---
id: specify-task-body-append-concurrency
name: Specify concurrency model for hub.task.addNote
status: completed
depends_on: []
scope: single
risk: high
impact: component
level: implementation
---

## Description

`hub.task.addNote` appends a timestamped note section to `body`. In a multi-agent system, read-modify-write is a race condition: Agent A reads body, Agent B reads body, both append, Agent A writes, Agent B overwrites A's addition.

The review recommends specifying: `hub.task.addNote` must use DB-level concatenation (`UPDATE tasks SET body = body || $note WHERE id = $taskId`), not a read-modify-write cycle. Or use optimistic locking with `updatedAt`.

## Acceptance Criteria

- [ ] `tasks.md` specifies the concurrency model for `hub.task.addNote` explicitly
- [ ] The recommended approach is DB-level concatenation: `UPDATE tasks SET body = body || $note WHERE id = $taskId`
- [ ] If optimistic locking is offered as an alternative, it is documented with the `updatedAt` check pattern
- [ ] The spec notes that the append-only approach (no read-modify-write) eliminates the race condition
- [ ] A note on `body` being nullable is addressed: `COALESCE(body, '') || $note`

## References

- docs/reviews/storage-architecture-review-2026-04-21.md#C08
- docs/architecture/storage/tasks.md:249-266

## Notes

> To be filled by implementation agent

## Summary

> To be filled on completion