Ship #72 — Fresh-on-return sync

What changed

The open app used to load your data once and only re-pull on a cold start or an offline→online flip. So a change made elsewhere — another device, or Claude editing your board via the MCP server — stayed invisible until you hit reload. Now the app refreshes itself the moment you return to it, and sibling tabs sync instantly.

Fresh-on-return: a debounced cloud pull on window focus / tab visibilitychange — skipped when offline or when you synced in the last few seconds (so your own edit isn't re-pulled).
Cross-tab: a same-origin BroadcastChannel lets one tab nudge its siblings to catch up from the shared local cache — no network round-trip.

Watch it: a second device catches up on focus

Two browsers signed into the same account, both viewing the same board (Sprint). Device A adds a task and it pushes to the cloud. Device B — never reloaded — pulls and shows the “Synced live ✅” card the instant its window regains focus. This is the headline cross-device scenario.

Device B’s board — the card appears the moment it regains focus.

Device B board — all columns empty — Before — every column empty, no card yet.

Device B board — one card in Backlog — After focus — “Synced live ✅” appears in Backlog.

Captured in a freshly-created throwaway board so the only thing that changes on screen is the one card. The board and every test fixture are deleted when the run finishes.

QA checklist

New behavior

Edit on device/tab B → switch back to the open app on A → the change appears without a reload.
Two tabs open → create/move something in tab A → tab B updates within ~1s, no reload.
Claude (MCP) creates a task while the app is open → click into the window → the task appears.

Regression watch

still works: normal editing persists and syncs; offline→online still pulls; outbox/retry unaffected.
still works: edit then immediately click away → no flicker/re-pull of your own change (recency guard).
still works: sign-out/sign-in → no duplicate listeners or stale data.

Confidence

15 unit tests on the sync engine (focus pull, visibility pull, focus+visibility coalesce, recency skip, offline skip, cross-tab match / wrong-user, teardown).
Full suite: 319 passing · typecheck · lint · format · build — all green.
CI on PR #72: checks + Cloudflare Pages — green.