Smart Xdebug

npm version npm downloads CI License: Apache-2.0 Node.js 18+

Let AI debug your PHP code.

Smart XDebug MCP connects Claude to your PHP application's debugger, enabling AI-assisted debugging that actually understands your code at runtime.

The Problem

Debugging PHP applications traditionally requires:

• Manually setting breakpoints in an IDE
• Stepping through code line by line
• Remembering to check the right variables at the right time
• Context-switching between your AI assistant and your debugger

When you ask an AI to help debug, it can only see your code statically. It can't see what's actually happening when your code runs—what values variables hold, where execution flows, or why that exception was thrown.

The Solution

Smart XDebug MCP gives Claude direct access to your PHP debugger. Instead of guessing what might be wrong, Claude can:

• Set breakpoints at suspicious locations
• Run your code and pause at those breakpoints
• Inspect variables to see actual runtime values
• Step through execution to understand the flow
• Track variable changes over time with built-in history

It's like pair programming with a debugger expert who never gets tired and can analyze complex state instantly.

Why This Matters

For Developers

• Faster debugging — Describe the bug, let AI investigate
• Better insights — AI can correlate patterns across variables you might miss
• Learning tool — Watch how an experienced debugger approaches problems

For AI

• Runtime context — See actual values, not just code structure
• Surgical precision — Request only the data needed, preventing context overload
• Time-travel — Query what variables were at previous breakpoints

How It Works

You: "My /api/orders endpoint returns empty for user 42, but they have orders in the database"

Claude: *Sets breakpoint in OrderController*
        *Triggers the API request*
        *Inspects $user, $query, $results at the breakpoint*

Claude: "Found it. The query filters by user_id but $user->id is null here
         because the auth middleware isn't running on this route."

No manual stepping. No guessing. Just answers.

Quick Start

1. Install

npm install -g smart-xdebug-mcp

2. Configure Claude Code

Add to your MCP settings (~/.config/claude/settings.json or project .mcp.json):

{
  "mcpServers": {
    "xdebug": {
      "command": "npx",
      "args": ["smart-xdebug-mcp"]
    }
  }
}

3. Configure XDebug

Ensure your PHP environment has XDebug configured:

xdebug.mode = debug
xdebug.start_with_request = trigger
xdebug.client_host = host.docker.internal  ; For Docker
xdebug.client_port = 9003

4. Debug

Ask Claude to debug your PHP code:

"Set a breakpoint at app/Services/PaymentService.php line 127,
then run: curl 'http://localhost/api/checkout?XDEBUG_SESSION=mcp'"

Features

Feature	What It Does
Natural Language Debugging	Tell Claude what to debug in plain English
Smart Variable Inspection	AI requests only relevant data, not full dumps
Time-Travel Queries	See what variables were at previous steps
Automatic Path Mapping	Works with Docker without manual configuration
Exception Detection	Auto-pause when errors occur
Session History	Review what happened in past debug sessions

Use Cases

• "Why is this returning null?" — Trace execution to find where values disappear
• "This loop seems slow" — Set conditional breakpoints to inspect specific iterations
• "The API works locally but fails in Docker" — Debug the containerized app directly
• "I inherited this codebase" — Let AI explore and explain runtime behavior

Requirements

• Node.js 18+
• PHP with XDebug 3.x configured for remote debugging
• Claude Code or another MCP-compatible AI assistant

Configuration

Environment variables for advanced configuration:

Variable	Default	Description
XDEBUG_MCP_PORT	9003	XDebug listener port
XDEBUG_MCP_TIMEOUT	30000	Connection timeout (ms)
XDEBUG_MCP_WATCHDOG_TIMEOUT	300000	Auto-terminate idle sessions (5 min)

Path mappings are auto-detected from .vscode/launch.json or docker-compose.yml.

Architecture

Smart XDebug MCP acts as a bridge:

Claude ←→ MCP Protocol ←→ Smart XDebug MCP ←→ DBGp Protocol ←→ XDebug ←→ PHP

The server translates high-level debugging intent into DBGp commands, handles the complexity of the protocol, and returns clean, AI-friendly responses.

Contributing

Contributions are welcome! See CONTRIBUTING.md for guidelines.

License

Copyright 2026 Tyler Wall

Licensed under the Apache License, Version 2.0. See LICENSE for details.

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Keywords: PHP debugging, AI debugging, Claude MCP, XDebug integration, autonomous debugging, Model Context Protocol, PHP development tools, AI-assisted development, remote debugging, Docker PHP debugging