders,
-	}
-	if resolver := provider.inner.oauthResolver; resolver != nil {
-		header, value, ok, err := resolver(ctx, forceRefresh)
-		if err != nil {
-			return nil, err
-		}
-		if ok {
-			providerio.ApplyAuthHeaders(request, providerio.AuthHeaders{CustomHeaders: provider.inner.customHeaders})
-			if strings.TrimSpace(header) == "" {
-				header = "Authorization"
-			}
-			request.Header.Set(header, value)
-		} else {
-			providerio.ApplyAuthHeaders(request, base)
-		}
-	} else {
-		providerio.ApplyAuthHeaders(request, base)
-	}
-	provider.injectCodexHeaders(request)
-	request.Header.Set(responsesWebSocketBetaHeader, responsesWebSocketBetaValue)
-	return request.Header.Clone(), nil
-}
-
-func responsesWebSocketURL(endpoint string) (string, error) {
-	parsed, err := url.Parse(strings.TrimSpace(endpoint))
-	if err != nil {
-		return "", err
-	}
-	switch parsed.Scheme {
-	case "http":
-		parsed.Scheme = "ws"
-	case "https":
-		parsed.Scheme = "wss"
-	default:
-		return "", fmt.Errorf("unsupported Responses websocket URL scheme %q", parsed.Scheme)
-	}
-	return parsed.String(), nil
-}

internal/providers/openai/codex_session_test.go

@@ -1,590 +0,0 @@
-package openai
-
-import (
-	"context"
-	"encoding/json"
-	"errors"
-	"fmt"
-	"net/http"
-	"net/http/httptest"
-	"strings"
-	"sync"
-	"testing"
-	"time"
-
-	"github.com/coder/websocket"
-
-	"github.com/Gitlawb/zero/internal/trace"
-	"github.com/Gitlawb/zero/internal/zeroruntime"
-)
-
-func TestCodexTurnSessionChainsOnlyAppendOnlyRequests(t *testing.T) {
-	var mu sync.Mutex
-	requests := []map[string]any{}
-	betaHeader := ""
-	server := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
-		if !strings.EqualFold(request.Header.Get("Upgrade"), "websocket") {
-			http.Error(writer, "websocket required", http.StatusUpgradeRequired)
-			return
-		}
-		mu.Lock()
-		betaHeader = request.Header.Get(responsesWebSocketBetaHeader)
-		mu.Unlock()
-		connection, err := websocket.Accept(writer, request, nil)
-		if err != nil {
-			return
-		}
-		defer connection.CloseNow()
-		for index := 0; index < 3; index++ {
-			_, body, err := connection.Read(request.Context())
-			if err != nil {
-				return
-			}
-			var payload map[string]any
-			if err := json.Unmarshal(body, &payload); err != nil {
-				return
-			}
-			mu.Lock()
-			requests = append(requests, payload)
-			mu.Unlock()
-			switch index {
-			case 0:
-				writeWebSocketEvents(request.Context(), connection,
-					`{"type":"response.created","response":{"id":"resp-1","status":"in_progress"}}`,
-					`{"type":"response.output_item.added","item_id":"call-1","item":{"type":"function_call","id":"call-1","call_id":"call-1","name":"read_file"}}`,
-					`{"type":"response.function_call_arguments.delta","item_id":"call-1","delta":"{}"}`,
-					`{"type":"response.output_item.done","item_id":"call-1","item":{"type":"function_call","id":"call-1","call_id":"call-1","name":"read_file","arguments":"{}"}}`,
-					`{"type":"response.completed","response":{"id":"resp-1","status":"completed"}}`,
-				)
-			case 1:
-				writeWebSocketEvents(request.Context(), connection,
-					`{"type":"response.output_text.delta","delta":"done"}`,
-					`{"type":"response.completed","response":{"id":"resp-2","status":"completed"}}`,
-				)
-			case 2:
-				writeWebSocketEvents(request.Context(), connection,
-					`{"type":"response.completed","response":{"id":"resp-3","status":"completed"}}`,
-				)
-			}
-		}
-	}))
-	defer server.Close()
-
-	provider := newCodexSessionTestProvider(t, server)
-	// A disabled stream watchdog must use the parent context rather than creating
-	// an immediately-expired read deadline.
-	provider.inner.streamIdleTimeout = 0
-	session := openCodexSession(t, provider)
-	defer session.Close()
-	recorder := trace.NewRecorder("session-1", "run-1", "test")
-	recorder.Start()
-	streamContext := trace.WithContext(t.Context(), recorder)
-
-	base := zeroruntime.CompletionRequest{
-		Messages: []zeroruntime.Message{
-			{Role: zeroruntime.MessageRoleSystem, Content: "Use tools carefully."},
-			{Role: zeroruntime.MessageRoleUser, Content: "Read the file."},
-		},
-		Tools:          []zeroruntime.ToolDefinition{{Name: "read_file", Parameters: map[string]any{"type": "object"}}},
-		PromptCacheKey: "session-1",
-	}
-	first := collectCodexSessionEvents(t, session, base)
-	if !hasToolCallEnd(first, "call-1") {
-		t.Fatalf("first stream did not produce the tool call: %#v", first)
-	}
-
-	second := base
-	second.Messages = append(append([]zeroruntime.Message(nil), base.Messages...),
-		zeroruntime.Message{Role: zeroruntime.MessageRoleAssistant, ToolCalls: []zeroruntime.ToolCall{{ID: "call-1", Name: "read_file", Arguments: "{}"}}},
-		zeroruntime.Message{Role: zeroruntime.MessageRoleTool, ToolCallID: "call-1", Content: "contents"},
-	)
-	secondEvents := collectCodexSessionEventsContext(t, streamContext, session, second)
-	if got := joinedText(secondEvents); got != "done" {
-		t.Fatalf("second stream text = %q, want done", got)
-	}
-
-	third := second
-	third.ReasoningEffort = "high"
-	third.Messages = append(append([]zeroruntime.Message(nil), second.Messages...),
-		zeroruntime.Message{Role: zeroruntime.MessageRoleAssistant, Content: "done"},
-		zeroruntime.Message{Role: zeroruntime.MessageRoleUser, Content: "Continue."},
-	)
-	collectCodexSessionEventsContext(t, streamContext, session, third)
-	finishedTrace := recorder.Finish()
-	if got := finishedTrace.Counter(trace.CounterResponseChainReused); got != 1 {
-		t.Fatalf("response-chain reuse count = %d, want 1", got)
-	}
-	if got := finishedTrace.Counter(trace.CounterResponseChainReset); got != 1 {
-		t.Fatalf("response-chain reset count = %d, want 1", got)
-	}
-
-	mu.Lock()
-	defer mu.Unlock()
-	if len(requests) != 3 {
-		t.Fatalf("websocket requests = %d, want 3", len(requests))
-	}
-	if betaHeader != responsesWebSocketBetaValue {
-		t.Fatalf("OpenAI-Beta = %q, want %q", betaHeader, responsesWebSocketBetaValue)
-	}
-	if requests[0]["type"] != responsesWebSocketRequest || requests[0]["previous_response_id"] != nil {
-		t.Fatalf("first request chaining fields = %#v", requests[0])
-	}
-	if requests[0]["parallel_tool_calls"] != true || requests[0]["prompt_cache_key"] != "session-1" {
-		t.Fatalf("first request stable fields = %#v", requests[0])
-	}
-	if requests[1]["previous_response_id"] != "resp-1" {
-		t.Fatalf("second previous_response_id = %#v", requests[1]["previous_response_id"])
-	}
-	secondInput, _ := requests[1]["input"].([]any)
-	if len(secondInput) != 1 || secondInput[0].(map[string]any)["type"] != "function_call_output" {
-		t.Fatalf("second incremental input = %#v", requests[1]["input"])
-	}
-	if requests[2]["previous_response_id"] != nil {
-		t.Fatalf("incompatible request reused response chain: %#v", requests[2])
-	}
-	thirdInput, _ := requests[2]["input"].([]any)
-	if len(thirdInput) <= 1 {
-		t.Fatalf("incompatible request did not send full input: %#v", thirdInput)
-	}
-}
-
-func TestCodexTurnSessionFallsBackWhenPreviousResponseIsMissing(t *testing.T) {
-	var mu sync.Mutex
-	webSocketRequests := 0
-	httpRequests := 0
-	server := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
-		if strings.EqualFold(request.Header.Get("Upgrade"), "websocket") {
-			connection, err := websocket.Accept(writer, request, nil)
-			if err != nil {
-				return
-			}
-			defer connection.CloseNow()
-			for index := 0; index < 2; index++ {
-				if _, _, err := connection.Read(request.Context()); err != nil {
-					return
-				}
-				mu.Lock()
-				webSocketRequests++
-				mu.Unlock()
-				if index == 0 {
-					writeWebSocketEvents(request.Context(), connection,
-						`{"type":"response.output_item.added","item_id":"call-1","item":{"type":"function_call","id":"call-1","call_id":"call-1","name":"read_file"}}`,
-						`{"type":"response.output_item.done","item_id":"call-1","item":{"type":"function_call","id":"call-1","call_id":"call-1","name":"read_file","arguments":"{}"}}`,
-						`{"type":"response.completed","response":{"id":"resp-1","status":"completed"}}`,
-					)
-					continue
-				}
-				writeWebSocketEvents(request.Context(), connection,
-					`{"type":"response.error","code":"previous_response_not_found","message":"missing"}`,
-				)
-			}
-			return
-		}
-
-		mu.Lock()
-		httpRequests++
-		mu.Unlock()
-		writer.Header().Set("Content-Type", "text/event-stream")
-		_, _ = fmt.Fprint(writer, "data: {\"type\":\"response.output_text.delta\",\"delta\":\"fallback\"}\n\n")
-		_, _ = fmt.Fprint(writer, "data: {\"type\":\"response.completed\",\"response\":{\"id\":\"resp-http\",\"status\":\"completed\"}}\n\n")
-	}))
-	defer server.Close()
-
-	provider := newCodexSessionTestProvider(t, server)
-	session := openCodexSession(t, provider)
-	defer session.Close()
-	base := zeroruntime.CompletionRequest{
-		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "Read it."}},
-		Tools:    []zeroruntime.ToolDefinition{{Name: "read_file", Parameters: map[string]any{"type": "object"}}},
-	}
-	collectCodexSessionEvents(t, session, base)
-	second := base
-	second.Messages = append(append([]zeroruntime.Message(nil), base.Messages...),
-		zeroruntime.Message{Role: zeroruntime.MessageRoleAssistant, ToolCalls: []zeroruntime.ToolCall{{ID: "call-1", Name: "read_file", Arguments: "{}"}}},
-		zeroruntime.Message{Role: zeroruntime.MessageRoleTool, ToolCallID: "call-1", Content: "contents"},
-	)
-	events := collectCodexSessionEvents(t, session, second)
-	if got := joinedText(events); got != "fallback" {
-		t.Fatalf("fallback stream text = %q, want fallback; events=%#v", got, events)
-	}
-	for _, event := range events {
-		if event.Type == zeroruntime.StreamEventError {
-			t.Fatalf("response-chain recovery leaked an error: %#v", event)
-		}
-	}
-	mu.Lock()
-	defer mu.Unlock()
-	if webSocketRequests != 2 || httpRequests != 1 {
-		t.Fatalf("requests = websocket:%d http:%d, want 2/1", webSocketRequests, httpRequests)
-	}
-}
-
-func TestCodexTurnSessionFallsBackWhenSocketClosesBeforeOutput(t *testing.T) {
-	var mu sync.Mutex
-	httpRequests := 0
-	server := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
-		if strings.EqualFold(request.Header.Get("Upgrade"), "websocket") {
-			connection, err := websocket.Accept(writer, request, nil)
-			if err != nil {
-				return
-			}
-			if _, _, err := connection.Read(request.Context()); err == nil {
-				_ = connection.CloseNow()
-			}
-			return
-		}
-		mu.Lock()
-		httpRequests++
-		mu.Unlock()
-		writer.Header().Set("Content-Type", "text/event-stream")
-		_, _ = fmt.Fprint(writer, "data: {\"type\":\"response.output_text.delta\",\"delta\":\"recovered\"}\n\n")
-		_, _ = fmt.Fprint(writer, "data: {\"type\":\"response.completed\",\"response\":{\"id\":\"resp-http\",\"status\":\"completed\"}}\n\n")
-	}))
-	defer server.Close()
-
-	provider := newCodexSessionTestProvider(t, server)
-	session := openCodexSession(t, provider)
-	defer session.Close()
-	recorder := trace.NewRecorder("session-fallback", "run-fallback", "test")
-	recorder.Start()
-	events := collectCodexSessionEventsContext(t, trace.WithContext(t.Context(), recorder), session, zeroruntime.CompletionRequest{
-		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "Hello"}},
-	})
-	if got := joinedText(events); got != "recovered" {
-		t.Fatalf("fallback text = %q, want recovered", got)
-	}
-	mu.Lock()
-	defer mu.Unlock()
-	if httpRequests != 1 {
-		t.Fatalf("HTTP fallback requests = %d, want 1", httpRequests)
-	}
-	if got := recorder.Finish().Counter(trace.CounterResponsesHTTPFallback); got != 1 {
-		t.Fatalf("responses HTTP fallback counter = %d, want 1", got)
-	}
-}
-
-func TestCodexTurnSessionKeepsWebSocketAfterIncompleteResponse(t *testing.T) {
-	var mu sync.Mutex
-	webSocketRequests := 0
-	httpRequests := 0
-	server := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
-		if strings.EqualFold(request.Header.Get("Upgrade"), "websocket") {
-			connection, err := websocket.Accept(writer, request, nil)
-			if err != nil {
-				return
-			}
-			defer connection.CloseNow()
-			for index := 0; index < 2; index++ {
-				if _, _, err := connection.Read(request.Context()); err != nil {
-					return
-				}
-				mu.Lock()
-				webSocketRequests++
-				mu.Unlock()
-				if index == 0 {
-					writeWebSocketEvents(request.Context(), connection,
-						`{"type":"response.incomplete","response":{"id":"resp-1","status":"incomplete"}}`,
-					)
-					continue
-				}
-				writeWebSocketEvents(request.Context(), connection,
-					`{"type":"response.output_text.delta","delta":"websocket"}`,
-					`{"type":"response.completed","response":{"id":"resp-2","status":"completed"}}`,
-				)
-			}
-			return
-		}
-
-		mu.Lock()
-		httpRequests++
-		mu.Unlock()
-		writer.Header().Set("Content-Type", "text/event-stream")
-		_, _ = fmt.Fprint(writer, "data: {\"type\":\"response.output_text.delta\",\"delta\":\"fallback\"}\n\n")
-		_, _ = fmt.Fprint(writer, "data: {\"type\":\"response.completed\",\"response\":{\"id\":\"resp-http\",\"status\":\"completed\"}}\n\n")
-	}))
-	defer server.Close()
-
-	provider := newCodexSessionTestProvider(t, server)
-	session := openCodexSession(t, provider)
-	defer session.Close()
-	request := zeroruntime.CompletionRequest{
-		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "Continue."}},
-	}
-	first := collectCodexSessionEvents(t, session, request)
-	if len(first) != 1 || first[0].Type != zeroruntime.StreamEventDone || first[0].FinishReason != zeroruntime.FinishReasonLength {
-		t.Fatalf("incomplete response events = %#v, want length completion", first)
-	}
-	second := collectCodexSessionEvents(t, session, request)
-	if got := joinedText(second); got != "websocket" {
-		t.Fatalf("second turn text = %q, want websocket; events=%#v", got, second)
-	}
-	mu.Lock()
-	defer mu.Unlock()
-	if webSocketRequests != 2 || httpRequests != 0 {
-		t.Fatalf("requests = websocket:%d http:%d, want 2/0", webSocketRequests, httpRequests)
-	}
-}
-
-func TestCodexTurnSessionDoesNotReplayAfterVisibleOutput(t *testing.T) {
-	var mu sync.Mutex
-	httpRequests := 0
-	server := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
-		if strings.EqualFold(request.Header.Get("Upgrade"), "websocket") {
-			connection, err := websocket.Accept(writer, request, nil)
-			if err != nil {
-				return
-			}
-			if _, _, err := connection.Read(request.Context()); err == nil {
-				writeWebSocketEvents(request.Context(), connection,
-					`{"type":"response.output_text.delta","delta":"visible"}`,
-				)
-			}
-			_ = connection.Close(websocket.StatusInternalError, "interrupted")
-			return
-		}
-		mu.Lock()
-		httpRequests++
-		mu.Unlock()
-	}))
-	defer server.Close()
-
-	provider := newCodexSessionTestProvider(t, server)
-	session := openCodexSession(t, provider)
-	defer session.Close()
-	stream, err := session.Stream(t.Context(), zeroruntime.CompletionRequest{
-		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "Hello"}},
-	})
-	if err != nil {
-		t.Fatalf("Stream: %v", err)
-	}
-	sawText, sawError := false, false
-	for event := range stream {
-		sawText = sawText || event.Type == zeroruntime.StreamEventText
-		sawError = sawError || event.Type == zeroruntime.StreamEventError
-	}
-	if !sawText || !sawError {
-		t.Fatalf("visible interrupted stream = text:%v error:%v", sawText, sawError)
-	}
-	mu.Lock()
-	defer mu.Unlock()
-	if httpRequests != 0 {
-		t.Fatalf("visible interrupted stream was replayed over HTTP %d time(s)", httpRequests)
-	}
-}
-
-func TestCodexTurnSessionReportsWebSocketIdleTimeout(t *testing.T) {
-	server := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
-		connection, err := websocket.Accept(writer, request, nil)
-		if err != nil {
-			return
-		}
-		defer connection.CloseNow()
-		if _, _, err := connection.Read(request.Context()); err != nil {
-			return
-		}
-		writeWebSocketEvents(request.Context(), connection,
-			`{"type":"response.output_text.delta","delta":"visible"}`,
-		)
-		<-request.Context().Done()
-	}))
-	defer server.Close()
-
-	provider := newCodexSessionTestProvider(t, server)
-	provider.inner.streamIdleTimeout = 200 * time.Millisecond
-	session := openCodexSession(t, provider)
-	defer session.Close()
-	stream, err := session.Stream(t.Context(), zeroruntime.CompletionRequest{
-		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "Hello"}},
-	})
-	if err != nil {
-		t.Fatalf("Stream: %v", err)
-	}
-
-	var streamError string
-	for event := range stream {
-		if event.Type == zeroruntime.StreamEventError {
-			streamError = event.Error
-			break
-		}
-	}
-	if !strings.Contains(streamError, "idle timeout after 200ms") {
-		t.Fatalf("stream error = %q, want idle-timeout detail", streamError)
-	}
-}
-
-func TestCodexTurnSessionRejectsOverlappingStreams(t *testing.T) {
-	started := make(chan struct{})
-	release := make(chan struct{})
-	var releaseOnce sync.Once
-	releaseStream := func() { releaseOnce.Do(func() { close(release) }) }
-	t.Cleanup(releaseStream)
-	server := httptest.NewServer(http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
-		connection, err := websocket.Accept(writer, request, nil)
-		if err != nil {
-			return
-		}
-		defer connection.CloseNow()
-		if _, _, err := connection.Read(request.Context()); err != nil {
-			return
-		}
-		close(started)
-		<-release
-		writeWebSocketEvents(request.Context(), connection,
-			`{"type":"response.completed","response":{"id":"resp-1","status":"completed"}}`,
-		)
-	}))
-	defer server.Close()
-
-	provider := newCodexSessionTestProvider(t, server)
-	session := openCodexSession(t, provider)
-	defer session.Close()
-	request := zeroruntime.CompletionRequest{
-		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "Hello"}},
-	}
-	first, err := session.Stream(t.Context(), request)
-	if err != nil {
-		t.Fatalf("first Stream: %v", err)
-	}
-	select {
-	case <-started:
-	case <-time.After(time.Second):
-		t.Fatal("first WebSocket stream did not start")
-	}
-	if _, err := session.Stream(t.Context(), request); !errors.Is(err, errCodexTurnSessionBusy) {
-		t.Fatalf("overlapping Stream error = %v, want %v", err, errCodexTurnSessionBusy)
-	}
-	releaseStream()
-	for range first {
-	}
-}
-
-func TestCodexTurnSessionHTTPFallbackRedactsSetupError(t *testing.T) {
-	const secret = "sk-secret-fallback"
-	provider, err := NewCodexProvider(CodexOptions{Options: Options{
-		APIKey:  secret,
-		BaseURL: "https://chatgpt.example/backend-api/codex",
-		Model:   "gpt-test",
-	}})
-	if err != nil {
-		t.Fatalf("NewCodexProvider: %v", err)
-	}
-	session := &codexTurnSession{provider: provider}
-	events := make(chan zeroruntime.StreamEvent, 1)
-	session.forwardHTTP(t.Context(), zeroruntime.CompletionRequest{
-		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRole(secret), Content: "invalid"}},
-	}, events)
-
-	select {
-	case event := <-events:
-		if event.Type != zeroruntime.StreamEventError {
-			t.Fatalf("fallback event type = %s, want error", event.Type)
-		}
-		if strings.Contains(event.Error, secret) {
-			t.Fatalf("fallback error leaked credential: %q", event.Error)
-		}
-	case <-time.After(time.Second):
-		t.Fatal("fallback did not emit setup error")
-	}
-}
-
-func TestCodexTurnSessionCloseDoesNotStartPrewarm(t *testing.T) {
-	provider, err := NewCodexProvider(CodexOptions{Options: Options{
-		APIKey:  "test-token",
-		BaseURL: "https://chatgpt.example/backend-api/codex",
-		Model:   "gpt-test",
-	}})
-	if err != nil {
-		t.Fatalf("NewCodexProvider: %v", err)
-	}
-	session, err := NewCodexTurnSessionProvider(provider, zeroruntime.ProviderCapabilities{}).OpenTurnSession(t.Context())
-	if err != nil {
-		t.Fatalf("OpenTurnSession: %v", err)
-	}
-	done := make(chan error, 1)
-	go func() { done <- session.Close() }()
-	select {
-	case err := <-done:
-		if err != nil {
-			t.Fatalf("Close() error = %v", err)
-		}
-	case <-time.After(200 * time.Millisecond):
-		t.Fatal("Close blocked without a prewarm attempt")
-	}
-}
-
-func newCodexSessionTestProvider(t *testing.T, server *httptest.Server) *CodexProvider {
-	t.Helper()
-	provider, err := NewCodexProvider(CodexOptions{
-		Options: Options{
-			APIKey:     "test-token",
-			BaseURL:    server.URL,
-			Model:      "gpt-test",
-			HTTPClient: server.Client(),
-		},
-		AccountID: "account-test",
-	})
-	if err != nil {
-		t.Fatalf("NewCodexProvider: %v", err)
-	}
-	return provider
-}
-
-func openCodexSession(t *testing.T, provider *CodexProvider) zeroruntime.TurnSession {
-	t.Helper()
-	session, err := NewCodexTurnSessionProvider(provider, zeroruntime.ProviderCapabilities{}).OpenTurnSession(t.Context())
-	if err != nil {
-		t.Fatalf("OpenTurnSession: %v", err)
-	}
-	if err := session.Prewarm(t.Context()); err != nil {
-		t.Fatalf("Prewarm: %v", err)
-	}
-	return session
-}
-
-func collectCodexSessionEvents(t *testing.T, session zeroruntime.TurnSession, request zeroruntime.CompletionRequest) []zeroruntime.StreamEvent {
-	t.Helper()
-	return collectCodexSessionEventsContext(t, t.Context(), session, request)
-}
-
-func collectCodexSessionEventsContext(t *testing.T, ctx context.Context, session zeroruntime.TurnSession, request zeroruntime.CompletionRequest) []zeroruntime.StreamEvent {
-	t.Helper()
-	stream, err := session.Stream(ctx, request)
-	if err != nil {
-		t.Fatalf("Stream: %v", err)
-	}
-	events := []zeroruntime.StreamEvent{}
-	for event := range stream {
-		events = append(events, event)
-		if event.Type == zeroruntime.StreamEventError {
-			t.Fatalf("stream error: %s", event.Error)
-		}
-	}
-	return events
-}
-
-func writeWebSocketEvents(ctx context.Context, connection *websocket.Conn, events ...string) {
-	for _, event := range events {
-		if err := connection.Write(ctx, websocket.MessageText, []byte(event)); err != nil {
-			return
-		}
-	}
-}
-
-func hasToolCallEnd(events []zeroruntime.StreamEvent, id string) bool {
-	for _, event := range events {
-		if event.Type == zeroruntime.StreamEventToolCallEnd && event.ToolCallID == id {
-			return true
-		}
-	}
-	return false
-}
-
-func joinedText(events []zeroruntime.StreamEvent) string {
-	var builder strings.Builder
-	for _, event := range events {
-		if event.Type == zeroruntime.StreamEventText {
-			builder.WriteString(event.Content)
-		}
-	}
-	return builder.String()
-}

internal/providers/openai/codex_terminal_test.go

@@ -2,8 +2,6 @@ package openai
 
 import (
 	"context"
-	"reflect"
-	"strings"
 	"testing"
 
