flynn/docs/api/PROTOCOL.md

# Gateway API Protocol

Flynn's gateway exposes a WebSocket-based JSON-RPC protocol for real-time communication with the AI agent. This document describes the protocol in detail.

## Table of Contents

- [Overview](#overview)
- [Connection](#connection)
- [Authentication](#authentication)
- [Message Format](#message-format)
- [Methods](#methods)
- [Events](#events)
- [Error Codes](#error-codes)
- [Example Client](#example-client)

## Overview

The gateway provides:

- **WebSocket Server**: Real-time bidirectional communication
- **JSON-RPC 2.0**: Structured request/response protocol
- **Streaming Events**: Real-time updates during agent processing
- **HTTP Server**: Serves static dashboard and handles webhook endpoints

### Execution Model (Sessions + Per-Session Queue)

Two concepts matter for correct clients:

- **connectionId**: a single WebSocket connection identity (assigned on connect)
- **sessionId**: the conversation/session the connection is attached to (defaults to a per-connection session, but can be switched to resume an old session)

The gateway serialises agent work **per session**, not per WebSocket connection:

- Requests that target the same `sessionId` run one-at-a-time (FIFO) in a per-session lane.
- Requests for different sessions can run in parallel.

This is implemented via a per-lane queue (`LaneQueue`) in the gateway server, and used by `agent.send` and `agent.cancel`.

```mermaid
sequenceDiagram
  autonumber
  participant C as Client
  participant G as Gateway (WS JSON-RPC)
  participant LQ as LaneQueue (per-session)
  participant SB as SessionBridge
  participant A as AgentOrchestrator

  C->>G: agent.send {connectionId, message}
  G->>SB: resolve sessionId for connectionId
  SB-->>G: sessionId (laneId)
  G->>LQ: enqueue(laneId, work)

  alt lane idle
    LQ-->>G: starts work immediately
  else lane busy
    Note over LQ: work queued (FIFO) for this lane
  end

  G->>A: process(message) in that session
  A-->>G: streaming events (content/tool_start/tool_end)
  G-->>C: events + final done

  C->>G: agent.cancel {connectionId}
  G->>LQ: cancel(laneId) (queued items rejected)
  G->>SB: cancel active op (best-effort)
  G-->>C: result.cancelled=true/false
```

### Base URL

- WebSocket: `ws://localhost:18800` (or `wss://` if using TLS)
- HTTP: `http://localhost:18800` (or `https://` if using TLS)
- Health check: `GET /health`

### Default Ports

- Gateway: `18800`
- Tailscale Serve (if enabled): `443` (HTTPS)

## Connection

### WebSocket Handshake

```javascript
// Browser
const ws = new WebSocket('ws://localhost:18800');

// Node.js (ws library)
const WebSocket = require('ws');
const ws = new WebSocket('ws://localhost:18800');
```

### Connection Lifecycle

1. Client connects to WebSocket endpoint
2. Server validates authentication (if configured)
3. Connection assigned unique ID
4. Client can start sending requests
5. Server sends responses and events asynchronously

### Disconnection

```javascript
ws.onclose = (event) => {
  console.log('Disconnected:', event.code, event.reason);
};
```

Common close codes:
- `1000`: Normal closure
- `1001`: Endpoint going away
- `1006`: Abnormal closure (network issue)

## Authentication

### Bearer Token Auth

If `server.token` is configured, all WebSocket connections must provide authentication:

```javascript
const ws = new WebSocket('ws://localhost:18800', {
  headers: {
    'Authorization': 'Bearer your-secret-token'
  }
});
```

### Tailscale Identity

If `server.tailscale_identity` is enabled, connections from Tailscale are trusted based on the `Tailscale-User-Login` header.

```javascript
// Automatic when connecting via Tailscale
// No additional auth required if server.tailscale_identity is enabled
```

### HTTP Auth

If `server.auth_http` is `true` (default: true), HTTP requests also require bearer token when `server.token` is set:

```javascript
fetch('http://localhost:18800/api/health', {
  headers: {
    'Authorization': 'Bearer your-secret-token'
  }
});
```

## Message Format

### Request (Client → Server)

```typescript
interface GatewayRequest {
  id: number;           // Unique request ID (integer)
  method: string;       // Method name (e.g., 'agent.send', 'system.info')
  params?: Record<string, unknown>;  // Method parameters (optional)
}
```

Example:
```json
{
  "id": 1,
  "method": "agent.send",
  "params": {
    "message": "Hello, Flynn!",
    "session": "telegram:123456"
  }
}
```

