Delphi LSP MCP Server

A Model Context Protocol (MCP) server that exposes Delphi Language Server Protocol (LSP) capabilities to AI assistants and other MCP clients.

Author: Skybuck Flying
Contact: skybuck2000@hotmail.com
Version: 0.01

Repository: https://github.com/SkybuckFlying/Delphi-LSP-MCP-Server

Specifications:

• MCP Specification (2025-11-25): https://modelcontextprotocol.io/specification/2025-11-25
• LSP Specification 3.17: https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/

This server acts as a bridge between:

• MCP Clients (like Claude Desktop, AI assistants) - communicate via JSON-RPC 2.0 over stdio
• DelphiLSP.exe - Embarcadero's Delphi Language Server

It allows AI assistants to perform code intelligence operations on Delphi source code, including:

• Go to Definition
• Find References
• Hover Information
• Code Completion
• Workspace Symbol Search

• Delphi 13 (RAD Studio 13.0 or later)
• DelphiLSP.exe (included with RAD Studio)
• Windows OS

1. Open DelphiLSPMCPServer.dpr in Delphi IDE
2. Build the project (Project → Build)
3. The executable will be created in the project directory

Or use the command line:

msbuild DelphiLSPMCPServer.dpr /p:Config=Release

DelphiLSPMCPServer [options]

Options:
  --lsp-path <path>      Path to DelphiLSP.exe 
                         (default: C:\Tools\RAD Studio\37.0\bin64\DelphiLSP.exe)
  --workspace <path>     Workspace root directory (default: current directory)
  --log-level <level>    Log level: debug, info, warning, error (default: info)
  --help                 Show help message

DelphiLSPMCPServer --workspace "C:\MyDelphiProject" --log-level debug

The server will:

1. Start DelphiLSP.exe as a child process
2. Initialize the LSP connection
3. Listen for MCP requests on stdin
4. Send MCP responses to stdout
5. Write logs to stderr

Add to your Claude Desktop MCP configuration (claude_desktop_config.json):

{
  "mcpServers": {
    "delphi-lsp": {
      "command": "K:\\Delphi\\Tests\\test Skybuck's LSP MCP server\\version 0.01\\DelphiLSPMCPServer.exe",
      "args": [
        "--workspace",
        "C:\\MyDelphiProject",
        "--log-level",
        "info",
        "--lsp-path",
        "C:\\Tools\\RAD Studio\\37.0\\bin64\\DelphiLSP.exe"
      ]
    }
  }
}

Find the definition of a symbol at a specific position.

Parameters:

• uri (string): File URI (e.g., file:///C:/path/to/file.pas)
• line (integer): Zero-based line number (NOTE: Delphi IDE displays line numbers starting at 1, so subtract 1 from the IDE line number)
• character (integer): Zero-based character offset

Example:

{
  "uri": "file:///C:/MyProject/Unit1.pas",
  "line": 10,
  "character": 15
}

Find all references to a symbol.

Parameters:

• uri (string): File URI
• line (integer): Zero-based line number (0-based)
• character (integer): Zero-based character offset
• includeDeclaration (boolean, optional): Include declaration in results (default: true)

Get hover information (documentation, type info) for a symbol.

Parameters:

• uri (string): File URI
• line (integer): Zero-based line number (0-based)
• character (integer): Zero-based character offset

Get code completion suggestions at a specific position.

Parameters:

• uri (string): File URI
• line (integer): Zero-based line number (0-based)
• character (integer): Zero-based character offset

Search for symbols across the entire workspace.

Parameters:

• query (string): Search query string

Example:

{
  "query": "TForm"
}

┌─────────────────────┐
│  MCP Client         │
│  (AI Assistant)     │
└──────────┬──────────┘
           │ JSON-RPC over stdio
           ▼
┌─────────────────────┐
│  Delphi LSP MCP     │
│  Server             │
│  ┌───────────────┐  │
│  │ MCP Server    │  │
│  │ Component     │  │
│  └───────┬───────┘  │
│          │          │
│  ┌───────▼───────┐  │
│  │ LSP Client    │  │
│  │ Component     │  │
│  └───────┬───────┘  │
└──────────┼──────────┘
           │ LSP JSON-RPC over stdio
           ▼
┌─────────────────────┐
│  DelphiLSP.exe      │
│  (Language Server)  │
└─────────────────────┘

• Version: 2024-11-05
• Transport: stdio with Content-Length headers
• Message Format: JSON-RPC 2.0

• Version: 3.17
• Transport: stdio with Content-Length headers
• Message Format: JSON-RPC 2.0

Logs are written to stderr with the following format:

[YYYY-MM-DD HH:MM:SS.mmm] [LEVEL] Message

Log levels:

• DEBUG: Detailed protocol messages
• INFO: General information (default)
• WARNING: Warning messages
• ERROR: Error messages

Ensure the path to DelphiLSP.exe is correct. Use --lsp-path to specify the location:

DelphiLSPMCPServer --lsp-path "C:\Program Files\Embarcadero\Studio\37.0\bin64\DelphiLSP.exe"

Check stderr logs for details. Common issues:

• Invalid workspace path
• DelphiLSP.exe crashes on startup
• Insufficient permissions

Ensure:

1. The workspace path is correct
2. The file URI uses the correct format (file:///C:/path/to/file.pas)
3. Line and character positions are zero-based
4. The file is part of a valid Delphi project

This is a demonstration project. Use at your own risk.

0.1.0 - Initial release

• Document symbols
• Code actions
• Formatting
• Rename

• Automatic LSP server restart on crash
• Improved timeout handling
• Retry logic for transient failures

• Project file support
• Search path configuration
• Compiler settings

• Connection pooling
• Response caching
• Async operations

• JSON‑RPC parsing
• Protocol type serialization
• Message transport

• Real Delphi projects
• Various file types
• Edge cases