Fixing Python Package Import Errors: A Chrome-devtools-mcp-fork Story

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Hey everyone! Today, we're diving deep into a tricky issue we encountered with the chrome-devtools-mcp-fork package. Specifically, we're going to break down those pesky import errors that popped up when using it with Claude Code CLI. If you've ever wrestled with Python package imports, or you're just curious about how we tackled this problem, you're in the right place!

🔍 Problem Description

So, what exactly went wrong? In version 1.0.4 of chrome-devtools-mcp-fork, we ran into some critical import errors that made the package unusable with Claude Code CLI. This meant that whenever Claude Code tried to use any MCP tool function, things would fall apart. The main culprits? These two error messages:

  • ❌ Error 1: attempted relative import beyond top-level package
  • ❌ Error 2: ModuleNotFoundError: No module named 'chrome_devtools_mcp_fork'

These errors were a real headache because they completely blocked the intended functionality of the package. Let's dig into what caused these issues.

🎯 Root Cause Analysis

To get to the bottom of these errors, we had to put on our detective hats and trace the root causes. Here’s what we uncovered:

1. Flat Installation Structure

Problem: The culprit here was the py-modules = ["main", "client", "cdp_context"] configuration in our pyproject.toml file. This setting caused modules to be installed directly into the site-packages/ directory without setting up the proper package hierarchy.

site-packages/
├── main.py              # standalone module  
├── client.py            # standalone module
├── cdp_context.py       # standalone module
└── tools/               # package directory
    ├── __init__.py
    └── *.py files

Why it breaks: This flat structure messes with relative imports. Imagine trying to find your way around a city without street names – that's what Python feels like when it can't figure out the package structure. Relative imports, like from .tools.utils import, failed because client was treated as a standalone module, not part of a package containing tools. It’s like trying to access a room in a house when the house itself isn't properly built!

2. Mixed Import Patterns

Problem: To make matters more complicated, the codebase was using a mix of different import styles. Some imports expected a proper package structure, while others assumed everything was in the same directory. This inconsistency created a tangled web of dependencies that were prone to breaking.

  • client.py (lines 216, 232, 279, 293): from .tools.utils import safe_timestamp_conversion (expected a package structure)
  • All 7 tools/*.py files: from cdp_context import require_cdp_client (expected a flat import)
  • main.py: from client import ChromeDevToolsClient (expected a flat import)

This mix-and-match approach was like speaking two different languages within the same sentence – confusing and likely to cause errors.

3. MCP Server Incompatibility

Problem: Claude Code CLI had certain expectations about how MCP servers should be packaged. It was looking for properly structured packages with correct import resolution, adhering to modern Python packaging standards (think 2025-level!). Our package, in its initial state, just wasn't up to par.

🔧 Solution Implemented

Okay, so we knew what was broken. Now, how did we fix it? We tackled this in three phases:

Phase 1: Package Configuration Modernization

First things first, we needed to update our pyproject.toml file to align with modern Python packaging best practices. This was like giving our package a complete makeover, ensuring it was structured correctly.

# REMOVED problematic flat installation:
# py-modules = ["main", "client", "cdp_context"]

# ADDED proper package discovery:
[tool.setuptools]
package-dir = {"chrome_devtools_mcp_fork" = "src"}
packages = ["chrome_devtools_mcp_fork", "chrome_devtools_mcp_fork.tools"]

# FIXED entry point:
[project.scripts]
chrome-devtools-mcp-fork = "chrome_devtools_mcp_fork.main:main"

# BUMPED version:
version = "1.0.5"

The key changes here were removing the flat installation configuration and adding proper package discovery. This tells Python, “Hey, this is how our package is structured!” We also fixed the entry point and bumped the version number to 1.0.5. Think of this as laying the foundation for a well-organized building.

Phase 2: Import System Standardization (9 files total)

Next up, we needed to standardize our import statements. This involved going through the codebase and making sure all imports were consistent and correct. It’s like ensuring everyone in a group speaks the same language.

