roslyn_mcp_server

Roslyn-backed MCP adapter for C# navigation.

Architecture:

• backend daemon
  • Owns the Roslyn process and workspace state.
  • Exposes a local HTTP API for health, find_definition, find_references, find_implementations, document_symbols, search_symbols, and read_span.
• MCP stdio adapter
  • Does not own Roslyn state.
  • Receives MCP tool calls and forwards them to the backend daemon.

Install:

• python3 -m pip install -e .
• LangGraph demo:
  • python3 -m pip install -e '.[demo]'

Entrypoints:

• roslyn-mcp-backend config.json
  • Runs the Roslyn backend daemon.
• roslyn-mcp-server config.json
  • Runs the MCP stdio adapter.
• roslyn-mcp-client --config config.json health
  • Calls the backend daemon directly over HTTP.

MCP tools:

• health
• find_definition
• find_references
• find_implementations
• document_symbols
• search_symbols
• read_span

Coordinate system:

• All line and character fields are 0-based, matching LSP.

Testing:

• pytest now runs real integration tests against:
  • a real backend daemon process
  • a real MCP adapter process
  • the real Roslyn Language Server from config.json
• To enable real find_definition and find_references tests, set:
  • ROSLYN_MCP_TEST_FILE_PATH
  • ROSLYN_MCP_TEST_LINE
  • ROSLYN_MCP_TEST_CHARACTER

Structure:

• src/roslyn_mcp_server/backend/: backend daemon and HTTP client
• src/roslyn_mcp_server/main.py: MCP stdio adapter entrypoint
• src/roslyn_mcp_server/mcp/: MCP transport and tool handlers
• src/roslyn_mcp_server/application/: services and request/result models
• src/roslyn_mcp_server/roslyn/: Roslyn session and LSP adapter
• src/roslyn_mcp_server/infrastructure/: config, logging, and compatibility wrapper for the old HTTP bridge path

Examples:

• Start the backend:
  • PYTHONPATH=src python3 -m roslyn_mcp_server.backend.server config.json
• Search workspace symbols:
  • PYTHONPATH=src python3 -m roslyn_mcp_server.client_cli --config config.json search-symbols --query IDataContractCalculator
• List document symbols:
  • PYTHONPATH=src python3 -m roslyn_mcp_server.client_cli --config config.json document-symbols --file /absolute/path/to/file.cs
• Find implementations from an interface or abstract member position:
  • PYTHONPATH=src python3 -m roslyn_mcp_server.client_cli --config config.json implementations --file /absolute/path/to/file.cs --line 10 --character 15
• Run the LangGraph demo:
  • python3 misc/langgraph_demo.py --config config.json
  • Then type your prompt in the terminal when you see Prompt>.