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I'm having trouble syncing. On the sync settings, it displays this:

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what is going on.

Update 1:
I was able to fix it by resetting remote data

Update 2: I seem to have the same problem again when I restart my computer (I do also have a lot of tabs open) I would love to see a solution I don't want to go though the same process of resetting my remote data setting a password and syncing again on my other devices every time I boot up my computer

Here is a comprehensive report on the issue
Vivaldi Sync Bug - Uploads Not Working After 8.2 Update

Started: September 13, 2026
Last updated: September 16, 2026

What's Going Wrong
My sync shows an error message after every restart:

"Upload: Conflict with another client's data occurred"

It works right after I reset everything, but then breaks again when I restart my computer.

Which devices are affected?
Device Version Problem
Windows Laptop 8.2.4133.52 Upload fails after restart
Steam Deck (Linux) 8.2.4133.52 Upload fails always
iPhone 8.2.4147.59 Upload fails always.
All three devices show the same problem.

What I've Tested
Test Result
Logging in with my username and password works on all devices
Entering the encryption password is working on all devices
"Sync is active" status shows green on all devices
Downloading data works
Uploading new bookmarks/tabs fails with a conflict error
So logging in works fine;the problem is only with sending new data to the server.

What triggers the error?
Right after reset: Upload works
After restarting the computer, the upload fails
Sleep mode instead of shutdown: No error
This means the problem happens when the browser tries to reconnect after closing completely.

Important Discovery
Sync worked before! I know this was working fine on my old version of Vivaldi. The problem started after I updated to version 8.2. This means something in the update broke it, rather than my account getting corrupted over time.

One other user is having Same Problem
That person is seeing the same error, I believe. So this isn't just me—it's a wider issue with version 8.2.

Current Workaround
Instead of shutting down my computer, I put it to sleep. This keeps the browser open, so it doesn't have to reconnect. It's not ideal, but it stops the error from appearing.

What I Need From Vivaldi Staff
Confirm you received my bug report (submitted September 13)
Let us know if you're looking into this
Tell us when a fix might be available
Summary
3 devices affected (Windows, Linux, iPhone)
All on Vivaldi version 8.2
Login works, but uploading new data fails
Started after the 8.2 update
Sleep mode avoids the error until a fix arrives

Another user reported today (2026-09-16):

  • Same breakage after 8.2 update
  • Must re-login after every browser close
  • Never needed to do this before

This suggests 8.2.x has multiple related bugs:

  1. Session persistence failure (auth not saved)
  2. Sync upload rejection (conflict error)
  3. Possibly other undocumented issues

MY SYSTEM SPECS (Full Details for Reference)

Device 1: Windows Laptop

  • OS: Windows 11 (version 25H2)
  • Vivaldi: 8.2.4133.52 Stable

Device 2: Steam Deck

  • OS: SteamOS 3.8.16 (Linux)
  • Vivaldi: 8.2.4133.52 Stable

Device 3: iPhone

  • OS: iOS 26.6.2
  • Vivaldi: 8.2.4147.59 Stable.

Note: Sync worked fine BEFORE updating to 8.2. Breakage started immediately after the 8.2 update on all devices.

Important finding about when breakage began:

Vivaldi 8.2 Released: September 4, 2026

  • First 8 days: Sync worked perfectly

Chromium Security Update: September 11, 2026

  • Minor patch for 8.2 branch (security fixes only)

Sync Problems Started: September 12, 2026 (Saturday)

  • Exactly 1 day AFTER the Chromium update

This suggests the Chromium security integration (Sept 11),
NOT the original 8.2 release, introduced the sync regression.

Other users: Did YOUR sync break around September 12 too,
or at different times? This helps identify if it's the
Chromium update or something else.

If you're also affected, did you get the same Chromium
update (152.0.7977.124 ESR)? This helps confirm if it's
the V8 security patch causing the regression.

Update: I've submited a bug report (I attempted before but it didn't go though but this one did) the ticket number is VB-131713