README.md

@@ -779,9 +779,9 @@ A running backup loses its lock when someone removes `backup.lock`, or when
 another backup takes it over because the running one left it untouched for 10
 seconds, as a stopped or stalled process does. The backup finds this out the
 next time it goes to touch the lock, which it does every 5 seconds, and then
-stops before it starts another file. The original it is downloading at that
+stops before it starts another file. The originals it is downloading at that
-moment is still stored. It leaves `failures.json` and `backup.lock` as they are,
+moment are still stored. It leaves `failures.json` and `backup.lock` as they
-since another backup may be using them. `quak backup` prints
+are, since another backup may be using them. `quak backup` prints
 `quak: lost the lock on <dir>: <reason>` as one line and exits 1, and
 `lib.backup()` rejects with `lost the lock on <dir>: <reason>`.
 

TODO.md

@@ -32,7 +32,8 @@ declares one.
   the work for one original, its `--verify` hashing included, so no more
   originals than that are open at once. `BackupLibrary` says the limit as
   `contentConcurrency`. A test holds each download at the fake Ente server to
-  count those in flight.
+  count those in flight. Each worker checks the backup's lock before it takes
+  the next file, so once the lock is lost no further original starts.
 
 - 2026-10-14: Next Step said the cache design, issue 36, waits on sneak's
   review, though that issue closed on 2026-10-03 (issue 194). It now names the

src/backup.ts

@@ -730,13 +730,17 @@ const runLockedBackup = async (
     // Up to the content pool's limit of originals are worked on at once,
     // their `verify` hashing included, so however large the account is, no
     // more than that many are open. Each worker takes the next file from the
-    // iterator they all share until none is left. A worker that throws, as
+    // iterator they all share until none is left, and throws instead once the
-    // one does when `onProgress` throws, fails the backup only once every
+    // lock is lost. A worker that throws, as one also does when `onProgress`
-    // worker has stopped, so none writes into the backup after it has ended.
+    // throws, fails the backup only once every worker has stopped, so none
+    // writes into the backup after it has ended.
     if (includeOriginals) {
         const pending = distinct.values();
         const worker = async (): Promise<void> => {
-            for (const file of pending) await storeOriginal(file);
+            for (const file of pending) {
+                if (lock.lost) throw lock.lost;
+                await storeOriginal(file);
+            }
         };
         const workers = await Promise.allSettled(
             Array.from({ length: lib.contentConcurrency }, worker),