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 except a page in a Firefox private window) 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