 	"github.com/Gitlawb/zero/internal/zeroruntime"
@@ -27,126 +25,6 @@ func TestToolCallKeyOutputIndexZero(t *testing.T) {
 	}
 }
 
-func TestResponsesStatePreservesDistinctCallID(t *testing.T) {
-	provider := &CodexProvider{}
-	state := newResponsesState()
-	events := make(chan zeroruntime.StreamEvent, 4)
-	provider.handleOutputItemAdded(context.Background(), &responsesEvent{
-		ItemID: "item-1",
-		Item: &itemPayload{
-			Type:   "function_call",
-			ID:     "item-1",
-			CallID: "call-1",
-			Name:   "read_file",
-		},
-	}, state, events)
-	items := state.outputInputItems()
-	if len(items) != 1 || items[0].ID != "item-1" || items[0].CallID != "call-1" {
-		t.Fatalf("captured function call = %#v, want item id item-1 and call id call-1", items)
-	}
-}
-
-func TestCodexCustomApplyPatchStreamProducesFreeformCall(t *testing.T) {
-	provider := &CodexProvider{}
-	state := newResponsesState()
-	events := make(chan zeroruntime.StreamEvent, 16)
-	patch := "*** Begin Patch\n*** Add File: hello.txt\n+hello\n*** End Patch\n"
-	for _, payload := range []string{
-		`{"type":"response.output_item.added","item_id":"item-1","item":{"type":"custom_tool_call","call_id":"call-1","name":"apply_patch"}}`,
-		`{"type":"response.custom_tool_call_input.delta","item_id":"item-1","call_id":"call-1","delta":"*** Begin Patch\n*** Add File: hello.txt\n"}`,
-		`{"type":"response.custom_tool_call_input.delta","item_id":"item-1","call_id":"call-1","delta":"+hello\n*** End Patch\n"}`,
-		`{"type":"response.output_item.done","item_id":"item-1","item":{"type":"custom_tool_call","call_id":"call-1","name":"apply_patch","input":"*** Begin Patch\n*** Add File: hello.txt\n+hello\n*** End Patch\n"}}`,
-		`{"type":"response.completed","response":{"id":"resp-1","status":"completed"}}`,
-	} {
-		if keepReading := provider.emitResponsesEvent(context.Background(), payload, state, events); !keepReading && !state.done {
-			t.Fatalf("stream stopped before terminal event for %s", payload)
-		}
-	}
-	close(events)
-	collected := zeroruntime.CollectStream(context.Background(), events)
-	if len(collected.ToolCalls) != 1 {
-		t.Fatalf("tool calls = %#v, want one", collected.ToolCalls)
-	}
-	call := collected.ToolCalls[0]
-	if call.ID != "item-1" || call.ProviderCallID != "call-1" || call.Name != "apply_patch" || !call.Freeform || call.Arguments != patch {
-		t.Fatalf("custom apply_patch call = %#v", call)
-	}
-}
-
-func TestCodexApplyPatchUsesFreeformWireContract(t *testing.T) {
-	provider, err := NewCodexProvider(CodexOptions{Options: Options{
-		APIKey:  "test-token",
-		BaseURL: "https://chatgpt.example/backend-api/codex",
-		Model:   "gpt-test",
-	}})
-	if err != nil {
-		t.Fatalf("NewCodexProvider: %v", err)
-	}
-	patch := "*** Begin Patch\n*** Add File: hello.txt\n+hello\n*** End Patch\n"
-	request, err := provider.buildResponsesRequest(zeroruntime.CompletionRequest{
-		Messages: []zeroruntime.Message{
-			{Role: zeroruntime.MessageRoleUser, Content: "Add the file."},
-			{Role: zeroruntime.MessageRoleAssistant, ToolCalls: []zeroruntime.ToolCall{{
-				ID: "item-1", ProviderCallID: "call-1", Name: "apply_patch", Arguments: patch, Freeform: true,
-			}}},
-			{Role: zeroruntime.MessageRoleTool, ToolCallID: "item-1", ToolCallProviderID: "call-1", Content: "Done!"},
-		},
-		Tools: []zeroruntime.ToolDefinition{{
-			Name: "apply_patch", Description: "Apply a patch.", Type: zeroruntime.ToolDefinitionFreeform,
-		}},
-	})
-	if err != nil {
-		t.Fatalf("buildResponsesRequest: %v", err)
-	}
-	if len(request.Tools) != 1 || request.Tools[0].Type != string(zeroruntime.ToolDefinitionFreeform) ||
-		request.Tools[0].Format == nil || request.Tools[0].Format.Syntax != "lark" || request.Tools[0].Parameters != nil {
-		t.Fatalf("apply_patch tool wire shape = %#v", request.Tools)
-	}
-	if !strings.Contains(request.Tools[0].Format.Definition, "*** Begin Patch") {
-		t.Fatalf("apply_patch grammar = %q", request.Tools[0].Format.Definition)
-	}
-	if !strings.Contains(request.Tools[0].Description, "absolute file paths") || !strings.Contains(request.Tools[0].Description, "granted extra write root") {
-		t.Fatalf("apply_patch description does not explain extra-root paths: %q", request.Tools[0].Description)
-	}
-	if len(request.Input) != 3 || request.Input[1].Type != "custom_tool_call" || request.Input[1].ID != "item-1" ||
-		request.Input[1].CallID != "call-1" || request.Input[1].Input != patch ||
-		request.Input[2].Type != "custom_tool_call_output" || request.Input[2].CallID != "call-1" {
-		t.Fatalf("custom apply_patch replay input = %#v", request.Input)
-	}
-}
-
-func TestCodexPreservesCustomApplyPatchFunction(t *testing.T) {
-	provider, err := NewCodexProvider(CodexOptions{Options: Options{
-		APIKey:  "test-token",
-		BaseURL: "https://chatgpt.example/backend-api/codex",
-		Model:   "gpt-test",
-	}})
-	if err != nil {
-		t.Fatalf("NewCodexProvider: %v", err)
-	}
-	parameters := map[string]any{
-		"type":       "object",
-		"properties": map[string]any{"value": map[string]any{"type": "string"}},
-	}
-	request, err := provider.buildResponsesRequest(zeroruntime.CompletionRequest{
-		Messages: []zeroruntime.Message{{Role: zeroruntime.MessageRoleUser, Content: "Call the custom tool."}},
-		Tools: []zeroruntime.ToolDefinition{{
-			Name: "apply_patch", Description: "Custom integration tool.", Parameters: parameters,
-		}},
-	})
-	if err != nil {
-		t.Fatalf("buildResponsesRequest: %v", err)
-	}
-	if len(request.Tools) != 1 {
-		t.Fatalf("tools = %#v, want one", request.Tools)
-	}
-	tool := request.Tools[0]
-	if tool.Type != string(zeroruntime.ToolDefinitionFunction) || tool.Format != nil ||
-		tool.Description != "Custom integration tool." || !reflect.DeepEqual(tool.Parameters, parameters) {
-		t.Fatalf("custom apply_patch function was rewritten: %#v", tool)
-	}
-}
-
 func TestHandleTerminalResponseNilPayload(t *testing.T) {
 	p := &CodexProvider{}
 
@@ -212,14 +90,11 @@ func TestHandleTerminalResponseFailedPayloadWithoutError(t *testing.T) {
 	// A response.completed with a payload and no error remains a clean done.
 	ok := make(chan zeroruntime.StreamEvent, 8)
 	p.handleTerminalResponse(context.Background(),
-		&responsesEvent{Type: responsesEventCompleted, Response: &responsePayload{ID: "resp-1", Status: "completed"}}, &responsesState{}, ok)
+		&responsesEvent{Type: responsesEventCompleted, Response: &responsePayload{Status: "completed"}}, &responsesState{}, ok)
 	close(ok)
 	for ev := range ok {
 		if ev.Type == zeroruntime.StreamEventError {
 			t.Error("response.completed with a non-error payload must NOT emit an error")
 		}
-		if ev.Type == zeroruntime.StreamEventDone && ev.ResponseID != "resp-1" {
-			t.Errorf("done response id = %q, want resp-1", ev.ResponseID)
-		}
 	}
 }

internal/providers/openai/codex_test.go

@@ -771,7 +771,7 @@ func TestCodexProviderParsesResponsesTextDeltas(t *testing.T) {
 		`{"type":"response.output_text.delta","delta":"hello "}`,
 		`{"type":"response.output_text.delta","delta":"world"}`,
 		`{"type":"response.output_text.delta","delta":"!"}`,
-		`{"type":"response.completed","response":{"id":"resp-1","status":"completed","usage":{"input_tokens":7,"output_tokens":3,"output_tokens_details":{"reasoning_tokens":1},"input_tokens_details":{"cached_tokens":2,"cache_write_tokens":1}}}}`,
+		`{"type":"response.completed","response":{"id":"resp-1","status":"completed","usage":{"input_tokens":7,"output_tokens":3,"output_tokens_details":{"reasoning_tokens":1},"input_tokens_details":{"cached_tokens":2}}}}`,
 	)
 	defer srv.Close()
 
@@ -809,8 +809,8 @@ func TestCodexProviderParsesResponsesTextDeltas(t *testing.T) {
 	if usage == nil {
 		t.Fatal("expected a usage event, got none")
 	}
-	if usage.InputTokens != 7 || usage.OutputTokens != 3 || usage.CachedInputTokens != 2 || usage.CacheWriteTokens != 1 || usage.ReasoningTokens != 1 {
-		t.Fatalf("usage = %+v, want input=7 output=3 cached=2 cache-write=1 reasoning=1", *usage)
+	if usage.InputTokens != 7 || usage.OutputTokens != 3 || usage.CachedInputTokens != 2 || usage.ReasoningTokens != 1 {
+		t.Fatalf("usage = %+v, want input=7 output=3 cached=2 reasoning=1", *usage)
 	}
 	if !gotDone {
 		t.Fatal("expected a done event, got none")

internal/providers/openai/provider.go

@@ -357,7 +357,6 @@ func (provider *Provider) emitChunk(
 				PromptTokens:      chunk.Usage.PromptTokens,
 				CompletionTokens:  chunk.Usage.CompletionTokens,
 				CachedInputTokens: chunk.Usage.PromptTokensDetails.CachedTokens,
-				CacheWriteTokens:  chunk.Usage.PromptTokensDetails.CacheWriteTokens,
 				ReasoningTokens:   chunk.Usage.CompletionTokensDetails.ReasoningTokens,
 			},
 		})

internal/providers/openai/provider_test.go

@@ -260,14 +260,14 @@ func TestStreamCompletionAppliesCustomAuthAndHeaders(t *testing.T) {
 func TestStreamCompletionEmitsTextUsageAndDone(t *testing.T) {
 	provider := newTestProvider(t, func(w http.ResponseWriter, r *http.Request) {
 		writeSSE(w, `{"choices":[{"delta":{"content":"hello "}}]}`)
-		writeSSE(w, `{"choices":[{"delta":{"content":"zero"}}],"usage":{"prompt_tokens":12,"completion_tokens":5,"prompt_tokens_details":{"cached_tokens":3,"cache_write_tokens":2}}}`)
+		writeSSE(w, `{"choices":[{"delta":{"content":"zero"}}],"usage":{"prompt_tokens":12,"completion_tokens":5,"prompt_tokens_details":{"cached_tokens":3}}}`)
 		writeSSE(w, `[DONE]`)
 	})
 
 	events := collectProviderEvents(t, provider)
 	assertEvent(t, events[0], zeroruntime.StreamEventText, "hello ")
 	assertEvent(t, events[1], zeroruntime.StreamEventText, "zero")
-	if events[2].Type != zeroruntime.StreamEventUsage || events[2].Usage.PromptTokens != 12 || events[2].Usage.CompletionTokens != 5 || events[2].Usage.CachedInputTokens != 3 || events[2].Usage.CacheWriteTokens != 2 {
+	if events[2].Type != zeroruntime.StreamEventUsage || events[2].Usage.PromptTokens != 12 || events[2].Usage.CompletionTokens != 5 || events[2].Usage.CachedInputTokens != 3 {
 		t.Fatalf("unexpected usage event: %#v", events[2])
 	}
 	if events[3].Type != zeroruntime.StreamEventDone {

internal/providers/openai/session.go

@@ -195,12 +195,7 @@ func (s *turnSession) computeFingerprint(request zeroruntime.CompletionRequest)
 func wireToolsDigest(tools []zeroruntime.ToolDefinition) string {
 	rendered := make([]string, 0, len(tools))
 	for _, tool := range tools {
-		wireShape := struct {
-			Type       zeroruntime.ToolDefinitionType    `json:"type,omitempty"`
-			Parameters map[string]any                    `json:"parameters,omitempty"`
-			Format     *zeroruntime.ToolDefinitionFormat `json:"format,omitempty"`
-		}{Type: tool.Type, Parameters: tool.Parameters, Format: tool.Format}
-		schema, err := json.Marshal(wireShape)
+		schema, err := json.Marshal(tool.Parameters)
 		if err != nil {
 			rendered = append(rendered, tool.Name+"\n"+tool.Description+"\n__non_json:"+tool.Name)
 			continue

internal/providers/openai/types.go

@@ -109,8 +109,7 @@ type usage struct {
 }
 
 type promptTokenDetails struct {
-	CachedTokens     int `json:"cached_tokens"`
-	CacheWriteTokens int `json:"cache_write_tokens"`
+	CachedTokens int `json:"cached_tokens"`
 }
 
 type completionTokenDetails struct {

internal/providers/turn_session.go

@@ -15,27 +15,9 @@ import (
 // value (e.g. "1") to enable — the same boolean idiom as ZERO_FORMAT_ON_WRITE.
 const openaiTurnSessionEnv = "ZERO_OPENAI_TURN_SESSION"
 
-// ChatGPT Responses sessions are enabled by default for their native provider.
-// Setting this to 0/false/off restores the stateless HTTP/SSE transport.
-const chatGPTTurnSessionEnv = "ZERO_CHATGPT_TURN_SESSION"
-
 func openaiTurnSessionEnabled() bool {
 	value := strings.TrimSpace(os.Getenv(openaiTurnSessionEnv))
-	return value != "" && !explicitEnvFalse(value)
-}
-
-func chatGPTTurnSessionEnabled() bool {
-	value := strings.TrimSpace(os.Getenv(chatGPTTurnSessionEnv))
-	return value == "" || !explicitEnvFalse(value)
-}
-
-func explicitEnvFalse(value string) bool {
-	switch strings.ToLower(strings.TrimSpace(value)) {
-	case "0", "false", "off":
-		return true
-	default:
-		return false
-	}
+	return value != "" && value != "0" && !strings.EqualFold(value, "false")
 }
 
 // OptimizedTurnSessions returns the gated optimized TurnSessionProvider for an
@@ -43,35 +25,22 @@ func explicitEnvFalse(value string) bool {
 // is ineligible. Callers leave agent Options.TurnSessionProvider nil on false,
 // so the loop's default wrap keeps today's behavior byte-identical.
 //
-// Eligibility is deliberately narrow: native ChatGPT Responses uses its
-// concrete Codex provider and defaults on with a kill switch; official OpenAI
-// chat-completions keeps its existing opt-in prewarm session. Compatible
-// gateways and foreign provider values always retain the default adapter.
+// Eligibility is deliberately narrow: the resolved provider kind must be
+// official OpenAI (NOT openai-compatible gateways — the constructor merges the
+// two, so this branches on the resolved kind explicitly), not the ChatGPT
+// Codex catalog, and the provider value must be the concrete *openai.Provider
+// (a fake, a Codex provider, or nil falls back to the default path safely).
+// No base-URL check on top of the kind: prewarm and fingerprint telemetry are
+// harmless against any host, and kind==openai mirrors the existing
+// official-OpenAI precedent used for prompt_cache_key.
 func OptimizedTurnSessions(profile config.ProviderProfile, provider zeroruntime.Provider, options Options) (zeroruntime.TurnSessionProvider, bool) {
-	resolved, err := resolveProfile(profile, options)
-	if err != nil {
-		return nil, false
-	}
-	if isCodexCatalog(profile, resolved) {
-		if !chatGPTTurnSessionEnabled() {
-			return nil, false
-		}
-		concrete, ok := provider.(*openai.CodexProvider)
-		if !ok {
-			return nil, false
-		}
-		caps, err := resolveCapabilities(profile, options)
-		if err != nil {
-			return nil, false
-		}
-		return openai.NewCodexTurnSessionProvider(concrete, caps), true
-	}
-	if resolved.providerKind != config.ProviderKindOpenAI {
-		return nil, false
-	}
 	if !openaiTurnSessionEnabled() {
 		return nil, false
 	}
+	resolved, err := resolveProfile(profile, options)
+	if err != nil || resolved.providerKind != config.ProviderKindOpenAI || isCodexCatalog(profile, resolved) {
+		return nil, false
+	}
 	concrete, ok := provider.(*openai.Provider)
 	if !ok {
 		return nil, false

internal/providers/turn_session_gate_test.go

@@ -5,7 +5,6 @@ import (
 	"testing"
 
 	"github.com/Gitlawb/zero/internal/config"
-	"github.com/Gitlawb/zero/internal/providers/openai"
 	"github.com/Gitlawb/zero/internal/zeroruntime"
 )
 
@@ -46,7 +45,7 @@ func TestOptimizedTurnSessionsDefaultOff(t *testing.T) {
 func TestOptimizedTurnSessionsFalseyValues(t *testing.T) {
 	profile := openaiEligibleProfile()
 	provider := buildGateProvider(t, profile)
-	for _, value := range []string{"0", "false", "FALSE", "False", "off", "OFF", " ", ""} {
+	for _, value := range []string{"0", "false", "FALSE", "False", " ", ""} {
 		t.Setenv(openaiTurnSessionEnv, value)
 		if _, ok := OptimizedTurnSessions(profile, provider, Options{}); ok {
 			t.Fatalf("gate enabled for falsey value %q", value)
@@ -60,21 +59,6 @@ func TestOptimizedTurnSessionsFalseyValues(t *testing.T) {
 	}
 }
 
-func TestChatGPTTurnSessionGateValues(t *testing.T) {
-	for _, value := range []string{"0", "false", "FALSE", "off", "OFF"} {
-		t.Setenv(chatGPTTurnSessionEnv, value)
-		if chatGPTTurnSessionEnabled() {
-			t.Fatalf("ChatGPT gate enabled for falsey value %q", value)
-		}
-	}
-	for _, value := range []string{"", " ", "1", "true", "on"} {
-		t.Setenv(chatGPTTurnSessionEnv, value)
-		if !chatGPTTurnSessionEnabled() {
-			t.Fatalf("ChatGPT gate disabled for default/truthy value %q", value)
-		}
-	}
-}
-
 func TestOptimizedTurnSessionsOpenAIEligible(t *testing.T) {
 	t.Setenv(openaiTurnSessionEnv, "1")
 	profile := openaiEligibleProfile()
@@ -104,64 +88,13 @@ func TestOptimizedTurnSessionsRejectsCompatible(t *testing.T) {
 }
 
 func TestOptimizedTurnSessionsRejectsCodexCatalog(t *testing.T) {
-	t.Setenv(chatGPTTurnSessionEnv, "0")
-	profile := openaiEligibleProfile()
-	profile.Name = "chatgpt"
-	profile.CatalogID = "chatgpt"
-	if _, ok := OptimizedTurnSessions(profile, buildChatGPTGateProvider(t, profile), Options{}); ok {
-		t.Fatal("the ChatGPT Codex catalog must honor the turn-session kill switch")
-	}
-}
-
-func TestOptimizedTurnSessionsEnablesChatGPTResponsesByDefault(t *testing.T) {
-	t.Setenv(chatGPTTurnSessionEnv, "")
-	profile := openaiEligibleProfile()
-	profile.Name = "chatgpt"
-	profile.CatalogID = "chatgpt"
-	provider := buildChatGPTGateProvider(t, profile)
-
-	turnSessions, ok := OptimizedTurnSessions(profile, provider, Options{})
-	if !ok || turnSessions == nil {
-		t.Fatal("ChatGPT Responses provider did not receive its default turn session")
-	}
-	if got := turnSessions.Capabilities().Model; got != profile.Model {
-		t.Fatalf("Capabilities().Model = %q, want %q", got, profile.Model)
-	}
-}
-
-func TestOptimizedTurnSessionsRecognizesCompatibleLabeledChatGPTProfile(t *testing.T) {
-	t.Setenv(chatGPTTurnSessionEnv, "")
-	profile := openaiEligibleProfile()
-	profile.Name = "chatgpt"
-	profile.CatalogID = "chatgpt"
-	profile.ProviderKind = config.ProviderKindOpenAICompatible
-	if turnSessions, ok := OptimizedTurnSessions(profile, buildChatGPTGateProvider(t, profile), Options{}); !ok || turnSessions == nil {
-		t.Fatal("ChatGPT catalog profile must use its native session regardless of the stored compatibility label")
-	}
-}
-
-func buildChatGPTGateProvider(t *testing.T, profile config.ProviderProfile) *openai.CodexProvider {
-	t.Helper()
-	provider, err := openai.NewCodexProvider(openai.CodexOptions{
-		Options: openai.Options{
-			APIKey:  "test-token",
-			BaseURL: "https://chatgpt.example/backend-api/codex",
-			Model:   profile.Model,
-		},
-		AccountID: "account-test",
-	})
-	if err != nil {
-		t.Fatalf("NewCodexProvider: %v", err)
-	}
-	return provider
-}
-
-func TestOptimizedTurnSessionsRejectsNonCodexProviderForChatGPT(t *testing.T) {
-	t.Setenv(chatGPTTurnSessionEnv, "1")
+	t.Setenv(openaiTurnSessionEnv, "1")
 	profile := openaiEligibleProfile()
 	profile.CatalogID = "chatgpt"
+	// Build the provider from the base profile: the point under test is the
+	// catalog check, not Codex construction (which needs OAuth wiring).
 	if _, ok := OptimizedTurnSessions(profile, buildGateProvider(t, openaiEligibleProfile()), Options{}); ok {
-		t.Fatal("a ChatGPT catalog profile with a non-Codex provider must use the default session")
+		t.Fatal("the ChatGPT Codex catalog must not get the optimized session")
 	}
 }
 

