Agent Communication Protocol (ACP)¶

┌─────────────────────────────┐
│     IDE Client (Editor)     │
└──────────────┬──────────────┘
               │
        JSON-RPC 2.0 (NDJSON)
               │
┌──────────────▼──────────────┐
│    Continuum Router (ACP)   │
│  ┌────────────────────────┐ │
│  │  AcpMethodRouter       │ │
│  │  SessionStore          │ │
│  │  PermissionPolicy      │ │
│  │  ToolExecutor          │ │
│  │  McpConnectionManager  │ │
│  └────────────────────────┘ │
└──────────────┬──────────────┘
               │
    ┌──────────┴──────────┐
    ▼                     ▼
┌────────┐         ┌───────────┐
│ OpenAI │   ...   │ Anthropic │
└────────┘         └───────────┘

{
  "jsonrpc": "2.0",
  "method": "initialize",
  "params": {
    "protocolVersion": 1,
    "clientCapabilities": {
      "readTextFile": true,
      "writeTextFile": true,
      "terminal": false
    },
    "clientInfo": {
      "name": "MyEditor",
      "version": "1.0.0"
    }
  },
  "id": 1
}

{
  "jsonrpc": "2.0",
  "result": {
    "protocolVersion": 1,
    "agentCapabilities": {
      "loadSession": true,
      "image": false,
      "audio": false,
      "embeddedContext": false,
      "mcp": true,
      "mcpCapabilities": { "acp": true }
    },
    "agentInfo": {
      "name": "Continuum Router",
      "version": "1.3.0-beta.1"
    },
    "authMethods": []
  },
  "id": 1
}

{
  "jsonrpc": "2.0",
  "method": "authenticate",
  "params": {
    "method": "api_key",
    "token": "your-api-key"
  },
  "id": 2
}

{
  "jsonrpc": "2.0",
  "method": "session/new",
  "params": { "mode": "code" },
  "id": 3
}

{
  "jsonrpc": "2.0",
  "result": {
    "sessionId": "550e8400-e29b-41d4-a716-446655440000",
    "createdAt": "2026-03-08T12:00:00Z",
    "updatedAt": "2026-03-08T12:00:00Z",
    "mode": "code",
    "historyLength": 0
  },
  "id": 3
}

{
  "jsonrpc": "2.0",
  "method": "session/load",
  "params": { "sessionId": "550e8400-e29b-41d4-a716-446655440000" },
  "id": 4
}

{
  "jsonrpc": "2.0",
  "method": "session/set_mode",
  "params": { "mode": "architect" },
  "id": 5
}

{
  "jsonrpc": "2.0",
  "result": {
    "mode": "architect",
    "previousMode": "code"
  },
  "id": 5
}

{
  "jsonrpc": "2.0",
  "method": "session/cancel",
  "id": 6
}

{
  "jsonrpc": "2.0",
  "method": "session/prompt",
  "params": {
    "sessionId": "550e8400-...",
    "content": [
      { "type": "text", "text": "Explain the architecture of this project" }
    ],
    "model": "gpt-4o",
    "stream": true,
    "temperature": 0.7,
    "maxTokens": 4096
  },
  "id": 7
}

{
  "jsonrpc": "2.0",
  "method": "session/update",
  "params": {
    "sessionId": "550e8400-...",
    "content": [{ "type": "text", "text": "The architecture..." }]
  }
}

{
  "jsonrpc": "2.0",
  "result": { "stopReason": "end_turn" },
  "id": 7
}

                    ┌─────────┐
                    │ Pending │
                    └────┬────┘
                         │
                    classify + permission check
                         │
                    ┌────▼────┐
         ┌─────────│   Ask   │─────────┐
         │         └─────────┘         │
    allow/always                  reject/always
         │                             │
    ┌────▼──────┐               ┌──────▼──┐
    │InProgress │               │ Failed  │
    └────┬──────┘               └─────────┘
         │
    execute tool
         │
    ┌────▼──────┐
    │ Completed │
    └───────────┘

