transcription/docs/mvp/mvp-step7.md

Step 7: Error Handling Standardization and Operational Visibility

Objective

Apply the canonical error policy from docs/error_handling.md to the MVP implementation so failures are:

• consistently classified
• visibly surfaced in the GUI
• paired with suggested corrective actions
• traceable through logs via error reference IDs
• validated through deterministic tests after each phase

This step extends MVP hardening by converting current ad hoc exception behavior into a stable cross-layer contract.

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Scope

In scope

• Introduce a shared application error contract and taxonomy implementation
• Normalize service/provider exceptions into taxonomy categories
• Improve GUI error visibility and suggested-action UX
• Standardize worker failure persistence and logging context
• Add API error-envelope policy hooks for current/future endpoints
• Add targeted tests and phase-level/full-suite validation gates

Out of scope

• Major architecture rewrites (distributed queue, multi-service decomposition)
• Post-MVP feature expansion unrelated to error handling
• Full observability platform rollout (tracing backends, APM)

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Policy Source of Truth

• Canonical policy document: docs/error_handling.md
• If implementation and policy diverge, policy is authoritative and code/tests must be updated.

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Planned Deliverables

Runtime code

• src/transcription/errors.py (new shared contract module)
• src/transcription/ui/error_presenter.py (new UI error rendering helper)
• Updates to:
  • src/transcription/services/upload.py
  • src/transcription/services/transcription.py
  • src/transcription/providers/openrouter.py
  • src/transcription/worker.py
  • src/transcription/ui/upload_page.py
  • src/transcription/ui/jobs_page.py
  • src/transcription/api/* (as needed for envelope/handlers)

Tests

• tests/test_errors.py (new shared error contract tests)
• updates/additions in:
  • tests/services/test_upload.py
  • tests/services/test_transcription.py (add if missing)
  • tests/providers/test_openrouter.py
  • tests/services/test_worker.py
  • tests/ui/test_upload_page.py
  • tests/ui/test_jobs_page.py
  • tests/api/test_error_responses.py (new, if API handlers added)

Documentation

• Update docs/error_handling.md only if implementation reveals policy gaps
• Capture validation evidence in a Step 7 results artifact (docs/step7-results.md)

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Design and Policy Decisions

1. Stable taxonomy contract

   • Use policy categories as stable identifiers (validation_error, user_input_error, etc.).

2. Actionable UX is mandatory

   • User-visible errors must include a suggested course of action.

3. Traceability by default

   • Non-trivial errors include an error_id in both logs and user-facing output.

4. Safe surface / rich logs

   • UI/API show safe summaries; logs retain diagnostic detail and traceback.

5. Deterministic verification cadence

   • Targeted tests after each change batch, then phase-level regression gates.

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Implementation Plan + Checklist

Phase A — Baseline Validation and Gap Confirmation

• Run baseline tests before changes
• Record baseline outputs and any known flaky behavior
• Confirm current behavior against docs/error_handling.md requirements

Validation gate

• uv run pytest -m "not external" -q
• uv run pytest -q

Phase B — Shared Error Contract Foundation

• Add src/transcription/errors.py with:
  • stable category enum
  • base AppError (category/message/suggestion/error_id/retriable)
  • helpers for error-id generation and fallback classification
• Keep category names aligned with docs/error_handling.md

Tests

• Add tests/test_errors.py
  • category stability assertions
  • error_id creation behavior
  • fallback classification for unexpected exceptions

Validation gate

• uv run pytest tests/test_errors.py -q
• uv run pytest -m "not external" -q

Phase C — Service and Provider Normalization

• Refactor upload service exceptions to shared taxonomy
• Refactor transcription service exceptions to shared taxonomy
• Normalize provider adapter failures into deterministic categories
• Preserve causal chaining (raise ... from exc)

Tests

• Extend tests/services/test_upload.py:
  • empty payload category/suggestion
  • unsupported extension category/suggestion
  • persistence failure category mapping
• Add/extend tests/services/test_transcription.py:
  • missing/empty prompt behavior
  • unsupported file type behavior
  • provider failure mapping behavior
• Extend tests/providers/test_openrouter.py:
  • auth error mapping
  • malformed response mapping