internal/proxydial/proxydial.go

@@ -1,93 +0,0 @@
-// Package proxydial answers one question for an SSRF-guarded dialer: is this
-// dial the connection dial of a request the transport routed through a forward
-// proxy?
-//
-// A guarded transport validates the TARGET of a request before dialing, and its
-// dialer refuses loopback, private and link-local addresses so a redirect or a
-// DNS rebind cannot walk the request onto the local network. When a forward
-// proxy is configured, the transport dials the PROXY first and tunnels the
-// request through it, and a local proxy is by far the common shape:
-// HTTPS_PROXY=http://127.0.0.1:3067. The dialer then sees 127.0.0.1, refuses it,
-// and the user gets "loopback hosts are blocked" for a request whose real target
-// was validated and public (#569).
-//
-// The proxy address is not the request target, and the guard was never about it.
-// It is configuration the user set on purpose, and the transport is going to dial
-// it for every request whether the guard likes it or not. So that dial is let
-// through, and only that dial.
-//
-// THE EXEMPTION FOLLOWS THE TRANSPORT'S OWN ROUTE DECISION, NOT A GUESS AT IT.
-// Asking the Proxy function a question of one's own invention answers for a
-// request the transport never made: with NO_PROXY excluding a host, the real
-// request to that host goes direct while a synthetic probe still comes back
-// proxied, and a direct dial whose address happens to equal the proxy endpoint
-// would then skip the guard entirely. Host-dependent proxy callbacks make the
-// mismatch general, and no amount of care over the probe's spelling closes it,
-// because the two calls are about different requests.
-//
-// So the decision is recorded where it is made, on the request, and read back on
-// the dial that request causes. Transport.RoundTrip asks the wrapped transport's
-// Proxy function about the actual request, stores the answer in that request's
-// context, and hands it on; the transport derives the dial context from the
-// request context, so the dialer reads back the route this very connection is
-// being opened for. Per-request, so concurrent requests cannot overwrite each
-// other, and unforgeable from outside the package: the context key is private.
-package proxydial
-
-import (
-	"context"
-	"net/http"
-	"net/url"
-)
-
-// selectedProxyKey addresses the route decision inside a request context. It is
-// unexported so nothing outside this package can plant one.
-type selectedProxyKey struct{}
-
-// Transport records the proxy its wrapped transport selects for each request in
-// that request's context, so a guarded DialContext installed on the same
-// transport can tell the dial to a proxy from a direct dial.
-//
-// The embedded transport stays reachable: callers configure Proxy, DialContext
-// and the rest on it exactly as before, and tests can read them back.
-type Transport struct {
-	*http.Transport
-}
-
-// Wrap returns a Transport around transport. The result is the http.RoundTripper
-// to install on the client; installing the bare transport instead leaves every
-// dial looking direct, which is safe (the guard applies) but reopens #569.
-func Wrap(transport *http.Transport) *Transport {
-	return &Transport{Transport: transport}
-}
-
-// RoundTrip resolves the route for this request and passes the decision down to
-// the dialer through the request context.
-func (transport *Transport) RoundTrip(request *http.Request) (*http.Response, error) {
-	if transport.Transport.Proxy != nil {
-		// A Proxy error is left for the transport to report: it fails the
-		// request before dialing, so there is no dial to classify. The function
-		// is called once here and once by the transport, which is what a
-		// host-dependent callback already expects from redirects and retries.
-		if proxyURL, err := transport.Transport.Proxy(request); err == nil && proxyURL != nil {
-			request = request.WithContext(context.WithValue(request.Context(), selectedProxyKey{}, proxyURL))
-		}
-	}
-	return transport.Transport.RoundTrip(request)
-}
-
-// IsProxyDial reports whether ctx belongs to a request this package's Transport
-// routed through a proxy, which makes the dial about to happen the dial to that
-// proxy.
-//
-// THE ADDRESS IS NOT COMPARED, AND DOES NOT NEED TO BE. A transport opens
-// exactly one connection dial per connection, and when a proxy is selected that
-// dial goes to the proxy; the target is reached through it, never dialed. So the
-// route decision on the context already identifies the dial, and matching the
-// address against the proxy URL on top of it could only ever disagree with the
-// transport, which is what a punycoded Unicode proxy hostname does: Go dials
-// xn--bro-hoa.example while the URL still spells buero as the user wrote it.
-func IsProxyDial(ctx context.Context) bool {
-	proxyURL, _ := ctx.Value(selectedProxyKey{}).(*url.URL)
-	return proxyURL != nil
-}

internal/proxydial/proxydial_test.go

@@ -1,224 +0,0 @@
-package proxydial
-
-import (
-	"context"
-	"errors"
-	"net"
-	"net/http"
-	"net/url"
-	"sync"
-	"testing"
-)
-
-// errDialed ends the request at the dial, after the route decision has been
-// observed. Nothing here needs a live server.
-var errDialed = errors.New("dial recorded")
-
-type dialRecord struct {
-	address string
-	proxied bool
-}
-
-// driveRequest sends one request through a wrapped transport whose dialer
-// records what it was asked for and whether the context says this dial belongs
-// to a proxied request.
-func driveRequest(t *testing.T, target string, proxyFor func(*http.Request) (*url.URL, error)) dialRecord {
-	t.Helper()
-	var record dialRecord
-	transport := &http.Transport{Proxy: proxyFor}
-	transport.DialContext = func(ctx context.Context, _, address string) (net.Conn, error) {
-		record = dialRecord{address: address, proxied: IsProxyDial(ctx)}
-		return nil, errDialed
-	}
-	client := &http.Client{Transport: Wrap(transport)}
-	request, err := http.NewRequest(http.MethodGet, target, nil)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if _, err := client.Do(request); !errors.Is(err, errDialed) {
-		t.Fatalf("%s: request ended before the dial: %v", target, err)
-	}
-	if record.address == "" {
-		t.Fatalf("%s: the dialer was never called", target)
-	}
-	return record
-}
-
-func fixedProxy(raw string) func(*http.Request) (*url.URL, error) {
-	parsed, err := url.Parse(raw)
-	if err != nil {
-		panic(err)
-	}
-	return func(*http.Request) (*url.URL, error) { return parsed, nil }
-}
-
-// THE DIAL TO A CONFIGURED PROXY IS THE ONE THAT IS EXEMPT. A proxied request
-// dials the proxy, never the target, so the route on the context is what
-// identifies the dial.
-func TestProxiedRequestDialsTheProxyAndSaysSo(t *testing.T) {
-	record := driveRequest(t, "https://api.example.com/v1/models", fixedProxy("http://127.0.0.1:3067"))
-	if !record.proxied {
-		t.Error("a request routed through a proxy did not reach the dialer as proxied")
-	}
-	if record.address != "127.0.0.1:3067" {
-		t.Errorf("dial address = %q, want the proxy endpoint", record.address)
-	}
-}
-
-// AND A DIRECT REQUEST IS NOT, EVEN WHEN ITS ORIGIN IS THE PROXY'S OWN ADDRESS.
-//
-// This is the NO_PROXY shape: the proxy function excludes one host, so a request
-// to that host goes direct. Asking that same function about a request of our own
-// invention would answer "proxied" (the invented host is not excluded) and the
-// direct dial, whose address equals the proxy endpoint, would skip the guard
-// while resolving to whatever the name resolves to at connect time.
-func TestDirectRequestToTheProxyEndpointIsNotAProxyDial(t *testing.T) {
-	proxyURL, err := url.Parse("http://rebind.example:80")
-	if err != nil {
-		t.Fatal(err)
-	}
-	noProxyForRebind := func(request *http.Request) (*url.URL, error) {
-		if request.URL.Hostname() == "rebind.example" {
-			return nil, nil
-		}
-		return proxyURL, nil
-	}
-
-	record := driveRequest(t, "http://rebind.example/data", noProxyForRebind)
-	if record.address != "rebind.example:80" {
-		t.Fatalf("SETUP INVALID: dial address = %q, want the direct origin, which is also the proxy endpoint", record.address)
-	}
-	if record.proxied {
-		t.Error("a direct dial was reported as the proxy dial because its address matched the configured proxy")
-	}
-
-	// The same function still routes another host through that proxy, so the
-	// exclusion above is a route difference and not a disabled proxy.
-	if record := driveRequest(t, "http://elsewhere.example/data", noProxyForRebind); !record.proxied {
-		t.Error("the configured proxy was not used for a host outside the exclusion")
-	}
-}
-
-// The inverse mismatch: a callback that routes by host must not have its answer
-// taken from some other host. A proxy selected only for the real target is
-// honoured.
-func TestHostDependentProxySelectionIsHonoured(t *testing.T) {
-	proxyURL, err := url.Parse("http://127.0.0.1:3067")
-	if err != nil {
-		t.Fatal(err)
-	}
-	onlyForOneHost := func(request *http.Request) (*url.URL, error) {
-		if request.URL.Hostname() == "api.example.com" {
-			return proxyURL, nil
-		}
-		return nil, nil
-	}
-	if record := driveRequest(t, "https://api.example.com/v1", onlyForOneHost); !record.proxied || record.address != "127.0.0.1:3067" {
-		t.Errorf("selected proxy not reached: %+v", record)
-	}
-	if record := driveRequest(t, "https://other.example/v1", onlyForOneHost); record.proxied {
-		t.Error("an unproxied host was reported as proxied")
-	}
-}
-
-// Scheme separation: an https-only proxy leaves an http request direct, and the
-// decision recorded is the one made for that request's own scheme.
-func TestSchemeSeparation(t *testing.T) {
-	proxyURL, err := url.Parse("http://127.0.0.1:3067")
-	if err != nil {
-		t.Fatal(err)
-	}
-	httpsOnly := func(request *http.Request) (*url.URL, error) {
-		if request.URL.Scheme == "https" {
-			return proxyURL, nil
-		}
-		return nil, nil
-	}
-	if record := driveRequest(t, "https://api.example.com/v1", httpsOnly); !record.proxied {
-		t.Error("the https proxy was not applied to an https request")
-	}
-	if record := driveRequest(t, "http://api.example.com/v1", httpsOnly); record.proxied {
-		t.Error("an http request was treated as proxied by an https-only proxy")
-	}
-}
-
-// A UNICODE PROXY HOSTNAME IS STILL THE PROXY. Go dials proxies by their
-// IDNA-encoded name, so a matcher comparing the URL's own spelling would call
-// this dial direct and refuse it as an ordinary private address. Nothing is
-// compared here, so both spellings of one host are one host.
-func TestUnicodeProxyHostnameIsRecognised(t *testing.T) {
-	unicodeRecord := driveRequest(t, "https://api.example.com/v1", fixedProxy("http://büro.example:3067"))
-	if !unicodeRecord.proxied {
-		t.Error("a proxy configured with a Unicode hostname was not recognised as the proxy")
-	}
-	asciiRecord := driveRequest(t, "https://api.example.com/v1", fixedProxy("http://xn--bro-hoa.example:3067"))
-	if !asciiRecord.proxied {
-		t.Error("a proxy configured with the ASCII spelling was not recognised as the proxy")
-	}
-	// The two spellings name one endpoint, and it is the ASCII one that is
-	// dialed. This is the mismatch a string comparison would have had to close.
-	if unicodeRecord.address != asciiRecord.address {
-		t.Errorf("dial addresses differ across spellings of one host: %q vs %q", unicodeRecord.address, asciiRecord.address)
-	}
-}
-
-// A transport with no proxy leaves every dial direct.
-func TestNoProxyMeansNoExemption(t *testing.T) {
-	if record := driveRequest(t, "http://127.0.0.1:3067/", nil); record.proxied {
-		t.Error("a dial was reported as proxied by a transport with no Proxy function")
-	}
-	if IsProxyDial(context.Background()) {
-		t.Error("a context that never went through the wrapper reported a proxy dial")
-	}
-}
-
-// THE DECISION IS PER REQUEST. A shared record of the last selected proxy would
-// let a proxied request hand its exemption to a direct one running beside it.
-func TestConcurrentRequestsKeepTheirOwnRoute(t *testing.T) {
-	proxyURL, err := url.Parse("http://127.0.0.1:3067")
-	if err != nil {
-		t.Fatal(err)
-	}
-	byHost := func(request *http.Request) (*url.URL, error) {
-		if request.URL.Hostname() == "proxied.example" {
-			return proxyURL, nil
-		}
-		return nil, nil
-	}
-
-	var mutex sync.Mutex
-	seen := map[string]bool{}
-	transport := &http.Transport{Proxy: byHost}
-	transport.DialContext = func(ctx context.Context, _, address string) (net.Conn, error) {
-		mutex.Lock()
-		seen[address] = IsProxyDial(ctx)
-		mutex.Unlock()
-		return nil, errDialed
-	}
-	client := &http.Client{Transport: Wrap(transport)}
-
-	var group sync.WaitGroup
-	for range 40 {
-		for _, target := range []string{"http://proxied.example/", "http://direct.example/"} {
-			group.Add(1)
-			go func() {
-				defer group.Done()
-				request, _ := http.NewRequest(http.MethodGet, target, nil)
-				_, _ = client.Do(request)
-			}()
-		}
-	}
-	group.Wait()
-
-	mutex.Lock()
-	defer mutex.Unlock()
-	if !seen["127.0.0.1:3067"] {
-		t.Error("the proxy dial was not recorded as proxied under concurrency")
-	}
-	if seen["direct.example:80"] {
-		t.Error("a direct dial picked up another request's proxy exemption")
-	}
-	if len(seen) != 2 {
-		t.Fatalf("SETUP INVALID: dialed %v, want exactly the proxy and the direct origin", seen)
-	}
-}

internal/sandbox/adapters.go

@@ -7,7 +7,6 @@ import (
 type BackendOptions struct {
 	GOOS             string
 	LookupExecutable func(string) (string, error)
-	DetectWSL        func() WSLInfo
 }
 
 type Backend struct {
@@ -54,7 +53,6 @@ func SelectBackend(options BackendOptions) Backend {
 	return NewSandboxManager(SandboxManagerOptions{
 		GOOS:             options.GOOS,
 		LookupExecutable: options.LookupExecutable,
-		DetectWSL:        options.DetectWSL,
 	}).Backend()
 }
 

internal/sandbox/adapters_test.go

@@ -45,7 +45,6 @@ func TestSelectBackendChoosesPlatformAdapterWithFallback(t *testing.T) {
 				}
 				return "", errors.New("missing")
 			},
-			DetectWSL: func() WSLInfo { return WSLInfo{} },
 		})
 		if backend.Name != BackendUnavailable || backend.Available {
 			t.Fatalf("linux backend = %#v, want native sandbox unavailable without Linux helper", backend)
@@ -55,20 +54,6 @@ func TestSelectBackendChoosesPlatformAdapterWithFallback(t *testing.T) {
 		}
 	})
 
-	t.Run("linux helper missing under WSL reports WSL fallback", func(t *testing.T) {
-		backend := SelectBackend(BackendOptions{
-			GOOS:             "linux",
-			LookupExecutable: func(string) (string, error) { return "", errors.New("missing") },
-			DetectWSL:        func() WSLInfo { return WSLInfo{IsWSL: true, IsWSL2: true} },
-		})
-		if backend.Name != BackendWSL || backend.Available || !backend.Fallback {
-			t.Fatalf("linux backend = %#v, want explicit WSL fallback", backend)
-		}
-		if !strings.Contains(backend.Message, "WSL2") {
-			t.Fatalf("linux fallback message = %q, want WSL2 diagnostic", backend.Message)
-		}
-	})
-
 	t.Run("darwin sandbox exec available", func(t *testing.T) {
 		backend := SelectBackend(BackendOptions{
 			GOOS: "darwin",

internal/sandbox/manager.go

@@ -51,7 +51,6 @@ const (
 type SandboxManagerOptions struct {
 	GOOS             string
 	LookupExecutable func(string) (string, error)
-	DetectWSL        func() WSLInfo
 	Backend          Backend
 }
 
@@ -97,7 +96,7 @@ func NewSandboxManager(options SandboxManagerOptions) SandboxManager {
 		goos = runtime.GOOS
 	}
 	if backend.Name == "" {
-		backend = selectPlatformBackend(goos, options.LookupExecutable, options.DetectWSL)
+		backend = selectPlatformBackend(goos, options.LookupExecutable)
 	}
 	if backend.Platform == "" {
 		backend.Platform = goos
@@ -169,13 +168,10 @@ func lookupExecutable(name string) (string, error) {
 	return "", errors.New("executable file not found")
 }
 
-func selectPlatformBackend(goos string, lookup func(string) (string, error), detect func() WSLInfo) Backend {
+func selectPlatformBackend(goos string, lookup func(string) (string, error)) Backend {
 	if lookup == nil {
 		lookup = lookupExecutable
 	}
-	if detect == nil {
-		detect = detectWSL
-	}
 	switch goos {
 	case "linux":
 		if helper, err := lookup(LinuxSandboxHelperName); err == nil && helper != "" {
@@ -184,7 +180,7 @@ func selectPlatformBackend(goos string, lookup func(string) (string, error), det
 			}
 			return nativeBackend(goos, BackendLinuxBwrap, helper, "Linux sandbox helper available")
 		}
-		if info := detect(); info.IsWSL {
+		if info := detectWSL(); info.IsWSL {
 			return wslBackend(goos, info)
 		}
 		return unavailableBackend(goos, "Linux sandbox helper is not available")

internal/sandbox/profile.go

@@ -96,28 +96,15 @@ var protectedMetadataNames = []string{".git", ".zero", ".agents"}
 // gitMetadataWriteCarveouts below.
 var sandboxFullyProtectedMetadataNames = []string{".zero", ".agents"}
 
-// gitMetadataWriteCarveouts returns the .git paths that stay write-denied under
-// the OS-level sandbox even though the rest of .git is writable to git
-// subprocesses. Worktrees and submodules store .git as a regular pointer file,
-// so they protect that file itself: constructing .git/hooks below it makes
-// bwrap fail before the command starts. All other entry and error states retain
-// the legacy child paths. The pointer is deliberately not parsed here;
-// repository-controlled metadata must not redirect sandbox rules elsewhere.
+// gitMetadataWriteCarveouts returns the .git subpaths that stay write-denied
+// under the OS-level sandbox even though the rest of .git is writable to git
+// subprocesses. Nonexistent paths are harmless no-ops in every backend's
+// enforcement (seatbelt regex, bwrap ro-bind, Windows ACL deny entry).
 func gitMetadataWriteCarveouts(root string) []string {
-	return gitMetadataWriteCarveoutsWithLstat(root, os.Lstat)
-}
-
-func gitMetadataWriteCarveoutsWithLstat(root string, lstat func(string) (os.FileInfo, error)) []string {
-	gitPath := filepath.Join(root, ".git")
-	children := []string{
-		filepath.Join(gitPath, "hooks"),
-		filepath.Join(gitPath, "config"),
+	return []string{
+		filepath.Join(root, ".git", "hooks"),
+		filepath.Join(root, ".git", "config"),
 	}
-	info, err := lstat(gitPath)
-	if err != nil || !info.Mode().IsRegular() {
-		return children
-	}
-	return []string{gitPath}
 }
 
 func PermissionProfileFromPolicy(workspaceRoot string, policy Policy, scope *Scope) PermissionProfile {

internal/sandbox/profile_worktree_test.go

@@ -1,115 +0,0 @@
-package sandbox
-
-import (
-	"errors"
-	"os"
-	"path/filepath"
-	"testing"
-)
-
-func mustEqualCarveouts(t *testing.T, got, want []string) {
-	t.Helper()
-	if len(got) != len(want) {
-		t.Fatalf("carveouts = %v, want %v", got, want)
-	}
-	for i := range want {
-		if got[i] != want[i] {
-			t.Fatalf("carveout[%d] = %q, want %q", i, got[i], want[i])
-		}
-	}
-}
-
-// Worktree/submodule checkouts store .git as a pointer file. Protect the file
-// itself and never create a bwrap mount target beneath it.
-func TestGitMetadataWriteCarveoutsProtectsWorktreePointer(t *testing.T) {
-	root := t.TempDir()
-	gitPath := filepath.Join(root, ".git")
-	if err := os.WriteFile(gitPath, []byte("gitdir: ../outside\n"), 0o644); err != nil {
-		t.Fatal(err)
-	}
-
-	got := gitMetadataWriteCarveouts(root)
-	mustEqualCarveouts(t, got, []string{gitPath})
-	for _, carveout := range got {
-		if carveout == filepath.Join(gitPath, "hooks") || carveout == filepath.Join(gitPath, "config") {
-			t.Fatalf("carveout points beneath .git file: %q", carveout)
-		}
-	}
-}
-
-func TestLinuxBwrapPlanDoesNotMountBelowWorktreePointer(t *testing.T) {
-	root := t.TempDir()
-	gitPath := filepath.Join(root, ".git")
-	if err := os.WriteFile(gitPath, []byte("gitdir: ../outside\n"), 0o644); err != nil {
-		t.Fatal(err)
-	}
-	profile := PermissionProfile{FileSystem: FileSystemPolicy{
-		Kind: FileSystemRestricted,
-		WriteRoots: []WritableRoot{{
-			Root:             root,
-			ReadOnlySubpaths: gitMetadataWriteCarveouts(root),
-		}},
-	}}
-	args := linuxBwrapFilesystemArgs(profile)
-	assertArgsContainSequence(t, args, "--ro-bind", gitPath, gitPath)
-	for _, child := range []string{"hooks", "config"} {
-		bogus := filepath.Join(gitPath, child)
-		if argsContainSequence(args, "--tmpfs", bogus) || argsContainSequence(args, "--ro-bind", bogus, bogus) {
-			t.Fatalf("bwrap args contain mount below .git file %q: %v", bogus, args)
-		}
-	}
-}
-
-func TestGitMetadataWriteCarveoutsPlainCheckout(t *testing.T) {
-	root := t.TempDir()
-	want := []string{
-		filepath.Join(root, ".git", "hooks"),
-		filepath.Join(root, ".git", "config"),
-	}
-	mustEqualCarveouts(t, gitMetadataWriteCarveouts(root), want)
-
-	if err := os.MkdirAll(filepath.Join(root, ".git"), 0o755); err != nil {
-		t.Fatal(err)
-	}
-	mustEqualCarveouts(t, gitMetadataWriteCarveouts(root), want)
-}
-
-func TestGitMetadataWriteCarveoutsPreservesSymlinkBehavior(t *testing.T) {
-	for _, targetKind := range []string{"directory", "file", "dangling"} {
-		t.Run(targetKind, func(t *testing.T) {
-			root := t.TempDir()
-			target := filepath.Join(root, "real.git")
-			switch targetKind {
-			case "directory":
-				if err := os.MkdirAll(target, 0o755); err != nil {
-					t.Fatal(err)
-				}
-			case "file":
-				if err := os.WriteFile(target, []byte("gitdir: ../outside\n"), 0o644); err != nil {
-					t.Fatal(err)
-				}
-			}
-			if err := os.Symlink(target, filepath.Join(root, ".git")); err != nil {
-				t.Skipf("symlink unavailable: %v", err)
-			}
-			want := []string{
-				filepath.Join(root, ".git", "hooks"),
-				filepath.Join(root, ".git", "config"),
-			}
-			mustEqualCarveouts(t, gitMetadataWriteCarveouts(root), want)
-		})
-	}
-}
-
-func TestGitMetadataWriteCarveoutsPreservesInspectionErrorBehavior(t *testing.T) {
-	root := t.TempDir()
-	gitPath := filepath.Join(root, ".git")
-	want := []string{
-		filepath.Join(gitPath, "hooks"),
-		filepath.Join(gitPath, "config"),
-	}
-	got := gitMetadataWriteCarveoutsWithLstat(root, func(string) (os.FileInfo, error) {
-		return nil, errors.New("inspection failed")
-	})
-	mustEqualCarveouts(t, got, want)
-}

internal/sandbox/profile_worktree_unix_test.go

@@ -1,21 +0,0 @@
-//go:build unix
-
-package sandbox
-
-import (
-	"path/filepath"
-	"syscall"
-	"testing"
-)
-
-func TestGitMetadataWriteCarveoutsPreservesSpecialGitEntryBehavior(t *testing.T) {
-	root := t.TempDir()
-	gitPath := filepath.Join(root, ".git")
-	if err := syscall.Mkfifo(gitPath, 0o644); err != nil {
-		t.Skip(err)
-	}
-	mustEqualCarveouts(t, gitMetadataWriteCarveouts(root), []string{
-		filepath.Join(gitPath, "hooks"),
-		filepath.Join(gitPath, "config"),
-	})
-}

internal/sandbox/scope.go

@@ -19,17 +19,6 @@ type Scope struct {
 	workspaceRoot string
 	readRoots     []string
 	extraRoots    []string
-	// tempReads / tempWrites count how many LIVE temporary grants depend on a
-	// root, so one holder's cleanup cannot revoke another's access.
-	//
-	// Without them a temporary grant was add-then-remove with no notion of who
-	// still needed it: the second caller to ask for a root already present got a
-	// NO-OP undo, and the first caller's cleanup removed the root out from under
-	// it. Two read-only tools in the same parallel batch, both blocked on the
-	// same directory, is exactly that shape — and read-only tools are precisely
-	// the ones the batch runs concurrently.
-	tempReads  map[string]int
-	tempWrites map[string]int
 }
 
