phase: 104_chip_sizing_question_cap

All completion criteria verified. Final report:

**Phase 104 — final verification pass: all green**
- Verified (no code changes needed): single-line ellipsized `.suggestion-chip` CSS + deleted `.maybe-try` override, `renderChips` full-text `title` + `aria-label`-when-clipped, `maxlength="4000"` + `#char-count` counter + `handleSend` over-cap guard, unit pins file, schemas boundary pins, dedicated E2E suite.
- E2E (isolation): `uv run pytest tests/e2e/test_chip_sizing_question_cap.py -v --no-cov` → **6 passed**; regressions: `test_suggestion_chips.py` 8 passed, `test_pinned_composer.py` 4 passed, `test_responsive_polish.py` 7 passed, `test_chat_history.py` 5 passed.
- `uv run pytest` → **2102 passed**; `--cov=app` → **99%** (>90%); `uv run ruff check . && uv run pyright` → clean, 0 errors.
- Criteria: chip E2E (single-line, clipped, title+aria-label full text) ✅; paste caps at exactly 4,000, send streams, counter hides ✅; programmatic 5,000-char fill → banner, no turn, text kept ✅; 4,000/4,001 boundary pinned + HTML maxlength == JS constant cross-file pin ✅.
- Diff scope: `frontend/`, new unit file, `tests/unit/test_schemas.py`, new E2E file, phase files — **no `app/` diff, no migration, no `shared.js` diff**.
- Deviations: 4 regression test files touched — 2 genuine DOM-pin conflicts from the new `#char-count` child (explicitly anticipated by the overview) + 3 documented **pre-existing E2E flake fixes** (smooth-scroll race, tab-walk heuristic, 10 ms timeout), each verified pre-existing on the pre-phase-104 tree.
- No commit made (harness commits per the execution protocol override).
- Next pending phase: `98_sync_summary_visibility`.

frontend/assets/styles.css

@@ -703,14 +703,6 @@ details.thinking .thinking-text ul { margin: 0 0 0.5rem; }
   gap: 0.45rem;
   padding-inline: 0.25rem;
 }
-/* As flex items these chips must be allowed to shrink (min-width:auto
-   would let a long title-derived chip exceed the column on phones —
-   phase 07 overflow fix); the label text then wraps inside the pill. */
-.maybe-try .suggestion-chip {
-  min-width: 0;
-  max-width: 100%;
-}
-
 /* ---------- Steering notes (phase 15) ---------- */
 /* "Tune" button in the meta row of every completed brain bubble: ghost
    pill, ≥44px, right-aligned after the source chips. ink-soft on surface
@@ -1230,6 +1222,21 @@ details.thinking .thinking-text ul { margin: 0 0 0.5rem; }
   margin: 0;
   padding: 0;
 }
+/* The shared chip pill — both chip rows (the onboarding row in the
+   empty state and the "Maybe try" row under a deflected bubble) reuse
+   it. Phase 104 (owner 2026-09-12, A1): a chip is ONE line at every
+   viewport width — `white-space: nowrap` stops a 400-char question
+   from wrapping the pill into a multi-line "chonk"; `overflow: hidden`
+   zeroes the flex item's automatic minimum size (min-width:auto would
+   pin the item to the full text width), so `max-width: 100%` binds and
+   `text-overflow: ellipsis` clips the text at the row edge — in the
+   desktop wrap row 100% is the chat column, in the ≤640px row
+   (nowrap + overflow-x: auto) 100% is the VISIBLE width and the row
+   scrolls. That clipping is the phase-07 overflow fix the old
+   "Maybe try" chip override used to carry (min-width:0 + max-width:
+   100%) — now fully subsumed here and deleted, provenance folded into
+   this comment so the history lives with the contract. The full text
+   stays one hover away (the title tooltip, phase 104 task 02). */
 .suggestion-chip {
   font: inherit;
   font-size: 0.92rem;
@@ -1242,6 +1249,11 @@ details.thinking .thinking-text ul { margin: 0 0 0.5rem; }
   min-height: 44px;
   cursor: pointer;
   transition: background 0.15s ease, transform 0.05s ease;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  max-width: 100%;
+  min-width: 0;
 }
 .suggestion-chip:hover { background: var(--brand-soft); }
 .suggestion-chip:active { transform: scale(0.98); }
@@ -1321,6 +1333,17 @@ details.thinking .thinking-text ul { margin: 0 0 0.5rem; }
 #view-chat:not(.chat-booted) .composer {
   position: static;
 }
+/* Phase 104 (owner 2026-09-12, A4): the question-length counter —
+   right-aligned above the composer, a child of the .chat-bottom sticky
+   unit (between the actions row and the form), hidden until 80% of the
+   4,000-char cap (app.js updateCharCount). It sits on the APP
+   background behind the transparent .chat-bottom unit, so both pairings
+   are verified against --bg: --ink-soft on --bg = 8.6:1 (≥4.5:1, WCAG
+   AA) and the .is-max state's --err-ink on --bg = 10.4:1 (AA). The
+   .is-max state ALSO changes the copy ("— character limit") — text +
+   color, never color alone (B3). */
+.char-count { margin: 0; text-align: right; font-size: 0.75rem; line-height: 1.2; color: var(--ink-soft); }
+.char-count.is-max { color: var(--err-ink); }
 .composer {
   display: flex;
   align-items: flex-end;