fix(pty): retain sends through cancellation polling

packages/pty/pty-local/src/session.ts

@@ -412,7 +412,7 @@ export class LocalPtySession implements PtyBackendSession {
         return
       }
       const foreground = await this.terminal.inspectForeground()
-      if (this.active !== operation || this.closing) return
+      if (this.active !== operation || this.closing || this.interrupting === operation) return
       const idleFor = Date.now() - this.lastOutputAt
       if (this.promptSeen && foreground !== undefined && this.shellPgid === undefined) {
         this.shellPgid = foreground.processGroupId
@@ -439,7 +439,7 @@ export class LocalPtySession implements PtyBackendSession {
         this.settleActive('inferred_idle')
       }
     } catch (error: unknown) {
-      if (this.active === operation && !this.closing) this.failActive(error)
+      if (this.active === operation && !this.closing && this.interrupting !== operation) this.failActive(error)
     } finally {
       this.polling = false
       const active = this.active

packages/pty/pty-local/tests/session.spec.ts

@@ -406,6 +406,7 @@ describe('LocalPtySession readiness and output', () => {
     await Promise.resolve()
     await vi.advanceTimersByTimeAsync(10)
     expect(inspections).toBe(2)
+    await vi.advanceTimersByTimeAsync(50)
     expect(operation.cancel()).toBe(true)
     let settled = false
     void operation.done.then(() => { settled = true })
@@ -423,6 +424,54 @@ describe('LocalPtySession readiness and output', () => {
     expect((await operation.done).waitReason).toBe('session_exit')
   })
 
+  it('does not let an in-flight readiness failure release a canceled send before signalling settles', async () => {
+    vi.useFakeTimers()
+    const terminal = new FakeTerminal()
+    const inspector = new FakeInspector()
+    const session = makeSession(terminal, inspector, config())
+    await initialize(session, terminal)
+
+    const readiness = Promise.withResolvers<never>()
+    let inspections = 0
+    terminal.inspectForeground = async () => {
+      inspections += 1
+      if (inspections === 1) return { processGroupId: 456, inputWaiting: false }
+      if (inspections === 2) return await readiness.promise
+      return { processGroupId: 456, inputWaiting: true }
+    }
+    const signalling = Promise.withResolvers<undefined>()
+    const signalled = Promise.withResolvers<number>()
+    terminal.signalForeground = async (signal) => {
+      await signalling.promise
+      const foreground = await terminal.inspectForeground()
+      if (foreground === undefined) throw new Error('cannot resolve foreground')
+      inspector.signalGroup(foreground.processGroupId, signal)
+      signalled.resolve(foreground.processGroupId)
+      return foreground.processGroupId
+    }
+
+    const operation = session.startSend({ text: 'first', submit: true })
+    await Promise.resolve()
+    await Promise.resolve()
+    await vi.advanceTimersByTimeAsync(10)
+    expect(inspections).toBe(2)
+    expect(operation.cancel()).toBe(true)
+    let settled = false
+    void operation.done.then(() => { settled = true })
+
+    readiness.reject(new Error('inspection failed during cancellation'))
+    await Promise.resolve()
+    await Promise.resolve()
+    expect(settled).toBe(false)
+    expect(() => session.startSend({ text: 'successor', submit: true })).toThrow(PtyError)
+
+    signalling.resolve(undefined)
+    expect(await signalled.promise).toBe(456)
+    expect(inspector.groups).toContainEqual([456, 'SIGINT'])
+    await session.close('test complete')
+    expect((await operation.done).waitReason).toBe('session_exit')
+  })
+
   it('signals only after an in-flight provider write lands', async () => {
     vi.useFakeTimers()
     const terminal = new FakeTerminal()