 // NewScope builds a scope for workspaceRoot plus the given extra roots. The
@@ -92,88 +81,15 @@ func (s *Scope) Add(path string) (string, error) {
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	// COVERED BY WHAT. extraRoots holds temporary write roots alongside
-	// permanent ones, so "something already covers this" was not the question
-	// worth asking: a permanent grant made over a path a temporary holder
-	// happened to cover recorded nothing, and vanished the moment that holder
-	// released. A session-scoped grant outliving the request that prompted it is
-	// the entire difference between Add and AddTemporaryWrite.
-	//
-	// Permanent coverage is looked for FIRST and across every root, because a
-	// path can be covered twice and the temporary cover must not decide the
-	// answer when a permanent one is also present.
-	if s.permanentWriteRootCoversLocked(root) {
-		return root, nil
-	}
-	for _, existing := range s.extraRoots {
-		// The same root, held temporarily: promote it in place. Its holders'
-		// releases become no-ops, which is what permanence means here.
-		if existing == root && s.temporaryWriteLocked(existing) {
-			delete(s.tempWrites, root)
+	for _, existing := range append([]string{s.workspaceRoot}, s.extraRoots...) {
+		if pathWithinRoot(existing, root) {
 			return root, nil
 		}
 	}
-	// Either uncovered, or covered only by a BROADER temporary root that is
-	// going to be released. Recording the narrower root in its own right is what
-	// survives that release.
 	s.extraRoots = append(s.extraRoots, root)
 	return root, nil
 }
 
-// temporaryWriteLocked reports whether root is held by a temporary write grant
-// rather than a session-scoped one. Callers must hold the lock.
-func (s *Scope) temporaryWriteLocked(root string) bool {
-	_, temporary := s.tempWrites[root]
-	return temporary
-}
-
-// permanentWriteRootCoversLocked reports whether root sits under write authority
-// that outlives every temporary holder: the workspace root, or a session-scoped
-// grant. Coverage by a TEMPORARY write root deliberately does not count —
-// it is going to be released, so nothing recorded on the strength of it
-// survives. Callers must hold the lock.
-//
-// One helper rather than a copy per caller because Add, AddRead and
-// AddTemporaryRead all turn on the same question, and three copies of "covered,
-// but by what" is how one of them ends up answering it differently.
-// permanentReadRootCoversLocked reports whether root is already readable by a
-// grant that outlives every temporary holder.
-//
-// SLICE ORDER MUST NOT DECIDE THIS. The old check walked readRoots and stopped at
-// the first entry covering the path, so a BROAD TEMPORARY root sitting earlier in
-// the slice shadowed a narrower PERMANENT one later — and the caller was handed a
-// reference on somebody else's grant when it needed no reference at all. Asking
-// the whole question first, over both lists, makes the answer independent of
-// insertion order.
-//
-// Write roots count: a grant that permits writing permits reading the same tree.
-func (s *Scope) permanentReadRootCoversLocked(root string) bool {
-	if s.permanentWriteRootCoversLocked(root) {
-		return true
-	}
-	for _, existing := range s.readRoots {
-		if pathWithinRoot(existing, root) && !s.temporaryReadLocked(existing) {
-			return true
-		}
-	}
-	return false
-}
-
-func (s *Scope) permanentWriteRootCoversLocked(root string) bool {
-	for _, existing := range append([]string{s.workspaceRoot}, s.extraRoots...) {
-		if pathWithinRoot(existing, root) && !s.temporaryWriteLocked(existing) {
-			return true
-		}
-	}
-	return false
-}
-
-// temporaryReadLocked is temporaryWriteLocked for read roots.
-func (s *Scope) temporaryReadLocked(root string) bool {
-	_, temporary := s.tempReads[root]
-	return temporary
-}
-
 // AddRead grants read-only access under path. If the path is already covered by
 // a writable root, no separate read root is stored.
 func (s *Scope) AddRead(path string) (string, error) {
@@ -183,19 +99,11 @@ func (s *Scope) AddRead(path string) (string, error) {
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	// Same rule as Add: coverage that is going to be released is not coverage a
-	// permanent grant can rely on, whichever side of the read/write boundary it
-	// sits on. A permanent read covered only by a temporary WRITE root died with
-	// that root just as surely.
-	if s.permanentWriteRootCoversLocked(root) {
-		return root, nil
-	}
-	if s.permanentReadRootCoversLocked(root) {
+	if s.writeRootCoversLocked(root) {
 		return root, nil
 	}
 	for _, existing := range s.readRoots {
-		if existing == root && s.temporaryReadLocked(existing) {
-			delete(s.tempReads, root)
+		if pathWithinRoot(existing, root) {
 			return root, nil
 		}
 	}
@@ -210,63 +118,16 @@ func (s *Scope) AddTemporaryRead(path string) (string, func(), error) {
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	// Genuinely permanent — the workspace root, or a session-scoped grant. It
-	// outlives this reader, so there is nothing to release.
-	if s.permanentWriteRootCoversLocked(root) {
+	if s.writeRootCoversLocked(root) {
 		return root, func() {}, nil
 	}
-	// A TEMPORARY write root covering this path is NOT borrowed, and this is the
-	// one place the distinction bites hardest.
-	//
-	// The dependency on that root is real — the write holder's cleanup must not
-	// revoke this reader, which is the defect the refcount exists to close,
-	// reached across the read/write boundary. But taking a reference on the
-	// WRITE root pays for the lifetime with the authority: the reference keeps
-	// the root in extraRoots, extraRoots is what Roots() feeds validate(), and
-	// validate() is WRITE authorization. So a reader outliving its writer went on
-	// writing anywhere under a write grant that had already ended — not merely
-	// under the path it asked to read.
-	//
-	// One reference cannot be both the lifetime and the capability. The lifetime
-	// is kept below, as a temporary READ root for the path this caller actually
-	// asked for. readRoots feeds ReadRoots(), which confers no write authority —
-	// validate() authorises writes from workspaceRoot plus extraRoots, and this
-	// path never enters that list. So the reader survives its writer with read
-	// authority and only read authority.
-	//
-	// That claim is the written justification for the whole design, so it has to
-	// stay exhaustive as the accessors change. It has already been wrong once, in
-	// both directions: an earlier draft said readRoots fed ReadRoots() and nothing
-	// else while ExtraReadRoots() also read it, and that accessor has since been
-	// removed as belonging to a different change.
-	if s.permanentReadRootCoversLocked(root) {
-		return root, func() {}, nil
+	for _, existing := range s.readRoots {
+		if pathWithinRoot(existing, root) {
+			return root, func() {}, nil
+		}
 	}
-	if s.tempReads == nil {
-		s.tempReads = map[string]int{}
-	}
-	// THE SAME ROOT, ANOTHER HOLDER: one entry, two references. Only an EXACT
-	// match shares — a narrower request must not, which is the whole point below.
-	if _, held := s.tempReads[root]; held {
-		s.tempReads[root]++
-		return root, oncePerHolder(func() { s.releaseTemporaryRead(root) }), nil
-	}
-	// A NARROWER REQUEST RECORDS ITS OWN ROOT, even under a broader temporary
-	// read that currently covers it.
-	//
-	// Borrowing the covering root's reference kept this reader alive by keeping
-	// the BROAD ROOT alive, and readRoots feeds validateRead and the native
-	// sandbox profile. So once the broad reader released, a caller that had asked
-	// to read one subdirectory was left able to read the whole tree its neighbour
-	// had asked for, siblings included. Reported by @jatmn, and it is the read
-	// twin of the write escalation fixed above: the refcount key decides not only
-	// WHEN an entry disappears but WHICH path stays authorised while it lives.
 	s.readRoots = append(s.readRoots, root)
-	if s.tempReads == nil {
-		s.tempReads = map[string]int{}
-	}
-	s.tempReads[root] = 1
-	return root, oncePerHolder(func() { s.releaseTemporaryRead(root) }), nil
+	return root, func() { s.removeReadRoot(root) }, nil
 }
 
 func (s *Scope) AddTemporaryWrite(path string) (string, func(), error) {
@@ -276,107 +137,32 @@ func (s *Scope) AddTemporaryWrite(path string) (string, func(), error) {
 	}
 	s.mu.Lock()
 	defer s.mu.Unlock()
-	// A PERMANENT grant is the only cover that needs no bookkeeping: it outlives
-	// every temporary holder, so there is nothing to keep alive and nothing to
-	// release.
-	if s.permanentWriteRootCoversLocked(root) {
+	if s.writeRootCoversLocked(root) {
 		return root, func() {}, nil
 	}
-	if s.tempWrites == nil {
-		s.tempWrites = map[string]int{}
-	}
-	// THE SAME ROOT, ANOTHER HOLDER: one entry, two references. Only an exact
-	// match shares an entry — a NARROWER request must not, which is the whole
-	// point below.
-	if _, held := s.tempWrites[root]; held {
-		s.tempWrites[root]++
-		return root, oncePerHolder(func() { s.releaseTemporaryWrite(root) }), nil
-	}
-	// A NARROWER REQUEST RECORDS ITS OWN ROOT, even when a broader temporary
-	// grant currently covers it.
-	//
-	// Borrowing a reference on the covering root kept this holder alive, which
-	// was the point, but it kept the COVERING ROOT alive to do it — and
-	// extraRoots is what validate() authorises writes from. So once the broad
-	// holder released, a caller that had asked to write one subdirectory was
-	// left holding write authority over the whole tree its neighbour had asked
-	// for, including siblings it never named. Reported by CodeRabbit, and it is
-	// the write-side twin of the read-side escalation @jatmn found: one
-	// reference cannot be both a lifetime and a capability, whichever side of
-	// the read/write boundary it sits on.
-	//
-	// Recording the requested root separately gives each holder exactly the
-	// authority it asked for and a lifetime of its own. The nesting costs an
-	// extra entry in extraRoots while both are live, which is redundant but not
-	// wrong — the broader root already permits everything the narrower one does.
 	s.extraRoots = append(s.extraRoots, root)
-	s.tempWrites[root] = 1
-	return root, oncePerHolder(func() { s.releaseTemporaryWrite(root) }), nil
+	return root, func() { s.removeWriteRoot(root) }, nil
 }
 
-// releaseTemporaryRead drops ONE holder's reference and removes the root only
-// when the last one is gone.
-//
-// The count alone cannot make this safe, and an earlier comment here claimed it
-// could — that each undo is called exactly once, and flooring at zero handled
-// the rest. Flooring stops the count going negative; it does not stop one
-// holder's second call consuming a DIFFERENT holder's reference. With two
-// readers, calling the first's undo twice took the count 2 -> 1 -> 0 and removed
-// a root the second was still using. Idempotency belongs to the closure, which
-// is the thing that knows whose reference it is, so every undo handed out is
-// wrapped in oncePerHolder.
-func (s *Scope) releaseTemporaryRead(root string) {
+func (s *Scope) writeRootCoversLocked(root string) bool {
+	for _, existing := range append([]string{s.workspaceRoot}, s.extraRoots...) {
+		if pathWithinRoot(existing, root) {
+			return true
+		}
+	}
+	return false
+}
+
+func (s *Scope) removeReadRoot(root string) {
 	s.mu.Lock()
-	remaining, tracked := s.tempReads[root]
-	if !tracked {
-		s.mu.Unlock()
-		return
-	}
-	remaining--
-	if remaining > 0 {
-		s.tempReads[root] = remaining
-		s.mu.Unlock()
-		return
-	}
-	// Both mutations under ONE hold. Dropping the lock between them opened a
-	// window where the root was still in readRoots but no longer in tempReads:
-	// a concurrent AddTemporaryRead landing there reads it as a PERMANENT root,
-	// hands its caller a no-op undo, and then this call strips the root — so
-	// that caller believes it holds access it has already silently lost.
-	delete(s.tempReads, root)
+	defer s.mu.Unlock()
 	s.readRoots = removeScopeRoot(s.readRoots, root)
-	s.mu.Unlock()
 }
 
-// releaseTemporaryWrite is releaseTemporaryRead for write roots. Two functions
-// rather than one generic helper because they guard different slices and the
-// generic version would take the slice by name — which is how the wrong one
-// gets passed.
-func (s *Scope) releaseTemporaryWrite(root string) {
+func (s *Scope) removeWriteRoot(root string) {
 	s.mu.Lock()
-	remaining, tracked := s.tempWrites[root]
-	if !tracked {
-		s.mu.Unlock()
-		return
-	}
-	remaining--
-	if remaining > 0 {
-		s.tempWrites[root] = remaining
-		s.mu.Unlock()
-		return
-	}
-	// Same single-hold rule as releaseTemporaryRead above.
-	delete(s.tempWrites, root)
+	defer s.mu.Unlock()
 	s.extraRoots = removeScopeRoot(s.extraRoots, root)
-	s.mu.Unlock()
-}
-
-// oncePerHolder makes one holder's undo safe to call more than once. The
-// reference it drops is that holder's own, so a second call must do nothing
-// rather than reach into the shared count and take somebody else's.
-func oncePerHolder(release func()) func() {
-	var once sync.Once
-	return func() { once.Do(release) }
 }
 
 func removeScopeRoot(roots []string, root string) []string {

internal/sandbox/scope_extra_read_test.go

@@ -1,56 +0,0 @@
-package sandbox
-
-import (
-	"path/filepath"
-	"testing"
-)
-
-// THE ANTI-ESCALATION PROPERTY. A read grant (AddRead, where --add-read-dir lands)
-// is READABLE but NOT WRITABLE. This is what makes propagating a parent's
-// request_permissions read grant to a child safe: the child can audit the granted
-// path but cannot modify it. Emitting the grant as a WRITE root (--add-dir) would
-// break exactly this.
-func TestAReadGrantIsReadableButNotWritable(t *testing.T) {
-	scope, granted := grantOutsideDefaults(t)
-	root, err := scope.AddRead(granted)
-	if err != nil {
-		t.Fatalf("AddRead: %v", err)
-	}
-	target := filepath.Join(root, "audit-me.go")
-
-	if block := scope.validateRead(target); block != nil {
-		t.Fatalf("a read grant did not allow READING %q: %v — the audit would fail 'outside the workspace'", target, block)
-	}
-	if block := scope.validate(target); block == nil {
-		t.Fatalf("a read grant ALLOWED WRITING %q — a read grant escalated to write", target)
-	}
-}
-
-// grantOutsideDefaults returns a scope and a directory that scope does not
-// already cover, both under test-owned storage.
-//
-// THE CAUSE, NOT THE SYMPTOM. NewScope seeds the system temporary directory as a
-// permanent write root, so a plain t.TempDir() grant is writable before any
-// grant exists and the anti-escalation assertions below prove nothing. The first
-// fix placed the fixture under os.UserHomeDir() to find ground the defaults do
-// not own. That worked and bought two problems: a hermetic runner may expose
-// HOME read-only, so these tests failed at MkdirTemp before asserting anything,
-// and on an ordinary machine they wrote into the developer's real home and left
-// zero-scope-* debris whenever a run was interrupted. Reported by @jatmn.
-//
-// Building the Scope directly removes the seeded defaults, which is what made
-// HOME necessary in the first place. t.TempDir() is then outside by
-// construction, the fixture is hermetic, and nothing touches HOME.
-func grantOutsideDefaults(t *testing.T) (*Scope, string) {
-	t.Helper()
-	workspace := resolvedFixturePath(t, t.TempDir())
-	granted := resolvedFixturePath(t, t.TempDir())
-	scope := &Scope{workspaceRoot: workspace}
-	// PROVED AGAINST THIS SCOPE. The point of the helper is that the grant is
-	// what changes access, so the target has to begin unauthorised — asserted
-	// here once rather than trusted in every caller.
-	if scope.validate(filepath.Join(granted, "probe.txt")) == nil {
-		t.Fatalf("%s is writable before any grant exists; the assertions below would prove nothing", granted)
-	}
-	return scope, granted
-}

