withYjs: one peer disconnecting wipes every peer's awareness for ~15s

Start in packages/y-partyserver/src/server/index.ts, reading the awareness update handling around lines 285-292 and onClose around lines 497-509. Reproduce with three relaying peers in workerd, then verify that ownership is reclaimed on added or updated states and that disconnecting one connection removes only its owned awareness states.

What happens

In withYjs, the connection→clientID ownership map is built from the added array of awareness update events. added means "the document hasn't seen this clientID before", which is a property of the document, not of the connection that sent the update.

Yjs clients relay other peers' awareness states without preserving the origin. So when peer B's socket forwards peer A's state, A's clientID is added under B's connection, and B gets recorded as A's owner. removeAwarenessStates deletes from states but keeps meta, so a clientID is only ever added once. The misattribution is permanent for the object's lifetime.

On onClose, that connection's whole ownership list goes to removeAwarenessStates. So closing one connection removes the awareness state of every peer whose clientID it happened to relay first. The remaining peers can't see each other until Yjs re-announces local state, about 15 seconds later.

Where

packages/y-partyserver/src/server/index.ts on current main:

L285-292, the ownership map is credited with added:

if (conn !== null) {
  const currentIds = new Set(getAwarenessIds(conn));
  for (const clientID of added) currentIds.add(clientID);
  for (const clientID of removed) currentIds.delete(clientID);
  setAwarenessIds(conn, [...currentIds]);
}

L497-509, onClose removes it:

const controlledIds = getAwarenessIds(connection);
if (controlledIds.length > 0)
  awarenessProtocol.removeAwarenessStates(this.document.awareness, controlledIds, null);

Reproduction

Three peers in one room, each sending only its own awareness state. Because clients relay, one connection ends up credited with the others' clientIDs. Close that connection and every peer's awareness is removed.

Reproduced in workerd (@cloudflare/vitest-pool-workers), both hibernate: true and hibernate: false. Present since #341 (2.1.0), still on main and in published 2.2.0.

Fix

Make ownership last-writer-wins and exclusive. Claim on added and updated so a peer's own refresh reclaims its clientID, and revoke the claimed ids from every other connection's list:

const claimed = new Set([...added, ...updated]);
for (const other of this.getConnections()) {
  if (other === conn) continue;
  const otherIds = getAwarenessIds(other);
  const kept = otherIds.filter((id) => !claimed.has(id));
  if (kept.length !== otherIds.length) setAwarenessIds(other, kept);
}
for (const clientID of claimed) currentIds.add(clientID);

A relayed clientID stays misattributed until its owner's next frame, so the window shrinks to the Yjs refresh interval rather than closing completely. Fully closing it would need an ownership signal in the protocol itself.