# MCP Compliance Enhancement Summary

## Overview
This document summarizes the enhanced Model Context Protocol (MCP) compliance features implemented in the Agent Coordinator system, focusing on session management, security, and real-time streaming capabilities.

## Implemented Features

### 1. 🔐 Enhanced Session Management

#### Session Token Authentication
- **Implementation**: Modified `register_agent` to return cryptographically secure session tokens
- **Token Format**: 32-byte secure random tokens, Base64 encoded
- **Expiry**: 60-minute session timeout with automatic cleanup
- **Headers**: Support for `Mcp-Session-Id` header (MCP compliant) and `X-Session-Id` (legacy)

#### Session Validation Flow
```
Client                    Server
  |                         |
  |-- POST /mcp/request ---->|
  |    register_agent        |
  |                         |
  |<-- session_token --------|
  |    expires_at            |
  |                         |
  |-- Subsequent requests -->|
  |    Mcp-Session-Id: token |
  |                         |
  |<-- Authenticated resp ---|
```

#### Key Components
- **SessionManager GenServer**: Manages token lifecycle and validation
- **Secure token generation**: Uses `:crypto.strong_rand_bytes/1`
- **Automatic cleanup**: Periodic removal of expired sessions
- **Backward compatibility**: Supports legacy X-Session-Id headers

### 2. 📋 MCP Protocol Version Compliance

#### Protocol Headers
- **MCP-Protocol-Version**: `2025-06-18` (current specification)
- **Server**: `AgentCoordinator/1.0` identification
- **Applied to**: All JSON responses via enhanced `send_json_response/3`

#### CORS Enhancement
- **Session Headers**: Added `mcp-session-id`, `mcp-protocol-version` to allowed headers
- **Exposed Headers**: Protocol version and server headers exposed to clients
- **Security**: Enhanced origin validation with localhost and HTTPS preference

### 3. 🔒 Security Enhancements

#### Origin Validation
```elixir
defp validate_origin(origin) do
  case URI.parse(origin) do
    %URI{host: host} when host in ["localhost", "127.0.0.1", "::1"] -> origin
    %URI{host: host} when is_binary(host) ->
      if String.starts_with?(origin, "https://") or
         String.contains?(host, ["localhost", "127.0.0.1", "dev", "local"]) do
        origin
      else
        Logger.warning("Potentially unsafe origin: #{origin}")
        "*"
      end
    _ -> "*"
  end
end
```

#### Authenticated Method Protection
Protected methods requiring valid session tokens:
- `agents/register` ✓
- `agents/unregister` ✓
- `agents/heartbeat` ✓
- `tasks/create` ✓
- `tasks/complete` ✓
- `codebase/register` ✓
- `stream/subscribe` ✓

### 4. 📡 Server-Sent Events (SSE) Support

#### Real-time Streaming Endpoint
- **Endpoint**: `GET /mcp/stream`
- **Transport**: Streamable HTTP (MCP specification)
- **Authentication**: Requires valid session token
- **Content-Type**: `text/event-stream`

#### SSE Event Format
```
event: connected
data: {"session_id":"agent_123","protocol_version":"2025-06-18","timestamp":"2025-01-11T..."}

event: heartbeat
data: {"timestamp":"2025-01-11T...","session_id":"agent_123"}
```

#### Features
- **Connection establishment**: Sends initial `connected` event
- **Heartbeat**: Periodic keepalive events
- **Session tracking**: Events include session context
- **Graceful disconnection**: Handles client disconnects

## Technical Implementation Details

### File Structure
```
lib/agent_coordinator/
├── session_manager.ex          # Session token management
├── mcp_server.ex              # Enhanced register_agent
├── http_interface.ex          # HTTP/SSE endpoints + security
└── application.ex             # Supervision tree
```

