bifrost/examples/plugins/multi-interface/README.md

Multi-Interface Plugin Example

This example demonstrates a plugin that implements all plugin interfaces:

• HTTPTransportPlugin
• LLMPlugin
• MCPPlugin
• ObservabilityPlugin

Features

HTTPTransportPlugin

• Tracks request count across all requests
• Adds request number header
• Calculates HTTP request duration
• Stores HTTP metadata in context for other hooks

LLMPlugin

• Accesses HTTP context metadata
• Adds dynamic system prompts
• Tracks LLM call duration
• Logs request/response details

MCPPlugin

• Accesses HTTP context metadata
• Logs all MCP tool/resource calls
• Tracks MCP call duration
• Implements governance for MCP calls

ObservabilityPlugin

• Receives completed traces asynchronously
• Formats traces as JSON
• Ready for integration with OTEL, Datadog, Jaeger, etc.
• Demonstrates end-to-end request tracking

Context Flow

This plugin demonstrates how context flows through different hooks:

1. HTTPTransportPreHook → Stores HTTP metadata
2. PreLLMHook/PreMCPHook → Accesses HTTP metadata, stores LLM/MCP metadata
3. PostLLMHook/PostMCPHook → Accesses stored timing data
4. HTTPTransportPostHook → Adds final headers
5. Inject → Receives complete trace asynchronously

Use Cases

• Full-stack observability - Track requests from HTTP to LLM/MCP and back
• Unified governance - Apply policies at multiple layers
• Performance monitoring - Measure duration at each layer
• Audit trails - Complete request/response logging
• Custom analytics - Correlate HTTP, LLM, and MCP metrics

Building

make build

This creates build/multi-interface.so

Configuration

Add to your Bifrost config:

{
  "plugins": [
    {
      "path": "/path/to/multi-interface.so",
      "name": "multi-interface",
      "display_name": "Full-Stack Observability",
      "enabled": true,
      "type": "auto",
      "config": {
        "enable_http_hooks": true,
        "enable_llm_hooks": true,
        "enable_mcp_hooks": true,
        "enable_observability": true,
        "enable_logging": true,
        "track_requests": true,
        "inject_uptime": true,
        "custom_header_prefix": "X-Multi-Plugin"
      }
    }
  ]
}

Note:

• name is the system identifier (from GetName()) and is not editable
• display_name is shown in the UI and is editable by users

Configuration Options

Option	Type	Default	Description
enable_http_hooks	boolean	true	Enable HTTP transport layer hooks
enable_llm_hooks	boolean	true	Enable LLM request/response hooks
enable_mcp_hooks	boolean	true	Enable MCP request/response hooks
enable_observability	boolean	true	Enable observability/trace injection
enable_logging	boolean	true	Enable detailed logging
track_requests	boolean	true	Track and count requests
inject_uptime	boolean	true	Inject server uptime in LLM system messages
custom_header_prefix	string	"X-Multi-Plugin"	Custom prefix for HTTP response headers

Example Configurations

LLM-only mode:

{
  "config": {
    "enable_http_hooks": false,
    "enable_llm_hooks": true,
    "enable_mcp_hooks": false,
    "enable_observability": false
  }
}

Observability-focused:

{
  "config": {
    "enable_http_hooks": true,
    "enable_llm_hooks": true,
    "enable_mcp_hooks": true,
    "enable_observability": true,
    "enable_logging": false,
    "track_requests": true
  }
}

Minimal overhead:

{
  "config": {
    "enable_logging": false,
    "track_requests": false,
    "inject_uptime": false
  }
}

Custom headers:

{
  "config": {
    "custom_header_prefix": "X-Custom-Plugin"
  }
}

Hook Execution Order

For a typical LLM request:

1. HTTPTransportPreHook (HTTP layer entry)
2. PreLLMHook (Before LLM provider)
3. LLM Provider Call
4. PostLLMHook (After LLM provider)
5. HTTPTransportPostHook (HTTP layer exit)
6. Inject (Asynchronous trace delivery)

For an MCP request:

1. HTTPTransportPreHook (HTTP layer entry)
2. PreMCPHook (Before MCP server)
3. MCP Server Call
4. PostMCPHook (After MCP server)
5. HTTPTransportPostHook (HTTP layer exit)
6. Inject (Asynchronous trace delivery)

Notes

• This plugin tracks state across requests (request count, start time)
• Context metadata flows from HTTP → LLM/MCP hooks
• Inject is called asynchronously after response is sent
• Perfect template for building comprehensive observability solutions