Language Server Protocol (LSP)

proto integrates with LSP language servers to give the model accurate code intelligence: go-to-definition, find-references, hover info, diagnostics, and code actions.

Enable LSP

Auto-enable — place a .lsp.json in your project root.

CLI flag:


proto --lsp

Settings:


{
  "general": { "lsp": true }
}

Install a language server

Language	Server	Install
TypeScript/JavaScript	typescript-language-server	`npm i -g typescript-language-server typescript`
Python	pylsp	`pip install python-lsp-server`
Go	gopls	`go install golang.org/x/tools/gopls@latest`
Rust	rust-analyzer	See rust-analyzer.github.io
C/C++	clangd	Install LLVM/clangd via your package manager
Java	jdtls	Install JDTLS + JDK

Configure `.lsp.json`


{
  "typescript": {
    "command": "typescript-language-server",
    "args": ["--stdio"],
    "extensionToLanguage": {
      ".ts": "typescript",
      ".tsx": "typescriptreact",
      ".js": "javascript"
    }
  }
}

Configuration options

Option	Type	Default	Description
`command`	string	—	LSP server executable (required)
`args`	string[]	`[]`	Command-line arguments
`transport`	string	`stdio`	`stdio`, `tcp`, or `socket`
`env`	object	—	Environment variables
`initializationOptions`	object	—	LSP initialization options
`settings`	object	—	Sent via `workspace/didChangeConfiguration`
`extensionToLanguage`	object	—	Maps file extensions to language IDs
`startupTimeout`	number	`10000`	Startup timeout (ms)
`restartOnCrash`	boolean	`false`	Auto-restart on crash
`maxRestarts`	number	`3`	Max restart attempts
`trustRequired`	boolean	`true`	Require trusted workspace

TCP/socket transport


{
  "remote-lsp": {
    "transport": "tcp",
    "socket": { "host": "127.0.0.1", "port": 9999 },
    "extensionToLanguage": { ".custom": "custom" }
  }
}

Available operations (via the `lsp` tool)

Operation	What it does
`goToDefinition`	Find where a symbol is defined
`findReferences`	Find all references to a symbol
`goToImplementation`	Find implementations of an interface/abstract method
`hover`	Get documentation and type info
`documentSymbol`	List all symbols in a file
`workspaceSymbol`	Search for symbols across the workspace
`prepareCallHierarchy`	Get call hierarchy at a position
`incomingCalls`	Functions that call the given function
`outgoingCalls`	Functions called by the given function
`diagnostics`	Errors/warnings for a file
`workspaceDiagnostics`	All diagnostics across the workspace
`codeActions`	Quick fixes and refactorings at a location

All operations take filePath, line (1-based), and character (1-based) parameters.

Security

LSP servers run with your user permissions and can execute code. By default, they only start in trusted workspaces. Override per server:


{
  "safe-server": {
    "command": "my-server",
    "trustRequired": false,
    "extensionToLanguage": { ".x": "x" }
  }
}

Trust a workspace with /trust or by configuring trusted folders in settings.

Check server status


/lsp status

Lists all configured servers and whether they are running.

Troubleshooting

Symptom	Fix
Server not starting	Verify binary is in PATH; check workspace is trusted
Slow performance	Exclude `node_modules`; increase `startupTimeout`
No results	Wait for indexing; save the file first
Multiple servers, no results	First server to return results wins

Debug logging:


DEBUG=lsp* proto --lsp

SDK usage


import { query } from '@protolabsai/sdk';
 
const conversation = query({
  prompt: 'Fix all type errors in the auth module',
  options: { lsp: true, permissionMode: 'auto-edit' },
});