async-state-safety

name	async-state-safety
description	This skill should be used when the user asks to change "worker lifecycle", "cancellation", "retrigger behavior", "state machine", "delivery receipts", "timeouts", or "race conditions". Enforces explicit async/state invariants and targeted race-safe verification.

Async State Safety

Goal

Prevent race regressions in async and stateful paths.

Required Invariants

• Define valid terminal states before coding.
• Define allowed state transitions before coding.
• Keep terminal transitions idempotent.
• Ensure duplicate events cannot double-apply terminal effects.
• Ensure retries do not corrupt state.

Race Checklist

• Cancellation racing completion
• Timeout racing completion
• Retry racing ack/receipt update
• Concurrent updates to the same worker/channel record
• Missing-handle and stale-handle behavior

Implementation Checklist

• Add or update transition guards.
• Keep error handling explicit and structured.
• Preserve status/event emission on all terminal branches.
• Document why each race path converges safely.

Verification Checklist

• Run targeted tests for each touched race path.
• Add at least one negative-path test for terminal convergence.
• Add at least one idempotency test where applicable.
• Run broad gate checks after targeted checks pass.

Handoff Requirements

• Terminal states and transition matrix
• Race windows analyzed
• Targeted commands and outcomes
• Residual risks and follow-up tests