[alecgibson]

Refs #771

At the moment, a presence re-created with the ID of one that's leaving can be transformed and published before the leave:

1. Destroy a presence, and hold its leave's transform in op middleware
2. Re-create it with the same ID, at the doc's version
3. Release the leave: subscribers drop the re-created presence, since its pv restarted, and then clear it with the leave

This change has any presence that gets through middleware wait until the newest leave of its ID has been handed to pubsub or rejected, so the leave goes out first. Each leave waits only for the one before it, and releases its waiters on the next tick, so a long run of leaves for one ID drains in order without recursing. Since presence can now sit waiting, a disconnect's leave is a copy, rather than the waiting presence turned into a second leave.

Waiters are released once the leave's publish() is called, not when it calls back, so we rely on pubsub delivering in call order, as both the memory and Redis adapters do. That way an adapter that never calls back can't hold up the ID.

🤖 Generated with Claude Code

Co-Authored-By: Claude noreply@anthropic.com

[coveralls]

coverage: 98.067% (+0.01%) from 98.057% — presence-leave-order into main

[Copilot]

🟡 Changes recommended

A critical queue-handling bug can acknowledge a valid presence update without publishing it when a newer queued update fails transformation, leaving subscribers without replacement presence.

1 open issue

• Publish queued presence update when its replacement fails · New

What changed in this PR

This PR addresses part of #771 by ordering server-side presence broadcasts so a re-created presence waits for an earlier leave with the same ID.

Changes:

• Queue same-ID broadcasts until the preceding leave is handed to pubsub or rejected, releasing waiters without recursion.
• Shallow-copy disconnect leaves to avoid mutating pending presence updates.
• Add regression tests for ordering, failures, disconnects, and long leave queues.

File	Description
test/​client/​presence/​doc-presence.js	Adds helpers and regression cases for queued presence broadcasts.
lib/​agent.js	Tracks in-flight leaves, orders broadcasts, and copies disconnect leaves.
docs/​middleware/​actions.md	Documents shallow-copy behavior for disconnect and unsubscribe leaves.

_{Review effort: Balanced}

[Copilot]

🟢 Approval recommended

No active review issues are recorded for the presence-ordering fix.

No open issues 🎉

1 resolved since last review

• Publish queued presence update when its replacement fails

_{Review effort: Balanced}