2026-06-29 01 — Scheduled Remote Conflict Detection

Status: Shipped Scope: Backend, frontend Settings UI, ops env, docs

What we set out to do

Resolve the "Dead Code — YouTubeSyncService.detectConflict()" backlog entry. Before this session, the method was fully implemented but never called; conflict handling as a user-facing flow was effectively broken:

Detection only happened on manual "Refresh from YouTube" per video.
Resolution either meant running a full channel refresh (clobbers every video's local fields) or re-pushing local (silently overwrites remote). Neither offered a per-video accept/reject choice and neither showed a diff.

Decision: wire detectConflict() up as a scheduled sweep AND build a proper per-video accept-remote path. Direction "push local" reuses the existing POST /videos/:id/sync.

Design decisions (locked in during the session)

Question	Decision
Granularity	Per-video accept/reject (v1). Field-level merge deferred.
Settings location	Per-team, with cadence global via env var
Skip already-conflicted videos in the sweep?	Yes — no point re-detecting an unresolved conflict
Add a `POST /videos/:id/force-local` endpoint?	No — reuse existing `POST /videos/:id/sync`
Scheduler mechanism	BullMQ repeatable job (no new dependency)
Selection strategy	Stalest-first per team, filtered by `lastSyncedAt < now - minAgeDays`, `remoteConflict = false`, `youtubeDeletedAt = null`

What changed

Backend

Schema — new migration 20260629000000_add_conflict_detection_settings:
- Team.conflictDetectionEnabled Boolean @default(false)
- Team.conflictDetectionBatchSize Int @default(50)
- Team.conflictDetectionMinAgeDays Int @default(7)
- Video.pendingRemoteSnapshot Json?
- Video.pendingRemoteDescription String?
YouTubeSyncService.detectConflict() (backend/src/modules/youtube-sync/youtube-sync.service.ts) — on hash mismatch now persists pendingRemoteSnapshot (mirrors youtubeSnapshot shape) and pendingRemoteDescription. On hash match with a stale flag, self-heals (clears flag + pending fields). No more dead code.
New queue CONFLICT_DETECTION in backend/src/queues/queues.constants.ts.
New processor backend/src/queues/processors/conflict-detection.processor.ts — iterates enabled teams, stalest-first selection, per-call quota guard, per-team batch cap. Logs summary. Stops the whole sweep on quota exhaustion.
New scheduler backend/src/queues/schedulers/conflict-detection.scheduler.ts — OnModuleInit registers a BullMQ repeatable driven by CONFLICT_DETECTION_CRON (default 0 3 * * *), gated by CONFLICT_DETECTION_ENABLED. Wipes stale repeatables on boot so config changes take effect.
Wired both into backend/src/worker.module.ts.
New endpoint POST /videos/:id/accept-remote (EDITOR role) in backend/src/modules/videos/videos.controller.ts + .service.ts. Zero YouTube API calls — promotes stored pendingRemoteSnapshot into live columns and youtubeSnapshot, sets renderedDescription = youtubeDescription = pendingRemoteDescription, recomputes lastSyncedHash, sets lastSyncedAt = now, clears pending + flag. Emits audit log entry action: 'accept-remote'.
Team settings — three new fields added to GET/PATCH /teams/:teamId/settings with bounds validation (batch 1–500, min-age ≥ 0).

Frontend

TeamSettings interface (frontend/src/lib/api.ts) extended with the three new fields.
New "Remote Conflict Detection" section on /settings: Enable toggle, "Videos per run" (number, 1–500), "Only check videos older than (days)" (number, ≥0). Admin-only edit. Own Save button (kept separate from the schedule section to avoid mixed-scope saves).

Ops / env

CONFLICT_DETECTION_ENABLED and CONFLICT_DETECTION_CRON added to:
- backend/.env (locally set to true / default cron)
- backend/.env.example (default false)
- infrastructure/.env.example
- infrastructure/docker-compose.yml worker service (uses :- defaults)

Documentation

Backlog entries removed from 06 - Backlog/01 - Technical Debt and Future Work.md:
- "Dead Code — YouTubeSyncService.detectConflict()"
- "Improvements Worth Considering — Automatic Remote Conflict Detection"
Docs brought back in sync (11 findings across 8 files identified by an audit agent, all applied):
- Rewrote the two aggressively-wrong sections (Gotchas remoteConflict Is Not Automatically Detected, Schema remoteConflict paragraph) which literally claimed the opposite of the new behavior.
- Filled content gaps in 04 - Database Schema, 05 - Queue System, 13 - Team Settings, 02 - Videos API, 09 - Teams API, 02 - Environment Variables, 05 - Deployment and Operations.
Vault gained a new 07 - Daily Notes/ section (this note is the first entry).

Verification

Backend tsc --noEmit clean after prisma generate.
Frontend tsc --noEmit clean for the touched files (settings/page.tsx, api.ts); pre-existing errors elsewhere untouched.
Migration file present but not yet applied on any prod DB — user ran prisma migrate locally.

Follow-ups worth flagging

UI for the conflict itself — the video editor should show a per-field diff between the current local state and pendingRemoteSnapshot when remoteConflict === true, with "Accept remote" and "Keep local" buttons. Backend is ready; frontend diff view doesn't exist yet.
Field-level merge — declined for v1; if requested later, the storage layer already supports it (fields are individually addressable in pendingRemoteSnapshot).
Multi-team frequency — if teams later want different cadences, frequency needs to move from env-var to a per-team column and the scheduler must manage a repeatable-per-team.

04 - Database Schema — new Team + Video columns
05 - Queue System — processor details, quota model
13 - Team Settings — per-team knobs, validation
02 - Videos API — accept-remote endpoint
04 - Gotchas — resolution options and self-heal
02 - Environment Variables — CONFLICT_DETECTION_*

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