Safeguarding sensitive files from Gen AI in a code repo

A simple way to grant safe access of your code repo to GenAI

Introduction

Generative AI coding assistants have become part of the development process but one prominent challenge still exists:

How do we stop AI tools from reading or referencing sensitive files in our code repositories?

We already rely on mechanisms like:

• .gitignore for version control

• .dockerignore for container builds

• .eslintignore for linting

• .npmignore for packaging

However, there is no standard way to explicitly tell AI assistants what NOT to access.

Most GenAI systems today follow a principle of least access — for example, they enable the user to choose files to be included in context window of the current chat session or coding session.
However things work differntly in below cases:

• Agent mode, or

• Full-folder access, or

• Any autonomous AI workflow where the assistant can “walk the repo.”

In such cases, we need a way to tell the AI up front what it must avoid before giving it permission to explore a folder. This is exactly where AI_IGNORE.md becomes valuable.

💡 The Concept: AI_IGNORE.md

A vendor-neutral Markdown file named as AI_IGNORE.md should be stored in the repo for team's reference. This file should clearly document below important points for prompt tuning the AI context before we start a chat session or agent session:

Immediate Workaround

Until AI vendors implement a native .ai-ignore feature, developers can already adopt a simple workaround: 

Add an AI_IGNORE.md file into your repo and attach it into your AI session before giving folder access. 

This ensures the assistant understands all restrictions before analyzing any files.

Sample AI_IGNORE.md File (Proposed Format)

Below is a sample format which you can refer and enhance based on your need

# AI Ignore Rules for This Repository

## 1. Sensitive Files and Folders

- secrets/**

- .env

- config/production.yml

- internal/security/**

- private_data/**

- *.pem

- *.key

- *token*

- *credential*

- *secret*

## 2. AI Behavior Rules

- Do not read, analyze, embed, vectorize, or reference any files listed above.

- Do not use functions, classes, or constants from ignored files in suggestions.

- If asked about an ignored file, respond:

  "I cannot access or analyze this file because it is restricted in AI_IGNORE.md."

## 3. Optional Patterns

- PATTERN_CREDENTIALS: "*.pem, *.key, *token*, *credential*"

- PATTERN_SENSITIVE: "private_data/**, user_data/**"

## 4. Rationale

These paths contain secrets, credentials, sensitive business logic, 

or regulated personal data. Exposure to AI tools may create security risks.

Conclusion

Until AI providers (OpenAI, Microsoft, Anthropic/Claude, GitHub, JetBrains, etc.) implement a true standard for ignoring sensitive files — especially in agent mode or folder-level access scenarios — the Markdown-based AI_IGNORE.md approach remains the most practical and immediately usable solution.