Detailed Feature Request: #4218

Implement MCP Streamable HTTP Support in same manner as SSE & stdio

The existing pinned version of the client SDK already supports Streamable HTTP transport—this PR simply exposes that capability in our extension alongside the existing stdio and SSE options.

I've been watching several efforts related to implementing Streamable HTTP but they seem to be tied to enormous refactors that fundamentally change the Roo backend and haven't been updated in nearly a month, so I figured others might benefit from my local branch, which cleanly adds streamable HTTP support in the same manner as stdio and SSE are implemented exactly.

Related GitHub Issue

Opened an issue at #4216
Will close that, #3627 and #2131

Description

This pull request introduces support for a new Model Context Protocol (MCP) server type: streamable-http. This allows Roo Code to connect to MCP servers that use a streamable HTTP-based transport, expanding its integration capabilities.

Key changes include:

• Added Streamable HTTP Transport to McpHub.ts (src/services/mcp/McpHub.ts):
  • Imported and integrated StreamableHTTPClientTransport from the MCP SDK.
  • Updated the McpConnection type to include StreamableHTTPClientTransport.
  • Enhanced server configuration validation (validateServerConfig) to:
    • Recognize the streamable-http type.
    • Provide specific error messages for streamable-http configurations (e.g., requiring a url).
    • Ensure that configurations with a url explicitly define their type as either sse or streamable-http.
  • Modified the connectServer method to:
    • Handle the instantiation and setup of StreamableHTTPClientTransport for streamable-http type servers.
    • Include appropriate onerror and onclose handlers for this new transport type, similar to the existing SSEClientTransport.
• New Transport Mock: Added src/__mocks__/@modelcontextprotocol/sdk/client/streamable-http.js to mock the StreamableHTTPClientTransport for testing purposes.

Test Procedure

1. Unit Tests:
   • Review existing unit tests for McpHub.ts to ensure they cover the new validation logic for streamable-http configurations.
   • If necessary, add new test cases specifically for streamable-http connection attempts, error handling, and successful connections using the new mock.
2. Manual Testing:
   • Add a new MCP server configuration to your settings.json with type: "streamable-http" and a valid (or mock) url.

     "mcp.servers": {
       "myStreamableServer": {
         "type": "streamable-http",
         "url": "http://localhost:8080/stream", // Replace with your test endpoint
         "displayName": "My Streamable HTTP Server"
       }
     }

   • Start Roo Code and verify:
     • The server attempts to connect.
     • The status of the server (connecting, connected, disconnected, error) is correctly displayed in the MCP panel.
     • If using a mock server, verify that tool calls or resource access (if implemented by the mock) function as expected.
   • Test error scenarios:
     • Invalid URL.
     • Server not reachable.
     • Server disconnects after connection.

Type of Change

• 🐛 Bug Fix: Non-breaking change that fixes an issue.
• ✨ New Feature: Non-breaking change that adds functionality.
• 💥 Breaking Change: Fix or feature that would cause existing functionality to not work as expected.
• ♻️ Refactor: Code change that neither fixes a bug nor adds a feature.
• 💅 Style: Changes that do not affect the meaning of the code (white-space, formatting, etc.).
• 📚 Documentation: Updates to documentation files.
• ⚙️ Build/CI: Changes to the build process or CI configuration.
• 🧹 Chore: Other changes that don't modify src or test files.

Pre-Submission Checklist

• Issue Linked: This PR is linked to an approved GitHub Issue (see "Related GitHub Issue" above).
• Scope: My changes are focused on the linked issue (one major feature/fix per PR).
• Self-Review: I have performed a thorough self-review of my code.
• Code Quality:
  • My code adheres to the project's style guidelines.
  • There are no new linting errors or warnings (npm run lint).
  • All debug code (e.g., console.log) has been removed.
• Testing:
  • New and/or updated tests have been added to cover my changes.
  • All tests pass locally (npm test).
  • The application builds successfully with my changes.
• Branch Hygiene: My branch is up-to-date (rebased) with the main branch.
• Documentation Impact: I have considered if my changes require documentation updates (see "Documentation Updates" section below).
• Changeset: A changeset has been created using npm run changeset if this PR includes user-facing changes or dependency updates.
• Contribution Guidelines: I have read and agree to the Contributor Guidelines.

Screenshots / Videos

Showing it running with Google Workspace MCP via Streamable HTTP

Documentation Updates

There is seemingly no references to MCP setup present in the README.md so I did not include that in the scope of this PR. Happy to add it myself, will follow with a second separate PR that covers stdio, sse & streamable-http. User-facing documentation regarding MCP server configuration will need to be updated to include the new streamable-http type, its purpose, and its specific configuration options (url, optional headers).

Additional Notes

This change aligns the MCP client capabilities more closely with the available transport mechanisms in the @modelcontextprotocol/sdk.

Get in Touch

taylorwilsdon