PartyKit Realtime Protocol

asyncapi: '2.6.0'
info:
  title: PartyKit Realtime Protocol
  version: '1.0.0'
  description: >-
    AsyncAPI description of the PartyKit realtime protocol. PartyKit is a
    realtime backend framework (acquired by Cloudflare) that wraps Cloudflare
    Durable Objects with an opinionated developer experience for building
    multiplayer applications. A "party" is a server instance backed by a
    Durable Object, and a "room" is a uniquely identified party instance.
    Clients connect over WebSockets (typically via the PartySocket client) to
    `/parties/{party}/{room}` on a deployed PartyKit project. The same URL
    also accepts standard HTTP requests, which are dispatched to the server's
    `onRequest` handler.

    This specification describes the platform protocol surface that PartyKit
    exposes to clients: room connections, server-to-client broadcast, and
    bidirectional message exchange. The shape of individual application
    messages is defined by the developer's Party.Server implementation; this
    spec models the transport contract.
  contact:
    name: PartyKit
    url: https://docs.partykit.io
  license:
    name: Documentation
    url: https://docs.partykit.io
defaultContentType: application/json
servers:
  production:
    url: '{project}.{user}.partykit.dev'
    protocol: wss
    description: >-
      Deployed PartyKit project endpoint. Each deployed project is served at
      `{project}.{user}.partykit.dev` and accepts both WebSocket upgrades and
      standard HTTP requests under `/parties/{party}/{room}`.
    variables:
      project:
        description: The deployed project name.
        default: my-project
      user:
        description: The PartyKit user (account) the project belongs to.
        default: my-user
  local:
    url: 'localhost:1999'
    protocol: ws
    description: >-
      Local development server started by `partykit dev`. Defaults to port
      1999.
channels:
  '/parties/{party}/{room}':
    description: >-
      A PartyKit room channel. The `party` segment identifies which Party
      class to route to (defaults to `main`), and the `room` segment is the
      room id. The PartyKit runtime guarantees that every connection using
      the same `room` id is routed to the same Durable Object instance, so a
      room represents a single, isolated, stateful server. Clients open a
      WebSocket against this path; the server invokes `onConnect` for each
      new connection and `onMessage` for each inbound message, and may use
      `Room.broadcast()` to deliver messages to all connected clients.
    parameters:
      party:
        description: >-
          The name of the Party (Party.Server class) to route to. PartyKit
          defaults this to `main` when omitted by the client.
        schema:
          type: string
          default: main
      room:
        description: >-
          The room id. Connections sharing the same room id are routed to
          the same party instance (Durable Object).
        schema:
          type: string
    bindings:
      ws:
        query:
          type: object
          description: >-
            Query parameters appended to the WebSocket URL. PartySocket
            clients may pass an optional `id` to identify the connection,
            and a developer-defined `query` async function may append
            additional parameters (for example, an auth token).
          properties:
            id:
              type: string
              description: Optional connection id supplied by the client.
        bindingVersion: '0.1.0'
    publish:
      operationId: clientSendMessage
      summary: Client sends a message to the party.
      description: >-
        A connected client sends a message over the WebSocket. The PartyKit
        runtime delivers it to the party's `onMessage(message, sender)`
        handler. Messages are either UTF-8 strings or binary `ArrayBuffer`
        payloads; application-level structure (for example, JSON envelopes)
        is defined by the developer.
      message:
        $ref: '#/components/messages/ClientMessage'
    subscribe:
      operationId: serverPushMessage
      summary: Server pushes a message to the client.
      description: >-
        The party sends a message to a connection. This covers both
        targeted sends via `connection.send()` and fan-out via
        `Room.broadcast(message, without?)`, which delivers the same
        payload to every connected client (optionally excluding a list of
        connection ids, typically used to skip the original sender).
      message:
        oneOf:
          - $ref: '#/components/messages/ServerMessage'
          - $ref: '#/components/messages/BroadcastMessage'
components:
  messages:
    ClientMessage:
      name: ClientMessage
      title: Client to Party Message
      summary: An inbound message from a connected client.
      contentType: application/json
      payload:
        $ref: '#/components/schemas/Payload'
    ServerMessage:
      name: ServerMessage
      title: Party to Client Message
      summary: A targeted message sent by the party to one connection.
      contentType: application/json
      payload:
        $ref: '#/components/schemas/Payload'
    BroadcastMessage:
      name: BroadcastMessage
      title: Party Broadcast Message
      summary: >-
        A message fanned out by the party to all connected clients via
        `Room.broadcast()`. The party may pass an optional list of
        connection ids to exclude from delivery.
      contentType: application/json
      payload:
        $ref: '#/components/schemas/Payload'
  schemas:
    Payload:
      description: >-
        PartyKit does not define a payload schema at the transport layer.
        The runtime delivers either a UTF-8 string or a binary
        `ArrayBuffer` to the developer's handlers; the application is
        responsible for serialization (commonly JSON).
      oneOf:
        - type: string
          description: A UTF-8 string payload.
        - type: string
          format: binary
          description: A binary payload delivered as an ArrayBuffer.