---
id: T01
parent: S04
milestone: M014
provides: []
requires: []
affects: []
key_files: ["backend/pipeline/stages.py"]
key_decisions: ["Compose detection queries all matching pages and warns on multiple matches, uses first", "pg_insert with on_conflict_do_nothing for idempotent TechniquePageVideo inserts"]
patterns_established: []
drill_down_paths: []
observability_surfaces: []
duration: ""
verification_result: "PYTHONPATH=backend python import of _build_compose_user_prompt and _compose_into_existing succeeded. grep confirmed body_sections_format, TechniquePageVideo, and stage5_compose strings present in stages.py."
completed_at: 2026-04-03T01:29:17.901Z
blocker_discovered: false
---

# T01: Added _build_compose_user_prompt(), _compose_into_existing(), and compose-or-create branching to stage5_synthesis with body_sections_format='v2' and TechniquePageVideo tracking

> Added _build_compose_user_prompt(), _compose_into_existing(), and compose-or-create branching to stage5_synthesis with body_sections_format='v2' and TechniquePageVideo tracking

## What Happened
---
id: T01
parent: S04
milestone: M014
key_files:
  - backend/pipeline/stages.py
key_decisions:
  - Compose detection queries all matching pages and warns on multiple matches, uses first
  - pg_insert with on_conflict_do_nothing for idempotent TechniquePageVideo inserts
duration: ""
verification_result: passed
completed_at: 2026-04-03T01:29:17.902Z
blocker_discovered: false
---

# T01: Added _build_compose_user_prompt(), _compose_into_existing(), and compose-or-create branching to stage5_synthesis with body_sections_format='v2' and TechniquePageVideo tracking

**Added _build_compose_user_prompt(), _compose_into_existing(), and compose-or-create branching to stage5_synthesis with body_sections_format='v2' and TechniquePageVideo tracking**

## What Happened

Added two compose helper functions and wired compose-or-create detection into the stage5_synthesis per-category loop. When an existing technique page matches by creator_id + LOWER(topic_category), the compose path calls the LLM with stage5_compose.txt instead of standard synthesis. All pages now get body_sections_format='v2' and TechniquePageVideo rows tracking contributing videos via idempotent pg_insert with on_conflict_do_nothing.

## Verification

PYTHONPATH=backend python import of _build_compose_user_prompt and _compose_into_existing succeeded. grep confirmed body_sections_format, TechniquePageVideo, and stage5_compose strings present in stages.py.

## Verification Evidence

| # | Command | Exit Code | Verdict | Duration |
|---|---------|-----------|---------|----------|
| 1 | `PYTHONPATH=backend python -c "from pipeline.stages import _build_compose_user_prompt, _compose_into_existing; print('imports OK')"` | 0 | ✅ pass | 2000ms |
| 2 | `grep -q 'body_sections_format' backend/pipeline/stages.py` | 0 | ✅ pass | 100ms |
| 3 | `grep -q 'TechniquePageVideo' backend/pipeline/stages.py` | 0 | ✅ pass | 100ms |
| 4 | `grep -q 'stage5_compose' backend/pipeline/stages.py` | 0 | ✅ pass | 100ms |


## Deviations

Used default=str in json.dumps() for page serialization to handle UUID/datetime fields — not in plan but necessary for robustness.

## Known Issues

None.

## Files Created/Modified

- `backend/pipeline/stages.py`


## Deviations
Used default=str in json.dumps() for page serialization to handle UUID/datetime fields — not in plan but necessary for robustness.

## Known Issues
None.
