Durable state, one shared definition

Durable Channel keeps realtime state at a URI and gives that state a small, explicit protocol. You define the state shape and every allowed change once. The hub owns the authoritative instance; clients mirror it by running the same pure reducers.

The model in one minute

A channel definition combines a Valibot state schema, an initial value, named actions, commands, and notifications. Mount definitions on URI templates to make a route map, then give that map to both the hub and the client.

The hub orders accepted and rejected actions under one global serverSeq. A connected client applies its own action optimistically, then reconciles when the authoritative envelope returns. Other clients apply that same envelope to the same reducer.

client dispatch → optimistic state → hub validates → reducer → persist
                                                       ↓
other clients ← same reducer ← committed envelope ← broadcast

Pick a path

• New to the library? Build the counter in Quick start, then read Core concepts.
• Designing your protocol? Start with Actions and validation, then separate server work in Commands and effects.
• Adding identity or access rules? Read Authentication and authorization to attach principals and gate client operations.
• Shipping a connection? Read Clients and reconnect, followed by Transport and storage.
• Generating tooling? Go to Schema document for the route description format.

What Durable Channel owns

Durable Channel owns state validation, ordered commits, subscriptions, optimistic reconciliation, replay, snapshots, and enforcement of declared channel permissions. It carries a host-authenticated, typed principal through connections and handlers, but your application still defines the authorization policy and owns credential verification, revocation, reconnect timing, backoff, deployment, and the transport host.

That boundary is deliberate. The core uses web-standard APIs, while the JSON-RPC and WebSocket layer lives separately in rpc.ts and transport.ts.

A useful vocabulary

Term	Meaning
Channel	A definition plus one stateful or stateless protocol
Route	A URI template mounted to a channel definition
Instance	The state stored at one concrete URI
Action	A named, validated state transition
Command	Typed server work with a result
Effect	Server work triggered after an action commits
Notification	A live, ephemeral message that is never replayed
Envelope	The ordered record broadcast for an action
Principal	Optional host-authenticated identity attached to a connection
Client policy	Server-side permission check for subscriptions, actions, and commands

Before you build

durable-channel is published to npm. Install it with npm install durable-channel or deno add npm:durable-channel; the examples in these guides import that package with Valibot.