The JavaScript client

yrby-client is the browser half of yrby. It has a provider for Action Cable and AnyCable, plus the pieces that provider is built from: a protocol session that works over any transport, and a queue that resends edits until the server confirms them. It's written in TypeScript, includes its own types, and works from plain JavaScript as ESM or CommonJS.

npm install yrby-client

yjs and y-protocols are optional peer dependencies, so install them alongside it. If you already use a Yjs editor binding, you have both.

The <yrby-document> element

yrby-rails' collaborative_document_tag renders a <yrby-document> element with a signed token in it, much like turbo_stream_from renders a <turbo-cable-stream-source>. Import the element once and it connects by itself:

import "yrby-client/element";

document.addEventListener("yrby:synced", ({ target, detail }) => {
  const editor = bindYourEditor(target, detail.doc, detail.provider);
  detail.signal.addEventListener("abort", () => editor.destroy(), { once: true });
});

bindYourEditor stands for however you attach your editor. When the signal aborts, remove the Yjs listeners and disable or remove the editor. Don't destroy the document, the provider, or the shared consumer, because yrby manages those. The signal fires before yrby sends any final update. Handle it even if the editor is already gone from the page.

Behind each element is a document session. It holds the Y.Doc, the provider, and any edits the server hasn't confirmed. When the last editor detaches, the session clears your presence, and it closes if nothing is waiting to be sent. If edits are still waiting, it keeps sending them with the original token until the server confirms them. If the server rejects the subscription, the session stops and keeps the unsent edits in memory so you can recover them.

The element works with Turbo and Turbolinks 5. A cached preview doesn't create a document or connect. When you go back to a page, the element picks up its old session if that session still has unsent edits. Otherwise it loads the saved content from Rails. If the page renders a new token, the element gets a new session, and the old session's edits reach it through the server like anyone else's. This all happens within one tab. Nothing is stored for offline use, so closing or reloading the tab loses edits the server hasn't confirmed.

Moving the element in the DOM keeps its editor and document, as long as you remove and reinsert it in the same synchronous block of code. If you put it back later, it reloads the saved content, and the old Y.Doc and undo history are gone. Changing the token, name, or channel tears down the old editor right away and connects to the new document. The old session still finishes sending its unsent edits with its original token.

The element exposes its current session, doc, and provider. They're undefined until it connects and while it switches documents, and reading them never creates one. whenSynced is always a promise, even before the consumer is set up. It resolves when the document first catches up with the server, and never resolves if the element gives up on that document. The yrby:synced event bubbles, fires once each time the element connects to a document, and includes detail.signal for cleanup. Synced doesn't mean the connection is up right now, or that every edit is confirmed. Check provider.synced and session.hasPending for those.

If the import fails or the server rejects the subscription, the element fires yrby:error with detail.error. A rejection also includes detail.session, so you can retry it. While the session is blocked, the element does nothing. After you retry, call element.activate() or remount the element to attach again. element.destroy() disconnects the element until it's put back on the page. It doesn't throw away unsent edits.

The refresh attribute is a same-origin URL that returns a new token for this document as { "grant": "..." }. When the server rejects the subscription, usually because the token expired, the session fetches that URL once and subscribes again with the new token. It keeps its document and unsent edits. See Grant lifetime and refresh in the main README. The element reads this attribute when it connects, so changing it later has no effect on the current editor.

By default the element needs @rails/actioncable, yjs, and y-protocols, and every element on the page shares one consumer. For AnyCable, set the consumer before adding any elements:

import { YrbyDocumentElement } from "yrby-client/element";
import { createConsumer } from "@anycable/web";

YrbyDocumentElement.consumer = createConsumer();

Importing the module registers the element, and any <yrby-document> tags already on the page start right away. So if you set a custom consumer on a page that's already rendered, put the tag inside a <template>. Set the consumer and add your yrby:synced listener first, then insert the template's content. The working example does it in that order, and its source is in site/frontend/src/document.js.

Document sessions and navigation

Each consumer has its own session store. Elements with the same channel, token, and name share one document and one queue of unsent edits. The store compares tokens as plain strings and never decodes them. Each session adds a random session_id to its subscription, so its acks don't get mixed up with another session's. The server doesn't use it to pick or authorize a document.

