feat(ui): compact 'Agent activity between turns' card — drop tool noise, show only final result (#269)

PR #268 hid the running tool list from the main card. The "Agent activity
between turns" spontaneous card had the same problem one layer deeper —
it accumulated every assistant message (including bare `tool_use` blocks
that rendered as `🔧 Bash`/`🔧 Read` lines) into a numbered list, exactly
the play-by-play we just hid from the main card.

Apply the same UX bet here:

- `extractSpontaneousSnippet`: tool_use-only assistant messages now
  return null. Text snippets (the agent's actual conclusion) still
  survive. Mixed messages still surface the text and ignore the
  adjacent tool_use, same as before.
- `formatSpontaneousCardBody`: render only the LATEST snippet (the
  conclusion of the burst), not a numbered list of all snippets. When
  N>1 were coalesced, append a small `_(N events coalesced; showing
  latest)_` footer so the user knows there was more activity if they
  want to dig into pm2 logs or the web UI.

Side effects:

- A between-turn burst that produced ONLY tool calls (no agent text)
  no longer triggers a card at all — the buffer stays empty, the
  30 s flush is a no-op. This is the correct outcome: nothing
  user-meaningful to report.
- The continuation-turn render path (handleContinuationTurn) was
  already covered by PR #268 since it goes through the same
  card-builder.ts surface. No change needed there.

Tests:
- extractSpontaneousSnippet: assert tool_use-only returns null,
  text+tool_use still returns the text, multi-tool_use returns null.
- formatSpontaneousCardBody: assert single-snippet renders without a
  numbered prefix; N>1 renders the latest snippet plus the
  coalesced-count footer, and the earlier snippets are NOT in the
  body.

290/290 vitest pass. Build + lint clean (2 pre-existing warnings).

Co-authored-by: Flood Sung <floodsung@xvirobotics.ai>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

Author: 3 people

src/bridge/message-bridge.ts

@@ -72,11 +72,16 @@ export const SPONTANEOUS_CARD_HEADER =
  * Extract a one-line summary from an SDK stream message for the spontaneous
  * activity card. Returns null if the message has nothing user-readable.
  *
- * Intentionally only handles `assistant` messages — `result` messages would
- * always duplicate the last assistant text block (SDK's `result.result` is a
- * verbatim echo), so including them caused the same content to show up twice
- * in the card with two different prefixes. Don't add a `result` branch back
- * without first verifying the SDK no longer echoes.
+ * Intentionally only handles `assistant` *text* blocks — same UX bet we made
+ * for the main card in PR #268: the user only cares about the agent's
+ * conclusion, not the per-tool play-by-play. `🔧 <ToolName>` lines used to
+ * be included for tool_use blocks but that's the exact intermediate noise
+ * we just hid from the live card; surfacing it on the spontaneous card
+ * would just re-introduce the same complaint between turns.
+ *
+ * Result-type messages are also ignored — SDK's `result.result` is a
+ * verbatim echo of the last assistant text block, so including them caused
+ * the same content to show up twice in the card.
  */
 export function extractSpontaneousSnippet(msg: unknown): string | null {
   const m = msg as { type?: string; message?: { content?: Array<{ type?: string; text?: string; name?: string }> } };
@@ -85,20 +90,29 @@ export function extractSpontaneousSnippet(msg: unknown): string | null {
     if (blk.type === 'text' && blk.text) {
       const trimmed = String(blk.text).trim();
       if (trimmed) return trimmed.slice(0, 400);
-    } else if (blk.type === 'tool_use' && blk.name) {
-      return `🔧 ${blk.name}`;
     }
+    // tool_use blocks intentionally fall through — see docstring above.
   }
   return null;
 }
 
-/** Build the markdown body of a spontaneous activity card from collected snippets. */
+/**
+ * Build the markdown body of a spontaneous activity card from collected
+ * snippets. Shows ONLY the latest snippet (the agent's conclusion of the
+ * burst); if multiple snippets were coalesced, a small footer notes the
+ * count so users know there was more activity if they want to dig into
+ * logs. Mirrors the "show only the final result, hide the play-by-play"
+ * pattern from PR #268's main-card tool indicator.
+ */
 export function formatSpontaneousCardBody(snippets: string[]): string {
-  return [
-    `_${SPONTANEOUS_CARD_HEADER}_`,
-    '',
-    ...snippets.map((s, i) => `**${i + 1}.** ${s}`),
-  ].join('\n');
+  const lines: string[] = [`_${SPONTANEOUS_CARD_HEADER}_`, ''];
+  if (snippets.length === 0) return lines.join('\n');
+  lines.push(snippets[snippets.length - 1]);
+  if (snippets.length > 1) {
+    lines.push('');
+    lines.push(`_(${snippets.length} events coalesced; showing latest)_`);
+  }
+  return lines.join('\n');
 }
 
 interface PendingBatch {

tests/message-bridge.test.ts

@@ -81,15 +81,20 @@ describe('extractSpontaneousSnippet', () => {
     expect(extractSpontaneousSnippet(msg)).toBe('Weather is sunny');
   });
 
