The get_tag_cloud cache key was built by loading and hashing every embedding
blob for the scope *before* checking the cache, so even a cache hit re-read
hundreds of MB on large libraries and stalled Explore for several seconds.
Validate the cache from a lightweight image-ID-set signature plus the embedding
revision instead, so a hit never loads embeddings. The ID-set hash keeps the key
membership-sensitive (add/remove/move between folders) and the revision covers
an image being re-embedded in place. Cache write failures are now logged rather
than silently ignored.
On the frontend, switching folders (or re-entering Explore) no longer leaves the
previous folder's clusters/tags on screen with no loading indicator:
loadTagCloud/loadExploreTags clear stale entries on a real folder switch. The
displayed folder is tracked separately (exploreTagsShownFolderId) from the
cache-dirty marker so a same-folder invalidation (tag edits, new AI tags) does
not masquerade as a switch and wipe the visible list mid-refresh.
LyAhn
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