qwen-code/docs/users/features/lsp.md

Language Server Protocol (LSP) Support

Qwen Code provides native Language Server Protocol (LSP) support, enabling advanced code intelligence features like go-to-definition, find references, diagnostics, and code actions. This integration allows the AI agent to understand your code more deeply and provide more accurate assistance.

Overview

LSP support in Qwen Code works by connecting to language servers that understand your code. When you work with TypeScript, Python, Go, or other supported languages, Qwen Code can automatically start the appropriate language server and use it to:

• Navigate to symbol definitions
• Find all references to a symbol
• Get hover information (documentation, type info)
• View diagnostic messages (errors, warnings)
• Access code actions (quick fixes, refactorings)
• Analyze call hierarchies

Quick Start

LSP is enabled by default in Qwen Code. For most common languages, Qwen Code will automatically detect and start the appropriate language server if it's installed on your system.

Prerequisites

You need to have the language server for your programming language installed:

Language	Language Server	Install Command
TypeScript/JavaScript	typescript-language-server	npm install -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	Installation guide

Configuration

Settings

You can configure LSP behavior in your settings.json:

{
  "lsp": {
    "enabled": true,
    "autoDetect": true,
    "serverTimeout": 10000,
    "allowed": [],
    "excluded": []
  }
}

Setting	Type	Default	Description
lsp.enabled	boolean	true	Enable/disable LSP support
lsp.autoDetect	boolean	true	Automatically detect and start language servers
lsp.serverTimeout	number	10000	Server startup timeout in milliseconds
lsp.allowed	string[]	[]	Allow only these servers (empty = allow all)
lsp.excluded	string[]	[]	Exclude these servers from starting

Custom Language Servers

You can configure custom language servers using a .lsp.json file in your project root:

{
  "languageServers": {
    "my-custom-lsp": {
      "languages": ["mylang"],
      "command": "my-lsp-server",
      "args": ["--stdio"],
      "transport": "stdio",
      "initializationOptions": {},
      "settings": {}
    }
  }
}

Configuration Options

Option	Type	Required	Description
languages	string[]	Yes	Languages this server handles
command	string	Yes*	Command to start the server
args	string[]	No	Command line arguments
transport	string	No	Transport type: stdio (default), tcp, or socket
env	object	No	Environment variables
initializationOptions	object	No	LSP initialization options
settings	object	No	Server settings
workspaceFolder	string	No	Override workspace folder
startupTimeout	number	No	Startup timeout in ms
shutdownTimeout	number	No	Shutdown timeout in ms
restartOnCrash	boolean	No	Auto-restart on crash
maxRestarts	number	No	Maximum restart attempts
trustRequired	boolean	No	Require trusted workspace

*Required for stdio transport

TCP/Socket Transport

For servers that use TCP or Unix socket transport:

{
  "languageServers": {
    "remote-lsp": {
      "languages": ["custom"],
      "transport": "tcp",
      "socket": {
        "host": "127.0.0.1",
        "port": 9999
      }
    }
  }
}

Available LSP Operations

Qwen Code exposes LSP functionality through the unified lsp tool. Here are the available operations:

Code Navigation

Go to Definition

Find where a symbol is defined.

Operation: goToDefinition
Parameters:
  - filePath: Path to the file
  - line: Line number (1-based)
  - character: Column number (1-based)

Find References

Find all references to a symbol.

Operation: findReferences
Parameters:
  - filePath: Path to the file
  - line: Line number (1-based)
  - character: Column number (1-based)
  - includeDeclaration: Include the declaration itself (optional)

Go to Implementation

Find implementations of an interface or abstract method.

Operation: goToImplementation
Parameters:
  - filePath: Path to the file
  - line: Line number (1-based)
  - character: Column number (1-based)

Symbol Information

Hover

Get documentation and type information for a symbol.

Operation: hover
Parameters:
  - filePath: Path to the file
  - line: Line number (1-based)
  - character: Column number (1-based)

Document Symbols

Get all symbols in a document.

Operation: documentSymbol
Parameters:
  - filePath: Path to the file

Workspace Symbol Search

Search for symbols across the workspace.

Operation: workspaceSymbol
Parameters:
  - query: Search query string
  - limit: Maximum results (optional)

Call Hierarchy

Prepare Call Hierarchy

Get the call hierarchy item at a position.