internal/sandbox/scope_temp_refcount_test.go

@@ -1,595 +0,0 @@
-package sandbox
-
-import (
-	"os"
-	"path/filepath"
-	"slices"
-	"sync"
-	"testing"
-)
-
-// scopeOutsideDefaults builds a Scope directly instead of through NewScope.
-//
-// NewScope adds the system temp directory as a write root, so a target under
-// t.TempDir() is already covered and AddTemporaryRead returns before it ever
-// touches the refcount. A test built that way exercises none of this and passes
-// against the bug — which is how the first version of this test passed.
-func scopeOutsideDefaults(t *testing.T) (*Scope, string) {
-	t.Helper()
-	workspace := t.TempDir()
-	target := filepath.Join(t.TempDir(), "shared")
-	if err := os.MkdirAll(target, 0o700); err != nil {
-		t.Fatalf("mkdir target: %v", err)
-	}
-	// Built directly, NOT via NewScope: real directories are needed because
-	// normalizeScopeRoot requires them to exist, but NewScope's default temp
-	// write root would then cover the target and short-circuit the path.
-	return &Scope{workspaceRoot: workspace}, target
-}
-
-// The refcount and the root list have to move together.
-//
-// Release used to delete the refcount, drop the lock, then strip the root in a
-// second acquisition. In that window the root was still in readRoots but no
-// longer in tempReads, so a concurrent AddTemporaryRead read it as a PERMANENT
-// root and handed its caller a no-op undo — then the release stripped it and
-// that caller silently lost access it believed it held.
-func TestReleasingATemporaryReadCannotStripALiveGrant(t *testing.T) {
-	scope, target := scopeOutsideDefaults(t)
-
-	// First holder establishes the root.
-	first, releaseFirst, err := scope.AddTemporaryRead(target)
-	if err != nil {
-		t.Fatalf("AddTemporaryRead: %v", err)
-	}
-	if len(scope.tempReads) == 0 {
-		t.Fatal("precondition: the grant should be refcounted, not covered by a default root")
-	}
-
-	// Second holder takes a reference on the same root.
-	second, releaseSecond, err := scope.AddTemporaryRead(target)
-	if err != nil {
-		t.Fatalf("AddTemporaryRead (second): %v", err)
-	}
-
-	// The first holder leaving must not revoke the second's access.
-	releaseFirst()
-	if block := scope.validateRead(second); block != nil {
-		t.Fatalf("the second holder lost its grant when the first released: %v", block)
-	}
-
-	// Only the last release retires the root.
-	releaseSecond()
-	if block := scope.validateRead(first); block == nil {
-		t.Error("the root outlived its last holder")
-	}
-}
-
-// Under contention the same invariant has to hold: while a grant is live, its
-// root is readable.
-func TestTemporaryReadGrantsSurviveConcurrentReleases(t *testing.T) {
-	scope, target := scopeOutsideDefaults(t)
-
-	var wg sync.WaitGroup
-	var mu sync.Mutex
-	var failures []string
-
-	for i := 0; i < 24; i++ {
-		wg.Add(1)
-		go func() {
-			defer wg.Done()
-			for j := 0; j < 200; j++ {
-				granted, undo, err := scope.AddTemporaryRead(target)
-				if err != nil {
-					mu.Lock()
-					failures = append(failures, "AddTemporaryRead: "+err.Error())
-					mu.Unlock()
-					return
-				}
-				if block := scope.validateRead(granted); block != nil {
-					mu.Lock()
-					failures = append(failures, "root not readable while a grant was live")
-					mu.Unlock()
-				}
-				undo()
-			}
-		}()
-	}
-	wg.Wait()
-
-	if len(failures) > 0 {
-		t.Fatalf("%d failures, first: %s", len(failures), failures[0])
-	}
-}
-
-// A read covered by a TEMPORARY WRITE root must take a reference too.
-//
-// permanentWriteRootCoversLocked scans extraRoots, and AddTemporaryWrite appends
-// temporary write roots there — so "covered by a write root" does not mean
-// "covered permanently". Without a reference the write holder's cleanup silently
-// revoked the reader's access: the same defect the refcount closes, reached
-// across the read/write boundary instead of within one side of it.
-func TestAReadCoveredByATemporaryWriteSurvivesItsRelease(t *testing.T) {
-	workspace := t.TempDir()
-	outer := filepath.Join(t.TempDir(), "outer")
-	inner := filepath.Join(outer, "inner")
-	if err := os.MkdirAll(inner, 0o700); err != nil {
-		t.Fatal(err)
-	}
-	// Built directly for the same reason scopeOutsideDefaults is: NewScope's
-	// default temp write root would cover the fixture and short-circuit this.
-	scope := &Scope{workspaceRoot: workspace}
-
-	_, releaseWrite, err := scope.AddTemporaryWrite(outer)
-	if err != nil {
-		t.Fatalf("temporary write: %v", err)
-	}
-	readRoot, releaseRead, err := scope.AddTemporaryRead(inner)
-	if err != nil {
-		t.Fatalf("temporary read: %v", err)
-	}
-
-	covered := func() bool {
-		for _, root := range scope.ReadRoots() {
-			if pathWithinRoot(root, readRoot) {
-				return true
-			}
-		}
-		return false
-	}
-	if !covered() {
-		t.Fatal("the reader did not hold access before any release")
-	}
-
-	// The WRITE holder finishes first; the reader has not released.
-	releaseWrite()
-	if !covered() {
-		t.Errorf("the write holder's cleanup revoked a live read grant on %s", readRoot)
-	}
-
-	// And once the reader releases too, the root is genuinely gone.
-	releaseRead()
-	if covered() {
-		t.Errorf("the root outlived its last holder: %v", scope.ReadRoots())
-	}
-}
-
-func hasExtraRoot(scope *Scope, root string) bool {
-	for _, existing := range writeRootsBeyondWorkspace(scope) {
-		if existing == root {
-			return true
-		}
-	}
-	return false
-}
-
-// A PERMANENT GRANT MUST OUTLIVE THE TEMPORARY ONE IT LANDED ON TOP OF.
-//
-// extraRoots holds temporary write roots alongside permanent ones, so Add asked
-// only "is this already covered" — and a session-scoped grant made while a
-// temporary holder happened to cover the path recorded nothing, then vanished
-// when that holder released. Outliving the request that prompted it is the
-// entire difference between Add and AddTemporaryWrite.
-func TestAPermanentGrantSurvivesTheTemporaryOneItCovered(t *testing.T) {
-	t.Run("write, same root", func(t *testing.T) {
-		scope, _, outside := scopeOutsideRoots(t)
-		_, releaseTemp, err := scope.AddTemporaryWrite(outside)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if _, err := scope.Add(outside); err != nil {
-			t.Fatal(err)
-		}
-		releaseTemp()
-		if !hasExtraRoot(scope, outside) {
-			t.Error("the temporary holder's release revoked a permanent write grant")
-		}
-	})
-
-	t.Run("read, same root", func(t *testing.T) {
-		scope, _, outside := scopeOutsideRoots(t)
-		_, releaseTemp, err := scope.AddTemporaryRead(outside)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if _, err := scope.AddRead(outside); err != nil {
-			t.Fatal(err)
-		}
-		releaseTemp()
-		if !hasReadRoot(scope, outside) {
-			t.Error("the temporary holder's release revoked a permanent read grant")
-		}
-	})
-
-	// The nested shape: a BROAD temporary root covering a NARROW permanent one.
-	// Promoting in place cannot help here — the narrow root has to be recorded
-	// in its own right, or it goes when the broad one does.
-	t.Run("broad temporary over narrow permanent", func(t *testing.T) {
-		scope, _, outside := scopeOutsideRoots(t)
-		inner := filepath.Join(outside, "inner")
-		if err := os.MkdirAll(inner, 0o700); err != nil {
-			t.Fatal(err)
-		}
-		_, releaseBroad, err := scope.AddTemporaryWrite(outside)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if _, err := scope.Add(inner); err != nil {
-			t.Fatal(err)
-		}
-		releaseBroad()
-		covered := false
-		for _, existing := range writeRootsBeyondWorkspace(scope) {
-			if pathWithinRoot(existing, inner) {
-				covered = true
-			}
-		}
-		if !covered {
-			t.Error("a narrower permanent grant died with the broader temporary root it sat under")
-		}
-	})
-
-	// THE READ MIRROR OF BOTH SHAPES ABOVE. AddRead makes two claims that the
-	// subtests so far only made for Add: the loop over extraRoots skips coverage
-	// that is a temporary WRITE, and the loop over readRoots skips coverage that
-	// is a temporary READ. Each claim is a separate branch, and neither was
-	// exercised from the read side.
-	t.Run("permanent read under a temporary write", func(t *testing.T) {
-		scope, _, outside := scopeOutsideRoots(t)
-		_, releaseWrite, err := scope.AddTemporaryWrite(outside)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if _, err := scope.AddRead(outside); err != nil {
-			t.Fatal(err)
-		}
-		releaseWrite()
-		if !hasReadRoot(scope, outside) {
-			t.Error("a temporary write holder's release revoked a permanent read grant")
-		}
-	})
-
-	t.Run("broad temporary read over narrow permanent read", func(t *testing.T) {
-		scope, _, outside := scopeOutsideRoots(t)
-		inner := filepath.Join(outside, "inner")
-		if err := os.MkdirAll(inner, 0o700); err != nil {
-			t.Fatal(err)
-		}
-		_, releaseBroad, err := scope.AddTemporaryRead(outside)
-		if err != nil {
-			t.Fatal(err)
-		}
-		if _, err := scope.AddRead(inner); err != nil {
-			t.Fatal(err)
-		}
-		releaseBroad()
-		if block := scope.validateRead(filepath.Join(inner, "audit-me.go")); block != nil {
-			t.Errorf("a narrower permanent read died with the broader temporary read it sat under: %v", block)
-		}
-	})
-}
-
-// ONE HOLDER'S UNDO DROPS ONE HOLDER'S REFERENCE, HOWEVER OFTEN IT IS CALLED.
-//
-// The count flooring at zero stops it going negative; it does not stop a
-// holder's second call consuming somebody else's reference. With two readers,
-// calling the first's undo twice took the count 2 -> 1 -> 0 and removed a root
-// the second was still using — the exact revocation this refcount exists to
-// prevent, reached through a duplicate call rather than a sibling's cleanup.
-// Deferred cleanups in a retry path are how a real caller does this by accident.
-func TestOneHoldersUndoIsIdempotent(t *testing.T) {
-	scope, workspace, outside := scopeOutsideRoots(t)
-	_, undoFirst, err := scope.AddTemporaryRead(outside)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, undoSecond, err := scope.AddTemporaryRead(outside)
-	if err != nil {
-		t.Fatal(err)
-	}
-	undoFirst()
-	undoFirst()
-	undoFirst()
-	if !hasReadRoot(scope, outside) {
-		t.Fatal("repeated calls to one holder's undo revoked a live holder's access")
-	}
-	undoSecond()
-	if hasReadRoot(scope, outside) {
-		t.Error("the root outlived its last holder")
-	}
-
-	// The write side takes the same rule. Built directly for the same reason the
-	// helper is: NewScope would seed the system temp directory as a permanent
-	// write root, which already covers this fixture and makes the grant vacuous.
-	writeScope := &Scope{workspaceRoot: workspace}
-	_, undoWriteFirst, err := writeScope.AddTemporaryWrite(outside)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, undoWriteSecond, err := writeScope.AddTemporaryWrite(outside)
-	if err != nil {
-		t.Fatal(err)
-	}
-	undoWriteFirst()
-	undoWriteFirst()
-	if !hasExtraRoot(writeScope, outside) {
-		t.Fatal("repeated calls to one write holder's undo revoked a live holder's access")
-	}
-	undoWriteSecond()
-	if hasExtraRoot(writeScope, outside) {
-		t.Error("the write root outlived its last holder")
-	}
-}
-
-// temporaryWriteFixture builds a nested pair of real directories and a scope
-// that covers neither: an OUTER directory a temporary write grant will take,
-// and an INNER one below it that a temporary read grant will ask for.
-//
-// Built directly rather than through NewScope, for the reason
-// scopeOutsideDefaults documents: NewScope seeds the system temp directory as a
-// PERMANENT write root, which would cover the whole fixture and send every
-// branch under test down the "genuinely permanent" path instead. Both paths are
-// returned symlink-resolved because normalizeScopeRoot resolves what it stores,
-// and on macOS the fixture's /var spelling is a symlink to /private/var.
-func temporaryWriteFixture(t *testing.T) (scope *Scope, workspace, outer, inner string) {
-	t.Helper()
-	outer = filepath.Join(t.TempDir(), "outer")
-	inner = filepath.Join(outer, "inner")
-	if err := os.MkdirAll(inner, 0o700); err != nil {
-		t.Fatal(err)
-	}
-	workspace = resolvedFixturePath(t, t.TempDir())
-	return &Scope{workspaceRoot: workspace}, workspace, resolvedFixturePath(t, outer), resolvedFixturePath(t, inner)
-}
-
-func resolvedFixturePath(t *testing.T, path string) string {
-	t.Helper()
-	resolved, err := filepath.EvalSymlinks(path)
-	if err != nil {
-		t.Fatalf("resolve fixture %s: %v", path, err)
-	}
-	return resolved
-}
-
-// A READER MUST NOT INHERIT ITS WRITER'S AUTHORITY.
-//
-// The reader's dependency on a covering TEMPORARY WRITE root was recorded as a
-// reference on that root — one reference standing for both the lifetime and the
-// capability. Release the WRITER first and the reference kept the path in
-// extraRoots, which is the list Roots() feeds validate(), so the surviving
-// read-only holder could WRITE anywhere below a write grant that had already
-// ended — including paths it never asked to read.
-//
-// This is TestAReadGrantIsReadableButNotWritable's property for temporary
-// grants: read authority stays read authority, whichever holder leaves first.
-func TestAReaderOutlivingItsWriterKeepsReadAuthorityOnly(t *testing.T) {
-	t.Run("the writer releases first", func(t *testing.T) {
-		scope, workspace, outer, inner := temporaryWriteFixture(t)
-
-		writeRoot, releaseWrite, err := scope.AddTemporaryWrite(outer)
-		if err != nil {
-			t.Fatalf("temporary write: %v", err)
-		}
-		if writeRoot != outer {
-			t.Fatalf("temporary write granted %q, want %q", writeRoot, outer)
-		}
-		readRoot, releaseRead, err := scope.AddTemporaryRead(inner)
-		if err != nil {
-			t.Fatalf("temporary read: %v", err)
-		}
-		if readRoot != inner {
-			t.Fatalf("temporary read granted %q, want %q", readRoot, inner)
-		}
-		// The reader holds a read root of its own and NO reference on the write
-		// root. Both halves matter: the first is what survives the writer, the
-		// second is what stops the write root surviving with it.
-		//
-		// Errorf, not Fatalf: these say WHY the behavior below breaks, and a
-		// bookkeeping check that aborts the run hides the behavior it explains.
-		scope.mu.RLock()
-		writeHolders := scope.tempWrites[outer]
-		readHolders := scope.tempReads[inner]
-		scope.mu.RUnlock()
-		if writeHolders != 1 {
-			t.Errorf("tempWrites[%s] = %d, want 1: the reader took a reference on the WRITE root", outer, writeHolders)
-		}
-		if readHolders != 1 {
-			t.Errorf("tempReads[%s] = %d, want 1: the reader kept no read root of its own", inner, readHolders)
-		}
-
-		// The WRITE holder finishes; only the read-only holder is left.
-		releaseWrite()
-
-		if got := writeRootsBeyondWorkspace(scope); len(got) != 0 {
-			t.Errorf("ExtraRoots() = %v, want none: the reader held the write root open", got)
-		}
-		if got, want := scope.ReadRoots(), []string{workspace, inner}; !slices.Equal(got, want) {
-			t.Errorf("ReadRoots() = %v, want %v", got, want)
-		}
-
-		target := filepath.Join(inner, "audit-me.go")
-		if block := scope.validateRead(target); block != nil {
-			t.Errorf("the writer's cleanup revoked a live read grant on %q: %v", target, block)
-		}
-		block := scope.validate(target)
-		if block == nil {
-			t.Fatalf("a read-only holder may still WRITE %q after the write grant ended", target)
-		}
-		if block.Code != BlockOutsideWorkspace {
-			t.Errorf("write block code = %q, want %q", block.Code, BlockOutsideWorkspace)
-		}
-		if block.Path != target {
-			t.Errorf("write block path = %q, want %q", block.Path, target)
-		}
-		// The escalation was never confined to the path the reader asked for —
-		// a borrowed reference carries the whole covering root — so a sibling
-		// the reader never named has to be denied too.
-		sibling := filepath.Join(outer, "sibling.txt")
-		if block := scope.validate(sibling); block == nil {
-			t.Errorf("a read-only holder of %q may still WRITE %q, which it never asked to read", inner, sibling)
-		}
-
-		releaseRead()
-		if got, want := scope.ReadRoots(), []string{workspace}; !slices.Equal(got, want) {
-			t.Errorf("ReadRoots() = %v, want %v: the read root outlived its last holder", got, want)
-		}
-	})
-
-	// A CONTROL, NOT COVERAGE FOR THE FINDING. This subtest passes on the
-	// unfixed tree too — the escalation needs the WRITER to go first, which the
-	// subtest above exercises. It earns its place by pinning that the opposite
-	// release order was not broken while fixing the dangerous one, and it is
-	// labelled so nobody counts it as evidence the finding is closed.
-	t.Run("the reader releases first (control: passes unfixed)", func(t *testing.T) {
-		scope, _, outer, inner := temporaryWriteFixture(t)
-
-		_, releaseWrite, err := scope.AddTemporaryWrite(outer)
-		if err != nil {
-			t.Fatalf("temporary write: %v", err)
-		}
-		_, releaseRead, err := scope.AddTemporaryRead(inner)
-		if err != nil {
-			t.Fatalf("temporary read: %v", err)
-		}
-
-		// The other order, which the fix must not break: the writer keeps FULL
-		// authority for as long as it holds the grant.
-		releaseRead()
-		buildLog := filepath.Join(outer, "build.log")
-		if block := scope.validate(buildLog); block != nil {
-			t.Fatalf("the reader's cleanup revoked the live write grant on %q: %v", buildLog, block)
-		}
-		if got, want := writeRootsBeyondWorkspace(scope), []string{outer}; !slices.Equal(got, want) {
-			t.Errorf("ExtraRoots() = %v, want %v", got, want)
-		}
-
-		releaseWrite()
-		if block := scope.validate(buildLog); block == nil {
-			t.Errorf("the write root %q outlived its only holder", outer)
-		}
-		if block := scope.validateRead(filepath.Join(inner, "audit-me.go")); block == nil {
-			t.Errorf("the read root %q outlived its only holder", inner)
-		}
-	})
-}
-
-// A NARROWER WRITE HOLDER MUST NOT INHERIT ITS NEIGHBOUR'S TREE.
-//
-// The write-side twin of the read-side escalation above, and the same root
-// cause: a nested holder used to take a reference on the BROADER temporary root
-// that happened to cover it. That kept the nested holder alive, which was the
-// point, but it kept the covering root alive to do it — and extraRoots is what
-// validate() authorises writes from. Once the broad holder released, a caller
-// that had asked for one subdirectory held write authority over the whole tree,
-// siblings included. Reported by CodeRabbit.
-func TestANestedWriteHolderKeepsOnlyItsOwnSubtree(t *testing.T) {
-	scope, _, outsideBase := scopeOutsideRoots(t)
-	outer := filepath.Join(outsideBase, "outer")
-	inner := filepath.Join(outer, "inner")
-	sibling := filepath.Join(outer, "sibling")
-	for _, dir := range []string{outer, inner, sibling} {
-		if err := os.MkdirAll(dir, 0o700); err != nil {
-			t.Fatal(err)
-		}
-	}
-	_, releaseOuter, err := scope.AddTemporaryWrite(outer)
-	if err != nil {
-		t.Fatalf("temporary write on the broad root: %v", err)
-	}
-	_, releaseInner, err := scope.AddTemporaryWrite(inner)
-	if err != nil {
-		t.Fatalf("temporary write on the nested root: %v", err)
-	}
-
-	// THE BROAD HOLDER GOES FIRST — the nested holder outliving it is what
-	// exposes whose authority it is actually holding.
-	releaseOuter()
-
-	if block := scope.validate(filepath.Join(inner, "mine.txt")); block != nil {
-		t.Errorf("the nested holder lost the subtree it asked for: %v", block.Reason)
-	}
-	if block := scope.validate(filepath.Join(sibling, "not-mine.txt")); block == nil {
-		t.Error("the nested holder can write a SIBLING it never asked for: the broad holder's authority outlived the broad holder")
-	}
-	if block := scope.validate(filepath.Join(outer, "not-mine.txt")); block == nil {
-		t.Error("the nested holder can write the covering root itself after its holder released")
-	}
-
-	releaseInner()
-	if block := scope.validate(filepath.Join(inner, "mine.txt")); block == nil {
-		t.Error("the nested root outlived its only holder")
-	}
-}
-
-// The opposite order, as a control: the nested holder releasing first must not
-// disturb the broad holder that is still live.
-func TestANestedWriteHolderReleasingFirstLeavesTheBroadGrant(t *testing.T) {
-	scope, _, outsideBase := scopeOutsideRoots(t)
-	outer := filepath.Join(outsideBase, "outer")
-	inner := filepath.Join(outer, "inner")
-	for _, dir := range []string{outer, inner} {
-		if err := os.MkdirAll(dir, 0o700); err != nil {
-			t.Fatal(err)
-		}
-	}
-	_, releaseOuter, err := scope.AddTemporaryWrite(outer)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, releaseInner, err := scope.AddTemporaryWrite(inner)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	releaseInner()
-	if block := scope.validate(filepath.Join(inner, "still-ok.txt")); block != nil {
-		t.Errorf("the nested holder's release revoked the broad holder's coverage: %v", block.Reason)
-	}
-	releaseOuter()
-	if block := scope.validate(filepath.Join(inner, "gone.txt")); block == nil {
-		t.Error("the tree outlived every holder")
-	}
-}
-
-// TWO HOLDERS OF THE SAME ROOT SHARE ONE ENTRY. Only an exact match shares —
-// a narrower request must not, which is what the escalation test above pins.
-func TestTwoHoldersOfTheSameWriteRootShareOneEntry(t *testing.T) {
-	scope, _, outsideBase := scopeOutsideRoots(t)
-	target := filepath.Join(outsideBase, "shared")
-	if err := os.MkdirAll(target, 0o700); err != nil {
-		t.Fatal(err)
-	}
-	_, releaseFirst, err := scope.AddTemporaryWrite(target)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, releaseSecond, err := scope.AddTemporaryWrite(target)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	releaseFirst()
-	if block := scope.validate(filepath.Join(target, "still-held.txt")); block != nil {
-		t.Errorf("one holder's release revoked the other's grant on the same root: %v", block.Reason)
-	}
-	releaseSecond()
-	if block := scope.validate(filepath.Join(target, "gone.txt")); block == nil {
-		t.Error("the shared root outlived both holders")
-	}
-}
-
-// writeRootsBeyondWorkspace is Roots() without the workspace entry.
-//
-// These tests need to see which BEYOND-WORKSPACE write roots a scope currently
-// holds. There was an ExtraRoots() accessor that answered exactly this, but it
-// had no production caller — it belongs to #829's child-grant propagation, whose
-// consumer side is not on this branch, and @jatmn was right that carrying it here
-// leaves unrelated production surface in a PR scoped to refcounting. The
-// inspection is a test concern, so it lives in the tests.
-func writeRootsBeyondWorkspace(scope *Scope) []string {
-	all := scope.Roots()
-	if len(all) == 0 {
-		return nil
-	}
-	return append([]string(nil), all[1:]...)
-}

internal/sandbox/scope_temporary_test.go

@@ -1,366 +0,0 @@
-package sandbox
-
-import (
-	"os"
-	"path/filepath"
-	"sync"
-	"testing"
-)
-
-// scopeOutsideRoots builds a workspace and an unrelated directory that no
-// default write root already covers.
-//
-// NOT t.TempDir(). /tmp and $TMPDIR are default write roots, so a temporary
-// grant for a path under one is a no-op — every assertion here would pass
-// against code that grants nothing at all. That is RULES §2.3 in its exact
-// form, and it caught the first version of this test.
-// scopeOutsideRoots builds a workspace and a directory outside it, both under
-// test-owned storage, and returns a Scope that treats the second as genuinely
-// outside.
-//
-// THE FIXTURE PROBLEM AND ITS ACTUAL CAUSE. NewScope seeds the system temporary
-// directory as a permanent write root, so an ordinary t.TempDir() grant is
-// covered before any temporary grant exists and every assertion built on it is
-// vacuous. The first fix for that reached into os.UserHomeDir() to find ground
-// the defaults do not already own — which worked, and bought two new problems:
-// a hermetic runner may expose HOME read-only, so the tests failed at MkdirTemp
-// before asserting anything; and on an ordinary machine they wrote fixtures into
-// the developer's real home and left zeromax-scope-* debris behind whenever a
-// run was interrupted. Reported by @jatmn.
-//
-// The cause is the seeded defaults, not the location, so the Scope is built
-// DIRECTLY here — the same pattern scopeOutsideDefaults and temporaryWriteFixture
-// already use. With no defaults seeded, t.TempDir() is outside by construction,
-// the fixture is hermetic, and nothing touches HOME.
-//
-// Paths are symlink-resolved because the scope stores resolved roots and macOS
-// hands out /var/... temp directories that resolve to /private/var/...; an
-// unresolved fixture path compares unequal to the root the scope just recorded.
-func scopeOutsideRoots(t *testing.T) (scope *Scope, workspace string, outside string) {
-	t.Helper()
-	workspace = resolvedFixturePath(t, t.TempDir())
-	outside = filepath.Join(resolvedFixturePath(t, t.TempDir()), "outside")
-	// FATAL, NOT SKIP. Every caller of this helper asserts an AUTHORIZATION
-	// boundary, so a skipped fixture means that assertion never ran and the build
-	// reported green anyway. t.TempDir() already failed the test if it could not
-	// provide storage, so a subdirectory failing under it is a broken machine.
-	if err := os.MkdirAll(outside, 0o700); err != nil {
-		t.Fatalf("cannot prepare %s: %v", outside, err)
-	}
-	scope = &Scope{workspaceRoot: workspace}
-	// PROVED AGAINST THIS SCOPE, not against production's default list. The point
-	// of the helper is that a grant here changes something, and the only thing
-	// that can answer that is the scope the test will actually use. Checking
-	// defaultTempWriteRoots() instead asks about a scope nobody builds here — and
-	// says "prove nothing" for a t.TempDir() path that this scope, seeded with no
-	// defaults, genuinely does not cover.
-	//
-	// Asserting the NEGATIVE up front is also what keeps every caller honest: it
-	// establishes that the target begins unauthorised, so a later success is the
-	// grant's doing and not the fixture's placement.
-	if scope.validate(filepath.Join(outside, "probe.txt")) == nil {
-		t.Fatalf("%s is writable before any grant exists, so a temporary grant here would prove nothing", outside)
-	}
-	if scope.validateRead(filepath.Join(outside, "probe.txt")) == nil {
-		t.Fatalf("%s is readable before any grant exists, so a temporary read grant here would prove nothing", outside)
-	}
-	return scope, workspace, outside
-}
-
-func hasReadRoot(scope *Scope, root string) bool {
-	for _, existing := range scope.ReadRoots() {
-		if existing == root {
-			return true
-		}
-	}
-	return false
-}
-
-// THE DEFECT: one holder's cleanup revoked another's access. Two read-only
-// tools in the same parallel batch, both blocked on the same directory, is
-// exactly this — and read-only tools are the ones the batch runs concurrently.
-func TestATemporaryReadSurvivesASiblingsCleanup(t *testing.T) {
-	scope, _, outside := scopeOutsideRoots(t)
-	// The probe that the fix must make unnecessary: without it this reads
-	// true -> false.
-	if hasReadRoot(scope, outside) {
-		t.Fatal("the outside root is already covered; this test proves nothing")
-	}
-
-	_, undoA, err := scope.AddTemporaryRead(outside)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, undoB, err := scope.AddTemporaryRead(outside)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if !hasReadRoot(scope, outside) {
-		t.Fatal("the grant did not take effect")
-	}
-
-	undoA()
-	if !hasReadRoot(scope, outside) {
-		t.Fatal("A's cleanup revoked the root while B still held a grant")
-	}
-	undoB()
-	if hasReadRoot(scope, outside) {
-		t.Fatal("the root outlived its last holder")
-	}
-}
-
-// A NARROWER REQUEST KEEPS ITS OWN SUBTREE AND NOTHING WIDER.
-//
-// THIS TEST USED TO ASSERT THE OPPOSITE, and the earlier version is worth
-// recording because it is how the escalation survived a review round. It was
-// written to prove a LIFETIME property — the broad holder's cleanup must not
-// revoke a live narrow holder — and it proved that by asserting the BROAD root
-// was still present afterwards. That is the defect stated as a requirement: the
-// narrow holder was keeping its neighbour's whole tree alive in order to keep
-// itself alive, so the surviving reader could read siblings it never asked for.
-//
-// Lifetime and capability are two properties and one reference cannot carry
-// both. The assertions below name them separately: the requested path stays
-// readable while its holder lives, AND a sibling under the released broad root
-// is denied as soon as the holder that authorised it exits. Reported by @jatmn.
-func TestANarrowerReaderKeepsOnlyItsOwnSubtree(t *testing.T) {
-	scope, _, outside := scopeOutsideRoots(t)
-	nested := filepath.Join(outside, "nested")
-	sibling := filepath.Join(outside, "sibling")
-	for _, dir := range []string{nested, sibling} {
-		// FATAL, NOT SKIP. These directories are the fixture, not a precondition
-		// the environment might reasonably withhold — skipping on them reports a
-		// broken setup as a passing run.
-		if err := os.MkdirAll(dir, 0o700); err != nil {
-			t.Fatal(err)
-		}
-	}
-
-	_, undoBroad, err := scope.AddTemporaryRead(outside)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, undoNarrow, err := scope.AddTemporaryRead(nested)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	// THE BROAD HOLDER GOES FIRST. The narrow holder outliving it is what exposes
-	// whose authority it is actually holding.
-	undoBroad()
-	if block := scope.validateRead(filepath.Join(nested, "mine.txt")); block != nil {
-		t.Errorf("the broad holder's cleanup revoked the subtree the narrow holder asked for: %v", block.Reason)
-	}
-	if block := scope.validateRead(filepath.Join(sibling, "not-mine.txt")); block == nil {
-		t.Error("the narrow reader can read a SIBLING it never asked for: the broad holder's authority outlived the broad holder")
-	}
-	if block := scope.validateRead(filepath.Join(outside, "not-mine.txt")); block == nil {
-		t.Error("the narrow reader can read the covering root itself after its holder released")
-	}
-
-	undoNarrow()
-	if block := scope.validateRead(filepath.Join(nested, "mine.txt")); block == nil {
-		t.Error("the nested root outlived its only holder")
-	}
-}
-
-// The opposite order, as a control: the narrow reader releasing first must not
-// disturb the broad reader that is still live.
-func TestANarrowerReaderReleasingFirstLeavesTheBroadGrant(t *testing.T) {
-	scope, _, outside := scopeOutsideRoots(t)
-	nested := filepath.Join(outside, "nested")
-	if err := os.MkdirAll(nested, 0o700); err != nil {
-		t.Fatal(err)
-	}
-	_, undoBroad, err := scope.AddTemporaryRead(outside)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, undoNarrow, err := scope.AddTemporaryRead(nested)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	undoNarrow()
-	if block := scope.validateRead(filepath.Join(nested, "still-ok.txt")); block != nil {
-		t.Errorf("the narrow holder's release revoked the broad holder's coverage: %v", block.Reason)
-	}
-	undoBroad()
-	if block := scope.validateRead(filepath.Join(nested, "gone.txt")); block == nil {
-		t.Error("the tree outlived every holder")
-	}
-}
-
-// TWO READERS OF THE SAME ROOT SHARE ONE ENTRY. Only an exact match shares; a
-// narrower one never does, which is what the escalation test above pins.
-func TestTwoReadersOfTheSameRootShareOneEntry(t *testing.T) {
-	scope, _, outside := scopeOutsideRoots(t)
-	_, undoFirst, err := scope.AddTemporaryRead(outside)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, undoSecond, err := scope.AddTemporaryRead(outside)
-	if err != nil {
-		t.Fatal(err)
-	}
-
-	undoFirst()
-	if block := scope.validateRead(filepath.Join(outside, "still-held.txt")); block != nil {
-		t.Errorf("one reader's release revoked the other's grant on the same root: %v", block.Reason)
-	}
-	undoSecond()
-	if block := scope.validateRead(filepath.Join(outside, "gone.txt")); block == nil {
-		t.Error("the shared root outlived both holders")
-	}
-}
-
-// A NARROW PERMANENT READ IS NOT BORROWED FROM A BROAD TEMPORARY ONE. The old
-// scan walked readRoots in order and stopped at the first entry covering the
-// path, so a broad TEMPORARY root earlier in the slice shadowed a narrower
-// PERMANENT one later — and the caller took a reference it did not need on a
-// grant that was about to end.
-func TestAPermanentReadIsNotShadowedByABroadTemporaryOne(t *testing.T) {
-	scope, _, outside := scopeOutsideRoots(t)
-	nested := filepath.Join(outside, "nested")
-	if err := os.MkdirAll(nested, 0o700); err != nil {
-		t.Fatal(err)
-	}
-	// The broad TEMPORARY grant is taken first, so it sits earlier in readRoots.
-	_, undoBroad, err := scope.AddTemporaryRead(outside)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if _, err := scope.AddRead(nested); err != nil {
-		t.Fatal(err)
-	}
-
-	undoBroad()
-	if block := scope.validateRead(filepath.Join(nested, "mine.txt")); block != nil {
-		t.Errorf("a PERMANENT read grant died with a broad temporary one that merely preceded it: %v", block.Reason)
-	}
-}
-
-// A PERMANENT root is not refcounted and must never be removed by a temporary
-// holder's cleanup — the undo for a request it already covers is genuinely
-// nothing.
-func TestATemporaryGrantNeverRevokesAPermanentRoot(t *testing.T) {
-	scope, _, outside := scopeOutsideRoots(t)
-	if _, err := scope.AddRead(outside); err != nil {
-		t.Fatal(err)
-	}
-	_, undo, err := scope.AddTemporaryRead(outside)
-	if err != nil {
-		t.Fatal(err)
-	}
-	undo()
-	if !hasReadRoot(scope, outside) {
-		t.Fatal("a temporary holder's cleanup removed a permanent read root")
-	}
-}
-
-// The same rule for WRITE roots, or a write grant keeps the bug reads no longer
-// have.
-func TestATemporaryWriteSurvivesASiblingsCleanup(t *testing.T) {
-	scope, _, outside := scopeOutsideRoots(t)
-	covered := func() bool {
-		for _, existing := range scope.Roots() {
-			if existing == outside {
-				return true
-			}
-		}
-		return false
-	}
-	_, undoA, err := scope.AddTemporaryWrite(outside)
-	if err != nil {
-		t.Fatal(err)
-	}
-	_, undoB, err := scope.AddTemporaryWrite(outside)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if !covered() {
-		t.Fatal("the write grant did not take effect")
-	}
-	undoA()
-	if !covered() {
-		t.Fatal("A's cleanup revoked the write root while B still held a grant")
-	}
-	undoB()
-	if covered() {
-		t.Fatal("the write root outlived its last holder")
-	}
-}
-
-// UNDER REAL CONCURRENCY, which is the shape the parallel tool batch produces:
-// eight holders taking and releasing the same root in overlapping windows. The
-// root must be present the whole time at least one holder has it, and gone once
-// the last releases.
-func TestConcurrentHoldersOfOneRoot(t *testing.T) {
-	scope, _, outside := scopeOutsideRoots(t)
-
-	const holders = 8
-	var wg sync.WaitGroup
-	start := make(chan struct{})
-	release := make(chan struct{})
-	// TWO PER HOLDER, because each one can report at both hasReadRoot checks. At
-	// one slot per holder the channel fills after eight reports, the ninth send
-	// blocks forever, wg.Done() is never reached and wg.Wait() hangs — so the
-	// test would DEADLOCK rather than fail in exactly the case it exists to
-	// catch, since nothing drains failures until after the wait.
-	failures := make(chan string, 2*holders)
-	// Signalled by EVERY holder once its own AddTemporaryRead has returned,
-	// failure included: the gate below waits for all of them, so a holder that
-	// returned early without signalling would hang this test rather than fail it.
-	acquired := make(chan struct{}, holders)
-	for i := 0; i < holders; i++ {
-		wg.Add(1)
-		go func() {
-			defer wg.Done()
-			<-start
-			_, undo, err := scope.AddTemporaryRead(outside)
-			acquired <- struct{}{}
-			if err != nil {
-				failures <- err.Error()
-				return
-			}
-			// Every holder must SEE its own grant for as long as it holds it.
-			if !hasReadRoot(scope, outside) {
-				failures <- "a holder could not see the root it had just been granted"
-			}
-			<-release
-			if !hasReadRoot(scope, outside) {
-				failures <- "a holder lost the root while still holding it"
-			}
-			undo()
-		}()
-	}
-	close(start)
-	// EVERY holder, not the first one. Spinning on hasReadRoot only waited for
-	// somebody to hold the root, and the spin is tight enough to win that race
-	// against the goroutines still being scheduled: measured over 200 runs, 194
-	// of them peaked at a single simultaneous holder and none ever reached
-	// eight. A test named for concurrent holders was testing one holder at a
-	// time, and would have passed against an implementation with no refcount at
-	// all. Counting the acquisitions makes the overlap real instead of hoped for.
-	for i := 0; i < holders; i++ {
-		<-acquired
-	}
-	close(release)
-	wg.Wait()
-	close(failures)
-	for failure := range failures {
-		t.Fatal(failure)
-	}
-	if hasReadRoot(scope, outside) {
-		t.Fatal("the root outlived every holder")
-	}
-	// AND THE BOOKKEEPING IS EMPTY, not merely invisible. hasReadRoot answers
-	// what a caller can see; a refcount entry left behind at zero is not visible
-	// that way and would still leak, one map entry per acquire/release cycle.
-	scope.mu.Lock()
-	leftover, stillCounted := scope.tempReads[outside]
-	scope.mu.Unlock()
-	if stillCounted {
-		t.Fatalf("the refcount table kept an entry for %q after every holder released: %v", outside, leftover)
-	}
-}

