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Amends the realtime row of 0084 and the trait list of 0096.

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Context

Users see changes live, and some documents are edited by several people at once. The owner’s realtime answers RT1, RT2 and CO1 (mem L812–814, 2026-10-20) fix the transport, the drivers, presence and co-editing. Presence and co-editing are no longer a Pro-only package (contradiction C-06).

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Decision

  1. Transport (RT1). WebSocket, with a server-sent-events fallback. Channels are authenticated, and presence is supported. Drivers: a native driver on Valkey or Postgres pub/sub, Centrifugo, Ably and Pusher. IAM authorises each channel.
  2. Presence and co-editing (RT2). Presence and cursors. Rich documents are co-edited with Yjs (a CRDT), and the state is saved as snapshots. Form records keep optimistic concurrency control instead.
  3. Commentable (CO1). A @Commentable trait adds comments to any model.

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Consequences

  • A form record cannot be lost to a concurrent edit, because forms keep the version check.
  • A rich document can be edited by several people without a lock, and its history is its snapshots.

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Enforcement

planned — the channel authorisation test; the Yjs snapshot round-trip test.

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Supersedes and sources

Supersedes: none. Amends: the realtime row of 0084, the trait list of 0096. Sources: owner realtime answers RT1, RT2, CO1 (stackra-decisions-2026-10-19.md L812–814, 2026-10-20). Contradiction C-06.