# Ver1 Step 2 Results: Error Handling & Reliability Hardening

## Summary

Step 2 implementation is complete for the planned reliability and error-handling hardening scope:

1. Worker retries are now explicit, bounded, and category-driven.
2. Error behavior is more consistent across worker/API/UI boundaries.
3. Logging now includes stronger boundary context in key failure paths.
4. Test coverage was expanded for retry policy and new reliability settings.

## Implemented Changes

### 1) Worker retry policy and terminal behavior

- Updated `src/transcription/models.py`:
  - Added `Job.retry_count` with default `0`.
- Updated `src/transcription/config.py`:
  - Added `worker_max_retries`.
  - Added `worker_retry_backoff_seconds`.
- Updated `src/transcription/worker.py`:
  - Added bounded retry decision path (`_should_retry`).
  - Added requeue behavior (`_requeue_for_retry`) for retriable errors.
  - Added deterministic terminal failure behavior (`_finalize_failed_job`).
  - Preserved transcript failure detail persistence (`error_id`, `category`, suggestion).

### 2) API fallback normalization hardening

- Updated `src/transcription/api/errors.py`:
  - Fallback handler now emits safe generic internal message for unhandled exceptions.
  - Added structured boundary logging fields including operation and exception type.

### 3) UI interaction reliability guard

- Updated `src/transcription/ui/upload_page.py`:
  - Added duplicate in-flight submission guard to prevent repeated upload handling while busy.

### 4) Observability/logging improvements

- Updated worker logs in `src/transcription/worker.py` to include operation and domain identifiers in key transitions:
  - pick
  - retry
  - transcribed
  - failed

## Test Coverage Added/Updated

- Updated `tests/test_models.py`:
  - Assert `retry_count` default.
- Updated `tests/test_config.py`:
  - Added worker retry settings default test.
- Updated `tests/services/test_worker.py`:
  - Added retriable requeue test.
  - Added retry-exhaustion terminal failure test.
  - Updated existing tests for settings-driven worker behavior.
- Existing API error tests remained green with fallback behavior updates:
  - `tests/api/test_error_responses.py`

## Verification Evidence

Executed and passing:

- `uv run pytest tests/services/test_worker.py tests/test_models.py tests/test_config.py tests/api/test_error_responses.py -q`
- `uv run pytest -q`

## Residual Risks / Follow-ups

1. Retry policy currently uses simple fixed backoff; richer strategy (exponential/jitter) can be added in later hardening.
2. Full cross-layer structured logging standardization can be expanded in Step 6 observability work.
3. A formal Step 2 error-path inventory artifact (`ver1-step2-audit.md`) is still recommended for governance completeness.

## Step 2 Exit Assessment

- Error taxonomy and envelope stability: **met**
- Bounded retry and terminal failure behavior: **met**
- Worker reliability controls: **met**
- UI interaction hardening for duplicate actions: **met**
- Test coverage expansion and full-suite regression safety: **met**

Step 2 is complete and ready to hand off to Ver1 Step 3.