Opera Sync and Account Backend: Conflict Resolution for Concurrent Offline Modifications

Question

Synchronization State Consistency
Opera Sync implements an end-to-end encryption model to synchronize profile data, including bookmarks and history, across desktop and mobile clients. The system typically employs a timestamp-based priority mechanism to resolve conflicts between the local client and the cloud-based backend.

Offline Modification Boundary
A specific challenge arises when multiple devices modify the same bookmark folder structure while offline. Upon reconnecting to the Opera Sync account system, the browser must reconcile these divergent states. While the general behavior favors the most recent timestamp, the deterministic outcome for nested folder modifications remains unclear.

Given the current synchronization protocol, what is the expected behavior when two devices create different sub-folders within the same parent directory while offline? Does the system merge these additions, or does the latest timestamp overwrite the entire folder state?

Tasadduq Burney · Answer

Answer: Both sub‑folders are merged
When two devices create different sub‑folders inside the same parent bookmark folder while offline, Opera Sync treats each folder as a separate sync item. After reconnection, both additions appear in the parent folder; the latest timestamp does not overwrite the entire hierarchy.

Likely explanation (per‑item sync)
Opera Sync stores each bookmark or folder as an individual sync entry with its own unique ID and timestamp. Conflict resolution is performed per entry using a last‑write‑wins rule. Because the two sub‑folders have distinct IDs, neither overwrites the other; the server (or client) merges the two entries under the common parent.

Confirmed facts (from Opera Sync design)

Each folder/bookmark is a separate sync item with a unique identifier.
Conflict resolution relies on client‑side timestamps; the server does not see plaintext due to end‑to‑end encryption.
If the protocol mistakenly treated a whole folder hierarchy as a single blob, the latest timestamp could replace the entire state, but this behavior is not documented for Opera Sync.

Steps to verify the behavior

Ensure Opera Sync is enabled and the parent folder (e.g., “Parent”) exists online.
On Device 1, go offline, create sub‑folder “A” inside “Parent”.
On Device 2, go offline, create sub‑folder “B” inside the same “Parent”.
Re‑enable sync on both devices and wait for synchronization to complete.
Check the bookmark tree on each device and via the Opera account web interface; both “A” and “B” should be present under “Parent”.
Optionally, open opera://sync-internals and look for log entries showing “merge” or “timestamp win” for the IDs of folders A and B.

Missing diagnostic detail
To be certain that the per‑item mechanism is in use, confirm the Opera Sync protocol version or client build (e.g., via opera://about) or share a snippet of the sync‑internals log showing how folder items are identified. This detail would change the recommendation only if the log indicated folder‑level blob handling.

Opera Sync and Account Backend: Conflict Resolution for Concurrent Offline Modifications

Synchronization State Consistency

Offline Modification Boundary

1 answer

Answer: Both sub‑folders are merged

Likely explanation (per‑item sync)

Confirmed facts (from Opera Sync design)

Steps to verify the behavior

Missing diagnostic detail

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