feat(webapp): the editor joins the document the hub is holding

[ssowonny]

TL;DR

• The client stops being a Yjs provider: y-websocket replaces the hand-rolled SSE-down/POST-up transport when the hub holds the document.
• What that buys is the part that was hand-rolled badly — a state-vector handshake instead of replaying the whole room log on every reconnect.
• Nothing seeds client-side any more. The hub built the document from the file before anyone attached, so the seed claim and its grace timer are unreachable.
• Verified in a real browser, not only in tests.

y-websocket, not @hocuspocus/provider

The PRD named Hocuspocus. ygo speaks y-websocket natively and Hocuspocus only behind a server flag — so this is one fewer thing that has to agree, for the same gain. Recorded as a deviation in the PRD.

The client is told, not left to guess

/api/config now carries collab.held.

A hub too old to serve the route and a proxy that refuses to upgrade a websocket fail in exactly the same way. Guessing wrong means either an editor waiting for a document nobody is going to send, or two clients seeding two documents of one file. The hub knows; it says.

Editor and VisualEdit read it through useConfig rather than threading a prop down four components — staleTime: Infinity, so it's a cache hit.

Two things that had to go quiet

• Client-side seeding, on the held path. The document already is the file.
• The relay's update and awareness POSTs. The socket carries both, so posting them too was the same bytes twice at a route that only serves GET — which is how I found it: 405s in a browser console.

Still here, deliberately

Both transports live in collab.ts. Deleting the relay, onSolo and the compensations is Stage 4 — this is what "the old relay stays reachable for a release" means in practice.

Verification

Driven with a real browser as well as the suite, because three of the failures on the way here were invisible to unit tests: a route that didn't match the URL y-websocket builds, a client dialling the relay's path, and a hub still serving a bundle compiled before any of it existed.

• Browser probe: websocket opens, editor mounts, no console errors.
• 25 editor e2e pass — including two people editing different paragraphs both land and the URL is the invitation: a teammate lands in the same document, both now running through the hub-held document.

🤖 Generated with Claude Code