Validation gate

• uv run pytest tests/services/test_upload.py -q
• uv run pytest tests/services/test_transcription.py -q
• uv run pytest tests/providers/test_openrouter.py -q
• uv run pytest -m "not external" -q

Phase D — GUI Visibility and Suggested Actions

• Add src/transcription/ui/error_presenter.py
• Update upload/jobs pages to use centralized error presentation
• Ensure GUI surfaces:
  • user-safe message
  • suggested action
  • error reference ID
  • optional technical details panel
• Replace raw str(exc) UX where policy requires safer messaging

Tests

• Extend tests/ui/test_upload_page.py for actionable error UX paths
• Extend tests/ui/test_jobs_page.py for refresh/detail error guidance
• Add tests/ui/test_error_presenter.py (optional but recommended)

Validation gate

• uv run pytest tests/ui/test_upload_page.py -q
• uv run pytest tests/ui/test_jobs_page.py -q
• uv run pytest -m "not external" -q

Phase E — Worker Failure Persistence and Logging Context

• Update worker failure handling to classify errors before persistence
• Ensure failed jobs persist actionable, structured error detail
• Add log context fields where available (error_id, category, operation, job_id)
• Ensure retry semantics are explicit and bounded (or clearly documented as deferred)

Tests

• Extend tests/services/test_worker.py:
  • missing document failure contract
  • provider/transcription failure contract
  • persisted error detail includes category/suggestion/error_id markers
• Validate integration failure flow in tests/integration/test_pipeline_flow.py

Validation gate

• uv run pytest tests/services/test_worker.py -q
• uv run pytest tests/integration/test_pipeline_flow.py -q
• uv run pytest -m "not external" -q

Phase F — API Error Envelope Alignment (Current + Future Routes)

• Add shared API error serialization utilities/handlers (as needed)
• Ensure API responses can include:
  • error_id
  • category
  • message
  • suggestion
  • timestamp
• Map categories to HTTP status guidance from docs/error_handling.md

Tests

• Add tests/api/test_error_responses.py (if handlers added)
• Keep tests/api/test_health.py passing

Validation gate

• uv run pytest tests/api/test_error_responses.py -q (if added)
• uv run pytest tests/api/test_health.py -q
• uv run pytest -m "not external" -q

Phase G — Final Regression and Documentation Closure

• Reconcile implementation details with docs/error_handling.md
• Update policy doc only where required by confirmed implementation learning
• Capture execution evidence in docs/step7-results.md

Final validation sequence (strict)

• uv run pytest --collect-only -q
• uv run pytest -m unit -q
• uv run pytest -m integration -q
• uv run pytest -m "not external" -q
• uv run pytest tests/integration/test_pipeline_flow.py -q
• uv run pytest tests/ui/test_upload_page.py -q
• uv run pytest tests/ui/test_jobs_page.py -q
• uv run pytest -q

Optional:

• uv run pytest -m external -q

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Guardrails

• Do not weaken user-facing clarity to expose raw internals.
• Do not introduce silent exception swallowing.
• Do not break category-name stability without policy update.
• Do not merge phase changes without passing that phase validation gate.
• Keep targeted tests fast and deterministic; isolate external-provider tests under external.

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Definition of Done (Step 7)

• Shared error taxonomy is implemented and used across MVP layers
• GUI error experiences are visible, actionable, and traceable
• Worker persists and logs failure context consistently
• API error contract path is aligned for current/future endpoints
• Phase-by-phase test gates pass
• Full suite remains green (uv run pytest -q)
• Step 7 results are documented with evidence

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PR Checklist (Step 7)

Implementation

• Added shared error contract module
• Updated service/provider/worker/UI error handling paths
• Added actionable GUI guidance for user-visible failures
• Added error reference IDs for traceability

Testing

• Added/updated tests per phase scope
• Ran targeted phase tests after each change batch
• Ran not external regression at each phase boundary
• Ran full suite before closeout

Documentation and Evidence

• docs/error_handling.md reviewed for alignment
• docs/step7-results.md includes executed command outputs
• Residual risks and deferred items explicitly recorded