fix(commands): harden registry and UI ordering

packages/ui/tui/src/index.ts

@@ -1229,6 +1229,7 @@ export function createTuiChat(
     commandControllers.add(controller)
     void ctx.commands.execute(agent, 'tui', text, controller.signal).then(
       (result) => {
+        if (disposed) return
         if (result === undefined) {
           appendNotice(`Unknown command: ${text}`, 'warning')
         } else if (result.text !== undefined && result.text !== '') {
@@ -1342,7 +1343,12 @@ export function createTuiChat(
   } catch (error: unknown) {
     disposed = true
     detachListeners()
-    void commandFiber.dispose()
+    void commandFiber.dispose().catch(
+      /* v8 ignore next 2 -- command registration cleanup is non-throwing; this guards a future disposer regression */
+      (cleanupError: unknown) => {
+        ctx.logger.warn(`ui-tui: command cleanup after startup failure failed: ${renderThrown(cleanupError)}`)
+      },
+    )
     clearStatus()
     disposeUserInteraction()
     ui.stop()

packages/ui/tui/tests/tui.spec.ts

@@ -510,6 +510,35 @@ describe('pi-tui chat lifecycle and transcript', () => {
     await result.ctx.fiber.dispose()
   })
 
+  it('suppresses a successful plugin result that settles as TUI disposal starts', async () => {
+    const result = await setup()
+    let started!: () => void
+    const ready = new Promise<void>((resolve) => { started = resolve })
+    let resolveCommand!: (result: { kind: 'success'; text: string }) => void
+    result.ctx.commands.register({
+      name: 'late-success',
+      description: 'Resolve while the TUI closes',
+      surfaces: ['tui'],
+      handler: () => new Promise((resolve) => {
+        resolveCommand = resolve
+        started()
+      }),
+    })
+
+    result.terminal.send('/late-success')
+    result.terminal.send('\r')
+    await ready
+    resolveCommand({ kind: 'success', text: 'must not render after disposal' })
+    // Let the command boundary accept the result before disposal, but leave the
+    // TUI continuation queued so the success-side disposal guard owns the race.
+    await Promise.resolve()
+    await result.controller.dispose()
+    await tick()
+
+    expect(result.terminal.output).not.toContain('must not render after disposal')
+    await result.ctx.fiber.dispose()
+  })
+
   it('cancels before /exit while running and handles agent errors/disposal', async () => {
     const result = await setup({ status: 'running' })
     result.terminal.send('/exit')