A Contextful document is a real-time collaborative room where humans and their agents are equal peers: one shared roster, live cursors, and the same edit stream for both. Under the hood every document is a Loro CRDT — a data structure whose edits merge without conflicts by construction — synced through a relay on your own machines. That's what makes collaboration local-first: the document on your device is the real document, with or without a connection.
Rooms: the collaboration unit
A room binds together one document, its members — people and agents, each with a
read / write / comment capability — and a paired
sandbox where the room's agents run. Sharing a
document never widens what anyone's agent can read from the brain: room membership and
data access are separate boundaries, and the narrower one always wins.
Agents edit through exactly the same path as humans. Every agent edit carries an origin tag, so provenance and per-peer undo work the same for a colleague and a copilot.
How sync works
The host's relay is the single authoritative peer; browsers, headless clients, and sandbox agents all sync through it over the company's own Tailscale network.
sequenceDiagram
participant C as Peer (browser / client / agent)
participant S as Relay (your host)
C->>S: HELLO { principal, capability token }
S->>S: verify token
S->>C: HELLO_OK
C->>S: SUBSCRIBE { doc, my version }
S->>C: SNAPSHOT { document state }
par live
C->>S: UPDATE { CRDT bytes }
S->>C: UPDATE { relayed from peers }
C-->>S: AWARENESS { cursor · selection · presence }
S-->>C: AWARENESS { ... }
end
Three details do the heavy lifting:
- CRDT payloads are opaque bytes to the relay. The relay authenticates peers and broadcasts updates; it doesn't need to understand your content to sync it.
- Version vectors make catch-up cheap. A returning peer sends what it has; the relay replies with exactly the missing delta, not the whole document.
- Authorization rides the wire protocol. The capability token arrives in the handshake and revocation is re-checked continuously — a principal revoked mid-session is dropped.
Presence: seeing each other (and the agents) work
Who is in the room — and whether they're reading or writing — rides an ephemeral awareness channel, separate from document edits and never persisted. Agents publish presence too: when an agent is drafting, you see it in the roster and its cursor moves in the document, exactly like a human collaborator. Awareness is deliberately dumb: it carries cursors and presence, never document content or brain data.
Offline is a feature, not a failure mode
Because the document is a CRDT, edits made offline are just updates that haven't been delivered yet. When a peer reconnects, both sides exchange deltas and converge — no locks, no "someone else has this open", no merge dialogs. The web editor persists locally in the browser, the desktop client syncs documents to plain local files, and the relay keeps a snapshot + oplog per document on the host's disk (see where your data lives).
The live demo at demo.contextful.work runs this exact stack — open it in two windows and watch the cursors.