### Response (Server → Client)

```typescript
interface GatewayResponse {
  id: number;           // Request ID this responds to
  result: unknown;      // Method result
}
```

Example:
```json
{
  "id": 1,
  "result": {
    "sessionId": "telegram:123456",
    "response": "Hello! How can I help you today?"
  }
}
```

### Error (Server → Client)

```typescript
interface GatewayError {
  id: number;
  error: {
    code: ErrorCode;     // Error code (integer)
    message: string;     // Human-readable error message
  };
}
```

Example:
```json
{
  "id": 1,
  "error": {
    "code": 4,
    "message": "Request cancelled by client"
  }
}
```

### Event (Server → Client)

```typescript
interface GatewayEvent {
  id: number;           // Request ID this relates to
  event: EventType;      // Event type string
  data: unknown;        // Event-specific data
}
```

Example:
```json
{
  "id": 1,
  "event": "content",
  "data": {
    "text": "Hello! How can I help you today?"
  }
}
```

## Methods

### System Methods

#### `system.info`

Get gateway information.

**Request:**
```json
{
  "id": 1,
  "method": "system.info"
}
```

**Response:**
```json
{
  "id": 1,
  "result": {
    "version": "0.1.0",
    "uptime": 12345,
    "connections": 2
  }
}
```

#### `system.disconnect`

Close the connection gracefully.

**Request:**
```json
{
  "id": 2,
  "method": "system.disconnect"
}
```

**Response:**
```json
{
  "id": 2,
  "result": {
    "success": true
  }
}
```

### Session Methods

#### `sessions.list`

List all sessions.

**Request:**
```json
{
  "id": 3,
  "method": "sessions.list"
}
```

**Response:**
```json
{
  "id": 3,
  "result": {
    "sessions": [
      {
        "id": "telegram:123456",
        "createdAt": "2025-02-13T10:00:00Z",
        "lastActiveAt": "2025-02-13T12:00:00Z",
        "messageCount": 42,
        "connectionCount": 1
      }
    ]
  }
}
```

#### `sessions.get`

Get session details.

**Request:**
```json
{
  "id": 4,
  "method": "sessions.get",
  "params": {
    "sessionId": "telegram:123456"
  }
}
```

**Response:**
```json
{
  "id": 4,
  "result": {
    "id": "telegram:123456",
    "createdAt": "2025-02-13T10:00:00Z",
    "lastActiveAt": "2025-02-13T12:00:00Z",
    "history": [
      {
        "role": "user",
        "content": "Hello"
      },
      {
        "role": "assistant",
        "content": "Hi there!"
      }
    ]
  }
}
```

#### `sessions.create`

Create or resume a session.

**Request:**
```json
{
  "id": 5,
  "method": "sessions.create",
  "params": {
    "sessionId": "telegram:123456"
  }
}
```

**Response:**
```json
{
  "id": 5,
  "result": {
    "sessionId": "telegram:123456",
    "created": true
  }
}
```

#### `sessions.delete`

Delete a session.

**Request:**
```json
{
  "id": 6,
  "method": "sessions.delete",
  "params": {
    "sessionId": "telegram:123456"
  }
}
```

**Response:**
```json
{
  "id": 6,
  "result": {
    "success": true
  }
}
```

### Agent Methods

#### `agent.send`

Send a message to the agent and stream response.

**Request:**
```json
{
  "id": 7,
  "method": "agent.send",
  "params": {
    "message": "What's the weather?",
    "sessionId": "telegram:123456",
    "attachments": [
      {
        "mimeType": "image/jpeg",
        "data": "base64encodedimage..."
      }
    ]
  }
}
```

**Response (final):**
```json
{
  "id": 7,
  "result": {
    "content": "I can't check the weather without access to weather APIs. Would you like me to help you with something else?",
    "usage": {
      "inputTokens": 25,
      "outputTokens": 30
    }
  }
}
```

**Events (streamed during processing):**

`content` event:
```json
{
  "id": 7,
  "event": "content",
  "data": {
    "text": "I can't check the weather"
  }
}
```

`tool_start` event:
```json
{
  "id": 7,
  "event": "tool_start",
  "data": {
    "tool": "shell.exec",
    "args": {
      "command": "echo 'Hello'"
    }
  }
}
```

`tool_end` event:
```json
{
  "id": 7,
  "event": "tool_end",
  "data": {
    "tool": "shell.exec",
    "result": {
      "success": true,
      "output": "Hello\n",
      "error": null
    }
  }
}
```

`attachment` event:
```json
{
  "id": 7,
  "event": "attachment",
  "data": {
    "mimeType": "image/png",
    "data": "base64encoded..."
  }
}
```

`done` event:
```json
{
  "id": 7,
  "event": "done",
  "data": {
    "content": "Complete response here..."
  }
}
```

#### `agent.cancel`

Cancel the current agent operation.

