---
id: T01
parent: S04
milestone: M004
provides: []
requires: []
affects: []
key_files: ["backend/models.py", "alembic/versions/002_technique_page_versions.py", "backend/pipeline/stages.py"]
key_decisions: ["Version snapshot is best-effort — INSERT failure logs ERROR but does not block page update", "source_quality enum stored as string value in snapshot for JSON serialization", "Composite unique index on (technique_page_id, version_number) enforces ordering at DB level"]
patterns_established: []
drill_down_paths: []
observability_surfaces: []
duration: ""
verification_result: "All four verification checks pass: model import OK, migration file exists, _capture_pipeline_metadata grep found, TechniquePageVersion grep found in stages.py. Additionally verified all 6 columns present on model, all 9 content fields in snapshot dict, and correct ordering of snapshot vs mutation in source."
completed_at: 2026-03-30T07:07:13.929Z
blocker_discovered: false
---

# T01: Added TechniquePageVersion model, Alembic migration 002, pipeline metadata capture, and pre-overwrite snapshot hook in stage 5 synthesis

> Added TechniquePageVersion model, Alembic migration 002, pipeline metadata capture, and pre-overwrite snapshot hook in stage 5 synthesis

## What Happened
---
id: T01
parent: S04
milestone: M004
key_files:
  - backend/models.py
  - alembic/versions/002_technique_page_versions.py
  - backend/pipeline/stages.py
key_decisions:
  - Version snapshot is best-effort — INSERT failure logs ERROR but does not block page update
  - source_quality enum stored as string value in snapshot for JSON serialization
  - Composite unique index on (technique_page_id, version_number) enforces ordering at DB level
duration: ""
verification_result: passed
completed_at: 2026-03-30T07:07:13.929Z
blocker_discovered: false
---

# T01: Added TechniquePageVersion model, Alembic migration 002, pipeline metadata capture, and pre-overwrite snapshot hook in stage 5 synthesis

**Added TechniquePageVersion model, Alembic migration 002, pipeline metadata capture, and pre-overwrite snapshot hook in stage 5 synthesis**

## What Happened

Added TechniquePageVersion model to backend/models.py with UUID PK, FK to technique_pages (CASCADE), version_number, content_snapshot (JSONB), pipeline_metadata (JSONB), and created_at. Added versions relationship on TechniquePage. Created Alembic migration 002 with composite unique index on (technique_page_id, version_number). Added _capture_pipeline_metadata() helper that hashes prompt files and collects model/modality config. Modified stage5_synthesis to snapshot all 9 content fields before attribute mutations, with best-effort error handling.

## Verification

All four verification checks pass: model import OK, migration file exists, _capture_pipeline_metadata grep found, TechniquePageVersion grep found in stages.py. Additionally verified all 6 columns present on model, all 9 content fields in snapshot dict, and correct ordering of snapshot vs mutation in source.

## Verification Evidence

| # | Command | Exit Code | Verdict | Duration |
|---|---------|-----------|---------|----------|
| 1 | `cd backend && python -c "from models import TechniquePageVersion; print('Model OK')"` | 0 | ✅ pass | 1000ms |
| 2 | `test -f alembic/versions/002_technique_page_versions.py` | 0 | ✅ pass | 100ms |
| 3 | `grep -q '_capture_pipeline_metadata' backend/pipeline/stages.py` | 0 | ✅ pass | 100ms |
| 4 | `grep -q 'TechniquePageVersion' backend/pipeline/stages.py` | 0 | ✅ pass | 100ms |


## Deviations

None.

## Known Issues

None.

## Files Created/Modified

- `backend/models.py`
- `alembic/versions/002_technique_page_versions.py`
- `backend/pipeline/stages.py`


## Deviations
None.

## Known Issues
None.