✅ main.py (2 imports fixed):

# FROM: from client import ChromeDevToolsClient
# TO:   from .client import ChromeDevToolsClient

# FROM: from tools import (register_chrome_tools, ...)
# TO:   from .tools import (register_chrome_tools, ...)

✅ cdp_context.py (1 import fixed):

# FROM: from tools.utils import create_error_response
# TO:   from .tools.utils import create_error_response

✅ ALL 7 tools/*.py files (1 import each):

# FROM: from cdp_context import require_cdp_client
# TO:   from ..cdp_context import require_cdp_client

Files: chrome_management.py, console.py, css.py, dom.py, network.py, performance.py, storage.py

We went through these files and adjusted the import statements to use relative imports where appropriate. This ensured that Python could correctly locate the necessary modules within the package structure.

Phase 3: Quality Assurance

Finally, we had to ensure our changes didn't introduce any new issues. This meant rigorous testing and verification. It's like the final inspection before opening a building to the public.

  • ✅ Auto-fixed linting issues with ruff --fix
  • ✅ Verified type checking passes with mypy
  • ✅ Comprehensive import testing

We used tools like ruff to automatically fix linting issues and mypy to verify type checking. We also conducted thorough import testing to confirm that everything was working as expected. This phase was all about making sure our package was not only functional but also clean and maintainable.

📦 Result: Proper Package Structure

After our efforts, the package now installs with a proper hierarchy. This is what the structure looks like:

chrome_devtools_mcp_fork/
├── __init__.py
├── main.py
├── client.py  
├── cdp_context.py
└── tools/
    ├── __init__.py
    ├── chrome_management.py
    ├── console.py
    ├── css.py
    ├── dom.py
    ├── network.py
    ├── performance.py
    ├── storage.py
    └── utils.py

This structure is clean, organized, and exactly what Python expects for a well-behaved package. It's like having a blueprint for our building, making it easy to navigate and maintain.

✅ Verification Results

To be absolutely sure our fixes worked, we ran a series of verification tests. Here’s what we found:

Package Installation & Import Testing:

✅ Package builds successfully (python -m build)
✅ Package installs correctly (pip install -e .)
✅ All imports work: import chrome_devtools_mcp_fork
✅ Main module imports: from chrome_devtools_mcp_fork.main import main
✅ Tools import: from chrome_devtools_mcp_fork.tools import register_chrome_tools
✅ Entry point works: chrome-devtools-mcp-fork --help
✅ MCP tools register successfully with Claude Code CLI

Code Quality:

✅ Linting passes: ruff check . (7 issues auto-fixed)
✅ Type checking passes: mypy src/ (0 errors)
✅ All relative imports resolve correctly

The results speak for themselves! The package builds, installs, and imports correctly. Our MCP tools register seamlessly with Claude Code CLI, and our code quality checks are all green. It’s like getting a perfect score on an exam – a testament to the hard work we put in.

🚀 Release Information

We’re excited to announce the release of version 1.0.5, which includes these important fixes and improvements:

Version 1.0.5 Changes:

  • 🐛 Bug Fix: Resolves critical import errors preventing MCP server functionality
  • 📦 Modernization: Updates package structure to follow 2025 Python packaging standards
  • 🔄 Compatibility: Ensures seamless integration with Claude Code CLI
  • ⚡ Performance: Proper package structure improves import performance
  • 🔒 Security: Uses modern packaging practices for better dependency resolution

This release is a significant step forward for chrome-devtools-mcp-fork, making it more reliable, efficient, and secure.

🧪 Testing Instructions

Want to verify the fix for yourself? Here’s how:

# Install the fixed version
pip install chrome-devtools-mcp-fork==1.0.5

# Test basic imports
python -c "import chrome_devtools_mcp_fork; print('✅ Package import successful!')"

# Test MCP server functionality  
chrome-devtools-mcp-fork  # Should start without errors

# Test with Claude Code CLI (if configured)
# All MCP tools should now work without import errors

These simple steps will help you confirm that the fixes are working as expected. It’s like taking a test drive before buying a car – you want to make sure everything runs smoothly.

📚 Technical References

For those of you who want to dive even deeper, here are some helpful resources:

These references provide a wealth of information on Python packaging best practices and the concepts we discussed in this article. It’s like having access to the architect’s blueprints and the engineer’s notes – a comprehensive view of the project.

Impact: This fix restores full functionality to chrome-devtools-mcp-fork for Claude Code CLI users and modernizes the package structure for long-term maintainability. We’re confident that these changes will make the package more robust and easier to use for everyone. Thanks for following along, guys! If you have any questions or want to share your own experiences with package import errors, drop a comment below. Let’s keep the conversation going!