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Open a document in two tabs, two browsers, or two continents: keystrokes appear live, and everyone always converges on the same result. There are no locks, no merge dialogs, and no “refresh to see changes.”

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CRDT sync with Yjs

Each document is a Yjs CRDT shared with every connected editor over a WebSocket. Edits are exchanged as small incremental updates, and the CRDT guarantees that all replicas converge to the same state regardless of the order updates arrive in — including edits made by two people in the same word at the same time. Because convergence is a property of the data type, brief disconnections are harmless: a client that drops offline keeps editing locally, resyncs its missed updates on reconnect, and merges cleanly with whatever happened while it was away. Undo is scoped per user: Cmd+Z reverts your own edits, never a collaborator’s.

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Presence

Everyone connected to a document sees:
  • Remote cursors and selections, colored per user and labeled with their name.
  • Avatars of active collaborators in the document header.
Presence uses the Yjs awareness protocol on the same WebSocket as document sync, so it costs no extra connections.

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One Durable Object per document

Every document is backed by its own Cloudflare Durable Object — a single-threaded authority that holds the live Y.Doc:
  • Sync and awareness run over hibernating WebSockets, so an idle document costs nothing while connections stay open.
  • Access control is enforced at connect time and per message: users with viewer or commenter roles get a read-only connection that receives every update live but cannot write.
  • The REST API goes through the same object. PUT /api/docs/{id}/content applies its change to the live CRDT as a diff, so an API write shows up in every open editor instantly — and concurrent human edits merge with it instead of being overwritten.
  • Snapshots of the CRDT state and its serialized markdown are persisted, so a document survives eviction, hibernation, and deploys.

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Comments stay anchored

Comment and suggestion threads reference Yjs relative positions rather than plain text offsets, so discussions stay attached to the right text while everyone edits around them.