**Request:**
```json
{
  "id": 8,
  "method": "agent.cancel",
  "params": {
    "sessionId": "telegram:123456"
  }
}
```

**Response:**
```json
{
  "id": 8,
  "result": {
    "cancelled": true
  }
}
```

#### `agent.setToolUseCallback`

Set callback for tool use events (for confirmation UI).

**Request:**
```json
{
  "id": 9,
  "method": "agent.setToolUseCallback",
  "params": {
    "sessionId": "telegram:123456",
    "enabled": true
  }
}
```

**Response:**
```json
{
  "id": 9,
  "result": {
    "success": true
  }
}
```

### Tool Methods

#### `tools.list`

List available tools.

**Request:**
```json
{
  "id": 10,
  "method": "tools.list",
  "params": {
    "sessionId": "telegram:123456"
  }
}
```

**Response:**
```json
{
  "id": 10,
  "result": {
    "tools": [
      {
        "name": "shell.exec",
        "description": "Execute a shell command...",
        "inputSchema": {
          "type": "object",
          "properties": {
            "command": { "type": "string" }
          }
        }
      }
    ]
  }
}
```

#### `tools.execute`

Execute a tool directly (bypass agent).

**Request:**
```json
{
  "id": 11,
  "method": "tools.execute",
  "params": {
    "sessionId": "telegram:123456",
    "tool": "shell.exec",
    "args": {
      "command": "echo 'Hello'"
    }
  }
}
```

**Response:**
```json
{
  "id": 11,
  "result": {
    "success": true,
    "output": "Hello\n"
  }
}
```

### Config Methods

#### `config.get`

Get current configuration (secrets redacted).

**Request:**
```json
{
  "id": 12,
  "method": "config.get"
}
```

**Response:**
```json
{
  "id": 12,
  "result": {
    "models": {
      "default": {
        "anthropic": {
          "apiKey": "***"
        }
      }
    }
  }
}
```

#### `config.reload`

Reload configuration from file.

**Request:**
```json
{
  "id": 13,
  "method": "config.reload"
}
```

**Response:**
```json
{
  "id": 13,
  "result": {
    "success": true
  }
}
```

### Pairing Methods

#### `pairing.generate`

Generate a pairing code for unknown senders.

**Request:**
```json
{
  "id": 14,
  "method": "pairing.generate",
  "params": {
    "channel": "telegram"
  }
}
```

**Response:**
```json
{
  "id": 14,
  "result": {
    "code": "ABC123",
    "expiresAt": "2025-02-13T12:05:00Z"
  }
}
```

#### `pairing.list`

List active pairing codes.

**Request:**
```json
{
  "id": 15,
  "method": "pairing.list"
}
```

**Response:**
```json
{
  "id": 15,
  "result": {
    "codes": [
      {
        "code": "ABC123",
        "channel": "telegram",
        "createdAt": "2025-02-13T12:00:00Z",
        "expiresAt": "2025-02-13T12:05:00Z"
      }
    ]
  }
}
```

## Events

### Event Types

#### `content`

Streamed text content from the agent.

```json
{
  "id": 1,
  "event": "content",
  "data": {
    "text": "Partial response..."
  }
}
```

#### `tool_start`

Tool execution started.

```json
{
  "id": 1,
  "event": "tool_start",
  "data": {
    "tool": "shell.exec",
    "args": {
      "command": "echo 'test'"
    }
  }
}
```

#### `tool_end`

Tool execution completed.

```json
{
  "id": 1,
  "event": "tool_end",
  "data": {
    "tool": "shell.exec",
    "result": {
      "success": true,
      "output": "test\n"
    }
  }
}
```

#### `attachment`

Outbound attachment (image, audio, file).

```json
{
  "id": 1,
  "event": "attachment",
  "data": {
    "mimeType": "image/jpeg",
    "data": "base64encoded...",
    "filename": "output.jpg"
  }
}
```

#### `done`

Agent processing complete (final response).

```json
{
  "id": 1,
  "event": "done",
  "data": {
    "content": "Complete final response..."
  }
}
```

#### `error`

Error occurred during processing.

```json
{
  "id": 1,
  "event": "error",
  "data": {
    "code": 5,
    "message": "Internal error: ..."
  }
}
```

