Claude Bug: Node.js Hooks Run On Python Projects

by Alex Johnson 49 views

This article delves into a peculiar bug encountered while using Claude Code in a multi-project workspace. Specifically, it addresses the issue of Node.js hooks being executed on Python projects, leading to errors and a degraded user experience. This comprehensive bug report outlines the problem, its impact, and potential solutions.

Problem Summary: Unexpected Node.js Hook Execution

The core issue is that Claude Code incorrectly triggers npm/biome PostToolUse hooks on Python FastAPI projects. These projects, by design, lack a package.json file, which is essential for Node.js projects. Consequently, this unwanted execution results in "ENOENT" errors appearing after each use of the Edit tool within Claude Code. This behavior is unexpected and disrupts the development workflow for Python projects.

Environment Details: Reproducing the Bug

To better understand the context of this bug, here's a breakdown of the environment where it was observed:

  • 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

This setup highlights that the bug occurs on a macOS environment with the latest Claude Code version when working on a Python-based machine learning service built with FastAPI.

Error Encountered: The "ENOENT" Nightmare

Each time the Edit tool is utilized, the following error surfaces, indicating the attempt to run Node.js-specific commands within a Python project:

⏺ 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 clearly demonstrates that Claude Code is trying to execute npm commands in a directory where a package.json file (a staple of Node.js projects) is absent, leading to the "ENOENT" (Error No Entry) error. This confirms the inappropriate triggering of Node.js hooks on a Python project.

Configuration Analysis: Where are these Hooks Coming From?

To pinpoint the origin of these erroneous hooks, a thorough examination of potential configuration locations was conducted. This involved scrutinizing project-specific and global settings files to identify any traces of npm or biome configurations.

Project Hook Configuration: Focused on Python

The project's hook configuration file, located at .claude/config/hooks.json, was inspected. Its content exclusively contained Python-specific hooks utilizing the code-style-guardian agent. There were absolutely no references to npm or biome found within this file.

Settings Files: Absence of Global Configuration

The following settings files were checked for any global configurations that might be triggering the Node.js hooks:

  • ~/.claude/settings.json - This file does not exist, indicating a lack of global settings.
  • .claude/settings.json - This file also does not exist, further reinforcing the absence of global settings.
  • .claude/settings.local.json - This file contains only Python-specific permissions and hook configuration references.
  • .claude/config/debug.json - This file is dedicated to Python debugging settings and does not contain any hook-related configurations.

Comprehensive Search: No Hidden Configurations

A comprehensive search was conducted within the entire .claude directory for keywords such as "npm", "biome", and "PostToolUse". The search yielded no matches, confirming that there are no explicit configurations within the project or Claude Code's settings that would explain the execution of Node.js hooks. Furthermore, the project does not contain a package.json file, as it is a purely Python-based project.

Project Context: A Pure Python Environment

To further emphasize the anomaly, it's crucial to understand the project's characteristics. This is a Python FastAPI ML service with the following attributes:

  • Utilizes Python 3.11+
  • Employs the FastAPI framework for building APIs
  • Leverages SQLAlchemy and PostgreSQL for database interactions
  • Uses scikit-learn and TensorFlow for machine learning tasks
  • Manages dependencies with Poetry/pip, utilizing requirements.txt and pyproject.toml
  • Includes alembic.ini for database migrations
  • Crucially, it has absolutely no JavaScript/Node.js components whatsoever.

This detailed description underscores that the project is a pure Python environment, making the execution of Node.js hooks entirely inappropriate.

Root Cause: Cross-Project Hook Inheritance

The most plausible explanation for this behavior is that Claude Code is executing a hardcoded or default npm/biome PostToolUse hook, irrespective of the project type, the absence of a package.json file, or the project-specific hook configurations that only define Python tooling. This points towards a potential issue of cross-project hook inheritance, where hooks from sibling Node.js projects are being incorrectly applied to Python projects within the same workspace.

This suggests that Claude Code isn't properly isolating hook execution based on project type, leading to the unintended application of Node.js hooks to Python projects.

Expected vs. Actual Behavior: A Discrepancy

Expected Behavior: Intelligent Hook Execution

Ideally, Claude Code should exhibit the following behavior:

  1. Accurately detect the project type: It should recognize that this is a Python FastAPI project based on the presence of requirements.txt, pyproject.toml, and Python files.
  2. Avoid executing JavaScript/Node.js hooks: Node.js hooks should only be executed on projects that are explicitly identified as JavaScript or Node.js projects.
  3. Respect project-specific hook configurations: It should prioritize and adhere to the hook configurations defined within the project itself, ensuring that only relevant hooks are executed.

Actual Behavior: Erroneous Node.js Execution

In reality, Claude Code is executing npm/biome hooks despite the project being a pure Python environment with no JavaScript dependencies or configuration. This contradicts the expected behavior and introduces unnecessary errors into the development workflow.

Reproduction Steps: Triggering the Bug

To reproduce this bug, follow these steps:

  1. Create or work within a Python project that does not contain a package.json file.
  2. Set up the .claude/config/hooks.json file with only Python-specific hooks.
  3. Use the Edit tool to modify any file within the project.
  4. Observe the npm/biome error in the output, confirming the erroneous execution of Node.js hooks.

These steps reliably trigger the bug, demonstrating its consistent and reproducible nature.

Impact Assessment: Annoyance and Confusion

Severity: Minor but Irritating

The bug itself is considered minor as it doesn't completely halt development. However, it is annoying due to the constant error messages.

Frequency: Constant Disruption

The issue occurs every time the Edit tool is used, making it a frequent source of disruption.

User Experience: Noise and Confusion

The error messages create noise and confusion regarding the project setup, as developers might mistakenly believe there's an issue with their Node.js configuration (even though there isn't any).

Suggested Fix: Context-Aware Hook Execution

To address this bug, Claude Code should implement the following fixes:

  1. Implement project type checking: Before executing any language-specific hooks, Claude Code should accurately determine the project type (e.g., Python, JavaScript, etc.).
  2. Conditional npm/biome hook execution: Only execute npm/biome hooks when a package.json file exists in the project or when the project is explicitly identified as JavaScript or TypeScript.
  3. Prioritize user-defined hook configurations: Respect the hook configurations defined by the user within the project, and avoid injecting default hooks that conflict with the project type.
  4. Enhance project type detection logic: Improve the project type detection logic to prevent cross-language hook contamination, ensuring that hooks are only executed in the appropriate context.

These fixes would ensure that hooks are executed contextually, based on the project type and configuration, preventing the erroneous execution of Node.js hooks on Python projects.

In essence, this bug highlights a case where a default or hardcoded hook is being applied universally instead of contextually, leading to unexpected and undesirable behavior. By implementing the suggested fixes, Claude Code can provide a more seamless and intuitive development experience for users working with multi-project workspaces.

For more information on managing Node.js projects, visit the Node.js official website.