Lean Transfer

Handoff written to: /tmp/handoff-20250308-1612.md

# Session handoff

## Session log path
`/workspace/project/.logs/session-20250308.jsonl`

## Scope
Migrate the billing webhook worker from a single process to a queue-backed worker.

## Status
The event schema is finalized. The retry policy remains undecided. The existing webhook endpoint will stay available during migration.

## Evidence
- Event schema: `docs/events.md` (provided as finalized in the session).
- Integration test fixture: `tests/fixtures/invoice-paid.json`.
- No deployment or queue implementation was reported as complete.

## Decisions
- Keep the existing endpoint during migration.

## Open questions
- What retry schedule and maximum attempt count should the queue use?
- What is the cutover and rollback procedure?

## Next actions
1. Decide and document the retry policy.
2. Add a queue-worker test using `tests/fixtures/invoice-paid.json`.
3. Define cutover and rollback checks before deployment.

Next steps

Start the next session by reviewing the two referenced files and resolving the retry policy before changing worker behavior.