internal/specialist/exec.go

@@ -76,17 +76,12 @@ type BuildArgsInput struct {
 }
 
 type BuildResumeArgsInput struct {
-	SessionID    string
-	Prompt       string
-	CurrentDepth int
-	Manifest     Manifest
-	Cwd          string
-	// ParentModel and ParentReasoningEffort are the same fallbacks the fresh
-	// path takes, and they are here for the same reason: appendModelArgs uses
-	// them only when the manifest pins nothing of its own.
-	ParentModel           string
-	ParentReasoningEffort string
-	PermissionMode        string
+	SessionID      string
+	Prompt         string
+	CurrentDepth   int
+	Manifest       Manifest
+	Cwd            string
+	PermissionMode string
 }
 
 type BuildArgsResult struct {
@@ -349,18 +344,6 @@ func (executor Executor) BuildResumeArgs(input BuildResumeArgsInput) (BuildArgsR
 	}
 	args := []string{"exec", "--resume", sessionID}
 	args = append(args, promptArgs...)
-	// A RESUMED SPECIALIST KEEPS THE MODEL ITS MANIFEST PINNED.
-	//
-	// The fresh path appends this and the resume path did not, so a specialist
-	// pinned to a cheap model ran on that model once and then silently reverted
-	// to the parent's configured model on every resume. Nothing reports it: the
-	// child starts normally and the only symptom is the bill.
-	//
-	// Resuming does not restore the recorded model on its own. sessions.PrepareExec
-	// records the model it ran under but never feeds it back into provider
-	// construction, so without this the child takes whatever the config default
-	// resolves to now.
-	args = appendModelArgs(args, input.Manifest, input.ParentModel, input.ParentReasoningEffort)
 	args = append(args, "--auto", specialistAutonomy(input.PermissionMode), "--output-format", "stream-json")
 	// See BuildArgs: only plan/spec-draft propagate --permission-mode so --auto
 	// remains the authority for member/auto/ask/unsafe child resolution.
@@ -441,14 +424,12 @@ func (executor Executor) runResume(ctx context.Context, params TaskParameters, o
 		return ExecResult{}, err
 	}
 	built, err := executor.BuildResumeArgs(BuildResumeArgsInput{
-		SessionID:             params.Resume,
-		Prompt:                params.Prompt,
-		CurrentDepth:          options.CurrentDepth,
-		Manifest:              manifest,
-		Cwd:                   options.Cwd,
-		ParentModel:           options.ParentModel,
-		ParentReasoningEffort: options.ParentReasoningEffort,
-		PermissionMode:        options.PermissionMode,
+		SessionID:      params.Resume,
+		Prompt:         params.Prompt,
+		CurrentDepth:   options.CurrentDepth,
+		Manifest:       manifest,
+		Cwd:            options.Cwd,
+		PermissionMode: options.PermissionMode,
 	})
 	if err != nil {
 		return ExecResult{}, err

internal/specialist/resume_model_test.go

@@ -1,303 +0,0 @@
-package specialist
-
-import (
-	"context"
-	"strings"
-	"testing"
-
-	"github.com/Gitlawb/zero/internal/sessions"
-	"github.com/Gitlawb/zero/internal/streamjson"
-)
-
-// argValue returns the value following flag in argv, and whether it was present.
-func argValue(args []string, flag string) (string, bool) {
-	for index, arg := range args {
-		if arg == flag && index+1 < len(args) {
-			return args[index+1], true
-		}
-	}
-	return "", false
-}
-
-func pinnedManifest(model string, effort string) Manifest {
-	return Manifest{
-		Metadata: Metadata{
-			Name:            "skim",
-			Description:     "Bounded read-only lookups.",
-			Model:           model,
-			ReasoningEffort: effort,
-			Tools:           []string{"read_file"},
-		},
-		SystemPrompt:  "Find the thing and stop.",
-		ResolvedTools: []string{"read_file"},
-	}
-}
-
-// A RESUMED SPECIALIST KEEPS THE MODEL ITS MANIFEST PINNED.
-//
-// Metadata.Model exists so a bounded, delegated task can run on a cheaper model
-// than its parent. BuildArgs appended it; BuildResumeArgs did not. So the
-// specialist ran on the cheap model once, and the moment the orchestrator
-// resumed it the child fell back to whatever the parent's configured model
-// resolved to. Nothing surfaced it: the resumed child starts normally, does the
-// work, and the only symptom is the bill.
-//
-// Resuming does not restore the recorded model on its own, which is why the flag
-// has to be passed again rather than relied upon.
-func TestAResumedSpecialistKeepsItsPinnedModel(t *testing.T) {
-	manifest := pinnedManifest("claude-haiku-4.5", "")
-
-	fresh, err := (Executor{}).BuildArgs(BuildArgsInput{
-		Manifest:     manifest,
-		Prompt:       "find the thing",
-		CurrentDepth: 0,
-		ParentModel:  "claude-opus-4.1",
-	})
-	if err != nil {
-		t.Fatalf("BuildArgs: %v", err)
-	}
-	// SETUP: the fresh path really does pin it, or the comparison below is
-	// asserting against a path that never worked either.
-	freshModel, ok := argValue(fresh.Args, "--model")
-	if !ok || freshModel != "claude-haiku-4.5" {
-		t.Fatalf("SETUP INVALID: the fresh path passed --model %q (present=%t), want the manifest's model", freshModel, ok)
-	}
-
-	resumed, err := (Executor{}).BuildResumeArgs(BuildResumeArgsInput{
-		SessionID:    "01HZZZZZZZZZZZZZZZZZZZZZZZ",
-		Prompt:       "keep going",
-		CurrentDepth: 0,
-		Manifest:     manifest,
-		ParentModel:  "claude-opus-4.1",
-	})
-	if err != nil {
-		t.Fatalf("BuildResumeArgs: %v", err)
-	}
-	resumedModel, ok := argValue(resumed.Args, "--model")
-	if !ok {
-		t.Fatalf("a resumed specialist carries no --model at all, so it reverts to the parent's configured model: %v", resumed.Args)
-	}
-	if resumedModel != "claude-haiku-4.5" {
-		t.Fatalf("a resumed specialist runs on %q, want the manifest's pinned %q", resumedModel, "claude-haiku-4.5")
-	}
-}
-
-// And a manifest that pins nothing still inherits the parent's model, which is
-// what makes the fallback in appendModelArgs meaningful rather than the pinned
-// case being special-cased.
-func TestAResumedSpecialistWithNoPinInheritsTheParentModel(t *testing.T) {
-	resumed, err := (Executor{}).BuildResumeArgs(BuildResumeArgsInput{
-		SessionID:    "01HZZZZZZZZZZZZZZZZZZZZZZZ",
-		Prompt:       "keep going",
-		CurrentDepth: 0,
-		Manifest:     pinnedManifest("", ""),
-		ParentModel:  "claude-opus-4.1",
-	})
-	if err != nil {
-		t.Fatalf("BuildResumeArgs: %v", err)
-	}
-	model, ok := argValue(resumed.Args, "--model")
-	if !ok || model != "claude-opus-4.1" {
-		t.Fatalf("a resumed specialist with no pinned model passed --model %q (present=%t), want the parent's", model, ok)
-	}
-}
-
-// The reasoning-effort rule travels with the model, or the two paths disagree
-// about what a pinned model implies. appendModelArgs inherits the parent's
-// effort ONLY when the manifest pins no model of its own: a manifest that chose
-// a different model has not agreed to the parent's effort for it.
-func TestAResumedSpecialistFollowsTheSameReasoningEffortRule(t *testing.T) {
-	t.Run("pinned model does not inherit parent effort", func(t *testing.T) {
-		resumed, err := (Executor{}).BuildResumeArgs(BuildResumeArgsInput{
-			SessionID:             "01HZZZZZZZZZZZZZZZZZZZZZZZ",
-			Prompt:                "keep going",
-			CurrentDepth:          0,
-			Manifest:              pinnedManifest("claude-haiku-4.5", ""),
-			ParentModel:           "claude-opus-4.1",
-			ParentReasoningEffort: "high",
-		})
-		if err != nil {
-			t.Fatalf("BuildResumeArgs: %v", err)
-		}
-		if effort, ok := argValue(resumed.Args, "--reasoning-effort"); ok {
-			t.Fatalf("a manifest that pinned its own model inherited the parent's effort %q", effort)
-		}
-	})
-
-	t.Run("no pinned model inherits parent effort", func(t *testing.T) {
-		resumed, err := (Executor{}).BuildResumeArgs(BuildResumeArgsInput{
-			SessionID:             "01HZZZZZZZZZZZZZZZZZZZZZZZ",
-			Prompt:                "keep going",
-			CurrentDepth:          0,
-			Manifest:              pinnedManifest("", ""),
-			ParentModel:           "claude-opus-4.1",
-			ParentReasoningEffort: "high",
-		})
-		if err != nil {
-			t.Fatalf("BuildResumeArgs: %v", err)
-		}
-		effort, ok := argValue(resumed.Args, "--reasoning-effort")
-		if !ok || effort != "high" {
-			t.Fatalf("a manifest pinning nothing passed --reasoning-effort %q (present=%t), want the parent's", effort, ok)
-		}
-	})
-}
-
-// The two builders agree on where the flag sits relative to the rest of the
-// argv, so a future change to one does not silently reorder only the other.
-func TestBothBuildersPlaceTheModelBeforeTheAutonomyFlag(t *testing.T) {
-	manifest := pinnedManifest("claude-haiku-4.5", "")
-	fresh, err := (Executor{}).BuildArgs(BuildArgsInput{Manifest: manifest, Prompt: "go", CurrentDepth: 0})
-	if err != nil {
-		t.Fatalf("BuildArgs: %v", err)
-	}
-	resumed, err := (Executor{}).BuildResumeArgs(BuildResumeArgsInput{
-		SessionID: "01HZZZZZZZZZZZZZZZZZZZZZZZ", Prompt: "go", CurrentDepth: 0, Manifest: manifest,
-	})
-	if err != nil {
-		t.Fatalf("BuildResumeArgs: %v", err)
-	}
-	for _, argv := range [][]string{fresh.Args, resumed.Args} {
-		model := indexOf(argv, "--model")
-		auto := indexOf(argv, "--auto")
-		if model < 0 || auto < 0 || model > auto {
-			t.Fatalf("--model at %d, --auto at %d in %s", model, auto, strings.Join(argv, " "))
-		}
-	}
-}
-
-func indexOf(args []string, want string) int {
-	for index, arg := range args {
-		if arg == want {
-			return index
-		}
-	}
-	return -1
-}
-
-// AND THE CALL SITE PASSES IT, WHICH THE BUILDER TESTS ABOVE CANNOT SEE.
-//
-// Every test above calls BuildResumeArgs directly. Dropping the ParentModel
-// field from the runResume call site still compiles and still passes all of
-// them, because the builder is doing its job with whatever it is handed. The
-// defect this fix repairs lived at the call site, not in the builder, so it
-// needs a test that goes through Run.
-//
-// Driven through the real Run dispatch with the RunChild seam capturing argv.
-func TestRunResumePassesTheParentModelThroughToTheChild(t *testing.T) {
-	store := sessions.NewStore(sessions.StoreOptions{RootDir: t.TempDir()})
-	parent, err := store.Create(sessions.CreateInput{SessionID: "parent_session"})
-	if err != nil {
-		t.Fatalf("create parent: %v", err)
-	}
-	if _, err := store.Create(sessions.CreateInput{
-		SessionID:       "child_task",
-		SessionKind:     sessions.SessionKindChild,
-		Tag:             SessionTagSpecialist,
-		Depth:           1,
-		ParentSessionID: parent.SessionID,
-		AgentName:       "skim",
-		TaskID:          "child_task",
-	}); err != nil {
-		t.Fatalf("create child: %v", err)
-	}
-
-	zero := 0
-	var captured []string
-	executor := Executor{
-		BinaryPath:   "/usr/local/bin/zero",
-		SessionStore: store,
-		NewSessionID: func() (string, error) { return "child_task", nil },
-		Load: func(LoadOptions) (LoadResult, error) {
-			// No pinned model, so the parent's is the only thing that can supply one.
-			return LoadResult{Specialists: []Manifest{pinnedManifest("", "")}}, nil
-		},
-		RunChild: func(_ context.Context, _ string, args []string, _ func(streamjson.Event)) (ChildRunResult, error) {
-			captured = append([]string(nil), args...)
-			return ChildRunResult{
-				Events: []streamjson.Event{
-					{Type: streamjson.EventRunStart, RunID: "run_1", SessionID: "child_task"},
-					{Type: streamjson.EventFinal, RunID: "run_1", Text: "done"},
-					{Type: streamjson.EventRunEnd, RunID: "run_1", Status: "success", ExitCode: &zero},
-				},
-			}, nil
-		},
-	}
-
-	if _, err := executor.Run(context.Background(), TaskParameters{
-		Name:   "skim",
-		Prompt: "keep going",
-		Resume: "child_task",
-	}, TaskRunOptions{
-		ParentSessionID: parent.SessionID,
-		ParentModel:     "claude-opus-4.1",
-	}); err != nil {
-		t.Fatalf("Run(resume): %v", err)
-	}
-
-	// SETUP: this really was the resume path, not a fresh spawn.
-	if index := indexOf(captured, "--resume"); index < 0 {
-		t.Fatalf("SETUP INVALID: the child was not resumed: %v", captured)
-	}
-	model, ok := argValue(captured, "--model")
-	if !ok {
-		t.Fatalf("the resumed child was launched with no --model, so it runs on whatever the config default resolves to: %v", captured)
-	}
-	if model != "claude-opus-4.1" {
-		t.Fatalf("the resumed child was launched with --model %q, want the parent's %q", model, "claude-opus-4.1")
-	}
-}
-
-// THE FRESH CALL SITE NEEDS THE SAME GUARD, FOR THE SAME REASON.
-//
-// runFresh and runResume both construct their builder input by hand, and both
-// have a byte-identical ParentModel line. Deleting either one compiles. The
-// resume half is what this change repairs; this covers the other half so the
-// pair cannot drift again in the direction nobody was looking.
-func TestRunFreshPassesTheParentModelThroughToTheChild(t *testing.T) {
-	store := sessions.NewStore(sessions.StoreOptions{RootDir: t.TempDir()})
-	parent, err := store.Create(sessions.CreateInput{SessionID: "parent_session"})
-	if err != nil {
-		t.Fatalf("create parent: %v", err)
-	}
-
-	zero := 0
-	var captured []string
-	executor := Executor{
-		BinaryPath:   "/usr/local/bin/zero",
-		SessionStore: store,
-		NewSessionID: func() (string, error) { return "child_task", nil },
-		Load: func(LoadOptions) (LoadResult, error) {
-			return LoadResult{Specialists: []Manifest{pinnedManifest("", "")}}, nil
-		},
-		RunChild: func(_ context.Context, _ string, args []string, _ func(streamjson.Event)) (ChildRunResult, error) {
-			captured = append([]string(nil), args...)
-			return ChildRunResult{
-				Events: []streamjson.Event{
-					{Type: streamjson.EventRunStart, RunID: "run_1", SessionID: "child_task"},
-					{Type: streamjson.EventFinal, RunID: "run_1", Text: "done"},
-					{Type: streamjson.EventRunEnd, RunID: "run_1", Status: "success", ExitCode: &zero},
-				},
-			}, nil
-		},
-	}
-
-	if _, err := executor.Run(context.Background(), TaskParameters{
-		Name:   "skim",
-		Prompt: "find the thing",
-	}, TaskRunOptions{
-		ParentSessionID: parent.SessionID,
-		ParentModel:     "claude-opus-4.1",
-	}); err != nil {
-		t.Fatalf("Run(fresh): %v", err)
-	}
-
-	// SETUP: a fresh spawn, not a resume, or this covers the wrong site.
-	if indexOf(captured, "--resume") >= 0 {
-		t.Fatalf("SETUP INVALID: the child was resumed rather than freshly spawned: %v", captured)
-	}
-	model, ok := argValue(captured, "--model")
-	if !ok || model != "claude-opus-4.1" {
-		t.Fatalf("the fresh child was launched with --model %q (present=%t), want the parent's", model, ok)
-	}
-}

internal/streamjson/streamjson.go

@@ -94,8 +94,6 @@ type Event struct {
 	Meta              map[string]string `json:"meta,omitempty"`
 	PromptTokens      *int              `json:"promptTokens,omitempty"`
 	CompletionTokens  *int              `json:"completionTokens,omitempty"`
-	CachedInputTokens *int              `json:"cachedInputTokens,omitempty"`
-	CacheWriteTokens  *int              `json:"cacheWriteTokens,omitempty"`
 	TotalTokens       *int              `json:"totalTokens,omitempty"`
 	CostUSD           *float64          `json:"costUsd,omitempty"`
 	Text              string            `json:"text,omitempty"`

internal/swarm/lock_other.go

@@ -0,0 +1,15 @@
+//go:build !windows
+
+package swarm
+
+import (
+	"errors"
+	"os"
+)
+
+// isLockContended reports whether an O_EXCL lock-create error means the lock is
+// currently held (so the caller should retry/wait) rather than a hard failure.
+// On POSIX an existing lock surfaces only as os.ErrExist.
+func isLockContended(err error) bool {
+	return errors.Is(err, os.ErrExist)
+}

internal/swarm/lock_redirect_other_test.go

@@ -1,18 +0,0 @@
-//go:build !windows
-
-package swarm
-
-import (
-	"os"
-	"path/filepath"
-	"testing"
-)
-
-func makeRedirectedLockPath(t *testing.T, root, target string) string {
-	t.Helper()
-	lockPath := filepath.Join(root, "redirected.lock")
-	if err := os.Symlink(target, lockPath); err != nil {
-		t.Fatalf("create redirected lock path: %v", err)
-	}
-	return lockPath
-}

internal/swarm/lock_redirect_windows_test.go

@@ -1,20 +0,0 @@
-//go:build windows
-
-package swarm
-
-import (
-	"os/exec"
-	"path/filepath"
-	"strings"
-	"testing"
-)
-
-func makeRedirectedLockPath(t *testing.T, root, target string) string {
-	t.Helper()
-	linkDir := filepath.Join(root, "redirected")
-	out, err := exec.Command("cmd", "/c", "mklink", "/J", linkDir, filepath.Dir(target)).CombinedOutput()
-	if err != nil {
-		t.Fatalf("create redirected lock junction: %v %s", err, strings.TrimSpace(string(out)))
-	}
-	return filepath.Join(linkDir, filepath.Base(target))
-}

internal/swarm/lock_windows.go

@@ -0,0 +1,30 @@
+//go:build windows
+
+package swarm
+
+import (
+	"errors"
+	"os"
+	"syscall"
+)
+
+// Windows error codes that an O_EXCL create (or a racing delete) can surface
+// when another writer holds the lock file open, instead of ERROR_FILE_EXISTS.
+// Treating them as "contended" makes the lock retry/wait rather than fail the
+// whole send/read spuriously under contention.
+const (
+	errorAccessDenied     = syscall.Errno(5)  // ERROR_ACCESS_DENIED
+	errorSharingViolation = syscall.Errno(32) // ERROR_SHARING_VIOLATION
+)
+
+// isLockContended reports whether an O_EXCL lock-create error means the lock is
+// currently held (so the caller should retry/wait) rather than a hard failure.
+// On Windows a held lock can appear as ERROR_FILE_EXISTS (mapped to os.ErrExist)
+// but also as ERROR_ACCESS_DENIED / ERROR_SHARING_VIOLATION when the file is
+// concurrently open or pending deletion.
+func isLockContended(err error) bool {
+	if errors.Is(err, os.ErrExist) {
+		return true
+	}
+	return errors.Is(err, errorAccessDenied) || errors.Is(err, errorSharingViolation)
+}

internal/swarm/mailbox.go

@@ -8,6 +8,7 @@ import (
 	"path/filepath"
 	"regexp"
 	"strings"
+	"sync/atomic"
 	"time"
 
