phase: 161_reasoning_bubble

All gates verified. Final check — AGENTS.md rules against the project (commands, gates, protocols) — the quick-reference commands all exist and the rules (PLAN §2/§7/§9 references, phase protocol, No CDN, Debugpy, git gates) accurately describe the project; the reasoning bubble is a pure UI change with no new commands or env vars, so no AGENTS.md change is needed.

**Verification complete — full results:**

- **Verified** (implemented by prior task passes, all in working tree): `createReasoningWrap`/`ensureReasoningWrap` live container (D1), `settleReasoning` fold at the 3 settle sites + not at delta (D2), 320px `.reasoning-body` window + pinned-tail follow (D3), zero persistence change (D4), collapsed restore + shared-page parity with D6 step counts, `styles.css` family treatment + reduced-motion still, mock `REASONING_MIDROUND_TRIGGER` flow, 6-test story suite, phase-158 pin updates
- **Full suite:** `uv run pytest` → **3738 passed, 0 failed** · `uv run pytest --cov=app --cov-report=term-missing` → **TOTAL 99% (>90%)** · `uv run ruff check .` → all checks passed · `uv run pyright` → **0 errors, 0 warnings**
- **E2E in isolation** (DB up; port-8123 collision with an unrelated `undercooked` service → `E2E_APP_PORT=8125`/`E2E_MOCK_PORT=8902`, no live change made): `test_reasoning_bubble.py` **6/6** · `test_thinking_timeline.py` ✓ · `test_thinking_display.py` ✓ · `test_tool_call_compact.py` ✓ · `test_big_read_progress.py` ✓ · `test_turn_progress_loader.py` ✓ · `test_share_chat.py` ✓ · `test_chat_persistence.py` ✓ · `test_smoke.py` ✓ (all exit 0, zero failures)
- **Completion criteria:** all 9 checked against the code + test outcomes — container open/live/nested ✓, stays open past mid-round delta ✓, folds at done ✓, restore + shared collapsed with "3 steps" ✓, plain turn = no container ✓, regression suites green ✓, suite/coverage/lint green ✓, diff scope limited to `frontend/assets/{app.js,shared.js,styles.css}` + `tests/` + `README.md` + phase files (no `app/` — D4) ✓
- **Documentation:** README.md "Thinking" section names the Reasoning bubble accurately (320px window, open-until-settle incl. mid-round deltas, "N steps", byte-identical no-container, collapsed on restore/shared) — verified consistent, no changes needed; AGENTS.md — verified consistent, no changes needed; all `.env.example` vars documented
- **Decisions:** commit + phase-dir move left to the harness (per pass rules — no git index/history commands executed); `undercooked` dev server on port 8123 untouched, E2E used the env port overrides
- **Next pending phase:** none — `161_reasoning_bubble` is the last in `todo/`

tests/e2e/test_thinking_display.py

@@ -164,7 +164,12 @@ def test_thinking_block_streams_open_then_collapses(
 
 # ---------------------------------------------------------------------------
 # 2. Toggle: after settle the block is closed; the summary re-opens it
-#    (a real keyboard-focusable control) and closes it again
+#    (a real keyboard-focusable control) and closes it again.
+#    Phase 161 (D2): at rest the run sits INSIDE the folded reasoning
+#    container — the container's summary is the at-rest focusable
+#    surface (native <details> nesting semantics: a closed details
+#    hides its content, so the inner summary is focusable only after
+#    the container opens).
 # ---------------------------------------------------------------------------
 
 
@@ -177,8 +182,18 @@ def test_thinking_toggle_after_done(page: Page, app_url: str, seeded_kb: None) -
     details = last.locator("details.thinking")
     expect(details).to_have_count(1)
     expect(details).not_to_have_attribute("open")  # auto-collapsed at first token
+    # Phase 161 (D2): the run nests in the reasoning container, which
+    # folds at done (the at-rest focusable surface is the container's
+    # summary — open it to reach the inner run's summary).
+    container = last.locator("details.reasoning")
+    expect(container).to_have_count(1)
+    expect(container).not_to_have_attribute("open")
+    container.locator("summary.reasoning-summary").focus()
+    assert page.evaluate("() => document.activeElement.tagName") == "SUMMARY"
+    container.locator("summary.reasoning-summary").click()
+    expect(container).to_have_attribute("open", "")
 
-    # The summary is a real, keyboard-focusable control.
+    # The inner run's summary is a real, keyboard-focusable control.
     details.locator("summary").focus()
     assert page.evaluate("() => document.activeElement.tagName") == "SUMMARY"