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`.

app/rag/llm.py

@@ -43,6 +43,21 @@ class EmbeddingError(RuntimeError):
     """The embeddings endpoint failed (network, HTTP, or malformed reply)."""
 
 
+class EmbeddingInputTooLargeError(EmbeddingError):
+    """A single text exceeded the endpoint's per-request input token cap
+    (phase 114, TODO L6).
+
+    The endpoint REACHED and answered — this is a deterministic input-
+    SIZE failure, not a reachability problem: retrying the same input is
+    guaranteed to repeat (locked A3), so the chat endpoint catches this
+    BEFORE :class:`EmbeddingError` and settles with the accurate
+    "question too long" terminal error (no phase-67 retry frames). The
+    importer keeps catching the parent :class:`EmbeddingError` — this
+    subclass is a drop-in there and its message text is byte-identical
+    to the pre-phase import-oriented copy.
+    """
+
+
 class EmbeddingDimensionError(EmbeddingError):
     """Embedding dimension != BOR_EMBEDDING_DIM — import must fail loudly."""
 
@@ -278,7 +293,13 @@ class LLMClient:
             return await self._post_embeddings(chunk)
         except _TooLarge:
             if len(chunk) == 1:
-                raise EmbeddingError(
+                # Phase 114 (TODO L6): a single text over the cap is a
+                # deterministic input-size failure (never reachability) —
+                # the subclass lets the chat endpoint map it to the
+                # accurate "question too long" error and skip the retry
+                # loop (locked A3). The message text stays byte-identical:
+                # the importer catches the parent EmbeddingError.
+                raise EmbeddingInputTooLargeError(
                     f"a single {len(chunk[0])}-char chunk exceeded the endpoint's "
                     "per-request input token cap — lower BOR_CHUNK_TARGET_CHARS "
                     "and re-import"