The popup's saveState() and the background's updateState() each read the stored record, change it and write it back, and each was ordered only within its own context, so a write by one could land between the other's read and write and be lost. Both now hold the browser's lock (navigator.locks, shared by every page and the background) from the read to the write, through withLock() in src/shared/browserApi.js; the recovery screen's reset takes it too. The lock also orders a page's own saves, so both per-context queues are gone. The unit tests get a small lock from a Jest setup file. Model: opus-5-5