 	"github.com/Gitlawb/zero/internal/fsutil"
@@ -16,10 +17,10 @@ import (
 
 // Mailbox is a per-agent, per-team message inbox persisted as a JSON array on
 // disk at <baseDir>/<team>/inboxes/<agent>.json, written atomically under a
-// advisory lock. It is hardened for untrusted input:
+// lock file. It is hardened for untrusted input:
 //
 //   - inbox files and their parent dirs are owner-only (0600/0700);
-//   - every write takes an exclusive advisory lock (bounded retry);
+//   - every write takes an exclusive lock file (bounded retry, stale-break);
 //   - message bodies and whole inboxes are size-capped (fail closed on oversize);
 //   - team/agent names are sanitized so a name can never escape the base dir;
 //   - malformed inbox JSON is rejected rather than silently reset (fail closed).
@@ -43,6 +44,7 @@ const (
 	defaultMaxMessageBytes = 64 * 1024 // 64 KiB per message
 	defaultMaxMessages     = 1000      // per inbox
 	defaultLockTimeout     = 5 * time.Second
+	lockStaleAfter         = 30 * time.Second
 	inboxFileMode          = 0o600
 	inboxDirMode           = 0o700
 )
@@ -204,7 +206,7 @@ func (m *Mailbox) Send(team, recipient string, msg Message) error {
 	if err := m.ensureInboxDir(path); err != nil {
 		return err
 	}
-	release, err := acquireLock(m.BaseDir, path+".lock", m.lockTimeout())
+	release, err := acquireLock(path+".lock", m.lockTimeout())
 	if err != nil {
 		return err
 	}
@@ -231,12 +233,12 @@ func (m *Mailbox) ReadAndConsume(team, recipient string) ([]Message, error) {
 	if err != nil {
 		return nil, err
 	}
-	// The stable lock file lives beside the inbox; create the dir so it can be taken
+	// The lock file lives beside the inbox; create the dir so it can be taken
 	// even on first read of a not-yet-existing inbox.
 	if err := m.ensureInboxDir(path); err != nil {
 		return nil, err
 	}
-	release, err := acquireLock(m.BaseDir, path+".lock", m.lockTimeout())
+	release, err := acquireLock(path+".lock", m.lockTimeout())
 	if err != nil {
 		return nil, err
 	}
@@ -332,19 +334,63 @@ func (m *Mailbox) atomicWriteJSON(path string, data any) error {
 	return nil
 }
 
-// acquireLock takes an exclusive advisory lock through a stable lock file. It
-// retries with a short backoff until timeout. The kernel releases the lock when
-// a holder exits, so crash recovery never moves or deletes the canonical path.
-func acquireLock(root, lockPath string, timeout time.Duration) (func(), error) {
+// lockSeq makes each lock token unique within the process even when two
+// goroutines acquire in the same nanosecond.
+var lockSeq atomic.Uint64
+
+// acquireLock takes an exclusive lock by creating lockPath with O_EXCL. It
+// retries with a short backoff until timeout, breaking a lock whose file is
+// older than lockStaleAfter (so a crashed holder cannot deadlock the swarm).
+//
+// Each holder writes a unique token into the lock file and release is
+// OWNERSHIP-AWARE: it removes the lock only if it still holds our token. After a
+// stale-break another writer may legitimately own the lock; unconditionally
+// removing it would let a third writer in and create split-brain writers that
+// can corrupt or drop mailbox updates.
+func acquireLock(lockPath string, timeout time.Duration) (func(), error) {
+	token := fmt.Sprintf("%d-%d-%d", os.Getpid(), time.Now().UnixNano(), lockSeq.Add(1))
 	deadline := time.Now().Add(timeout)
 	for {
-		lock, err := lockutil.TryAcquireFileLockAt(root, lockPath)
+		f, err := os.OpenFile(lockPath, os.O_CREATE|os.O_EXCL|os.O_WRONLY, inboxFileMode)
 		if err == nil {
-			return func() { _ = lock.Release() }, nil
+			// Record our ownership token; the exclusive create already holds the
+			// lock, so a write error only weakens diagnostics, not safety.
+			_, _ = f.WriteString(token)
+			f.Close()
+			var released bool
+			return func() {
+				if released {
+					return
+				}
+				released = true
+				if data, rerr := os.ReadFile(lockPath); rerr == nil && string(data) == token {
+					_ = lockutil.RemoveLockFile(lockPath)
+				}
+			}, nil
 		}
-		if !errors.Is(err, lockutil.ErrLockHeld) {
+		if !isLockContended(err) {
 			return nil, fmt.Errorf("swarm: acquire lock: %w", err)
 		}
+		// Lock held: break it if stale via the atomic rename-with-verify in
+		// lockutil.ReclaimStaleLock (AUDIT-M13), otherwise wait.
+		if info, statErr := os.Stat(lockPath); statErr == nil && time.Since(info.ModTime()) > lockStaleAfter {
+			cleared, rerr := lockutil.ReclaimStaleLock(lockPath, token, func(reclaimedPath string) bool {
+				info, err := os.Stat(reclaimedPath)
+				return err == nil && time.Since(info.ModTime()) <= lockStaleAfter
+			})
+			if rerr != nil {
+				// Reclaim hit a hard failure: the rename aside failed outright, or a
+				// live holder's lock could not be put back (the lock path may be
+				// missing, so re-acquiring would break mutual exclusion). Fail closed
+				// instead of spinning to the deadline.
+				return nil, fmt.Errorf("swarm: reclaim stale lock: %w", rerr)
+			}
+			if cleared {
+				continue // cleared a genuinely stale lock; retry the O_EXCL create now
+			}
+			// Lost the reclaim race (or it was actually fresh) — fall through to the
+			// bounded wait instead of hot-spinning on a reclaim that never wins.
+		}
 		if time.Now().After(deadline) {
 			return nil, fmt.Errorf("swarm: timed out acquiring lock %s", filepath.Base(lockPath))
 		}

internal/swarm/mailbox_test.go

@@ -219,75 +219,64 @@ func TestMailboxRejectsSymlinkedInboxDir(t *testing.T) {
 	}
 }
 
-func TestMailboxLockReleaseKeepsStablePath(t *testing.T) {
+func TestMailboxLockReleaseIsOwnershipAware(t *testing.T) {
 	mb := newTestMailbox(t)
 	path, _ := mb.inboxPath("team", "bob")
 	if err := mb.ensureInboxDir(path); err != nil {
 		t.Fatalf("ensureInboxDir: %v", err)
 	}
 	lockPath := path + ".lock"
-	releaseA, err := acquireLock(mb.BaseDir, lockPath, time.Second)
+	// Writer A acquires the lock.
+	releaseA, err := acquireLock(lockPath, time.Second)
 	if err != nil {
 		t.Fatalf("acquire A: %v", err)
 	}
+	// Simulate a stale-break + takeover by writer B: overwrite the lock content
+	// with B's token (as a fresh acquire after a break would).
+	if err := os.WriteFile(lockPath, []byte("writer-B-token"), 0o600); err != nil {
+		t.Fatalf("simulate B takeover: %v", err)
+	}
+	// A's release must NOT delete B's lock (ownership-aware).
 	releaseA()
 	if _, err := os.Stat(lockPath); err != nil {
-		t.Fatalf("release removed stable advisory-lock path: %v", err)
+		t.Fatalf("A's release deleted B's lock (split-brain): %v", err)
 	}
+	// B's own release removes it.
+	os.Remove(lockPath)
 }
 
-func TestAcquireLockIgnoresOldUnlockedFile(t *testing.T) {
-	// A crashed holder can leave an old file behind, but the kernel releases its
-	// advisory lock. Acquisition must succeed without renaming the stable path.
+func TestAcquireLockReclaimsStaleLock(t *testing.T) {
+	// A crashed holder's stale lock (old mtime) must be reclaimed via the atomic
+	// rename-with-verify path, leaving no sidelined .stale.* file (AUDIT-M13).
 	lockPath := filepath.Join(t.TempDir(), "x.lock")
 	if err := os.WriteFile(lockPath, []byte("dead-holder"), 0o600); err != nil {
-		t.Fatalf("seed old lock metadata: %v", err)
+		t.Fatalf("seed stale lock: %v", err)
 	}
-	old := time.Now().Add(-time.Hour)
+	old := time.Now().Add(-2 * lockStaleAfter)
 	if err := os.Chtimes(lockPath, old, old); err != nil {
 		t.Fatalf("chtimes: %v", err)
 	}
-	release, err := acquireLock(filepath.Dir(lockPath), lockPath, time.Second)
+	release, err := acquireLock(lockPath, time.Second)
 	if err != nil {
-		t.Fatalf("acquire over old unlocked file: %v", err)
+		t.Fatalf("acquireLock should reclaim a genuinely stale lock, got %v", err)
 	}
 	release()
-	if _, err := os.Stat(lockPath); err != nil {
-		t.Fatalf("stable lock path missing after release: %v", err)
+	if matches, _ := filepath.Glob(lockPath + ".stale.*"); len(matches) != 0 {
+		t.Fatalf("reclaim left sidelined files: %v", matches)
 	}
 }
 
-func TestAcquireLockDoesNotBreakHeldLock(t *testing.T) {
-	// File age is irrelevant while the kernel reports an active holder.
+func TestAcquireLockDoesNotBreakFreshLock(t *testing.T) {
+	// A fresh, held lock (recent mtime) must never be broken — the stale-break must
+	// not steal a live lock (AUDIT-M13).
 	lockPath := filepath.Join(t.TempDir(), "x.lock")
-	release, err := acquireLock(filepath.Dir(lockPath), lockPath, time.Second)
+	release, err := acquireLock(lockPath, time.Second)
 	if err != nil {
 		t.Fatalf("first acquire: %v", err)
 	}
 	defer release()
-	if _, err := acquireLock(filepath.Dir(lockPath), lockPath, 50*time.Millisecond); err == nil {
-		t.Fatal("acquireLock admitted a second holder")
-	}
-}
-
-func TestAcquireLockRefusesRedirectedPath(t *testing.T) {
-	root := t.TempDir()
-	target := filepath.Join(t.TempDir(), "target")
-	const sentinel = "do not overwrite"
-	if err := os.WriteFile(target, []byte(sentinel), 0o600); err != nil {
-		t.Fatal(err)
-	}
-	lockPath := makeRedirectedLockPath(t, root, target)
-	if release, err := acquireLock(root, lockPath, time.Second); err == nil {
-		release()
-		t.Fatal("acquireLock followed a redirected lock path")
-	}
-	data, err := os.ReadFile(target)
-	if err != nil {
-		t.Fatal(err)
-	}
-	if string(data) != sentinel {
-		t.Fatalf("redirected target was modified: %q", data)
+	if _, err := acquireLock(lockPath, 50*time.Millisecond); err == nil {
+		t.Fatal("acquireLock broke a fresh, held lock (split-brain risk)")
 	}
 }
 

internal/tools/apply_patch.go

@@ -16,101 +16,6 @@ type applyPatchTool struct {
 	scope         PathScope
 }
 
-func (applyPatchTool) isBuiltInApplyPatch() {}
-
-// PrepareFreeformApplyPatchArguments converts native structured-patch input
-// into the ordinary apply_patch argument map used by permission checks and tool
-// execution. Absolute patch-header paths select a granted write root and are
-// rewritten relative to that root; relative-only patches keep workspace-root
-// behavior.
-func PrepareFreeformApplyPatchArguments(tool Tool, patch string) (map[string]any, error) {
-	preparer, ok := tool.(interface {
-		prepareFreeformArguments(string) (map[string]any, error)
-	})
-	if !ok {
-		return nil, fmt.Errorf("tool is not Zero's built-in apply_patch")
-	}
-	return preparer.prepareFreeformArguments(patch)
-}
-
-func (tool applyPatchTool) prepareFreeformArguments(patch string) (map[string]any, error) {
-	args := map[string]any{"patch": patch}
-	if !isStructuredPatch(patch) {
-		return args, nil
-	}
-
-	lines := strings.Split(strings.ReplaceAll(patch, "\r\n", "\n"), "\n")
-	selectedRoot := ""
-	hasRelativeHeader := false
-	for index, line := range lines {
-		prefix := ""
-		switch {
-		case strings.HasPrefix(line, structuredAddFile):
-			prefix = structuredAddFile
-		case strings.HasPrefix(line, structuredDeleteFile):
-			prefix = structuredDeleteFile
-		case strings.HasPrefix(line, structuredUpdateFile):
-			prefix = structuredUpdateFile
-		case strings.HasPrefix(line, structuredMoveTo):
-			prefix = structuredMoveTo
-		default:
-			continue
-		}
-		path := strings.TrimSpace(strings.TrimPrefix(line, prefix))
-		if !filepath.IsAbs(path) {
-			hasRelativeHeader = true
-			continue
-		}
-		root, relative, err := tool.freeformPatchRoot(path)
-		if err != nil {
-			return nil, err
-		}
-		if selectedRoot != "" && selectedRoot != root {
-			return nil, fmt.Errorf("freeform patch spans multiple write roots")
-		}
-		selectedRoot = root
-		lines[index] = prefix + filepath.ToSlash(relative)
-	}
-	if selectedRoot != "" {
-		roots, err := scopedRoots(tool.workspaceRoot, tool.scope)
-		if err != nil {
-			return nil, err
-		}
-		if hasRelativeHeader && selectedRoot != roots[0] {
-			return nil, fmt.Errorf("freeform patch mixes workspace-relative paths with an extra write root")
-		}
-		args["cwd"] = selectedRoot
-		args["patch"] = strings.Join(lines, "\n")
-	}
-	return args, nil
-}
-
-func (tool applyPatchTool) freeformPatchRoot(path string) (string, string, error) {
-	roots, err := scopedRoots(tool.workspaceRoot, tool.scope)
-	if err != nil {
-		return "", "", err
-	}
-	var firstErr error
-	for _, root := range roots {
-		candidate := sandbox.NormalizePrefixForRoot(path, root)
-		candidate, err = filepath.Abs(candidate)
-		if err != nil {
-			if firstErr == nil {
-				firstErr = err
-			}
-			continue
-		}
-		relative, err := filepath.Rel(root, candidate)
-		if err == nil && relative != ".." && !strings.HasPrefix(relative, ".."+string(filepath.Separator)) && !filepath.IsAbs(relative) {
-			return root, filepath.ToSlash(relative), nil
-		}
-		if firstErr == nil {
-			firstErr = outsideWorkspaceError(path)
-		}
-	}
-	return "", "", firstErr
-}
-
 func NewScopedApplyPatchTool(workspaceRoot string, scope PathScope) Tool {
 	return applyPatchTool{
 		baseTool: baseTool{

internal/tools/edit_file.go

@@ -140,6 +140,7 @@ func (tool editFileTool) RunWithOptions(ctx context.Context, args map[string]any
 		return errorResult(fileUnseenMessage(relativePath))
 	}
 
+	previouslySeenWhole := options.FileTracker.SeenWhole(absolutePath)
 	updated := strings.Replace(content, oldString, newString, 1)
 	replacedCount := 1
 	if replaceAll {
@@ -164,28 +165,15 @@ func (tool editFileTool) RunWithOptions(ctx context.Context, args map[string]any
 	// Re-baseline to the content we just wrote so subsequent edits in this session
 	// compare against the current on-disk state, not the pre-edit version.
 	newInfo, _ := os.Stat(absolutePath)
+	options.FileTracker.Record(absolutePath, []byte(updated), newInfo)
 	if updated == modelKnownContent {
-		// OUR edit, so we know precisely which lines moved: RecordEdit carries
-		// across the reads this edit did not disturb instead of dropping them.
-		//
-		// Record would drop all of them, and did — a file read in three pieces
-		// lost every piece to a single two-line edit, and the next six edits into
-		// regions that had been read were refused as unseen. See RecordEdit.
-		//
-		// This SUBSUMES the previouslySeenWhole special-case #956 added here.
-		// That branch re-recorded 1..total when the file had been read whole;
-		// RecordEdit does the same thing one level down (its seenWhole arm
-		// re-baselines as a single covering observation) and additionally keeps
-		// the partial reads the old else-branch discarded. Two copies of the
-		// rule would drift, and only one of them sees the pre-edit observation.
-		options.FileTracker.RecordEdit(absolutePath, []byte(content), []byte(updated), newInfo)
-		for _, span := range editedSpans {
-			options.FileTracker.RecordSeenBytes(absolutePath, span.start, span.end, len(updated))
+		if previouslySeenWhole {
+			options.FileTracker.RecordSeenRange(absolutePath, 1, trackedLineTotal(updated), trackedLineTotal(updated))
+		} else {
+			for _, span := range editedSpans {
+				options.FileTracker.RecordSeenBytes(absolutePath, span.start, span.end, len(updated))
+			}
 		}
-	} else {
-		// A formatter rewrote the file after us. We no longer know which line
-		// holds what was read, so the conservative drop is the right answer here.
-		options.FileTracker.Record(absolutePath, []byte(updated), newInfo)
 	}
 
 	suffix := ""