{
  "jsonrpc": "2.0",
  "method": "session/request_permission",
  "params": {
    "sessionId": "...",
    "toolCallId": "tc-1",
    "title": "Edit File",
    "kind": "edit",
    "locations": [{ "uri": "file:///src/main.rs", "startLine": 42 }]
  }
}

IDE Client ←→ [ACP stdio] ←→ Continuum Router ←→ [MCP stdio] ←→ MCP Server

{
  "jsonrpc": "2.0",
  "method": "mcp/connect",
  "params": { "id": "filesystem" },
  "id": 10
}

{
  "jsonrpc": "2.0",
  "result": { "connectionId": "uuid-..." },
  "id": 10
}

{
  "jsonrpc": "2.0",
  "method": "mcp/message",
  "params": {
    "connectionId": "uuid-...",
    "message": {
      "jsonrpc": "2.0",
      "method": "tools/list",
      "id": 1
    }
  },
  "id": 11
}

{
  "jsonrpc": "2.0",
  "method": "mcp/disconnect",
  "params": { "connectionId": "uuid-..." },
  "id": 12
}

{
  "name": "continuum-router",
  "displayName": "Continuum Router",
  "version": "1.3.0-beta.1",
  "description": "Local LLM inference agent with multi-backend routing",
  "transport": [
    { "type": "stdio" }
  ],
  "capabilities": {
    "loadSession": true,
    "mcp": true
  }
}

acp:
  enabled: true

  transport:
    stdio:
      enabled: true

  agent:
    name: "Continuum Router"
    version: "1.0.0"
    description: "Local LLM inference agent"

  capabilities:
    load_session: true
    image: false
    audio: false
    embedded_context: false
    mcp: true

  # Default model for ACP sessions (optional)
  default_model: "gpt-4o"

  # System prompt injection (optional)
  system_prompt: "You are a helpful coding assistant."

  # Enable coding agent mode
  coding_agent_mode: true

  permissions:
    # Default policy: ask_always, allow_read, or allow_all
    default_policy: ask_always
    auto_allow:
      - read
      - search
      - think
    always_ask:
      - edit
      - delete
      - execute

  sessions:
    max_concurrent: 10
    idle_timeout: "1h"
    storage: "memory"

  mcp:
    max_connections_per_session: 5
    allowed_servers: []        # Empty = all configured servers allowed
    server_spawn_timeout: "10s"

src/acp/
├── mod.rs              # Module root
├── jsonrpc.rs          # JSON-RPC 2.0 protocol types
├── types.rs            # ACP content blocks and messages
├── error.rs            # Error types
├── capabilities.rs     # Capability negotiation
├── config.rs           # Configuration structures
├── config_validate.rs  # Configuration validation
├── metadata.rs         # Agent registry metadata (agent.json)
├── transport/
│   ├── mod.rs          # AcpTransport trait
│   └── stdio.rs        # NDJSON over stdin/stdout
├── session.rs          # Session lifecycle and storage
├── router.rs           # Method dispatch router
├── handlers/
│   ├── initialize.rs   # Protocol initialization
│   ├── authenticate.rs # Authentication (stub)
│   ├── session.rs      # session/* methods
│   ├── prompt.rs       # session/prompt handler
│   ├── prompt_stream.rs # SSE streaming processor
│   └── translate.rs    # ACP → OpenAI format translation
├── tools/
│   ├── mod.rs          # Tool call types
│   ├── classifier.rs   # Tool kind classification
│   ├── permission.rs   # Permission policy engine
│   ├── executor.rs     # Tool execution orchestrator
│   └── client_methods.rs # Client-side methods (fs/*, terminal/*)
├── mcp_bridge/
│   ├── mod.rs          # MCP capabilities
│   ├── handlers.rs     # connect/message/disconnect handlers
│   ├── connection.rs   # Connection manager
│   ├── process.rs      # MCP server process spawning
│   └── schema_translate.rs # MCP ↔ ACP schema conversion
└── admin.rs            # Admin API endpoints