fix(tui): ignore late thinking deltas after completion (#31055)

* fix(tui): ignore late thinking deltas after completion

Prevent stale reasoning events from repainting the TUI status after a turn has already completed and the UI is idle.

* test(tui): restore timers after thinking delta assertion

Keep fake timer cleanup in a finally block so assertion failures cannot leak timer mode into later tests.

ui-tui/src/__tests__/createGatewayEventHandler.test.ts

@@ -139,6 +139,7 @@ describe('createGatewayEventHandler', () => {
     const verdict = '✓ Goal achieved: long judge reason goes only in transcript, not merged with cwd label.'
 
     vi.useFakeTimers()
+
     try {
       onEvent({
         payload: { kind: 'goal', text: verdict },
@@ -303,14 +304,40 @@ describe('createGatewayEventHandler', () => {
     vi.useFakeTimers()
     const appended: Msg[] = []
     const streamed = 'short streamed reasoning'
+    const onEvent = createGatewayEventHandler(buildCtx(appended))
 
-    createGatewayEventHandler(buildCtx(appended))({ payload: { text: streamed }, type: 'thinking.delta' } as any)
-    vi.runOnlyPendingTimers()
+    try {
+      onEvent({ payload: {}, type: 'message.start' } as any)
+      onEvent({ payload: { text: streamed }, type: 'thinking.delta' } as any)
+      vi.runOnlyPendingTimers()
 
-    expect(getTurnState().reasoning).toBe(streamed)
-    expect(getTurnState().reasoningActive).toBe(true)
-    expect(getTurnState().reasoningTokens).toBe(estimateTokensRough(streamed))
-    vi.useRealTimers()
+      expect(getTurnState().reasoning).toBe(streamed)
+      expect(getTurnState().reasoningActive).toBe(true)
+      expect(getTurnState().reasoningTokens).toBe(estimateTokensRough(streamed))
+    } finally {
+      vi.useRealTimers()
+    }
+  })
+
+  it('ignores late thinking.delta after the turn has already completed', () => {
+    vi.useFakeTimers()
+    const appended: Msg[] = []
+    const onEvent = createGatewayEventHandler(buildCtx(appended))
+
+    try {
+      onEvent({ payload: {}, type: 'message.start' } as any)
+      onEvent({ payload: { text: 'final answer' }, type: 'message.complete' } as any)
+      expect(getUiState().busy).toBe(false)
+      expect(getUiState().status).toBe('ready')
+
+      onEvent({ payload: { text: 'thinking...' }, type: 'thinking.delta' } as any)
+      vi.runOnlyPendingTimers()
+
+      expect(getUiState().status).toBe('ready')
+      expect(getTurnState().reasoning).toBe('')
+    } finally {
+      vi.useRealTimers()
+    }
   })
 
   it('preserves streamed reasoning as one completed thinking panel after segment flushes', () => {

ui-tui/src/app/createGatewayEventHandler.ts

@@ -1,6 +1,6 @@
 import { STARTUP_IMAGE, STARTUP_QUERY } from '../config/env.js'
 import { STREAM_BATCH_MS } from '../config/timing.js'
-import { SETUP_REQUIRED_TITLE, buildSetupRequiredSections } from '../content/setup.js'
+import { buildSetupRequiredSections, SETUP_REQUIRED_TITLE } from '../content/setup.js'
 import type {
   CommandsCatalogResponse,
   ConfigFullResponse,
@@ -313,6 +313,10 @@ export function createGatewayEventHandler(ctx: GatewayEventHandlerContext): (ev:
       }
 
       case 'thinking.delta': {
+        if (!getUiState().busy) {
+          return
+        }
+
         const text = ev.payload?.text
 
         if (text !== undefined) {
@@ -340,6 +344,7 @@ export function createGatewayEventHandler(ctx: GatewayEventHandlerContext): (ev:
 
         if (p.kind === 'goal') {
           sys(p.text)
+
           const brief = p.text.startsWith('✓')
             ? '✓ goal complete'
             : p.text.startsWith('↻')
@@ -347,8 +352,10 @@ export function createGatewayEventHandler(ctx: GatewayEventHandlerContext): (ev:
               : p.text.startsWith('⏸')
                 ? '⏸ goal paused'
                 : 'ready'
+
           setStatus(brief)
           restoreStatusAfter(6000)
+
           return
         }
 
@@ -356,6 +363,7 @@ export function createGatewayEventHandler(ctx: GatewayEventHandlerContext): (ev:
 
         if (p.kind === 'compressing') {
           sys(p.text)
+
           return
         }
 
@@ -528,6 +536,7 @@ export function createGatewayEventHandler(ctx: GatewayEventHandlerContext): (ev:
       case 'tool.complete': {
         const inlineDiffText =
           ev.payload.inline_diff && getUiState().inlineDiffs ? stripAnsi(String(ev.payload.inline_diff)).trim() : ''
+
         const resultText = ev.payload.result_text ? stripAnsi(String(ev.payload.result_text)) : undefined
 
         if (inlineDiffText) {
@@ -589,7 +598,6 @@ export function createGatewayEventHandler(ctx: GatewayEventHandlerContext): (ev:
         sys(`[bg ${ev.payload.task_id}] ${ev.payload.text}`)
 
         return
-
       case 'review.summary': {
         // Self-improvement background review emitted a persistent summary
         // of what it saved to memory/skills. Surface it as a system line
@@ -597,6 +605,7 @@ export function createGatewayEventHandler(ctx: GatewayEventHandlerContext): (ev:
         // flash. Python-side already formats it as "💾 Self-improvement
         // review: …".
         const text = String(ev.payload?.text ?? '').trim()
+
         if (text) {
           sys(text)
         }