Operation: prepareCallHierarchy
Parameters:
  - filePath: Path to the file
  - line: Line number (1-based)
  - character: Column number (1-based)

Incoming Calls

Find all functions that call the given function.

Operation: incomingCalls
Parameters:
  - callHierarchyItem: Item from prepareCallHierarchy

Outgoing Calls

Find all functions called by the given function.

Operation: outgoingCalls
Parameters:
  - callHierarchyItem: Item from prepareCallHierarchy

Diagnostics

File Diagnostics

Get diagnostic messages (errors, warnings) for a file.

Operation: diagnostics
Parameters:
  - filePath: Path to the file

Workspace Diagnostics

Get all diagnostic messages across the workspace.

Operation: workspaceDiagnostics
Parameters:
  - limit: Maximum results (optional)

Code Actions

Get Code Actions

Get available code actions (quick fixes, refactorings) at a location.

Operation: codeActions
Parameters:
  - filePath: Path to the file
  - line: Start line number (1-based)
  - character: Start column number (1-based)
  - endLine: End line number (optional, defaults to line)
  - endCharacter: End column (optional, defaults to character)
  - diagnostics: Diagnostics to get actions for (optional)
  - codeActionKinds: Filter by action kind (optional)

Code action kinds:

• quickfix - Quick fixes for errors/warnings
• refactor - Refactoring operations
• refactor.extract - Extract to function/variable
• refactor.inline - Inline function/variable
• source - Source code actions
• source.organizeImports - Organize imports
• source.fixAll - Fix all auto-fixable issues

Security

LSP servers are only started in trusted workspaces by default. This is because language servers run with your user permissions and can execute code.

Trust Controls

• Trusted Workspace: LSP servers start automatically
• Untrusted Workspace: LSP servers won't start unless trustRequired: false

To mark a workspace as trusted, use the /trust command or configure trusted folders in settings.

Server Allowlists

You can restrict which servers are allowed to run:

{
  "lsp": {
    "allowed": ["typescript-language-server", "gopls"],
    "excluded": ["untrusted-server"]
  }
}

Troubleshooting

Server Not Starting

1. Check if the server is installed: Run the command manually to verify
2. Check the PATH: Ensure the server binary is in your system PATH
3. Check workspace trust: The workspace must be trusted for LSP
4. Check logs: Look for error messages in the console output

Slow Performance

1. Large projects: Consider excluding node_modules and other large directories
2. Server timeout: Increase lsp.serverTimeout for slow servers
3. Multiple servers: Exclude unused language servers

No Results

1. Server not ready: The server may still be indexing
2. File not saved: Save your file for the server to pick up changes
3. Wrong language: Check if the correct server is running for your language

Debugging

Enable debug logging to see LSP communication:

DEBUG=lsp* qwen

Or check the LSP debugging guide at packages/cli/LSP_DEBUGGING_GUIDE.md.

Claude Code Compatibility

Qwen Code supports Claude Code-style .lsp.json configuration files. If you're migrating from Claude Code, your existing LSP configuration should work with minimal changes.

Legacy Format

The legacy format (used by earlier versions) is still supported but deprecated:

{
  "typescript": {
    "command": "typescript-language-server",
    "args": ["--stdio"],
    "transport": "stdio"
  }
}

We recommend migrating to the new languageServers format:

{
  "languageServers": {
    "typescript-language-server": {
      "languages": ["typescript", "javascript"],
      "command": "typescript-language-server",
      "args": ["--stdio"],
      "transport": "stdio"
    }
  }
}

Best Practices

1. Install language servers globally: This ensures they're available in all projects
2. Use project-specific settings: Configure server options per project when needed
3. Keep servers updated: Update your language servers regularly for best results
4. Trust wisely: Only trust workspaces from trusted sources

FAQ

Q: How do I know which language servers are running?

Use the /lsp status command to see all configured and running language servers.

Q: Can I use multiple language servers for the same file type?

Yes, but only one will be used for each operation. The first server that returns results wins.

Q: Does LSP work in sandbox mode?

LSP servers run outside the sandbox to access your code. They're subject to workspace trust controls.

Q: How do I disable LSP for a specific project?

Add to your project's .qwen/settings.json:

{
  "lsp": {
    "enabled": false
  }
}