[Bug] kobo-sync: bogus "Sync to last page read?" popup after device auto-sleep

[leahjessie]

Description
After reading on a Kobo device, it occasionally shows a "Return to last page read?" popup. Accepting it jumps to a previous reading position that is not actually behind where the user left off, no reading progress was lost.

A previous fix #3585 addressed related popup triggers (float/int mismatch and dropped fields in bookmark responses). This issue identifies behavior that persists after that fix.

To Reproduce

1. Open a book on a Kobo device synced to Calibre-Web and read to any position
2. Set the device down with the book open and let it auto-sleep from inactivity (do not press the sleep button - manual sleep appears to trigger a sync/update first)
3. Wait a few minutes
4. Wake the device with the book open - the popup may take a few seconds and does not appear on every attempt, but reproduces more reliably with auto-sleep

Hypothesis

• The /v1/library/<uuid>/state PUT handler saves the new reading position and advances priority_timestamp server-side, but the PUT response does not include the updated timestamp
• The device sends a PUT when saving position (turning pages, manually going to sleep), but sends a GET passively on wake or WiFi reconnect - without necessarily sending a PUT first
• The device's cached priority_timestamp is only updated from GET responses, not PUT responses - leaving it stale between the two events
• When the device wakes and sends a GET, the server returns a priority_timestamp the device has never been told about → popup

Proposed Fix
Include PriorityTimestamp in the PUT response UpdateResults so the device can update its cached value immediately, closing the window between PUT and the next GET.

I am testing this locally and will follow up with a PR if it holds up.

Environment

• OS: macOS (server-side issue, not OS-specific)
• Python version: 3.13
• Calibre-Web version: nightly
• Docker: None
• Kobo firmware: recent testing on 4.44.23552, but observed on earlier firmware before

[OzzieIsaacs]

Possibly fixed in the newest nightly

[leahjessie]

I've seen popup while running nightly. Proposal of including PriorityTimestamp in PUT /state response didn't fix issue or wasn't sufficient.

[leahjessie]

Cautiously optimistic #3607 is the fix. Been running locally for a few weeks and haven't seen a popup since.

Fix is to echo the Kobo's own timestamp back instead of generating one server-side, thus an apparent newer timestamp is never returned to device.

[new-usemame]

Worth trying Calibre-Web-NextGen — a CWA-derived community build (calibre-web plus the CWA continuation) that ships the 1fd6c50 HandleStateRequest fix (@hsttlrjeff) and the d8300288 Kobo OIDC overhaul (@mihneabulu). Both patches tighten the state-request shape that drives the "return to last page read?" popup, so it may resolve the after-auto-sleep variant you're seeing as well.

If it still pops up after switching, that's worth a thread on our tracker so we can confirm whether the auto-sleep-induced trigger needs a separate fix beyond #3585. Drop-in image: ghcr.io/new-usemame/calibre-web-nextgen:latest. Note the build also adds auto-ingest, kepubify, and KOReader sync on top of stock calibre-web. Fork tracker: https://github.com/new-usemame/Calibre-Web-NextGen/issues.