LSP Server Configuration

Radius uses Language Server Protocol (LSP) for semantic code operations. You can configure custom LSP servers or override defaults.

Configuration File

Create ~/.radius/lsp-servers.json:

{
  "servers": {
    "python": {
      "command": "pylsp",
      "args": []
    },
    "go": {
      "command": "gopls",
      "args": ["serve"]
    },
    "cpp": {
      "command": "clangd",
      "args": ["--background-index"]
    }
  }
}

Resolution Priority

LSP servers are resolved in this order:

1. Extensions - Installed VSCode extensions with bundled servers
2. User Config - ~/.radius/lsp-servers.json
3. Fallback Table - Built-in defaults

Higher priority sources override lower ones for the same language.

View Active Servers

radius lsp list

Output:

language            command                                 source
--------------------------------------------------------------------------------
typescript          typescript-language-server --stdio      extension (test.test-extension)
rust                rust-analyzer                           extension (rust-lang.rust-analyzer)
python              pylsp                                   user-config (~/.radius/lsp-servers.json)
go                  gopls serve                             fallback
java                jdtls                                   fallback

Built-in Fallbacks

Language	Command	Args
typescript	typescript-language-server	--stdio
typescriptreact	typescript-language-server	--stdio
javascript	typescript-language-server	--stdio
javascriptreact	typescript-language-server	--stdio
rust	rust-analyzer
python	pylsp
go	gopls
java	jdtls
csharp	omnisharp

Examples

Pyright instead of pylsp

{
  "servers": {
    "python": {
      "command": "pyright-langserver",
      "args": ["--stdio"]
    }
  }
}

Clangd for C/C++

{
  "servers": {
    "c": {
      "command": "clangd",
      "args": ["--background-index", "--clang-tidy"]
    },
    "cpp": {
      "command": "clangd",
      "args": ["--background-index", "--clang-tidy"]
    }
  }
}

Zls for Zig

{
  "servers": {
    "zig": {
      "command": "zls",
      "args": []
    }
  }
}

Error Handling

If the config file has invalid JSON:

• Radius logs a warning
• Daemon continues with fallback/extension servers
• No crash or interruption

[extension-host] Failed to parse ~/.radius/lsp-servers.json: JSON Parse error...

Troubleshooting

Server not found

[lsp] failed to start: Executable not found in $PATH: "my-server"

Ensure the server binary is in your PATH:

which my-server

Server crashes

Check if the server works standalone:

echo '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{}}' | my-server --stdio

Wrong language ID

Verify the language ID matches what extensions expect:

radius ext list
# Check language IDs in brackets: [typescript, rust, ...]

Language IDs are case-sensitive.