Can't make it work with Claude Code

[jdvor]

Summary

• Installed both csharp-ls and csharp-lsp-mcp as donet tools
• Can run them from command line with no errors and they stay open; I assume they are listening
• I run csharp-lsp-mcp with verbose and traces on
• Claude Code (2.1.41) never successfully calls the csharp_set_workspace; the call timeouts after 30s.
• I have attached both the Claude Code MCP server config and the logs I was able to locate regarding the situation (again from Claude Code)

Details

Environment:

• OS: Windows 11 Pro 10.0.26200
• csharp-lsp-mcp: Latest version (installed via dotnet tool)
• MCP Client: Claude Code 2.1.41
• Configuration: MCP_DEBUG=1, --verbose flag enabled

dotnet tool update csharp-ls -g
dotnet tool update csharplspmcp -g

Configuration (.claude.json):

"csharp-lsp-mcp": {
  "type": "stdio",
  "command": "csharp-lsp-mcp",
  "args": ["--verbose"],
  "env": {
    "MCP_DEBUG": "1"
  }
}

Issue:
When calling the csharp_set_workspace tool, the MCP server hangs for exactly 30 seconds with no log output, then times out with "MCP error -32603: An error occurred."

Expected behavior:

• Tool should execute and set workspace
• Should see trace logs about tool execution (method handler called, parameters received, csharp-ls launch attempts, etc.)
• Should complete in < 1 second or fail with descriptive error

Actual behavior:

• Server initializes successfully
• Tool call is received
• No trace logs after tool call (despite MCP_DEBUG=1 and --verbose)
• Hangs silently for 30 seconds
• Times out with generic error -32603

Logs showing the issue:

2026-02-13T16:26:04.511Z [ERROR] MCP server "csharp-lsp-mcp" Server stderr: dbug: Microsoft.Extensions.Hosting.Internal.Host[1]
Hosting starting
info: ModelContextProtocol.Server.StdioServerTransport[857250842]
Server (stream) (csharp-lsp-mcp) transport reading messages.
trce: ModelContextProtocol.Server.StdioServerTransport[551200620]
Server (stream) (csharp-lsp-mcp) transport received message. Message: '{"method":"initialize","params":{"protocolVersion":"2025-11-25","capabilities":{"roots":{}},"clientInfo":{"name":"claude-code","version":"2.1.41"}},"jsonrpc":"2.0","id":0}'.
dbug: ModelContextProtocol.Server.StdioServerTransport[1000831420]
Server (stream) (csharp-lsp-mcp) transport received message with ID '0'.
trce: ModelContextProtocol.Server.McpServer[1361998181]
Server (csharp-lsp-mcp 1.0.0) session 5a5f09a2d4e84b599dbcef6b6c86f12b created with transport stdio
info: Microsoft.Hosting.Lifetime[0]
Application started. Press Ctrl+C to shut down.
info: Microsoft.Hosting.Lifetime[0]
Hosting environment: Production
info: Microsoft.Hosting.Lifetime[0]
Content root path: C:\dev\terraverse-trading
dbug: Microsoft.Extensions.Hosting.Internal.Host[2]
Hosting started
dbug: ModelContextProtocol.Server.McpServer[330297028]
Server (csharp-lsp-mcp 1.0.0) read JsonRpcRequest message from channel.
info: ModelContextProtocol.Server.McpServer[570385771]
Server (csharp-lsp-mcp 1.0.0) method 'initialize' request handler called.
info: ModelContextProtocol.Server.McpServer[1867955179]
Server (csharp-lsp-mcp 1.0.0), Client (claude-code 2.1.41) method 'initialize' request handler completed.
trce: ModelContextProtocol.Server.McpServer[1672174748]
Server (csharp-lsp-mcp 1.0.0), Client (claude-code 2.1.41) sending message. Message: '{"result":{"protocolVersion":"2025-06-18","capabilities":{"logging":{},"tools":{"listChanged":true}},"serverInfo":{"name":"csharp-lsp-mcp","version":"1.0.0"}},"id":0,"jsonrpc":"2.0"}'.

[SERVER INITIALIZED SUCCESSFULLY AT 16:26:04.511]

2026-02-13T16:26:04.511Z [DEBUG] MCP server "csharp-lsp-mcp": Successfully connected to stdio server in 286ms
2026-02-13T16:26:04.511Z [DEBUG] MCP server "csharp-lsp-mcp": Connection established with capabilities: {"hasTools":true,"hasPrompts":false,"hasResources":false,"serverVersion":{"name":"csharp-lsp-mcp","version":"1.0.0"}}

[TOOL CALLED AT 16:26:04.511]

2026-02-13T16:26:04.511Z [DEBUG] MCP server "csharp-lsp-mcp": Calling MCP tool: csharp_set_workspace

[NO MORE LOGS FROM MCP SERVER - HANGING SILENTLY]
[UNRELATED LOGS FROM OTHER SERVICES OMITTED - SHOWING JUST ELAPSED TIME]

... 5 seconds elapsed ...
... 10 seconds elapsed ...
... 15 seconds elapsed ...
... 20 seconds elapsed ...
... 25 seconds elapsed ...
... 30 seconds elapsed ...

[TIMEOUT AT 16:26:34.534 - EXACTLY 30 SECONDS LATER]

2026-02-13T16:26:34.534Z [DEBUG] MCP server "csharp-lsp-mcp": Tool 'csharp_set_workspace' still running (30s elapsed)
2026-02-13T16:26:34.833Z [DEBUG] MCP server "csharp-lsp-mcp": Tool 'csharp_set_workspace' failed after 30s: MCP error -32603: An error occurred.

Key observations:

1. ✅ Server starts and initializes successfully
2. ✅ Session created, capabilities exchanged
3. ❌ After tool call, zero log output from tool handler
4. ❌ Should see "method 'tools/call' request handler called" - but don't
5. ❌ Should see trace logs about launching csharp-ls - but don't
6. ❌ Hangs for exactly 30 seconds (likely client timeout)
7. ❌ Generic error -32603 with no details

Reproduction:

1. Configure csharp-lsp-mcp in Claude Code with --verbose and MCP_DEBUG=1
2. Call csharp_set_workspace with path parameter
3. Observe 30-second hang with no logs
4. Receive timeout error

Tool call parameters:

{
  "name": "csharp_set_workspace",
  "arguments": {
    "path": "C:\\dev\\terraverse-trading"
  }
}

Additional context:

• csharp-ls is installed and available in PATH
• Directory exists and is a valid C# workspace with .sln file
• Same issue occurs on multiple calls
• Killing and restarting MCP server doesn't help