fix(tui): scope prompt drafts to sessions

packages/tui/src/component/prompt/index.tsx

@@ -130,7 +130,7 @@ function formatEditorContext(selection: EditorSelection) {
   return `<system-reminder>${ranges.join("\n")} This may or may not be relevant to the current task.</system-reminder>\n`
 }
 
-let stashed: { prompt: PromptInfo; cursor: number } | undefined
+const drafts = new Map<string | undefined, { prompt: PromptInfo; cursor: number }>()
 
 function argumentSlash(input: string, commands: readonly KeymapCommand[]) {
   const head = parseSlashHead(input, /\s/)
@@ -600,22 +600,40 @@ export function Prompt(props: PromptProps) {
     },
   }
 
-  onMount(() => {
-    const saved = stashed
-    stashed = undefined
-    if (store.prompt.text) return
-    if (saved && saved.prompt.text) {
-      input.setText(saved.prompt.text)
-      setStore("prompt", saved.prompt)
-      restoreExtmarksFromPrompt(saved.prompt)
-      input.cursorOffset = saved.cursor
+  function saveDraft(sessionID: string | undefined) {
+    if (!store.prompt.text) {
+      drafts.delete(sessionID)
+      return
     }
-  })
+    drafts.set(sessionID, { prompt: unwrap(store.prompt), cursor: input.cursorOffset })
+  }
+
+  function restoreDraft(sessionID: string | undefined) {
+    const saved = drafts.get(sessionID)
+    drafts.delete(sessionID)
+    ref.reset()
+    if (!saved?.prompt.text) return
+    ref.set(saved.prompt)
+    input.cursorOffset = saved.cursor
+  }
+
+  let draftSessionID = props.sessionID
+  onMount(() => restoreDraft(draftSessionID))
+
+  createEffect(
+    on(
+      () => props.sessionID,
+      (sessionID) => {
+        saveDraft(draftSessionID)
+        draftSessionID = sessionID
+        restoreDraft(sessionID)
+      },
+      { defer: true },
+    ),
+  )
 
   onCleanup(() => {
-    if (store.prompt.text) {
-      stashed = { prompt: unwrap(store.prompt), cursor: input.cursorOffset }
-    }
+    saveDraft(draftSessionID)
     setInputTarget(undefined)
     props.ref?.(undefined)
   })

packages/tui/test/app-lifecycle.test.tsx

@@ -294,3 +294,72 @@ test("session startup prompt is submitted exactly once", async () => {
     await server.stop()
   }
 })
+
+test("new session does not inherit the current session prompt draft", async () => {
+  const setup = await createTestRenderer({ width: 80, height: 24, useThread: false })
+  const events = createEventStream()
+  const cwd = process.cwd()
+  const location = { directory: cwd, project: { id: "project", directory: cwd } }
+  const session = {
+    id: "dummy",
+    title: "Demo session",
+    projectID: "project",
+    location: { directory: cwd },
+    agent: "build",
+    model: { providerID: "provider", id: "model" },
+    cost: 0,
+    tokens: { input: 0, output: 0, reasoning: 0, cache: { read: 0, write: 0 } },
+    time: { created: 0, updated: 0 },
+  }
+  const calls = createFetch((url) => {
+    if (url.pathname === "/api/location") return json(location)
+    if (url.pathname === "/api/session") return json({ data: [session], cursor: {} })
+    if (url.pathname === "/api/session/dummy") return json({ data: session })
+    if (url.pathname === "/api/session/dummy/message") return json({ data: [], cursor: {} })
+    if (url.pathname === "/api/session/dummy/pending") return json({ data: [] })
+    if (url.pathname === "/api/session/dummy/permission") return json({ data: [] })
+    if (url.pathname === "/api/agent")
+      return json({ location, data: [{ id: "build", mode: "primary", hidden: false, permissions: [] }] })
+    if (url.pathname === "/api/model")
+      return json({ location, data: [{ id: "model", providerID: "provider", name: "Model", variants: [] }] })
+  }, events)
+  const server = Bun.serve({ port: 0, fetch: (request) => calls.fetch(request) })
+
+  try {
+    const { run } = await import("../src/app")
+    const task = Effect.runPromise(
+      run({
+        app: { name: "test", version: "test", channel: "test" },
+        server: { endpoint: { url: server.url.toString() } },
+        config: { get: async () => ({}), update: async () => ({}) },
+        packages: { resolve: async () => undefined },
+        terminalHandoff: async () => ({ renderer: setup.renderer, mode: "dark", complete: () => {} }),
+        args: { sessionID: "dummy" },
+        log: () => {},
+      }).pipe(Effect.provide(AppNodeBuilder.build(Global.node)), Effect.provide(FileSystem.layerNoop({}))),
+    )
+
+    await Promise.race([
+      (async () => {
+        while (!setup.renderer.currentFocusedEditor) await Bun.sleep(10)
+      })(),
+      Bun.sleep(2_000).then(() => {
+        throw new Error("session prompt did not focus")
+      }),
+    ])
+    await setup.mockInput.typeText("keep this draft")
+    expect(setup.renderer.currentFocusedEditor?.plainText).toBe("keep this draft")
+
+    setup.mockInput.pressKey("x", { ctrl: true })
+    await Bun.sleep(10)
+    setup.mockInput.pressKey("n")
+    await Bun.sleep(20)
+
+    expect(setup.renderer.currentFocusedEditor?.plainText).toBe("")
+    setup.renderer.destroy()
+    await task
+  } finally {
+    if (!setup.renderer.isDestroyed) setup.renderer.destroy()
+    await server.stop()
+  }
+})