Code without an editor can hold a lease for as long as it needs the document:

import { DocumentSessionStore } from "yrby-client";

const store = DocumentSessionStore.for(consumer);
const lease = store.acquire({ grant, name: "body" });
const { session } = lease;
await session.whenSynced;
// Work with session.doc, and hold the lease until the workflow finishes.
lease.release(); // safe to call more than once; pending edits keep sending

Call lease.setPresence(state) when an editor gets focus and lease.setPresence(null) when it loses it. Every view of a session shares one presence, so the last call wins. Your editor code gets its lease from detail.lease on yrby:synced.

session.state is open, blocked, or closed. It doesn't tell you whether the provider is connected. The store fires change with the session in event.detail. Use it to report edits that couldn't be delivered, even after the page that made them is gone.

store.addEventListener("change", ({ detail: session }) => {
  if (session.state === "blocked") reportDeliveryFailure(session.error, session);
});

Sessions keep their queues while the consumer is down and send them when it reconnects. A new consumer gets a new store and doesn't pick up another consumer's queued work.

A blocked session keeps its document and unsent edits in memory. retry() reconnects with its current token, which is the original or the last one its refresh URL returned. discard() throws the edits away. A token that arrives any other way, such as a new element attribute, starts a separate session and leaves the blocked one alone.

ActionCableProvider

The element uses this provider. Use it directly when you wire things up yourself. With a channel you wrote, the params are whatever that channel reads, such as a document key or a room token.

const provider = new ActionCableProvider(
  ydoc,
  createConsumer(),
  "DocumentChannel",
  { id: "post/1/body" },
)

The constructor takes the document, the consumer, the channel name, and the channel params. Consumers from @rails/actioncable and @anycable/web both work without adapters or type casts. On AnyCable, the provider sends presence as whispers, so cursor updates go straight between browsers through AnyCable and never reach your Ruby code. This site's demos are public, so they turn that off and send presence through the server, where it's rate-limited and checked. See Presence.

Bind after the first sync

provider.connect()
await provider.whenSynced
// now hand ydoc to the editor binding

whenSynced resolves when the document first catches up with the server. Most editor bindings add an empty paragraph when they start. If you attach the editor before the server's copy arrives, every client adds its own empty paragraph to the shared document.

If that already happened, whenSynced resolves right away, even while disconnected. It resolves once, and later reconnects don't trigger it again. That makes it a good place to add starter content, since it won't refill a document someone emptied on purpose.

Connection status

The provider reports four states through one listener:

Status	Meaning
connecting	Subscription created, transport not up yet
connected	Transport up and exchanging sync steps (show it as "syncing")
synced	Caught up with the server
disconnected	You called disconnect() or destroy()

When the connection drops and Action Cable retries, the status goes back to connecting. You only see disconnected after you disconnect or destroy the provider yourself.

const off = provider.onStatusChange(({ status }) => {
  statusEl.textContent = status
})

onStatusChange returns an unsubscribe function. provider.status is the current value, and provider.synced is true once the document has caught up.

Reliable delivery

provider.hasPending is true while local edits are waiting to be confirmed. The provider merges everything in its queue into one update and tags it with the highest sequence number in the batch. When the server replies { ack: id }, every edit up to that id is confirmed.

If the server gets an update it already has, nothing changes. On reconnect, the provider sends its whole queue again. That's also how the server fills gaps. If it's missing an update, the client that made it still hasn't had it confirmed, so that client keeps resending it.

Seeding from an HTTP response

applyRemoteUpdate loads state into the document without sending it back to the server as a new edit. Call it for each piece of state the server already has, before connect().

provider.applyRemoteUpdate(fromBase64(initialState))
priorUpdates.forEach((u) => provider.applyRemoteUpdate(fromBase64(u)))
provider.connect()

If you call Y.applyUpdate directly, the provider treats the update as a local change and sends it to the server again.

Teardown

disconnect() closes the subscription and clears this client's presence. destroy() does the same and then releases the provider.

If you reconnect by hand, set your presence again. disconnect() clears it, and setLocalStateField does nothing while it's null. So after disconnect() and connect(), call setLocalState again, or other people won't see you.

provider.onStatusChange(({ status }) => {
  if (status !== "disconnected" && !provider.awareness.getLocalState()) {
    provider.awareness.setLocalState({ user })
  }
})

Bundling: one copy of yjs

Make sure your bundle has only one copy of yjs. With two, the provider and the editor binding each get their own. Yjs warns that it was already imported, instanceof checks fail, and y-prosemirror throws "Method unimplemented" on remote updates. The editor never shows other people's changes, and your next keystroke overwrites them. None of these errors point at the duplicate import, so it's hard to track down.

Pin the shared packages (yjs, y-protocols, lib0) to one path in your bundler config. This site's build.mjs does it with a small Bun resolve plugin. In Vite, use resolve.dedupe. In webpack, use resolve.alias.