Claude Code Bug: Node.js Hooks On Python Projects

h1. Claude Code Bug: Node.js Hooks on Python Projects

h2. The Unexpected Encounter: Node.js Hooks in Your Python World

Have you ever found yourself working diligently on a pristine Python project, perhaps a FastAPI ML service humming with SQLAlchemy and TensorFlow, only to be interrupted by a cryptic npm error code ENOENT? It's a bewildering experience, and one that we've recently uncovered within Claude Code's behavior. Claude Code, in certain multi-project workspace configurations, seems to be erroneously executing Node.js-specific hooks, like those from npm or biome, on projects that have absolutely no business touching JavaScript. This isn't just a minor glitch; it's a fundamental misunderstanding of project context that can lead to frustrating errors after every Edit tool usage. Imagine meticulously crafting your Python code, managing dependencies with Poetry or pip, and then seeing an error message complaining about a missing package.json file – a file that shouldn't exist in your Python environment. This is precisely the issue reported, where the toolchain seems to be firing off Node.js commands without verifying the project's actual language or tooling. The implications are significant for developers who maintain diverse codebases, ensuring that the right tools are applied to the right projects without contamination. This article delves deep into this peculiar bug, dissecting its symptoms, exploring the potential root causes, and outlining the expected behavior that would restore sanity to mixed-language development workflows. We'll walk through the specific error messages, analyze the project configurations that shed light on the problem, and propose concrete solutions to prevent this cross-language hook contamination from disrupting your productivity. Understanding this bug is the first step toward a smoother, more reliable development experience with Claude Code, especially when navigating complex workspaces with both Python and Node.js components.

h2. Deconstructing the Error: The ENOENT Mystery in a Python Project

The core of the problem manifests as a persistent npm error code ENOENT, specifically referencing an inability to find or read a package.json file. This error surfaces every time the Edit tool is invoked within the affected Python FastAPI ML service project. Let's break down the specific error message you might encounter: ⏺ 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 output is quite telling. It reveals that Claude Code is attempting to execute a command npm run biome:check within the project's directory. The error ENOENT (Error NO ENTry) is a standard operating system error indicating that a file or directory specified in a path does not exist. In this case, the missing file is package.json at the root of the Python project. The fact that this error occurs after every Edit tool use highlights a consistent, albeit misplaced, execution of these Node.js hooks. It's crucial to understand that this project is explicitly defined as a Python FastAPI ML service, utilizing technologies like Python 3.11+, FastAPI, SQLAlchemy, PostgreSQL, scikit-learn, and TensorFlow. Dependency management is handled by Poetry or pip, evidenced by files like requirements.txt and pyproject.toml. There are no JavaScript or Node.js components whatsoever. The absence of a package.json file is not an oversight; it's a deliberate reflection of the project's pure Python nature. This leads us to suspect that Claude Code is either operating on a default or hardcoded hook configuration that is being applied universally, or there's an issue with how it's discerning project boundaries and associated toolchains in a multi-project setup. The investigation into Claude Code's configuration files further deepens this mystery, as we'll see next.

h3. Digging into Configurations: Where Are These Hooks Defined?

To truly understand why Node.js hooks are being triggered in a Python project, a thorough examination of Claude Code's configuration files is essential. The user has meticulously checked several locations, and the findings are illuminating, albeit pointing towards an external or default configuration issue.

Project Hook Configuration (.claude/config/hooks.json): This file is intended to house project-specific hooks. In this case, it contains only Python-specific hooks, utilizing an agent named code-style-guardian. Critically, there are no references to npm, biome, or any PostToolUse hooks related to Node.js. This suggests that the project itself is not explicitly instructing Claude Code to run these JavaScript tools.

Settings Files Checked: The investigation extended to various settings files, both project-local and global:

• ~/.claude/settings.json: This file does not exist, ruling out a global user-level setting as the source.
• .claude/settings.json: This file also does not exist within the project, indicating no project-specific override at this level.
• .claude/settings.local.json: This file does exist and contains configurations primarily related to Python-specific permissions and hook configurations. Again, no Node.js hooks are defined here.
• .claude/config/debug.json: This file contains settings for Python debugging, further reinforcing the project's Python identity.

Search Results within .claude Directory: A comprehensive search within the entire .claude directory for keywords like "npm", "biome", and "PostToolUse" yielded no matches. This is a pivotal finding. If these hooks aren't defined in the project's local .claude configuration, and a global configuration is absent or also clean, where are they originating from?

Absence of package.json: As reiterated, the project is pure Python and intentionally does not have a package.json file. This file is the cornerstone of Node.js project management and is where npm and biome typically find their configuration and scripts. Its absence should be a clear signal to any intelligent toolchain that Node.js hooks are not applicable.

These configuration checks strongly suggest that the problematic npm/biome hooks are not being explicitly defined or intended by the project's configuration. This leads to the hypothesis that these hooks might be inherited from sibling projects within a larger workspace or are part of a default, hardcoded behavior within Claude Code itself that is not being correctly suppressed based on project context.

h3. Project Context: A Pure Python FastAPI ML Service

To truly appreciate the anomaly, let's firmly establish the nature of the project experiencing this bug. This is not a hybrid project with some JavaScript sprinkled in; it is a pure Python FastAPI ML service. The description provided is detailed and paints a clear picture:

• Language Version: It runs on Python 3.11 or newer, adhering to modern Python standards.
• Web Framework: It utilizes the FastAPI framework, a high-performance, asynchronous web framework for building APIs with Python.
• Database: The project employs SQLAlchemy for Object-Relational Mapping (ORM) and interacts with a PostgreSQL database, common for robust backend services.
• Machine Learning Stack: For its machine learning capabilities, the project relies on established libraries such as scikit-learn and TensorFlow. This is a significant indicator of its primary function being data science and AI-driven services.
• Dependency Management: Instead of npm or yarn, the project uses Python-native tools like Poetry or pip for managing its dependencies. The presence of files such as requirements.txt and pyproject.toml is definitive proof of this Python-centric approach.
• Infrastructure & Configuration: Files like alembic.ini further suggest a typical Python backend setup, often used for database migrations with SQLAlchemy.

