GitHub Issue Report: Request for Sensitive File Exclusion in OpenAI Codex

Issue #2847 was opened by user mkusaka on August 28, 2025, regarding a critical missing functionality in the openai/codex repository. The core of the problem is the lack of a formal system to prevent the AI agent from accessing or transmitting private data.

🎯 Feature Request Overview

The author is proposing a robust mechanism to explicitly designate specific files or directory paths that the agent is forbidden from reading or sending to the underlying model.

"A mechanism to explicitly mark files/paths that the agent must not read or send to the model, at both repository and global levels."

Proposed Implementation

The user suggests a dual-layered approach to configuration:

1. Repository-specific: A local file, such as .codexignore.
2. Global-specific: A system-wide ignore file for user-defined defaults.

This ensures that the configuration is deterministic and shareable across a development team, moving away from a reliance on simple project conventions or manual documentation.

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🛠 Technical Details & Use Cases

The primary goal is to balance utility with security. For instance, a developer might want the agent to see node_modules/ to verify implementation details, but strictly forbid the transmission of secrets.

Exclusion Examples

The following patterns should be blocked:

• .env and .env.* (Environment variables)
• .pem (Privacy Enhanced Mail certificates)
• id_ (Private keys)
• .aws/ (AWS configuration/credentials)
• .ssh/ (SSH keys)

Primary Objectives

• Security: $\text{Prevent leakage of sensitive credentials} \rightarrow \text{Model}$
• Efficiency: $\text{Exclude large/irrelevant files} \rightarrow \text{Reduced Token Usage}$

Mathematically, the set of files sent to the model ($F_{sent}$) should be defined as: $F_{sent} = F_{total} \setminus (F_{global\_ignore} \cup F_{repo\_ignore})$

Logic Flow

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📋 Status and Tracking

The original issue was closed in favor of a Rust-based implementation known as codex-rs. However, as of 2025-08-28, the requested functionality is still missing from the codex-rs codebase.

Feature Checklist

• Implement .codexignore support
• Implement global ignore configuration
• Ensure deterministic behavior across environments
• Integrate with codex-rs

Issue Metadata

Example Configuration Concept

If a .codexignore file were implemented, it might look like this:

# Ignore all environment files
.env*

# Ignore sensitive SSH and AWS folders
.ssh/
.aws/

# Ignore private keys
*.pem
id_rsa

The user emphasizes that this must be a formal feature rather than a suggestion in a README.md, as the agent must programmatically adhere to these boundaries.