Sync Behavior

Sync Behavior

Mimick uses two sync paths: a startup catch-up scan and live filesystem monitoring.

Startup Catch-Up

When Mimick launches, it scans the configured watch folders for supported media files.

It keeps a local sync index in ~/.cache/mimick/synced_index.json so it can:

• skip unchanged files that are already known to be synced
• detect files whose content changed and requeue them
• detect when a watch folder's target album changed

Live Monitoring

While the app is running, Mimick watches the selected folders for new or modified files.

Before upload, it:

1. waits for file writes to settle
2. computes a SHA-1 checksum
3. uploads the file to Immich
4. adds the asset to the target album

Live monitoring and startup scans both use the most specific matching watch-folder configuration, so nested folders inherit the correct album and rule set instead of falling back to a less-specific parent path.

Album Reassociation

If you retarget a watch folder to a different Immich album, Mimick can reassociate unchanged files on a later startup without forcing a full reupload.

If the old album was deleted or the stored album ID is stale, Mimick refreshes album resolution and retries using the current configured album name.

Retry and Duplicate Handling

• Failed uploads are stored in ~/.cache/mimick/retries.json and retried on the next run.
• Duplicate detection uses SHA-1 checksums and Immich's upload-check behavior.
• Existing assets can be looked up and reused instead of uploading the file bytes again.
• The Status page can pause/resume syncing, trigger Sync Now, and expose queue recovery actions while Mimick is already running.

Album Synchronization (Bidirectional)

With the introduction of the built-in Library View, an on-demand bidirectional sync between local folders and remote albums is supported. When a local folder is linked to a remote album:

1. Difference Calculation: Mimick compares existing local files to assets in the remote album using their SHA-1 checksums.
2. Uploading: Files inside the local folder that are missing remotely are queued for upload to the target album.
3. Downloading: Assets in the target album missing locally are downloaded to the linked watch folder.
4. Collision Handling: If a file with an identical name already exists but hasn't fully matched via SHA-1 or needs renaming, Mimick automatically appends a numeric suffix (e.g. file (1).jpg) to prevent clobbering existing local data.