-  it('returns 🔧 prefixed tool name for tool_use blocks', () => {
+  // Tool-use blocks used to render as `🔧 <ToolName>` lines in the
+  // spontaneous card. That's the exact intermediate noise we hid from the
+  // main card in PR #268 — surfacing it between turns would just put it
+  // right back. extractSpontaneousSnippet now drops tool_use blocks
+  // entirely; only text snippets (the agent's actual conclusion) survive.
+  it('returns null for tool_use-only assistant messages (intermediate noise dropped)', () => {
     const msg = {
       type: 'assistant',
       message: { content: [{ type: 'tool_use', name: 'Bash' }] },
     };
-    expect(extractSpontaneousSnippet(msg)).toBe('🔧 Bash');
+    expect(extractSpontaneousSnippet(msg)).toBeNull();
   });
 
-  it('prefers the first usable block (text wins over later tool_use)', () => {
+  it('returns text and ignores adjacent tool_use blocks', () => {
     const msg = {
       type: 'assistant',
       message: { content: [
@@ -100,6 +105,17 @@ describe('extractSpontaneousSnippet', () => {
     expect(extractSpontaneousSnippet(msg)).toBe('hello');
   });
 
+  it('returns null when only tool_use blocks are present (text-less burst)', () => {
+    const msg = {
+      type: 'assistant',
+      message: { content: [
+        { type: 'tool_use', name: 'Read' },
+        { type: 'tool_use', name: 'Bash' },
+      ] },
+    };
+    expect(extractSpontaneousSnippet(msg)).toBeNull();
+  });
+
   it('truncates very long text to 400 chars', () => {
     const long = 'x'.repeat(800);
     const out = extractSpontaneousSnippet({
@@ -124,7 +140,7 @@ describe('extractSpontaneousSnippet', () => {
     expect(extractSpontaneousSnippet({})).toBeNull();
   });
 
-  it('returns null for assistant messages with no text/tool_use content', () => {
+  it('returns null for assistant messages with no usable text content', () => {
     const msg = {
       type: 'assistant',
       message: { content: [{ type: 'thinking', text: 'silent' }, { type: 'image' }] },
@@ -142,11 +158,34 @@ describe('extractSpontaneousSnippet', () => {
 });
 
 describe('formatSpontaneousCardBody', () => {
-  it('renders snippets as a numbered list under the header', () => {
-    const body = formatSpontaneousCardBody(['🔧 Bash', 'Weather is sunny']);
+  // After the post-#268 simplification, the card shows ONLY the latest
+  // snippet (the agent's conclusion of the burst). Earlier snippets are
+  // hidden — same UX bet as the main card's single-line tool indicator,
+  // i.e. surface only the final result, not the play-by-play. If the user
+  // wants the intermediate steps, they can read pm2 logs or the web UI's
+  // expandable tool view.
+  it('renders only the latest snippet when a single snippet is present', () => {
+    const body = formatSpontaneousCardBody(['Weather is sunny']);
+    expect(body).toContain(SPONTANEOUS_CARD_HEADER);
+    expect(body).toContain('Weather is sunny');
+    // No numbered prefix — single snippet doesn't need one.
+    expect(body).not.toMatch(/\*\*1\.\*\*/);
+  });
+
+  it('renders only the latest snippet + a coalesced-count footer when N>1', () => {
+    const body = formatSpontaneousCardBody([
+      'Looking at the PR comments…',
+      'Found 3 things to address.',
+      'Pushed commit abc1234 to the branch.',
+    ]);
     expect(body).toContain(SPONTANEOUS_CARD_HEADER);
-    expect(body).toMatch(/\*\*1\.\*\*\s+🔧 Bash/);
-    expect(body).toMatch(/\*\*2\.\*\*\s+Weather is sunny/);
+    expect(body).toContain('Pushed commit abc1234 to the branch.');
+    expect(body).toMatch(/3 events coalesced/);
+    // Earlier snippets must NOT appear in the body.
+    expect(body).not.toContain('Looking at the PR comments');
+    expect(body).not.toContain('Found 3 things to address');
+    // No numbered list prefixes either.
+    expect(body).not.toMatch(/\*\*1\.\*\*/);
   });
 
   // Regression for Bug A (misleading title): the header used to say