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TypeBox as protocol source of truth

Last updated: 2026-01-10 TypeBox is a TypeScript-first schema library. We use it to define the Gateway WebSocket protocol (handshake, request/response, server events). Those schemas drive runtime validation, JSON Schema export, and Swift codegen for the macOS app. One source of truth; everything else is generated. If you want the higher-level protocol context, start with Gateway architecture.

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Mental model (30 seconds)

Every Gateway WS message is one of three frames:
  • Request: { type: "req", id, method, params }
  • Response: { type: "res", id, ok, payload | error }
  • Event: { type: "event", event, payload, seq?, stateVersion? }
The first frame must be a connect request. After that, clients can call methods (e.g. health, send, chat.send) and subscribe to events (e.g. presence, tick, agent). Connection flow (minimal): 
Client                    Gateway
  |---- req:connect -------->|
  |<---- res:hello-ok --------|
  |<---- event:tick ----------|
  |---- req:health ---------->|
  |<---- res:health ----------|
Common methods + events:
Category Examples Notes
Core connect, health, status connect must be first
Messaging send, poll, agent, agent.wait side-effects need idempotencyKey
Chat chat.history, chat.send, chat.abort, chat.inject WebChat uses these
Sessions sessions.list, sessions.patch, sessions.delete session admin
Nodes node.list, node.invoke, node.pair.* Gateway WS + node actions
Events tick, presence, agent, chat, health, shutdown server push
Authoritative list lives in src/gateway/server.ts (METHODS, EVENTS).

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Where the schemas live

  • Source: src/gateway/protocol/schema.ts
  • Runtime validators (AJV): src/gateway/protocol/index.ts
  • Server handshake + method dispatch: src/gateway/server.ts
  • Node client: src/gateway/client.ts
  • Generated JSON Schema: dist/protocol.schema.json
  • Generated Swift models: apps/macos/Sources/OpenClawProtocol/GatewayModels.swift

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Current pipeline

  • pnpm protocol:gen
    • writes JSON Schema (draft‑07) to dist/protocol.schema.json
  • pnpm protocol:gen:swift
    • generates Swift gateway models
  • pnpm protocol:check
    • runs both generators and verifies the output is committed

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How the schemas are used at runtime

  • Server side: every inbound frame is validated with AJV. The handshake only accepts a connect request whose params match ConnectParams.
  • Client side: the JS client validates event and response frames before using them.
  • Method surface: the Gateway advertises the supported methods and events in hello-ok.

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Example frames

Connect (first message): 
{
  "type": "req",
  "id": "c1",
  "method": "connect",
  "params": {
    "minProtocol": 2,
    "maxProtocol": 2,
    "client": {
      "id": "openclaw-macos",
      "displayName": "macos",
      "version": "1.0.0",
      "platform": "macos 15.1",
      "mode": "ui",
      "instanceId": "A1B2"
    }
  }
}
Hello-ok response: 
{
  "type": "res",
  "id": "c1",
  "ok": true,
  "payload": {
    "type": "hello-ok",
    "protocol": 2,
    "server": { "version": "dev", "connId": "ws-1" },
    "features": { "methods": ["health"], "events": ["tick"] },
    "snapshot": {
      "presence": [],
      "health": {},
      "stateVersion": { "presence": 0, "health": 0 },
      "uptimeMs": 0
    },
    "policy": { "maxPayload": 1048576, "maxBufferedBytes": 1048576, "tickIntervalMs": 30000 }
  }
}
Request + response: 
{ "type": "req", "id": "r1", "method": "health" }

{ "type": "res", "id": "r1", "ok": true, "payload": { "ok": true } }
Event: 
{ "type": "event", "event": "tick", "payload": { "ts": 1730000000 }, "seq": 12 }

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Minimal client (Node.js)

Smallest useful flow: connect + health. 
import { WebSocket } from "ws";

const ws = new WebSocket("ws://127.0.0.1:18789");

ws.on("open", () => {
  ws.send(
    JSON.stringify({
      type: "req",
      id: "c1",
      method: "connect",
      params: {
        minProtocol: 3,
        maxProtocol: 3,
        client: {
          id: "cli",
          displayName: "example",
          version: "dev",
          platform: "node",
          mode: "cli",
        },
      },
    }),
  );
});

ws.on("message", (data) => {
  const msg = JSON.parse(String(data));
  if (msg.type === "res" && msg.id === "c1" && msg.ok) {
    ws.send(JSON.stringify({ type: "req", id: "h1", method: "health" }));
  }
  if (msg.type === "res" && msg.id === "h1") {
    console.log("health:", msg.payload);
    ws.close();
  }
});

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Worked example: add a method end‑to‑end

Example: add a new system.echo request that returns { ok: true, text }.
  1. Schema (source of truth)
Add to src/gateway/protocol/schema.ts: 
export const SystemEchoParamsSchema = Type.Object(
  { text: NonEmptyString },
  { additionalProperties: false },
);

export const SystemEchoResultSchema = Type.Object(
  { ok: Type.Boolean(), text: NonEmptyString },
  { additionalProperties: false },
);
Add both to ProtocolSchemas and export types: 
  SystemEchoParams: SystemEchoParamsSchema,
  SystemEchoResult: SystemEchoResultSchema,

export type SystemEchoParams = Static<typeof SystemEchoParamsSchema>;
export type SystemEchoResult = Static<typeof SystemEchoResultSchema>;
  1. Validation
In src/gateway/protocol/index.ts, export an AJV validator: 
export const validateSystemEchoParams = ajv.compile<SystemEchoParams>(SystemEchoParamsSchema);
  1. Server behavior
Add a handler in src/gateway/server-methods/system.ts: 
export const systemHandlers: GatewayRequestHandlers = {
  "system.echo": ({ params, respond }) => {
    const text = String(params.text ?? "");
    respond(true, { ok: true, text });
  },
};
Register it in src/gateway/server-methods.ts (already merges systemHandlers), then add "system.echo" to METHODS in src/gateway/server.ts.
  1. Regenerate
pnpm protocol:check
  1. Tests + docs
Add a server test in src/gateway/server.*.test.ts and note the method in docs.

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Swift codegen behavior

The Swift generator emits:
  • GatewayFrame enum with req, res, event, and unknown cases
  • Strongly typed payload structs/enums
  • ErrorCode values and GATEWAY_PROTOCOL_VERSION
Unknown frame types are preserved as raw payloads for forward compatibility.

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Versioning + compatibility

  • PROTOCOL_VERSION lives in src/gateway/protocol/schema.ts.
  • Clients send minProtocol + maxProtocol; the server rejects mismatches.
  • The Swift models keep unknown frame types to avoid breaking older clients.

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Schema patterns and conventions

  • Most objects use additionalProperties: false for strict payloads.
  • NonEmptyString is the default for IDs and method/event names.
  • The top-level GatewayFrame uses a discriminator on type.
  • Methods with side effects usually require an idempotencyKey in params (example: send, poll, agent, chat.send).

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Live schema JSON

Generated JSON Schema is in the repo at dist/protocol.schema.json. The published raw file is typically available at:

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When you change schemas

  1. Update the TypeBox schemas.
  2. Run pnpm protocol:check.
  3. Commit the regenerated schema + Swift models.