What problem does it solve? Sync-related changes in this codebase (LWW stamps, SSE handlers, reset epochs, wake handoffs) have repeatedly caused production incidents like reverted run lifecycles, wiped run values, and stale data resurrection. This Skill gives an agent a concrete pre-ship checklist so every sync change is verified against the invariants that trace back to real incidents. ## Core Features & Use Cases - Change-to-invariant mapping: A quick-reference table maps the file or area you modified (e.g. PUT /sync/today, protectRunValues, buildSyncPayload) to the exact invariant sections that must be checked. - Eight invariant sections: Covers run-meta LWW stamps, SSE stamp source via overlayRunMetaStamps, ?today= client date scoping, the 10 MB body limit, fail-closed epoch/reset guards, empty-over-populated protection, sleeping-device wake handoff, and per-run auto-track claim ownership. - Focused validation commands: Provides the exact vitest invocations for the sync, reset, wake-guard, and blank-value regression suites, plus a copy-paste PR review checklist. - Use Case: After editing home.tsx sync handlers, run through the checklist to confirm SSE receive uses overlayRunMetaStamps, ?today= is threaded on every request, and the wake-handoff regression tests pass before merging. ## Quick Start Review my changes to routes/sync.ts and home.tsx against the sync invariant checklist and tell me which invariants I need to verify.
