Subscriptions and recovery

A StreamCursor is { stream, processedSeq }. It means every sequenced event through processedSeq has been successfully applied for that stream.

Resume

Reconnect does not carry cursors in hello. After ready, the client sends its current exact cursor set through stream.subscription.set. The server resolves each cursor against { latestSeq, earliestAvailableSeq }:

• equal to latestSeq: live;
• behind but still retained: replay;
• ahead of latestSeq, or older than earliestAvailableSeq - 1: snapshot_required;
• unknown to the server (for example a deleted conversation): unavailable.

For replay, the server reads from processedSeq + 1 in bounded dense pages. Events arriving while that stream replays are buffered and released afterward. Streams recover independently.

An unavailable stream is excluded from activation without rejecting the rest of the set. The client drops its cursor and dependent state; a stale stream must never be able to silence live delivery for the remaining streams. Client subscription synchronization is self-healing: a sync that cannot run (session not ready) or fails stays dirty and is retried until the desired set is acknowledged.

Defensive gaps

The client validates dense continuity even after the server accepted a subscription. If a batch starts after the expected next sequence, the client does not advance its cursor and automatically reinstalls subscriptions from the last applied cursor.

Snapshots

For snapshot_required, the application loads the authorized workspace or conversation snapshot for that stream, installs snapshot state first, installs the snapshot cursor, and then resubscribes.

Reducer lifecycle violations use the same recovery boundary: mark state corrupted, remove or suspend the affected stream, load a fresh snapshot, then subscribe from that snapshot cursor.

Retention and migration

Stream readers expose their earliest retained sequence. A retention gap is never represented as a synthetic event or sparse sequence. Legacy sparse workbench logs are archived into a pre-dense epoch and new streams begin from sequence 1.