---
id: ML-169.1
title: "Phase 3: Concurrent state change safety audit"
status: Done
assignee: []
created_date: "2026-05-08 08:59"
updated_date: "2026-05-19 08:50"
labels:
  - audit
  - ready
dependencies: []
references:
  - lib/music_library/worker/
  - lib/music_library/records.ex
  - lib/music_library_web/components/record_form.ex
modified_files:
  - >-
    docs/audits/phase3-concurrent-state-safety/doc-26 -
    Audit-Report-Concurrent-State-Change-Safety-Phase-3.md
parent_task_id: ML-169
priority: medium
ordinal: 4000
---

## Description

<!-- SECTION:DESCRIPTION:BEGIN -->

Audit whether background Oban worker record mutations are safely reflected in LiveView state without data corruption or stale UI.

Key risks to investigate:

1. Worker-broadcast consistency: do all record-modifying workers call Records.notify_update/1?
2. Form edit + background update race: editing in RecordForm modal while worker updates record
3. Double-update handling: two workers updating same record simultaneously
<!-- SECTION:DESCRIPTION:END -->

## Acceptance Criteria

<!-- AC:BEGIN -->

- [x] #1 Every record-modifying Oban worker audited for notify_update/1 call after success (RefreshCover, PopulateGenres, GenerateRecordEmbedding, RecordRefreshMusicBrainzData, ImportFromMusicbrainzRelease, ImportFromMusicbrainzReleaseGroup, all RecordAll\* batch workers)
- [x] #2 Workers that do NOT modify records confirmed as correctly NOT broadcasting (PruneAssets, ApplyScrobbleRules, all ArtistRefresh\*, etc.)
- [x] #3 Form edit + background update race evaluated: trace what happens when RecordForm holds stale @record assign while worker broadcasts {:update, record} to parent Show page
- [x] #4 Double-update race evaluated: confirm both handle_info calls apply safely (workers touch different fields, second wins)
- [x] #5 ArtistLive.Show confirmed as intentionally not handling {:update, record} (artist updates use ArtistLive.Form → {:saved, artist_info} path)
- [x] #6 Findings report written as a Backlog.md document with file:line references, severity ratings, and fix recommendations
<!-- AC:END -->

## Implementation Notes

<!-- SECTION:NOTES:BEGIN -->

Audit complete. Report written at docs/audits/phase3-concurrent-state-safety/doc-26.

Key findings:

- All 8 record-modifying workers correctly broadcast notify_update or broadcast_index_changed
- 18 non-record workers confirmed as correctly NOT broadcasting
- MEDIUM finding: form edit + background update race — handle_info({:update, record}) overwrites @record during :edit. Recommended fix: add live_action guard to both Show LiveViews.
- Double-update race is SAFE: Ecto changesets only UPDATE SET changed fields, SQLite serializes writes
- ArtistLive.Show confirmed intentionally not handling {:update, record}
<!-- SECTION:NOTES:END -->