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TypeBox as protocol source of truth

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Mental model (30 seconds)

• Request: { type: "req", id, method, params }
• Response: { type: "res", id, ok, payload | error }
• Event: { type: "event", event, payload, seq?, stateVersion? }

Client                    Gateway
  |---- req:connect -------->|
  |<---- res:hello-ok --------|
  |<---- event:tick ----------|
  |---- req:health ---------->|
  |<---- res:health ----------|

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Where the schemas live

• Source: src/gateway/protocol/schema.ts and src/gateway/protocol/schema/*
• 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/FasedAgentProtocol/GatewayModels.swift and apps/shared/FasedAgentKit/Sources/FasedAgentProtocol/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

{
  "type": "req",
  "id": "c1",
  "method": "connect",
  "params": {
    "minProtocol": 3,
    "maxProtocol": 3,
    "client": {
      "id": "fased-macos",
      "displayName": "macos",
      "version": "1.0.0",
      "platform": "macos 15.1",
      "mode": "ui",
      "instanceId": "A1B2"
    }
  }
}

{
  "type": "res",
  "id": "c1",
  "ok": true,
  "payload": {
    "type": "hello-ok",
    "protocol": 3,
    "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 }
  }
}

{ "type": "req", "id": "r1", "method": "health" }

{ "type": "res", "id": "r1", "ok": true, "payload": { "ok": true } }

{ "type": "event", "event": "tick", "payload": { "ts": 1730000000 }, "seq": 12 }

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Adding a method

1. Add params/result schemas under src/gateway/protocol/schema/*.
2. Export them through ProtocolSchemas and generated TypeScript types.
3. Compile any needed AJV validator in src/gateway/protocol/index.ts.
4. Add the handler under src/gateway/server-methods/*.
5. Add the method name to src/gateway/server-methods-list.ts or the appropriate channel/plugin registry.
6. Regenerate and verify:

pnpm protocol:check

7. Add server/protocol tests and update docs when the method is public.

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Swift codegen behavior

• GatewayFrame enum with req, res, event, and unknown cases
• Strongly typed payload structs/enums
• ErrorCode values and GATEWAY_PROTOCOL_VERSION

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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 protocol schema

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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.