🚀 Feature Request: Support streamable HTTP with MCP servers

[hejtmii]

🎤 Tell us your idea

SSE communication has been deprecated in a new revision of the MCP protocol, in favor of streamable HTTP

https://modelcontextprotocol.io/specification/2025-03-26/basic/transports#streamable-http
https://levelup.gitconnected.com/mcp-server-and-client-with-sse-the-new-streamable-http-d860850d9d9d

SSE is also problematic to use in case of multiple clients connected to a single MCP server

Please add support for streamable HTTP MCP connection

[linear]

CPK-4065 🚀 Feature Request: Support streamable HTTP with MCP servers

[copilotkit-support-bot]

CopilotKit currently supports experimental MCP (Model Context Protocol) integration using SSE (Server-Sent Events) transport only. To add support for streamable HTTP MCP connections as per the new protocol specification, you will need to extend the transport configuration and update relevant interfaces to allow HTTP streaming alongside SSE.

Details

Current MCP Implementation Status

CopilotKit already has experimental MCP (Model Context Protocol) support, but it currently only supports SSE (Server-Sent Events) transport:

• Current transport configuration:

async createMCPClient(config) {
  return await experimental_createMCPClient({
    transport: {
      type: "sse",  // Only SSE supported currently
      url: config.endpoint,
      headers: config.apiKey ? { Authorization: `Bearer ${config.apiKey}` } : undefined,
    },
  });
}

• Key implementation files:

• Runtime: CopilotKit/packages/runtime/src/lib/runtime/copilot-runtime.ts
• MCP utilities: CopilotKit/packages/runtime/src/lib/runtime/mcp-tools-utils.ts

Implementation Approach for HTTP Streaming

To add streamable HTTP MCP connection support, you would need to:

• Extend the transport type options in the createMCPClient function:

async createMCPClient(config) {
  return await experimental_createMCPClient({
    transport: {
      type: config.transportType || "sse", // Allow both "sse" and "http"
      url: config.endpoint,
      headers: config.apiKey ? { Authorization: `Bearer ${config.apiKey}` } : undefined,
      // Additional HTTP-specific options
      ...(config.transportType === "http" && {
        method: "POST",
        body: config.requestBody,
        streaming: true
      })
    },
  });
}

• Update the MCPEndpointConfig interface to support transport type selection:

interface MCPEndpointConfig {
  endpoint: string;
  apiKey?: string;
  transportType?: "sse" | "http"; // New field
  requestBody?: any; // For HTTP requests
}

• Configure MCP servers with transport type:

const copilotRuntime = new CopilotRuntime({
  mcpServers: [
    {
      endpoint: "http://localhost:3001/mcp-http",
      transportType: "http", // New HTTP transport
      apiKey: "your-api-key"
    },
    {
      endpoint: "http://localhost:3001/mcp-sse", 
      transportType: "sse", // Existing SSE transport
      apiKey: "your-api-key"
    }
  ],
  createMCPClient: async (config) => {
    // Implementation with both transport types
  }
});

Important Considerations

• Vercel AI Library Dependency: The current implementation relies on experimental_createMCPClient from the Vercel AI library. HTTP streaming support would depend on whether this library supports HTTP transport.

• Protocol Specification: Regarding the "2025-03-26 MCP protocol specification" you mentioned - I cannot verify the specific details of this specification as it's beyond my current knowledge. You should refer to the official MCP documentation for the exact HTTP streaming implementation requirements.

• Backward Compatibility: Ensure the implementation maintains backward compatibility with existing SSE-based MCP integrations.

Alternative Implementation Path

If the Vercel AI library doesn't support HTTP streaming for MCP, you might need to:

• Implement a custom MCP client that handles HTTP streaming directly
• Create transport abstraction layer that can switch between SSE and HTTP based on configuration
• Extend the existing MCP tools conversion logic to work with both transport types

Documentation References:

• CopilotKit Runtime Configuration

Source Code References:

• MCP Runtime Implementation
• MCP Tools Utils

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[hejtmii]

I found this example using the currently proposed experimental_createMCPClient with streaming HTTP support, so I will try to set it up.

https://github.com/vercel/ai/blob/main/examples/mcp/src/http/client.ts

[NathanTarbert]

Hey @hejtmii, thanks for opening this issue. We are planning on switching our implementation from the SSE transport to HTTP very soon, but please keep us updated.

[hellolukeding]

Hey @hejtmii, thanks for opening this issue. We are planning on switching our implementation from the SSE transport to HTTP very soon, but please keep us updated.嘿@hejtmii，感谢您打开本期。我们计划很快将我们的实现从 SSE 传输切换到 HTTP，但请及时更新我们。

nice!