Sync

Every device holds a full copy of your boards and reads and writes it directly. The UI doesn't wait on the network.

Sync runs behind that copy, reconciling it with the server. With no server configured, or while signed out, sync doesn't run.

Two channels

Sync is two independent engines:

• The dashboard list, your boards and their metadata. Account-level, so it is always active.
• The board channel, the columns and cards of the open board, plus any board you are watching in a cross-board view, plus any board holding edits that haven't reached the server yet.

One reconcile

Each pass, per board:

1. Read the stored cursor for that board.
2. Collect the locally-changed records for it.
3. Push changes with cursor.
4. The server applies each change, then answers with everything changed past the cursor plus a new cursor.
5. Only once that answer arrives are the pushed records dropped from the dirty queue.
6. Apply the returned changes locally and store the new cursor.

The cursor is not a timestamp. The server keeps a counter per board, bumped once per accepted write and stamped on the row, and a pull is "every row stamped higher than what you last saw".

Conflicts

Card body: line by line. A push carries the body the device last synced, and the server merges the pushed and stored bodies against it. When merge fails, a banner appears with Keep mine and Use theirs buttons to clear it.

Everything else: last-writer-wins per field on a hybrid logical clock.

Cadence

While the app is in front of you it reconciles periodically, and immediately when you open a board, sign in, or the network comes back. Backgrounded, the poll stops.

A failed push leaves its records queued and is retried on the next tick.

Deletes

Deleting anything writes a tombstone. Tombstones are kept for 14 days.