fix(pty): detach cancellation before close drain

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

@@ -518,13 +518,16 @@ export class LocalPtySession implements PtyBackendSession {
     if (!quiescent) {
       throw new Error(`PTY cleanup failed (${reason}); terminal session did not reach quiescence`)
     }
+    // Quiescence is the active send's terminal outcome. Detach its abort
+    // listener before snapshotting provider operations so no late interrupt
+    // can enter the owned set after the drain starts.
+    this.settleActive('session_exit')
     await Promise.all(this.terminalOperations)
     // Whole-session cleanup can fail before the top-level process exits. Wait
     // for it first so that failure is reported instead of blocking forever on
     // `done`; successful quiescence guarantees `done` can now settle status and
     // drain the terminal output.
     await this.completion
-    this.settleActive('session_exit')
     this.terminal.output.off('data', this.onTerminalData)
     this.terminal.output.off('end', this.onTerminalEnd)
     this.terminal.output.off('error', this.onTerminalError)

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

@@ -954,4 +954,26 @@ describe('LocalPtySession bounds, signals, and teardown', () => {
     expect((await operation.done).waitReason).toBe('session_exit')
   })
 
+  it('detaches active cancellation before draining terminal operations', async () => {
+    vi.useFakeTimers()
+    const terminal = new FakeTerminal()
+    const session = new LocalPtySession(terminal, config())
+    await initialize(session, terminal)
+
+    const inspection = Promise.withResolvers<{ processGroupId: number; inputWaiting: boolean }>()
+    terminal.inspectForeground = async () => await inspection.promise
+    const signalForeground = vi.spyOn(terminal, 'signalForeground')
+    const controller = new AbortController()
+    const operation = session.startSend({ text: 'pending inspection', submit: true, signal: controller.signal })
+    const closing = session.close('pending cancellation')
+    await Promise.resolve()
+    await Promise.resolve()
+
+    controller.abort('late cancellation')
+    expect(signalForeground).not.toHaveBeenCalled()
+    inspection.resolve({ processGroupId: 456, inputWaiting: false })
+    await closing
+    expect((await operation.done).waitReason).toBe('session_exit')
+  })
+
 })