🏷️ fix: Title an Open Live Card by Its Newest Label, Not a Line of Its Text

client/src/components/Chat/Messages/Content/ActivityPhaseGroup.tsx

@@ -263,6 +263,7 @@ function SpanGlyph({
 function LivePhaseHeader({
   parts,
   animate,
+  expanded,
   lineId,
   comboId,
   detailId,
@@ -271,6 +272,9 @@ function LivePhaseHeader({
 }: {
   parts: ReadonlyArray<TMessageContentParts | undefined>;
   animate: boolean;
+  /** The rows are on screen: title the span by its newest label rather than
+   *  repeat a line the reader can see below. */
+  expanded: boolean;
   lineId: string;
   comboId: string;
   detailId: string;
@@ -282,8 +286,8 @@ function LivePhaseHeader({
   const mcpServerNames = useMCPServerNames();
   const attachmentsById = useMemo(() => mapAttachments(attachments ?? []), [attachments]);
   const activity = useMemo(
-    () => getLiveActivity(parts, localize, mcpServerNames, attachmentsById),
-    [parts, localize, mcpServerNames, attachmentsById],
+    () => getLiveActivity(parts, localize, mcpServerNames, attachmentsById, expanded),
+    [parts, localize, mcpServerNames, attachmentsById, expanded],
   );
   /** A code card names its sandbox startup from events outside the content
    *  array. The row reads the same signal for its newest call, so the span
@@ -774,6 +778,7 @@ export default function ActivityPhaseGroup({
               <LivePhaseHeader
                 parts={liveParts}
                 animate={smoothStreaming}
+                expanded={isExpanded}
                 lineId={lineId}
                 comboId={comboId}
                 detailId={detailId}

client/src/components/Chat/Messages/Content/__tests__/ActivityPhaseGroup.test.tsx

@@ -547,3 +547,62 @@ describe('ActivityPhaseGroup open header', () => {
     expect(screen.getByTestId('activity-phase-panel').firstElementChild).toHaveClass('pl-6');
   });
 });
+
+describe('ActivityPhaseGroup open live header', () => {
+  beforeEach(() => {
+    jest.useFakeTimers();
+  });
+  afterEach(() => {
+    jest.useRealTimers();
+  });
+  /** A thought's line holds for a second; the retired line lingers in the
+   *  ticker, so the current line is read from its own title. */
+  const settle = () => act(() => jest.advanceTimersByTime(1000));
+  const thought = (reasoning_label?: string): TMessageContentParts =>
+    ({
+      type: ContentTypes.THINK,
+      think: 'The refs share a commit. Next I check the ordering.',
+      ...(reasoning_label == null ? {} : { reasoning_label }),
+    }) as unknown as TMessageContentParts;
+
+  test('previews the newest finished sentence while collapsed', () => {
+    render(
+      <ActivityPhaseGroup
+        labelPart={makeLabelPart('')}
+        hasContent
+        liveParts={[thought('Comparing refs')]}
+      >
+        <div data-testid="phase-content" />
+      </ActivityPhaseGroup>,
+    );
+    expect(screen.getByRole('button')).toHaveTextContent('Next I check the ordering.');
+  });
+
+  test("titles an open card by the thought's label instead of repeating its text", () => {
+    render(
+      <ActivityPhaseGroup
+        labelPart={makeLabelPart('')}
+        hasContent
+        liveParts={[thought('Comparing refs')]}
+      >
+        <div data-testid="phase-content" />
+      </ActivityPhaseGroup>,
+    );
+    fireEvent.click(screen.getByRole('button'));
+    settle();
+    const header = screen.getByRole('button');
+    expect(within(header).getByTitle('Comparing refs')).toBeInTheDocument();
+    expect(within(header).queryByTitle('Next I check the ordering.')).toBeNull();
+  });
+
+  test('falls back to the generic thinking line when no label has landed', () => {
+    render(
+      <ActivityPhaseGroup labelPart={makeLabelPart('')} hasContent liveParts={[thought()]}>
+        <div data-testid="phase-content" />
+      </ActivityPhaseGroup>,
+    );
+    fireEvent.click(screen.getByRole('button'));
+    settle();
+    expect(within(screen.getByRole('button')).getByTitle('com_ui_thinking')).toBeInTheDocument();
+  });
+});

client/src/components/Chat/Messages/Content/live.ts

@@ -269,6 +269,7 @@ function newestLine(
   localize: Localize,
   serverNames: readonly string[],
   span: SpanSummary,
+  preferLabels: boolean,
 ): Pick<LiveActivity, 'text' | 'source' | 'pendingToolCallId' | 'comboCount'> {
   for (let position = parts.length - 1; position >= 0; position -= 1) {
     const part = parts[position];
@@ -278,9 +279,12 @@ function newestLine(
     if (part.type === ContentTypes.THINK) {
       /** Reached before any call or label, this thought IS the tail — the
        *  model is reasoning about its next step. Its multi-line peek stays
-       *  inside the fold, so the header previews it one sentence at a time. */
+       *  inside the fold, so the header previews it one sentence at a time.
+       *  Unless the fold is open: the text is on screen then, and a header
+       *  repeating a line of it under the reader's eyes is noise, so the
+       *  header keeps to the thought's label. */
       const reasoning = typeof part.think === 'string' ? part.think : (part.think?.value ?? '');
-      const sentence = lastReasoningSentence(reasoning);
+      const sentence = preferLabels ? undefined : lastReasoningSentence(reasoning);
       if (sentence != null) {
         return { text: sentence, source: `think:${position}`, comboCount: 1 };
       }
@@ -300,7 +304,7 @@ function newestLine(
        *  leaving it unnamed would hold a stale call on screen while new prose
        *  piles up behind the disclosure. */
       const value = typeof part.text === 'string' ? part.text : (part.text?.value ?? '');
-      const commentary = boundIntentLabel(value);
+      const commentary = preferLabels ? undefined : boundIntentLabel(value);
       if (commentary != null) {
         return { text: commentary, source: `text:${position}`, comboCount: 1 };
       }
@@ -346,10 +350,15 @@ export function getLiveActivity(
   localize: Localize,
   serverNames: readonly string[],
   attachmentsById?: Record<string, TAttachment[] | undefined>,
+  /** Name the span by its newest LABEL: a thought's generated label or the
+   *  generic thinking line, a batch label, a call's line — never a line of
+   *  reasoning or commentary. For a header whose rows are on screen, where
+   *  quoting them back is repetition. */
+  preferLabels = false,
 ): LiveActivity {
   const span = summarizeSpan(parts, attachmentsById);
   return {
-    ...newestLine(parts, localize, serverNames, span),
+    ...newestLine(parts, localize, serverNames, span, preferLabels),
     outcome: { failed: span.failed, cancelled: span.cancelled },
     iconNames: getSpanIconNames(parts),
   };