phase: 114_embed_question_length

All verification passes complete — the phase was already fully implemented in the working tree, and every gate is green. No defects found; no code changes were needed.

**Final verification pass — Phase 114 (embed question length):**
- Verified truncation: `chat.py:459` embeds `request.message[:settings.embed_question_max_chars]` (default 1200, `BOR_EMBED_QUESTION_MAX_CHARS`, `>0` validator); full question still reaches the LLM prompt/log.
- Verified error mapping: `EmbeddingInputTooLargeError(EmbeddingError)` (byte-identical message) caught **before** `EmbeddingError` → no retry, terminal frame `detail="Question too long — trim it and re-ask."` + reachability-fine hint; `ChatErrorEvent.hint` additive.
- Verified frontend chain: frame `hint` → `err.hint` → `setUiState(error, …, {hint})` → `showErrorBanner(…, {retryable: true})` — hint replaces default `ERROR_HINT`, phase-111 `#banner-retry` button revealed. 4,000-char clamp untouched (A2).
- `uv run pytest tests/unit/test_embed_question_length.py -v --no-cov` → 21 passed
- `uv run pytest tests/e2e/test_embed_question_length.py -v --no-cov` (isolation, DB up) → 1 passed (4,000-char question → done, no banner)
- Regression: `test_llm_retry.py` 4 passed · `test_oneshot_llm_retry.py` 2 passed · `test_chip_sizing_question_cap.py` 6 passed
- `uv run pytest --cov=app --cov-report=term-missing` → 2444 passed, TOTAL **99%** (>90% gate)
- `uv run ruff check .` → All checks passed; `uv run pyright` → 0 errors, 0 warnings

**Completion criteria:** (1) 4,000-char question embeds prefix + full prompt ✅ · (2) too-large → accurate frame + hint + Retry button ✅ · (3) reachability failure byte-identical (retries + old copy) ✅ · (4) all gates green ✅ · (5) commit/phase-move → left to the harness per instructions (no `git add`/`commit` run).
**Deviations:** none. **Next pending phase:** `115_doc_draft_discard`.

frontend/assets/app.js

@@ -1251,7 +1251,7 @@ document.addEventListener("visibilitychange", () => {
  * turn is in flight (click or Enter aborts it). It is never disabled
  * anymore, and the spinner never shows: the "Stop" label + the .is-stop
  * treatment carry the in-flight state. */
-export function setUiState(state, errorDetail = "") {
+export function setUiState(state, errorDetail = "", opts = {}) {
   uiState = state;
   stopThinkingClock();
   clearTurnTimeout(); // the guard only owns the pre-token window
@@ -1278,7 +1278,11 @@ export function setUiState(state, errorDetail = "") {
   } else {
     removeTyping();
   }
-  if (state === UI_STATE.error) showErrorBanner(errorDetail, { retryable: true });
+  // Phase 114 (TODO L6): turn-error opts (the SSE error frame's optional
+  // hint) merge into the banner call — the frame's hint replaces the
+  // default reachability hint when present (showErrorBanner's opts.hint).
+  if (state === UI_STATE.error)
+    showErrorBanner(errorDetail, { retryable: true, ...opts });
 }
 
 /* Phase 104 (owner 2026-09-12, A3/A4): the visible question-length cap.
@@ -2135,7 +2139,12 @@ function showErrorBanner(detail, opts = {}) {
   banner.hidden = false;
   banner.classList.add("is-error");
   banner.setAttribute("role", "alert");
-  bannerText.textContent = detail ? `${detail} ${ERROR_HINT}` : ERROR_HINT;
+  // Phase 114 (TODO L6): a frame-carried hint (the "question too long"
+  // case — reachability is fine, only the length is the problem) replaces
+  // the default reachability hint when present.
+  bannerText.textContent = detail
+    ? `${detail} ${opts.hint ?? ERROR_HINT}`
+    : (opts.hint ?? ERROR_HINT);
   // Phase 111 (task 01): reveal the banner Retry button only for failed
   // chat turns (opts.retryable) AND when a retryable bubble exists.
   if (opts.retryable) {
@@ -2558,7 +2567,12 @@ async function runTurn(text, { reask = false } = {}) {
           }
         }
       } else if (ev.type === "error") {
-        throw new Error(ev.detail || "Something went wrong on my side.");
+        // Phase 114 (TODO L6): carry the frame's optional hint (the
+        // "question too long" frame has one) through the throw — the
+        // banner shows it in place of the default reachability hint.
+        const err = new Error(ev.detail || "Something went wrong on my side.");
+        err.hint = ev.hint;
+        throw err;
       }
     });
     // Stream-drop guard (phase 17): frames arrived but no `done` event —
@@ -2619,7 +2633,10 @@ async function runTurn(text, { reask = false } = {}) {
         err instanceof Error && err.message
           ? err.message
           : "Something went wrong on my side.";
-      setUiState(UI_STATE.error, detail);
+      // Phase 114 (TODO L6): the SSE error frame's optional hint flows to
+      // the banner (setUiState → showErrorBanner's opts.hint); the
+      // phase-111 Retry button rides along on the same turn-error path.
+      setUiState(UI_STATE.error, detail, err instanceof Error ? { hint: err.hint } : {});
     }
   } finally {
     // done | error | stop → idle: always settle, always focus back.