How to protect .env files when using AI coding assistants
A .env file kept out of Git can still enter an AI assistant's context. