- With Preferences > File Handling > Enable Background Save / Export on, File >
Save, Save As, Save a Copy and exports encode and write a snapshot of the
document on a worker thread; the call returns at once ({path, background}).
- The status bar shows a spinner and what is being written; ui.inspect lists
the running jobs under `background`.
- The document takes the path and counts as saved as of the snapshot once the
file is written: edits made meanwhile keep it modified.
- Quit and Close wait for running saves; the Save Changes dialog saves at once.
- The host gives a thread-safe writer (Services::write_shared, atomic on the
desktop); without one (web, tests) everything runs at once as before.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>