Recover when a reconnect cursor is older than retained history
A laptop wakes after the room’s replay window has expired. The gateway returns recent events after the old cursor, leaving an invisible gap in the task state.
- Focused work estimate
- 2h 45m + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Replay protocols · Snapshot consistency · Recovery
Estimated field mix
- Real-time systems60%
- Distributed systems40%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
Review it, then add it to your workspace.
The board opens an editable draft; nothing is saved until you confirm it. Sign-in and workspace permissions apply, and Demo boards remain ephemeral.
Project context
The fictional Harbor operations team coordinates synthetic incidents in a shared room. Engineers post status notes and claim response tasks while connections come and go. Scope is one application gateway, a durable room event store, and fixture clients; alert paging and external chat delivery are excluded.
Setup prerequisites
- Room membership and command contracts
- Synthetic incident events and a controllable transport harness
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- An expired cursor receives an explicit resync-required response.
- The client replaces state from a room-scoped snapshot and resumes after its exact sequence boundary.
- Snapshot and post-snapshot events cannot combine data from different rooms or snapshot revisions.
Implementation constraints
- Keep the prior timeline visibly stale until the replacement state is validated.
Verification to include
- Resume a retained cursor and confirm ordinary incremental replay.
- Use an expired cursor and deliver a live event during snapshot loading; apply it once after the snapshot boundary, or reject mismatched room data.
Deliverables
- Snapshot/replay recovery protocol and expired-cursor tests
Rollout and recovery
Pilot with a short synthetic retention window; disable writes during unresolved resync and retain safe read-only context.
Value of the work
For the engineer: Practice event identity, ordering, replay, authorization, and bounded backpressure in one understandable system.
For the team: Inspect how an engineer keeps collaborative state trustworthy during failures without relying on optimistic success messages.
Evidence boundaries
Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.
Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.