Claude Code Bug: Node.js Hooks Run On Python Projects

by Alex Johnson 54 views

Have you ever experienced a situation where your coding tool seems to be doing things it shouldn't? A recent bug report highlights an issue with Claude Code, where it's running Node.js hooks on Python projects, leading to unnecessary errors. Let's dive into the details of this bug, its impact, and potential solutions.

Problem Summary: The Wrong Hooks at the Wrong Time

The core of the issue is that Claude Code is incorrectly executing npm/biome PostToolUse hooks on Python FastAPI projects. These projects don't even have a package.json file, which is essential for Node.js projects. This leads to frustrating "ENOENT" errors every time the Edit tool is used. Imagine trying to bake a cake, and your oven suddenly starts trying to brew coffee – that's the level of mismatch we're talking about!

Environment Details

  • Platform: macOS (Darwin 24.5.0)
  • Claude Code Version: Latest
  • Project Type: Python FastAPI ML service
  • Working Directory: /Users/devhub/WebstormProjects/polirate/political-fraud-detection-ml

The Annoying Error: ENOENT Strikes Again

Every time the Edit tool is used, this error pops up:

⏺ PostToolUse:Edit [cd "$CLAUDE_PROJECT_DIR" && npm run biome:check] failed with non-blocking status 
  code 254: npm error code ENOENT
  npm error syscall open
  npm error path /Users/devhub/WebstormProjects/polirate/political-fraud-detection-ml/package.json
  npm error errno -2
  npm error enoent Could not read package.json: Error: ENOENT: no such file or directory, open 
  '/Users/devhub/WebstormProjects/polirate/political-fraud-detection-ml/package.json'

This error is a clear indicator that Claude Code is trying to run Node.js-related commands in a Python project, which is like trying to fit a square peg into a round hole.

Detailed Project Configuration Analysis: Digging for Clues

To understand why this is happening, the user meticulously checked all possible hook configuration locations.

Project Hook Configuration

  • File: .claude/config/hooks.json
  • Content: Only contains Python-specific hooks using code-style-guardian agent
  • No npm/biome references found

This confirms that the project itself is not configured to run any Node.js-related hooks. It's purely a Python environment.

Settings Files Checked

  • ~/.claude/settings.json - Does not exist
  • .claude/settings.json - Does not exist
  • .claude/settings.local.json - Contains only Python-specific permissions and hook config references
  • .claude/config/debug.json - Contains only Python debugging settings

None of these settings files contain any references to npm or biome, further reinforcing the idea that the issue is not due to misconfiguration.

Search Results: A Needle in a Haystack

A thorough search of the entire .claude directory for "npm", "biome", and "PostToolUse" yielded no matches. This indicates that the problematic hooks are not explicitly defined within the project or its Claude Code configuration.

Project Context: A Pure Python Paradise

This is a Python FastAPI ML service with the following characteristics:

  • Uses Python 3.11+
  • FastAPI framework
  • SQLAlchemy + PostgreSQL
  • scikit-learn + TensorFlow for ML
  • Poetry/pip for dependency management
  • Has requirements.txt, pyproject.toml, alembic.ini
  • No JavaScript/Node.js components whatsoever

The project is a quintessential Python project, complete with all the trappings of a modern Python development environment. There's absolutely no reason for Node.js hooks to be running here.

Root Cause Analysis: The Mystery Unravels

Claude Code appears to be executing a hardcoded or default npm/biome PostToolUse hook regardless of:

  • Project type (Python vs JavaScript)
  • Absence of package.json
  • Project-specific hook configuration that only defines Python tooling

This suggests cross-project hook inheritance, where hooks from sibling Node.js projects are being inappropriately applied to Python projects. It's as if Claude Code is assuming that every project is a Node.js project, which is a dangerous assumption to make.

Expected Behavior: What Should Happen

Claude Code should:

  1. Detect project type correctly - This is clearly a Python FastAPI project with requirements.txt, pyproject.toml, Python files, etc.
  2. Not execute JavaScript/Node.js hooks on Python projects
  3. Respect project-specific hook configurations that only define Python tooling

In essence, Claude Code should be smart enough to recognize the project type and only execute relevant hooks. It should also respect the user's configuration and not try to be too clever by injecting default hooks.

Actual Behavior: The Reality of the Bug

Claude Code is executing npm/biome hooks despite the project being pure Python with no JavaScript dependencies or configuration. This is a clear violation of the principle of least surprise and can lead to a lot of confusion and frustration for developers.

Reproduction Steps: How to Trigger the Bug

  1. Create or work in a Python project (no package.json)
  2. Set up .claude/config/hooks.json with only Python-specific hooks
  3. Use the Edit tool to modify any file
  4. Observe the npm/biome error in the output

These steps reliably reproduce the bug, making it easy to verify and fix.

Impact: The Ripple Effects

  • Severity: Minor (non-blocking but annoying)
  • Frequency: Every Edit tool usage
  • User Experience: Creates noise and confusion about project setup

While the bug is not a showstopper, it does detract from the overall user experience. It creates unnecessary noise in the output and can lead developers to waste time investigating the issue.

Suggested Fix: A Prescription for a Cure

Claude Code should:

  1. Check for project type before executing language-specific hooks
  2. Only run npm/biome hooks when package.json exists or project is explicitly JavaScript/TypeScript
  3. Respect user-defined hook configurations and not inject default hooks that conflict with project type
  4. Add project type detection logic to prevent cross-language hook contamination

These fixes would ensure that Claude Code behaves in a more predictable and intuitive way, reducing the likelihood of unexpected errors and improving the overall developer experience.

This appears to be a case where a default or hardcoded hook is being applied universally instead of contextually based on project type. It's a classic example of a bug that can be easily fixed with a little bit of extra logic.

Conclusion: Taming the Errant Hooks

In conclusion, the bug in Claude Code where Node.js hooks are executed on Python projects is a minor but annoying issue that can be resolved by implementing project type detection and respecting user-defined hook configurations. By addressing this bug, Claude Code can become an even more reliable and user-friendly tool for developers.

To further explore the topic of debugging and error handling in software development, you might find valuable insights on the **Mozilla Developer Network (MDN)