[bug] Koreader Sync doesn't seem to sync progress across different formats of the same ebook

[jetpacktuxedo]

Describe the bug
As the title says, most of my books have both an epub and a kepub (I have a kobo device), and nothing seems to allow these to sync to one another.

To Reproduce

1. Use two devices to download two different formats of the same book
2. Flip a bit into the book on one device
3. Push progress
4. Switch to the other device using the different format
5. Pull progress
6. Observe that nothing is pulled

Expected behavior
CWA clearly understands the progress, as it is displayed in the UI as KOReader Progress and that updates correctly when both devices push... but when they go to pull it seems to see the two formats as separate books.

Screenshots
See below

Configuration(please complete the following information):

• OS: docker on a debian host
• Hardware: koreader on android with cwa kosync plugin, xteink x4 running crosspoint-reader with their native kosync plugin
• Version 4.0.6

Additional context
Pull progress from other devices now on koreader on android always returns Latest progress is coming from this device
This always results in only the following two log lines:

[2026-03-17 11:50:10,899]  INFO {cps.progress_syncing.protocols.kosync:202} User authenticated successfully: <username>
[2026-03-17 11:50:10,908] DEBUG {cps.progress_syncing.protocols.kosync:289} Found book match: Silver Nitrate (ID 520, format EPUB, checksum vkoreader)

Push progress from this device now gets me these logs:

[2026-03-17 11:52:11,071]  INFO {cps.progress_syncing.protocols.kosync:202} User authenticated successfully: <username>
[2026-03-17 11:52:11,072] DEBUG {cps.progress_syncing.protocols.kosync:680} Updated kosync progress for user 3, document 287e86ec900ed4386a90b989ad2a7b32
[2026-03-17 11:52:11,154]  INFO {cps.progress_syncing.protocols.kosync:699} Saved kosync progress: user=3, document=287e86ec900ed4386a90b989ad2a7b32, prog
ress=0.84%
[2026-03-17 11:52:11,156] DEBUG {cps.progress_syncing.protocols.kosync:289} Found book match: Silver Nitrate (ID 520, format EPUB, checksum vkoreader)
[2026-03-17 11:52:11,156] DEBUG {cps.progress_syncing.protocols.kosync:363} update_book_read_status: user 3, book 520, percentage 0.84% -> status 2
[2026-03-17 11:52:11,159] DEBUG {cps.progress_syncing.protocols.kosync:375} Found existing ReadBook: old_status=2, new_status=2
[2026-03-17 11:52:11,159] DEBUG {cps.progress_syncing.protocols.kosync:390} ReadBook status unchanged: 2
[2026-03-17 11:52:11,180]  INFO {cps.progress_syncing.protocols.kosync:722} Updated ReadBook status: user=3, book=520 (Silver Nitrate), status based on 0.
8%

and updates the progress in CWA:

Sync from the xteink x4 (where I inadvertently pulled the kepub instead of epub) loosely works in that it finds progress, but only the progress that it uploaded last:

The logs for pushing current progress look like this:

[2026-03-17 11:58:02,668]  INFO {cps.progress_syncing.protocols.kosync:202} User authenticated successfully: <username>
[2026-03-17 11:58:02,669] DEBUG {cps.progress_syncing.protocols.kosync:680} Updated kosync progress for user 3, document 7352a57ff5c7928ef3c08817e86904cb
[2026-03-17 11:58:02,681]  INFO {cps.progress_syncing.protocols.kosync:699} Saved kosync progress: user=3, document=7352a57ff5c7928ef3c08817e86904cb, progress=33.81%
[2026-03-17 11:58:02,682] DEBUG {cps.progress_syncing.protocols.kosync:289} Found book match: Silver Nitrate (ID 520, format KEPUB, checksum vkoreader)   [2026-03-17 11:58:02,682] DEBUG {cps.progress_syncing.protocols.kosync:363} update_book_read_status: user 3, book 520, percentage 33.81% -> status 2
[2026-03-17 11:58:02,683] DEBUG {cps.progress_syncing.protocols.kosync:375} Found existing ReadBook: old_status=2, new_status=2
[2026-03-17 11:58:02,683] DEBUG {cps.progress_syncing.protocols.kosync:390} ReadBook status unchanged: 2
[2026-03-17 11:58:02,692]  INFO {cps.progress_syncing.protocols.kosync:722} Updated ReadBook status: user=3, book=520 (Silver Nitrate), status based on 33.8%

and that updates the progress in CWA as well:

but neither device can see progress uploaded by the other, seemingly because the hashes don't match because of the different formats (epub vs kepub).

[jjgara]

@jetpacktuxedo having similar issue but unable to leverage CrossPoint native plugin -- were you able to authenticate to your CWA server within Crosspoint?

[jetpacktuxedo]

Yeah crosspoint made some auth changes in their kosync module recently specifically to support sync to calibre:
crosspoint-reader/crosspoint-reader#594

Should be in the 1.0.0 firmware but I've only tested on 1.1.1

[jjgara]

Hmm interesting, I’m on 1.1.1 but couldn’t get the sync to work using my CWA server IP while on my LAN. I keep getting auth issues. I don’t want to clutter this issue with unrelated but do you mind sharing (here or elsewhere) how you got this to work?

[jetpacktuxedo]

I wonder if you're having SSL issues or something maybe? Mine is set up using a hostname and https which is the only thing I can think of that might be different about my setup. Maybe you can disable SSL validation? Or run DNS in a our network to point to it?

[new-usemame]

This is the cross-format kosync bug — your epub and kepub are the same Calibre book but produce different file checksums, so each format gets its own KOSyncProgress record and the two never converge. Pushing from device A under checksum-A leaves the record for checksum-B (the other device) untouched.

Fixed in Calibre-Web-NextGen — community-maintained CWA build. v4.0.29 at dad33813 (port of @SethMilliken's #1225) looks up the calibre book_id first and stores progress under that, so all formats / checksums for the same book share one record. Cross-device progress stays in sync.

Drop-in image: ghcr.io/new-usemame/calibre-web-nextgen:v4.0.29. Existing per-checksum records won't auto-merge, but the next progress push from any device will start writing under the book_id and pulls from the other format will find it. Fork tracker: https://github.com/new-usemame/Calibre-Web-NextGen/issues.