Problem

Currently, we feature detect for extension-based MCP registration by feature-detection (lm.registerMcpServerDefinitionProvider). While this works fine for VS Code, this causes issues with Kiro as it has the API, but no-ops the registration.

Solution

Lock-down extension-based registration to only VS Code as we cannot rely on clones to implement the API even if the API is available. In the future, we'll just opt-in IDEs when we know it works.

Note: After blocking extension-based registration, the MCP Install URL Handler is also not available in Kiro, but that will be handled by the GK CLI.

I've opened Issues with Kiro for both MCP install scenarios:

• MCP Extension Registration: Support programmatic MCP server registration through extensions kirodotdev/Kiro#2974
• MCP Install URL Handler: MCP install URL handler is not working kirodotdev/Kiro#2977