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+# AGENTS.md
+
+Orientation for AI agents working in this repository. This file is a **router**, not a spec:
+it points at canonical authority and flags the traps that are expensive to discover by trial.
+Where this file and `docs/*` disagree, `docs/*` wins.
+
+## What This Is
+
+A document transcription system that preserves durable archival records (Documents, Sources,
+People) and executes page transcription asynchronously through vision/LLM providers. Its
+defining constraint is **evidence**: every machine attempt is recorded append-only with
+request/response provenance. Features that would lose, mutate, or obscure that history are
+wrong regardless of how convenient they are.
+
+Stack: Python 3.12+ · FastAPI + NiceGUI · SQLModel/SQLAlchemy (SQLite-first, PostgreSQL-
+compatible) · Pydantic V2 · asyncio worker · OpenRouter adapter.
+
+## Commands
+
+This is a `uv` project. **Nothing is on `PATH`** — `ruff`, `ty`, and `pytest` all require
+`uv run`. Bare invocations fail with command-not-found.
+
+```bash
+uv run ruff check .                  # lint (blocking in pre-commit)
+uv run ruff format --check .         # format (blocking in pre-commit)
+uv run ty check                      # types (blocking in pre-commit)
+uv run pytest -q -m "not external"   # default verification run
+```
+
+`external` marks tests that hit live services; always exclude it unless explicitly asked.
+All four commands are expected to pass clean — there is no tolerated baseline of failures.
+If `ty` reports something, fix it or suppress it inline *with a rationale comment*; a bare
+`ignore` will not survive review.
+
+## Authority Order
+
+Resolve every question in this order, and stop at the first that answers it:
+
+1. **`docs/*`** — canonical. Start at [`docs/index.md`](docs/index.md), which defines the
+   reading order. `docs/invariant/*` holds cross-version rules that outlive any release.
+2. **`.github/instructions/*.md`** — active steering, auto-attached when you edit matching
+   paths. Covers services, UI, error handling, and documentation sync.
+3. **`.github/skills/*`** — periodic audit procedures (code review, provenance, test
+   effectiveness).
+4. **`tests/`** — deterministic enforcement. A guard test is the ground truth for whatever
+   rule it encodes.
+
+`docs/reviews/**` is **not** canonical. Those are dated, opinionated snapshots that were
+accurate when written and may since have been fixed, superseded, or found wrong.
+
+## Layout
+
+| Path | Role |
+| :--- | :--- |
+| `src/transcription/ui/**`, `api/**` | Interface. No direct persistence access. |
+| `src/transcription/services/**` | Domain logic and transaction ownership. |
+| `src/transcription/db/**` | Models and persistence. |
+| `src/transcription/providers/**` | Provider adapters; provider details stop here. |
+| `src/transcription/worker.py` | Asyncio worker loop. |
+| `tests/` | Includes boundary/contract guards, not just behavior tests. |
+
+## Enforced Boundaries
+
+These are not conventions — a test fails if you break them:
+
+- **No service-to-service imports** (`test_service_boundaries.py`). Compose in the caller.
+- **No persistence access from pages/components** (`test_ui_boundaries.py`, allowlist-based).
+- **No hand-rolled error notifications in UI** — use the shared error presenter.
+- **No stringly-typed status literals** — use the enums (`test_model_contract_guards.py`).
+- **Attempt history is append-only** (`test_v42_evidence.py`).
+- **`docs/schema.md` stays field-accurate** with `db/models.py`.
+- **Orphans are tracked, not tolerated** — `test_orphan_sweep.py` records each retained
+  orphan with rationale in `KNOWN_ORPHANS`.
+
+## Traps
+
+Non-obvious things that have already caused real bugs here:
+
+- **`AppError.message` vs `AppError.detail`.** `message` is user/API-facing and must stay
+  generic — never put exception text or filesystem paths in it. `detail` is internal-only and
+  is what reaches logs and `ExecutionAttempt.error_detail`. Putting root-cause data in
+  `message` leaks; removing it from `detail` silently degrades provenance. See
+  `docs/error_handling.md`.
+- **Two competing atomicity invariants in `services/workflows.py`.** Intermediate pages must
+  commit individually (durability across a long multi-page job); the *final* page must commit
+  atomically with the terminal job status. Collapsing the batch into one transaction satisfies
+  the second and destroys the first. Both are guarded — `test_workflows_reliability.py` and
+  `tests/integration/test_pipeline_atomicity.py`.
+- **Shared symbols have more consumers than the obvious one.** Before changing a model field,
+  exception attribute, or helper return value, grep for every consumer including tests.
+  Evidence and logging paths frequently read the same fields the UI does.
+- **Import style:** ruff `isort` runs with `force-single-line = true`. One import per line.
+- **Latent defects have ordering constraints.** Some code is unreachable only because of a
+  current setting or single-instance deployment. Fix it *before* the change that unblocks it,
+  not after.
+
+## Change Protocol
+
+- **Write the failing test first** for behavioral fixes, and confirm it actually fails for the
+  reason you think. Several bugs here were subtle enough that a test written afterward would
+  have passed against the broken code.
+- **Update docs in the same change** when you alter a contract, behavior, or scope — see
+  `.github/instructions/documentation-sync.instructions.md`.
+- **Do not commit unless asked.** Making a requested change is not consent to commit it.
+- **Do not push or open PRs on your own initiative.**
+- **Scope discipline:** fix what was asked plus what your change genuinely breaks. Pre-existing
+  unrelated issues are a separate conversation.