## Error Codes

| Code | Name | Description |
|------|------|-------------|
| -1 | `ParseError` | Invalid JSON in request |
| -2 | `InvalidRequest` | Missing required fields |
| -3 | `MethodNotFound` | Unknown method name |
| -4 | `AuthRequired` | Authentication required but not provided |
| -5 | `AuthFailed` | Authentication failed |
| 1 | `SessionNotFound` | Session ID doesn't exist |
| 2 | `ToolNotFound` | Tool name doesn't exist |
| 3 | `AgentBusy` | Agent is processing another request |
| 4 | `RequestCancelled` | Request was cancelled by client |
| 5 | `InternalError` | Unexpected server error |

## Example Client

### Browser Client

```javascript
class FlynnClient {
  constructor(url, token) {
    this.url = url;
    this.token = token;
    this.requestId = 0;
    this.pending = new Map();
  }

  connect() {
    const headers = {};
    if (this.token) {
      headers['Authorization'] = `Bearer ${this.token}`;
    }

    this.ws = new WebSocket(this.url, { headers });

    this.ws.onopen = () => {
      console.log('Connected to Flynn gateway');
    };

    this.ws.onmessage = (event) => {
      const message = JSON.parse(event.data);
      this.handleMessage(message);
    };

    this.ws.onerror = (error) => {
      console.error('WebSocket error:', error);
    };

    this.ws.onclose = () => {
      console.log('Disconnected from Flynn gateway');
    };
  }

  sendRequest(method, params = {}) {
    return new Promise((resolve, reject) => {
      const id = ++this.requestId;

      const request = {
        id,
        method,
        params
      };

      this.ws.send(JSON.stringify(request));

      // Store promise for response
      this.pending.set(id, { resolve, reject });

      // Set timeout
      setTimeout(() => {
        if (this.pending.has(id)) {
          this.pending.delete(id);
          reject(new Error('Request timeout'));
        }
      }, 30000);
    });
  }

  handleMessage(message) {
    // Response
    if ('result' in message) {
      const { id, result } = message;
      const pending = this.pending.get(id);
      if (pending) {
        this.pending.delete(id);
        pending.resolve(result);
      }
    }

    // Error
    else if ('error' in message) {
      const { id, error } = message;
      const pending = this.pending.get(id);
      if (pending) {
        this.pending.delete(id);
        const err = new Error(error.message);
        err.code = error.code;
        pending.reject(err);
      }
    }

    // Event
    else if ('event' in message) {
      this.handleEvent(message);
    }
  }

  handleEvent(event) {
    const { id, event: eventType, data } = event;

    switch (eventType) {
      case 'content':
        console.log('Content:', data.text);
        break;
      case 'tool_start':
        console.log('Tool started:', data.tool, data.args);
        break;
      case 'tool_end':
        console.log('Tool completed:', data.tool, data.result);
        break;
      case 'attachment':
        console.log('Attachment received:', data.mimeType);
        break;
      case 'done':
        console.log('Done:', data.content);
        break;
      case 'error':
        console.error('Error:', data.code, data.message);
        break;
    }
  }

  // Convenience methods
  async systemInfo() {
    return this.sendRequest('system.info');
  }

  async listSessions() {
    return this.sendRequest('sessions.list');
  }

  async sendMessage(message, sessionId, attachments = []) {
    return this.sendRequest('agent.send', {
      message,
      sessionId,
      attachments
    });
  }

  async listTools(sessionId) {
    return this.sendRequest('tools.list', { sessionId });
  }
}

// Usage
const client = new FlynnClient('ws://localhost:18800', 'your-token');
client.connect();

client.onopen = async () => {
  const info = await client.systemInfo();
  console.log('Gateway info:', info);

  const response = await client.sendMessage('Hello, Flynn!', 'telegram:123456');
  console.log('Response:', response);
};
```

### Node.js Client

```javascript
const WebSocket = require('ws');

class FlynnNodeClient extends FlynnClient {
  connect() {
    const options = {};
    if (this.token) {
      options.headers = { 'Authorization': `Bearer ${this.token}` };
    }

    this.ws = new WebSocket(this.url, options);

    // ... same as browser client
  }
}

// Usage
const client = new FlynnNodeClient('ws://localhost:18800', 'your-token');
client.connect();
```

### HTTP Fetch Example

```javascript
// Health check
async function checkHealth() {
  const response = await fetch('http://localhost:18800/health', {
    headers: {
      'Authorization': 'Bearer your-token'
    }
  });

  const status = await response.json();
  console.log('Health:', status);
}

checkHealth();
```

---

For more implementation details, see:
- Protocol types: `src/gateway/protocol.ts`
- Handlers: `src/gateway/handlers/`
- Gateway server: `src/gateway/server.ts`