internal/tools/edit_preserves_reads_test.go

@@ -1,296 +0,0 @@
-package tools
-
-import (
-	"context"
-	"os"
-	"path/filepath"
-	"strings"
-	"testing"
-)
-
-// editTrackerFixture writes a numbered file and returns its real path plus a
-// tracker that has already recorded the whole content as the current version.
-//
-// EvalSymlinks matters: on macOS t.TempDir() hands back /var/..., the tools
-// resolve it to /private/var/..., and a tracker keyed on the unresolved path
-// silently misses every lookup — which makes an edit fail for the very reason
-// this file is about, and for entirely the wrong cause.
-func editTrackerFixture(t *testing.T, lines []string) (string, *FileTracker, Tool) {
-	t.Helper()
-	root, err := filepath.EvalSymlinks(t.TempDir())
-	if err != nil {
-		t.Fatal(err)
-	}
-	path := filepath.Join(root, "index.go")
-	if err := os.WriteFile(path, []byte(strings.Join(lines, "\n")), 0o644); err != nil {
-		t.Fatal(err)
-	}
-	tracker := NewFileTracker()
-	content, _ := os.ReadFile(path)
-	info, _ := os.Stat(path)
-	tracker.Record(path, content, info)
-	return path, tracker, NewScopedEditFileTool(root, nil)
-}
-
-func numberedLines(total int, special map[int]string) []string {
-	lines := make([]string, 0, total)
-	for i := 1; i <= total; i++ {
-		if text, ok := special[i]; ok {
-			lines = append(lines, text)
-			continue
-		}
-		lines = append(lines, "filler")
-	}
-	return lines
-}
-
-func runTrackedEdit(t *testing.T, tool Tool, tracker *FileTracker, path, oldString, newString string) Result {
-	t.Helper()
-	return tool.(optionsAwareTool).RunWithOptions(context.Background(), map[string]any{
-		"path": path, "old_string": oldString, "new_string": newString,
-	}, RunOptions{FileTracker: tracker})
-}
-
-// ONE EDIT MUST NOT ERASE EVERY OTHER READ, and this is the run that made the
-// point: a 371-line file read in three pieces (40-45, 85-260, 260-371), one
-// two-line edit at line 92, and then six consecutive refusals to edit regions
-// that HAD been read and that the edit never touched — until the
-// repeated-failure guard halted the run. The error told the model to re-read,
-// which its next successful edit would have undone again.
-func TestASuccessfulEditKeepsTheReadsItDidNotDisturb(t *testing.T) {
-	path, tracker, tool := editTrackerFixture(t, numberedLines(371, map[int]string{
-		92:  "cmp := keyCmp(k, n.split)",
-		200: "prio: l.prio, split: l.split,",
-	}))
-	tracker.RecordSeenRange(path, 40, 45, 371)
-	tracker.RecordSeenRange(path, 85, 260, 371)
-	tracker.RecordSeenRange(path, 260, 371, 371)
-
-	if !tracker.SeenRange(path, 200, 200) {
-		t.Fatal("setup: line 200 sits inside the 85-260 read and must start out seen")
-	}
-
-	first := runTrackedEdit(t, tool, tracker, path, "cmp := keyCmp(k, n.split)", "cmp := keyCmp(k, n.pivot)")
-	if strings.Contains(first.Output, "Error") {
-		t.Fatalf("the first edit failed, so the test never reaches its subject: %s", first.Output)
-	}
-
-	if !tracker.SeenRange(path, 200, 200) {
-		t.Error("line 200 was read, the edit at line 92 did not touch it, and the file still has 371 lines — but it is no longer considered seen")
-	}
-	// The assertion that matters: the SECOND edit is what the run could never do.
-	second := runTrackedEdit(t, tool, tracker, path, "prio: l.prio, split: l.split,", "prio: l.prio, pivot: l.pivot,")
-	if strings.Contains(second.Output, "not been read exactly in this session") {
-		t.Fatalf("a second edit into an already-read region was refused as unseen: %s", second.Output)
-	}
-	if strings.Contains(second.Output, "Error") {
-		t.Fatalf("the second edit failed: %s", second.Output)
-	}
-}
-
-// LINE NUMBERS MOVE WHEN AN EDIT CHANGES THE LINE COUNT, so a range after the
-// edit has to be carried across SHIFTED, not left where it was.
-func TestReadsAfterAnEditAreShiftedByTheLineDelta(t *testing.T) {
-	path, tracker, tool := editTrackerFixture(t, numberedLines(100, map[int]string{
-		10: "short",
-		80: "target line",
-	}))
-	tracker.RecordSeenRange(path, 5, 20, 100)
-	tracker.RecordSeenRange(path, 70, 90, 100)
-
-	// Replace one line with three: everything after line 10 moves down by two.
-	res := runTrackedEdit(t, tool, tracker, path, "short", "one\ntwo\nthree")
-	if strings.Contains(res.Output, "Error") {
-		t.Fatalf("setup edit failed: %s", res.Output)
-	}
-
-	// "target line" was line 80 and is now line 82. It was read either way.
-	content, _ := os.ReadFile(path)
-	moved := strings.Count(strings.SplitN(string(content), "target line", 2)[0], "\n") + 1
-	if moved != 82 {
-		t.Fatalf("fixture moved the target to line %d, expected 82", moved)
-	}
-	if !tracker.SeenRange(path, moved, moved) {
-		t.Errorf("the read at lines 70-90 was not shifted with the content: line %d reads as unseen", moved)
-	}
-	second := runTrackedEdit(t, tool, tracker, path, "target line", "target changed")
-	if strings.Contains(second.Output, "Error") {
-		t.Fatalf("editing a line that was read and merely moved was refused: %s", second.Output)
-	}
-}
-
-// THE GUARD STILL GUARDS. Carrying reads across must not credit the model with
-// content it never saw — that is the whole reason the check exists.
-func TestAnUnreadRegionIsStillRefusedAfterAnEdit(t *testing.T) {
-	path, tracker, tool := editTrackerFixture(t, numberedLines(300, map[int]string{
-		50:  "seen line",
-		250: "never read line",
-	}))
-	// Only 40-60 is read. Line 250 is not.
-	tracker.RecordSeenRange(path, 40, 60, 300)
-
-	if res := runTrackedEdit(t, tool, tracker, path, "seen line", "seen line edited"); strings.Contains(res.Output, "Error") {
-		t.Fatalf("setup edit failed: %s", res.Output)
-	}
-	res := runTrackedEdit(t, tool, tracker, path, "never read line", "sneaky")
-	if !strings.Contains(res.Output, "not been read exactly in this session") {
-		t.Fatalf("an edit into a region that was NEVER read was allowed: %s", res.Output)
-	}
-}
-
-// A RANGE THE EDIT SPANS IS SPLIT, NOT DROPPED — and getting this wrong is not
-// hypothetical: dropping on overlap was my first attempt, and it left the
-// original defect exactly in place. A read almost always CONTAINS the line it
-// is about to edit, because containing it is why it was read.
-//
-// So the flanks survive and only the rewritten lines stop being known.
-func TestARangeTheEditSpansIsSplitAroundIt(t *testing.T) {
-	path, tracker, tool := editTrackerFixture(t, numberedLines(100, map[int]string{
-		20: "alpha",
-		21: "beta",
-		22: "gamma",
-	}))
-	tracker.RecordSeenRange(path, 15, 30, 100)
-
-	// Replace a three-line span with one line, entirely inside the read range.
-	if res := runTrackedEdit(t, tool, tracker, path, "alpha\nbeta\ngamma", "merged"); strings.Contains(res.Output, "Error") {
-		t.Fatalf("setup edit failed: %s", res.Output)
-	}
-
-	// Before the edit: still known, still at the same line numbers.
-	if !tracker.SeenRange(path, 15, 19) {
-		t.Error("lines 15-19 sit before the edit and did not move, but were forgotten")
-	}
-	// After it: still known, shifted up by the two lines the edit removed.
-	if !tracker.SeenRange(path, 21, 28) {
-		t.Error("lines 23-30 were read and merely moved to 21-28, but were forgotten")
-	}
-	// The rewritten span itself is no longer described by that read.
-	if tracker.SeenRange(path, 15, 30) {
-		t.Error("the whole original range still reads as seen, so the model is credited with content the edit replaced")
-	}
-}
-
-// AN EXTERNAL CHANGE STILL INVALIDATES EVERYTHING. RecordEdit is only for edits
-// we made; a file changed behind our back is exactly the case the blanket drop
-// is right for, and it must keep working.
-func TestAnExternalChangeStillDropsEveryRead(t *testing.T) {
-	path, tracker, _ := editTrackerFixture(t, numberedLines(100, map[int]string{50: "hello"}))
-	tracker.RecordSeenRange(path, 40, 60, 100)
-	if !tracker.SeenRange(path, 50, 50) {
-		t.Fatal("setup: line 50 should be seen")
-	}
-
-	// Something outside Zero rewrites the file.
-	changed := strings.Repeat("different\n", 100)
-	if err := os.WriteFile(path, []byte(changed), 0o644); err != nil {
-		t.Fatal(err)
-	}
-	info, _ := os.Stat(path)
-	tracker.Record(path, []byte(changed), info)
-
-	if tracker.SeenRange(path, 50, 50) {
-		t.Error("an external rewrite left the old read ranges in place")
-	}
-}
-
-// A file read in FULL stays read in full: an edit of ours does not make that
-// untrue, and re-reading a whole file after every edit is the cost this avoids.
-func TestAWhollyReadFileStaysWhollyRead(t *testing.T) {
-	path, tracker, tool := editTrackerFixture(t, numberedLines(40, map[int]string{5: "one"}))
-	tracker.RecordSeenRange(path, 1, 40, 40)
-	if !tracker.SeenWhole(path) {
-		t.Fatal("setup: the file should read as wholly seen")
-	}
-
-	if res := runTrackedEdit(t, tool, tracker, path, "one", "one\ntwo"); strings.Contains(res.Output, "Error") {
-		t.Fatalf("edit failed: %s", res.Output)
-	}
-	if !tracker.SeenWhole(path) {
-		t.Error("a wholly-read file stopped being wholly read after an edit")
-	}
-}
-
-// The span helpers, directly: these decide what survives, so their edges are
-// worth pinning independently of the tool.
-func TestChangedSpanHelpers(t *testing.T) {
-	t.Run("a single line replaced in place", func(t *testing.T) {
-		first, last, delta := changedLineSpan("a\nb\nc", "a\nB\nc")
-		if first != 2 || last != 2 || delta != 0 {
-			t.Fatalf("got (%d,%d,%d), want (2,2,0)", first, last, delta)
-		}
-	})
-	t.Run("one line becomes three", func(t *testing.T) {
-		first, last, delta := changedLineSpan("a\nb\nc", "a\nx\ny\nz\nc")
-		if first != 2 || last != 2 || delta != 2 {
-			t.Fatalf("got (%d,%d,%d), want (2,2,2)", first, last, delta)
-		}
-	})
-	t.Run("lines removed", func(t *testing.T) {
-		first, last, delta := changedLineSpan("a\nb\nc\nd", "a\nd")
-		if first != 2 || last != 3 || delta != -2 {
-			t.Fatalf("got (%d,%d,%d), want (2,3,-2)", first, last, delta)
-		}
-	})
-	t.Run("bytes", func(t *testing.T) {
-		first, last, delta := changedByteSpan([]byte("abcdef"), []byte("abXYef"))
-		if first != 2 || last != 4 || delta != 0 {
-			t.Fatalf("got (%d,%d,%d), want (2,4,0)", first, last, delta)
-		}
-	})
-}
-
-// A file read whole IN PIECES must stay seen-whole after an edit. SeenWhole
-// derives its answer from the ranges precisely because the raw flag is only set
-// by a single covering read; RecordEdit branching on the flag instead sent this
-// case down the split path, and the write_file refusal the derived answer exists
-// to prevent came back within one edit.
-func TestAFileReadWholeInPiecesStaysWholeAfterAnEdit(t *testing.T) {
-	dir := t.TempDir()
-	path := filepath.Join(dir, "chunked.go")
-	content := "l1\nl2\nl3\nl4\n"
-	if err := os.WriteFile(path, []byte(content), 0o600); err != nil {
-		t.Fatal(err)
-	}
-	tracker := NewFileTracker()
-	info, _ := os.Stat(path)
-	tracker.Record(path, []byte(content), info)
-	// Two reads that together cover the file, neither covering it alone.
-	tracker.RecordSeenRange(path, 1, 2, 4)
-	tracker.RecordSeenRange(path, 3, 4, 4)
-	if !tracker.SeenWhole(path) {
-		t.Fatal("two chunked reads did not add up to seen-whole")
-	}
-
-	updated := "l1\nl2X\nl3\nl4\n"
-	if err := os.WriteFile(path, []byte(updated), 0o600); err != nil {
-		t.Fatal(err)
-	}
-	newInfo, _ := os.Stat(path)
-	tracker.RecordEdit(path, []byte(content), []byte(updated), newInfo)
-
-	if !tracker.SeenWhole(path) {
-		t.Error("a file read whole in two chunks stopped being seen whole after one edit")
-	}
-}
-
-// observation.total is compared against read ranges, so it has to be the line
-// count a READER would give. strings.Split leaves an empty final element for
-// content ending in a newline, which counted one line too many — and since
-// SeenWhole asks whether the ranges cover 1..total, that made full coverage
-// unreachable for a file that had just been read in full.
-func TestCountLinesMatchesWhatAReaderWouldSay(t *testing.T) {
-	for _, testCase := range []struct {
-		content string
-		want    int
-	}{
-		{"a\nb\nc\n", 3}, // the common case: trailing newline opens no line
-		{"a\nb\nc", 3},
-		{"\n", 1},
-		{"", 0},
-	} {
-		if got := countLines([]byte(testCase.content)); got != testCase.want {
-			t.Errorf("countLines(%q) = %d, want %d", testCase.content, got, testCase.want)
-		}
-	}
-}

internal/tools/file_tracker.go

@@ -1,13 +1,11 @@
 package tools
 
 import (
-	"bytes"
 	"crypto/sha256"
 	"encoding/hex"
 	"errors"
 	"os"
 	"sort"
-	"strings"
 	"sync"
 	"time"
 )
@@ -167,241 +165,6 @@ func (tracker *FileTracker) RecordSeenBytes(absPath string, start, end, total in
 	tracker.seen[absPath] = observation
 }
 
-// RecordEdit re-baselines absPath after an edit THIS SESSION made, keeping the
-// reads the edit did not disturb.
-//
-// WHY THIS EXISTS RATHER THAN Record. RecordHash drops every recorded range when
-// the content hash moves, which is right for a change we did not make: we cannot
-// say which lines still hold what was read. After our own edit we can say
-// exactly. The content before the first changed line is byte-identical and sits
-// at the same line numbers; the content after the last changed line is
-// byte-identical and has moved by a known delta. Only the lines the edit
-// actually spans stop describing the file.
-//
-// Dropping the lot instead cost a real run. A 371-line file was read in three
-// pieces (40-45, 85-260, 260-371) and one two-line edit at line 92 erased the
-// credit for all three: the next six edits — into regions that had been read,
-// that the edit did not touch, in a file whose line count had not changed — were
-// each refused as content "not read in this session", and the repeated-failure
-// guard halted the run. The error even told the model to re-read, which would
-// have been undone by its next successful edit. The guard is right that a model
-// must not edit what it has not seen; it was wrong about what it had seen.
-func (tracker *FileTracker) RecordEdit(absPath string, before, after []byte, info os.FileInfo) {
-	if tracker == nil {
-		return
-	}
-	firstLine, lastLineBefore, lineDelta := changedLineSpan(string(before), string(after))
-	firstByte, lastByteBefore, byteDelta := changedByteSpan(before, after)
-
-	tracker.mu.Lock()
-	defer tracker.mu.Unlock()
-
-	version := FileVersion{Hash: HashContent(after)}
-	if info != nil {
-		version.Size = info.Size()
-		version.MTime = info.ModTime()
-	}
-	tracker.versions[absPath] = version
-
-	observation, tracked := tracker.seen[absPath]
-	if !tracked {
-		return
-	}
-	// The DERIVED answer, not the raw flag. Branching on observation.whole here
-	// sent a file read whole in two chunks — seenWhole true, flag false — into
-	// the split path below, where it stopped being seen whole after one edit.
-	if seenWhole(observation) {
-		// Still whole: every line was read, and an edit of ours does not make
-		// that untrue. Re-baseline as a single covering observation so the
-		// answer survives regardless of how the ranges shifted.
-		observation.whole = true
-		observation.ranges = nil
-		observation.byteRanges = nil
-		observation.total = countLines(after)
-		observation.totalBytes = len(after)
-		tracker.seen[absPath] = observation
-		return
-	}
-
-	// SPLIT AROUND THE EDIT, never drop the whole range. A read almost always
-	// SPANS the line it is about to edit — that is why it was read — so dropping
-	// on overlap would have thrown away 85-260 to change line 92 and left the
-	// original defect in place under a longer implementation.
-	kept := make([]lineRange, 0, len(observation.ranges)+1)
-	for _, seen := range observation.ranges {
-		if end := min(seen.end, firstLine-1); seen.start <= end {
-			kept = append(kept, lineRange{start: seen.start, end: end})
-		}
-		if start := max(seen.start, lastLineBefore+1); start <= seen.end {
-			kept = append(kept, lineRange{start: start + lineDelta, end: seen.end + lineDelta})
-		}
-	}
-	observation.ranges = kept
-	if observation.total != 0 {
-		observation.total = countLines(after)
-	}
-
-	// Same split, on half-open byte intervals.
-	keptBytes := make([]lineRange, 0, len(observation.byteRanges)+1)
-	for _, seen := range observation.byteRanges {
-		if end := min(seen.end, firstByte); seen.start < end {
-			keptBytes = append(keptBytes, lineRange{start: seen.start, end: end})
-		}
-		if start := max(seen.start, lastByteBefore); start < seen.end {
-			keptBytes = append(keptBytes, lineRange{start: start + byteDelta, end: seen.end + byteDelta})
-		}
-	}
-	observation.byteRanges = keptBytes
-	if observation.totalBytes != 0 {
-		observation.totalBytes = len(after)
-	}
-	tracker.seen[absPath] = observation
-}
-
-// changedLineSpan reports the 1-based first line that differs between before and
-// after, the 1-based last line of BEFORE that differs, and the line-count delta.
-//
-// Computed from a common prefix and suffix rather than from the caller's
-// replacement spans: one edit_file call with replace_all can rewrite many
-// scattered occurrences, and the span between the outermost two is the only
-// region that is honestly unknown afterwards.
-// The span is derived by scanning BYTES, not by materialising lines.
-//
-// The first version split both versions into []string. That allocates one string
-// header per line for each version — work that scales with the SIZE OF THE FILE
-// rather than the size of the edit, and it ran before RecordEdit had even checked
-// whether there was a tracked observation to update. @jatmn measured 32,036,640
-// bytes for two 2 MB versions of a million short lines, and extrapolated roughly
-// 1.6 GB of headers for a 100 MB file before counting the content and hashes
-// already live alongside them.
-//
-// That mattered beyond memory pressure: edit_file writes the updated bytes BEFORE
-// calling RecordEdit, so an out-of-memory kill lands after the user's file has
-// changed and before the tracker baseline catches up — the file and the record of
-// it disagree, and nothing says so.
-//
-// Bytes give the same answer in bounded memory. Two identical byte prefixes share
-// every line that ends inside them, so counting newlines in the common prefix
-// counts the unchanged leading lines directly.
-func changedLineSpan(before, after string) (firstChanged, lastChangedBefore, delta int) {
-	beforeCount := countTrackedLines(before)
-	afterCount := countTrackedLines(after)
-
-	prefix := commonLinePrefix(before, after)
-	// Never more leading lines than the shorter version has. The byte scan can
-	// otherwise claim a line that only one side possesses — two empty versions
-	// share a whole "line" that neither actually contains.
-	prefix = min(prefix, min(beforeCount, afterCount))
-	// The suffix may not reach back past the lines the prefix already claimed,
-	// exactly as the line-array loop bounded itself.
-	suffix := commonLineSuffix(before, after, min(beforeCount-prefix, afterCount-prefix))
-	return prefix + 1, beforeCount - suffix, afterCount - beforeCount
-}
-
-// commonLinePrefix counts the leading lines that are byte-identical in both.
-func commonLinePrefix(before, after string) int {
-	limit := min(len(before), len(after))
-	at := 0
-	for at < limit && before[at] == after[at] {
-		at++
-	}
-	lines := strings.Count(before[:at], "\n")
-	// A LINE THAT ENDS EXACTLY WHERE THE SCAN STOPPED IS STILL SHARED. Scanning
-	// halts where the bytes diverge OR where the shorter version runs out, and in
-	// the second case the line containing that point can be complete and equal on
-	// both sides — "a\nb" against "a\nb\nc" diverges only because the first ended,
-	// and "b" is a whole matching line in each.
-	if lineBoundary(before, at) && lineBoundary(after, at) {
-		lines++
-	}
-	return lines
-}
-
-// commonLineSuffix counts the trailing lines that are byte-identical in both, up
-// to the ceiling the prefix leaves.
-func commonLineSuffix(before, after string, ceiling int) int {
-	if ceiling <= 0 {
-		return 0
-	}
-	limit := min(len(before), len(after))
-	back := 0
-	for back < limit && before[len(before)-1-back] == after[len(after)-1-back] {
-		back++
-	}
-	beforeAt, afterAt := len(before)-back, len(after)-back
-	// Each newline inside the shared tail closes a line that lies wholly within
-	// it. The line the tail STARTS in is shared only when the tail begins on a
-	// line boundary in both versions — otherwise its opening bytes differ and it
-	// is a changed line that merely ends the same way.
-	lines := strings.Count(before[beforeAt:], "\n")
-	if lineStart(before, beforeAt) && lineStart(after, afterAt) {
-		lines++
-	}
-	return min(lines, ceiling)
-}
-
-// lineBoundary reports whether at is the end of a line: the end of the text, or
-// the position of the newline that closes it.
-func lineBoundary(text string, at int) bool { return at == len(text) || text[at] == '\n' }
-
-// lineStart reports whether at begins a line.
-func lineStart(text string, at int) bool { return at == 0 || text[at-1] == '\n' }
-
-// changedByteSpan is changedLineSpan in bytes: the first differing offset, the
-// end offset of the changed region in BEFORE, and the size delta.
-func changedByteSpan(before, after []byte) (firstChanged, lastChangedBefore, delta int) {
-	prefix := 0
-	for prefix < len(before) && prefix < len(after) && before[prefix] == after[prefix] {
-		prefix++
-	}
-	suffix := 0
-	for suffix < len(before)-prefix && suffix < len(after)-prefix &&
-		before[len(before)-1-suffix] == after[len(after)-1-suffix] {
-		suffix++
-	}
-	return prefix, len(before) - suffix, len(after) - len(before)
-}
-
-// countLines reports the line count a READER would give the content, which is
-// what observation.total is compared against.
-//
-// The trailing newline does not open a line. strings.Split leaves an empty final
-// element for "a\nb\nc\n" and so counted 4 where a read reports 3 — and because
-// SeenWhole asks whether the ranges cover 1..total, an inflated total made full
-// coverage unreachable for the very file that had just been read in full. Almost
-// every text file ends in a newline, so this was the common case rather than an
-// edge one.
-//
-// countTrackedLines keeps the OTHER rule deliberately: the span arithmetic has to
-// match the indices strings.Split produced, so it counts the empty element after
-// a trailing newline where this one does not. Two rules, two names, both stated —
-// they were one function with an if, and that is how they were confused.
-func countLines(content []byte) int {
-	// Counted, not split. This only ever needed a number, and building a slice of
-	// every line to take its length was the third full per-line allocation in the
-	// same call path.
-	if len(content) == 0 {
-		return 0
-	}
-	lines := bytes.Count(content, []byte{'\n'})
-	if content[len(content)-1] != '\n' {
-		lines++
-	}
-	return lines
-}
-
-// countTrackedLines is countLines' rule for the string form: the number of
-// elements strings.Split would produce, which counts the empty element after a
-// trailing newline. The two differ deliberately — observation.total compares
-// against what a READER reports, while the span arithmetic has to match the
-// indices the split produced.
-func countTrackedLines(text string) int {
-	if text == "" {
-		return 0
-	}
-	return strings.Count(text, "\n") + 1
-}
-
 // coversFully reports whether ranges together cover every line in [start, end].
 //
 // Ranges are merged rather than scanned line by line: a caller asking about a
@@ -511,27 +274,14 @@ func (tracker *FileTracker) SeenWhole(absPath string) bool {
 	if !ok {
 		return false
 	}
-	return seenWhole(observation)
-}
-
-// seenWhole is the DERIVED answer to "has every line been seen", and the single
-// place that decides it. Callers must hold the lock.
-//
-// Derived from the ranges rather than read off the flag, because the flag is
-// only ever set by a SINGLE read covering the file: a file read in two halves
-// stayed "not seen whole" forever even though SeenRange agreed every line had
-// been seen, and write_file, which gates on this, refused the overwrite with
-// advice to read the file that could not change the answer.
-//
-// IT HAS TO BE ONE FUNCTION. RecordEdit branched on the raw flag while this
-// derived the answer, so the very case the derivation exists to rescue fell into
-// the wrong arm and lost: a file read whole in two chunks reported SeenWhole
-// true, then reported false after a single edit, putting the write_file refusal
-// back within one edit of where it was fixed.
-func seenWhole(observation fileObservation) bool {
 	if observation.whole {
 		return true
 	}
+	// Derived from the ranges rather than tracked as its own flag. The flag was
+	// only ever set by a SINGLE read covering the file, so a file read in two
+	// halves stayed "not seen whole" forever even though SeenRange agreed every
+	// line had been seen — and write_file, which gates on this, then refused the
+	// overwrite with advice to read the file that could not change the answer.
 	if observation.total > 0 && coversFully(observation.ranges, 1, observation.total) {
 		return true
 	}

internal/tools/file_tracker_test.go

@@ -3,7 +3,6 @@ package tools
 import (
 	"os"
 	"path/filepath"
-	"strings"
 	"testing"
 )
 
@@ -154,85 +153,3 @@ func TestNilFileTrackerCreatedFilesIsANoop(t *testing.T) {
 		t.Fatalf("CreatedFiles() on nil tracker = %v, want nil", got)
 	}
 }
-
-// THE SPAN IS DERIVED IN BOUNDED MEMORY, whatever the file size.
-//
-// changedLineSpan used to split both versions into []string, so it allocated one
-// string header per line for each — work scaling with the SIZE OF THE FILE rather
-// than the size of the edit, and it ran before RecordEdit had even checked whether
-// there was an observation to update. @jatmn measured 32,036,640 bytes for two
-// 2 MB versions of a million short lines.
-//
-// The cost was not only memory. edit_file writes the updated bytes BEFORE calling
-// RecordEdit, so an out-of-memory kill lands after the user's file has changed and
-// before the tracker baseline catches up — file and record disagree, silently.
-//
-// This asserts an absolute ceiling rather than a ratio, so a future rewrite that
-// reintroduces per-line slices fails here rather than merely getting slower.
-func TestTheChangedSpanDoesNotAllocatePerLine(t *testing.T) {
-	before := strings.Repeat("x\n", 200_000)
-	after := before[:len(before)-2] + "y\n"
-
-	spanBytes := testing.Benchmark(func(b *testing.B) {
-		b.ReportAllocs()
-		for i := 0; i < b.N; i++ {
-			changedLineSpan(before, after)
-		}
-	}).AllocedBytesPerOp()
-	if spanBytes > 4096 {
-		t.Errorf("changedLineSpan allocated %d bytes for a %d-line pair; per-line slices are back", spanBytes, 200_000)
-	}
-
-	content := []byte(before)
-	countBytes := testing.Benchmark(func(b *testing.B) {
-		b.ReportAllocs()
-		for i := 0; i < b.N; i++ {
-			countLines(content)
-		}
-	}).AllocedBytesPerOp()
-	if countBytes > 4096 {
-		t.Errorf("countLines allocated %d bytes to return a number", countBytes)
-	}
-}
-
-// AND IT GIVES THE SAME ANSWERS THE LINE-ARRAY VERSION DID. The rewrite is only
-// safe if it is behaviour-preserving, so the replaced implementation is kept here
-// as an oracle and both are asked the same questions. This caught 206 mismatches
-// in the first attempt at the byte scan — empty versions and partially shared
-// trailing lines, neither of which the hand-written cases below would have found.
-func TestTheByteScanAgreesWithTheLineSplit(t *testing.T) {
-	oracle := func(before, after string) (int, int, int) {
-		split := func(text string) []string {
-			if text == "" {
-				return nil
-			}
-			return strings.Split(text, "\n")
-		}
-		beforeLines, afterLines := split(before), split(after)
-		prefix := 0
-		for prefix < len(beforeLines) && prefix < len(afterLines) && beforeLines[prefix] == afterLines[prefix] {
-			prefix++
-		}
-		suffix := 0
-		for suffix < len(beforeLines)-prefix && suffix < len(afterLines)-prefix &&
-			beforeLines[len(beforeLines)-1-suffix] == afterLines[len(afterLines)-1-suffix] {
-			suffix++
-		}
-		return prefix + 1, len(beforeLines) - suffix, len(afterLines) - len(beforeLines)
-	}
-
-	versions := []string{
-		"", "a", "\n", "a\n", "a\nb", "a\nb\n", "a\nb\nc", "a\nb\nc\n",
-		"\n\n", "x\n\ny", "a\nb\nc\nd\ne", "same\nsame\nsame\n", "ab\nc", "b\nc",
-	}
-	for _, before := range versions {
-		for _, after := range versions {
-			wantFirst, wantLast, wantDelta := oracle(before, after)
-			gotFirst, gotLast, gotDelta := changedLineSpan(before, after)
-			if wantFirst != gotFirst || wantLast != gotLast || wantDelta != gotDelta {
-				t.Errorf("changedLineSpan(%q, %q) = (%d, %d, %d), want (%d, %d, %d)",
-					before, after, gotFirst, gotLast, gotDelta, wantFirst, wantLast, wantDelta)
-			}
-		}
-	}
-}