### Session Manager API
```elixir
# Create new session
{:ok, session_info} = SessionManager.create_session(agent_id, capabilities)

# Validate existing session
{:ok, session_info} = SessionManager.validate_session(token)
{:error, :expired} = SessionManager.validate_session(old_token)

# Manual cleanup (automatic via timer)
SessionManager.cleanup_expired_sessions()
```

### HTTP Interface Enhancements
```elixir
# Session validation middleware
case validate_session_for_method(method, conn, context) do
  {:ok, session_info} -> # Process request
  {:error, auth_error} -> # Return 401 Unauthorized
end

# MCP headers on all responses
defp put_mcp_headers(conn) do
  conn
  |> put_resp_header("mcp-protocol-version", "2025-06-18")
  |> put_resp_header("server", "AgentCoordinator/1.0")
end
```

## Usage Examples

### 1. Agent Registration with Session Token
```bash
curl -X POST http://localhost:4000/mcp/request \
  -H "Content-Type: application/json" \
  -d '{
    "jsonrpc": "2.0",
    "id": "1",
    "method": "agents/register",
    "params": {
      "name": "My Agent Blue Koala",
      "capabilities": ["coding", "testing"],
      "codebase_id": "my_project"
    }
  }'

# Response:
{
  "jsonrpc": "2.0",
  "id": "1",
  "result": {
    "agent_id": "My Agent Blue Koala",
    "session_token": "abc123...",
    "expires_at": "2025-01-11T15:30:00Z"
  }
}
```

### 2. Authenticated Tool Call
```bash
curl -X POST http://localhost:4000/mcp/request \
  -H "Content-Type: application/json" \
  -H "Mcp-Session-Id: abc123..." \
  -d '{
    "jsonrpc": "2.0",
    "id": "2",
    "method": "tools/call",
    "params": {
      "name": "get_task_board",
      "arguments": {"agent_id": "My Agent Blue Koala"}
    }
  }'
```

### 3. Server-Sent Events Stream
```javascript
const eventSource = new EventSource('/mcp/stream', {
  headers: {
    'Mcp-Session-Id': 'abc123...'
  }
});

eventSource.onmessage = function(event) {
  const data = JSON.parse(event.data);
  console.log('Received:', data);
};
```

## Testing and Verification

### Automated Test Script
- **File**: `test_session_management.exs`
- **Coverage**: Registration flow, session validation, protocol headers
- **Usage**: `elixir test_session_management.exs`

### Manual Testing
1. Start server: `mix phx.server`
2. Register agent via `/mcp/request`
3. Use returned session token for authenticated calls
4. Verify MCP headers in responses
5. Test SSE stream endpoint

## Benefits

### 🔐 Security
- **Token-based authentication**: Prevents unauthorized access
- **Session expiry**: Limits exposure of compromised tokens
- **Origin validation**: Mitigates CSRF and unauthorized origins
- **Method-level protection**: Granular access control

### 📋 MCP Compliance
- **Official protocol version**: Headers indicate MCP 2025-06-18 support
- **Streamable HTTP**: Real-time capabilities via SSE
- **Proper error handling**: Standard JSON-RPC error responses
- **Session context**: Request metadata for debugging

### 🚀 Developer Experience
- **Backward compatibility**: Legacy headers still supported
- **Clear error messages**: Detailed authentication failure reasons
- **Real-time updates**: Live agent status via SSE
- **Easy testing**: Comprehensive test utilities

## Future Enhancements

### Planned Features
- **PubSub integration**: Event-driven SSE updates
- **Session persistence**: Redis/database backing
- **Rate limiting**: Per-session request throttling
- **Audit logging**: Session activity tracking
- **WebSocket upgrade**: Bidirectional real-time communication

### Configuration Options
- **Session timeout**: Configurable expiry duration
- **Security levels**: Strict/permissive origin validation
- **Token rotation**: Automatic refresh mechanisms
- **Multi-tenancy**: Workspace-scoped sessions

---

*This implementation provides a solid foundation for MCP-compliant session management while maintaining the flexibility to extend with additional features as requirements evolve.*