Reject malformed room events before they reach the reducer
A gateway change sends a string sequence number and crashes every open room tab. Define a versioned event envelope with deliberate unknown-version behavior.
- Focused work estimate
- 1h 30m + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Schema validation · Protocol design · Untrusted input
Estimated field mix
- Real-time systems50%
- API design30%
- Security20%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
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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
No earlier ticket is required. Complete the project setup above.
Acceptance criteria
- The boundary validates version, room ID, event ID, sequence, type, and bounded payload.
- Malformed or unsupported events never enter the state reducer.
- Protocol errors expose a safe category and recovery action without echoing raw note content.
Implementation constraints
- Treat transport input as untrusted and impose a documented frame-size limit.
Verification to include
- Accept a valid status-note envelope and verify its typed reducer input.
- Send an oversized frame, invalid sequence, and unknown version; reject each without crashing or leaking raw payloads.
Deliverables
- Versioned event parser and invalid-envelope fixture suite
Rollout and recovery
Deploy readers that understand the new version before changing writers; pause the stream on unsupported contracts.
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.