Sync and safety.

Local first, cloud second

When you add a task on your Mac, it is written to the local SQLite file instantly. A background worker then sends the change to the Supabase cloud mirror. If the network is down, the change queues locally until it isn't.

Slot-level merge

If you edit the same month on your laptop and your phone, Cumulus merges by individual slot — one task, one objective, one journal field — rather than by the whole month. The slot with the latest edit time wins. You can't accidentally erase someone else's change by ticking a different box in the same view.

60-day deletion markers

When you delete a plan on one device, Cumulus doesn't just remove it; it leaves a marker that says 'this was deleted at this time.' Other devices read the marker and delete their copies too.

• Markers live for 60 days.
• Enough runway for a weekend-only device to catch up.
• After 60 days, the marker is cleaned up locally.

15-day grace dialog

If a device has been offline more than 15 days and still has unsynced local edits, Cumulus pauses and asks before it merges. You see a dialog with three choices:

• Pull from cloud — overwrite local with the cloud copy. Local edits since the last sync are lost.
• Push local — overwrite cloud with the local copy. Edits made on other devices since are lost.
• Later — close the dialog without syncing. Keep working offline.

The dialog only shows when both conditions are true: long offline and local changes still pending. On a device you open regularly, you'll never see it.

Backups are your underwrite

Everything above is designed to be safe. Backups are the belt and the suspenders. See Backups for how to roll back if something ever goes sideways.

Related

• Data safety brief — see /data-safety for the public summary.
• Backups page — snapshots, JSON export, restore.