Crucially, the project explicitly states: "No JavaScript/Node.js components whatsoever." This isn't an understatement. There are no front-end frameworks (like React, Vue, or Angular), no Node.js build tools, and no server-side Node.js applications running alongside. The entire development ecosystem is built around Python.

Given this context, the execution of npm or biome hooks is not just unexpected; it's fundamentally incorrect. It signifies a failure in Claude Code's ability to correctly identify the project's language and associated toolchain. Instead of recognizing the Python environment and its native tooling, it's attempting to apply JavaScript development tools. This mismatch suggests a potential flaw in how Claude Code analyzes the workspace, possibly leading to a scenario where hooks from one project type are bleeding into another, or where a default set of hooks is being applied without proper contextual checks. The impact of this misclassification, while perhaps minor in terms of blocking progress, is a significant annoyance and can create confusion about the project's setup and Claude Code's internal logic.

h3. Root Cause Analysis: The Specter of Cross-Project Hook Inheritance

Based on the detailed investigation, the most plausible root cause analysis points towards a mechanism within Claude Code where hooks, particularly default or framework-specific ones like PostToolUse hooks for npm or biome, are being inappropriately applied across different project types in a multi-project workspace. The error logs clearly show Claude Code attempting to execute npm run biome:check in a directory where package.json does not exist, and where the project's configuration files (.claude/config/hooks.json, .claude/settings.local.json) explicitly define only Python-specific tooling.

The absence of any Node.js-related configurations within the project's own .claude directory, combined with the explicit statement that the project is pure Python with no JavaScript components, strongly indicates that these hooks are not intended by the user or the project setup. This leads to the hypothesis that Claude Code might be suffering from cross-project hook inheritance. In a workspace containing multiple projects, where perhaps a sibling project is a Node.js project, Claude Code might be incorrectly inheriting or applying the hooks defined for that Node.js project onto the Python project. This could happen if the toolchain's logic for determining applicable hooks is not robust enough to differentiate project types accurately, or if it's failing to properly isolate hooks to their intended project contexts.

Another possibility is that Claude Code has a default set of hooks that are always considered, and the logic to disable these default hooks for specific project types (like Python projects without a package.json) is flawed or missing. Instead of checking for the presence of project-specific configurations or detecting the project's language and build tools first, it might be blindly attempting to execute common hooks, assuming a JavaScript/Node.js environment. This would explain why the error occurs consistently after Edit tool usage, as this action might be a trigger for executing post-edit hooks.

Essentially, Claude Code appears to be executing a hardcoded or default npm/biome PostToolUse hook without respecting:

1. The actual project type: It fails to recognize this is a Python project.
2. The absence of necessary files: It proceeds even though package.json is missing.
3. Project-specific configurations: It ignores the .claude/config/hooks.json which only defines Python tools.

This behavior deviates significantly from what a context-aware development tool should provide. The goal should be to apply tools that are relevant to the project's technology stack, not to inject errors by running irrelevant commands. The issue seems to stem from a lack of sophisticated project type detection and a potentially flawed hook management system in multi-project environments.

h2. Expected vs. Actual Behavior: Restoring Contextual Integrity

In an ideal world, a development tool like Claude Code should possess a keen understanding of the project it's interacting with. This understanding is crucial for applying the correct tools and configurations, thereby enhancing productivity and minimizing errors. When we talk about Claude Code's behavior in a multi-project workspace, especially when dealing with different language ecosystems, the contrast between expected and actual behavior becomes starkly apparent.

Expected Behavior: A Context-Aware Assistant

Claude Code should accurately detect the project type. In our scenario, upon analyzing the directory structure, file extensions (like .py), presence of Python-specific configuration files (pyproject.toml, requirements.txt), and absence of JavaScript/Node.js artifacts (package.json, .js files), it should unequivocally identify the project as a Python FastAPI ML service.

Following this detection, Claude Code should refrain from executing language-specific hooks that are irrelevant to the project's technology stack. This means that Node.js hooks, such as npm run biome:check or any other PostToolUse scripts tied to the Node.js ecosystem, should simply not be invoked. If the project is pure Python, only Python-relevant tooling (like linters, formatters, or static analysis tools configured for Python) should be considered.

Furthermore, Claude Code must respect the project-specific hook configurations defined by the user. If .claude/config/hooks.json only lists Python linters and formatters, Claude Code should adhere to that definition and not attempt to inject or execute other types of hooks. The user's explicit configuration should take precedence.

In essence, the expected behavior is one of intelligent context awareness, where Claude Code acts as a helpful assistant that knows which tools belong to which project, preventing unnecessary errors and workflow disruptions.

Actual Behavior: A Misplaced Toolchain

In contrast, the actual behavior observed is a clear deviation from these expectations. Claude Code is executing npm/biome hooks despite the project being pure Python. It seems to be failing to correctly identify the project type, overlooking the clear indicators of a Python environment and the absence of any Node.js components. Consequently, it's attempting to run JavaScript/Node.js hooks, leading directly to the npm error code ENOENT because the prerequisite package.json file is missing. This happens irrespective of the project's actual configuration, which, as confirmed, only specifies Python tooling. The toolchain is effectively injecting itself into the wrong context, causing confusion and generating noise in the form of error messages after every Edit operation. This suggests a potential bug in how Claude Code handles hook execution in multi-project workspaces, possibly leading to a