feat: Message Bookmarks (MSC4438)

[Just-Insane]

Message Bookmarks — MSC4438

Tracking issue for the Message Bookmarks feature (MSC4438).

Bookmarks let you save individual messages for later access from a dedicated Bookmarks sidebar page, synced across all your devices via account data.

Implementation

• Bookmark items are stored as org.matrix.msc4438.bookmark.<id> account data events
• A bookmark index is stored as org.matrix.msc4438.bookmarks.index for fast lookup
• Bookmark IDs use a djb2-style hash of "roomId|eventId" with a bmk_ prefix (matching the Cinny reference implementation for cross-client compatibility)
• Bookmarks are synced across devices via the account data mechanism

Feature Status

Currently experimental — enable via Settings → Experimental → Message Bookmarks (MSC4438).

Known Limitations / To-Do

• Body preview is stored in unencrypted account data (known MSC limitation; see spec discussion)
• No reminder/snooze support (deferred pending spec stabilisation)
• No time-marker support (deferred pending spec stabilisation)

Related

• MSC4438
• Reference Implementation

[dozro]

is “cinny reference implementation” supposed to just go to the cinny repo root in the dev branch?

[hazre]

Are we not encrypting the data with SSSS? As per spec

[Just-Insane]

Are we not encrypting the data with SSSS? As per spec

@hazre

The MSC explicitly covers this in its Security Considerations — bookmark data is intentionally stored as unencrypted account data, consistent with other account data like m.direct and m.push_rules. SSSS isn't required or mentioned. The MSC does note that a future encrypted account data MSC (see MSC4441) would benefit bookmarks along with everything else. As a privacy mitigation in the meantime, the MSC suggests clients may omit the optional cached fields (body_preview, room_name, sender) for bookmarks from encrypted rooms, storing only room_id, event_id, and uri.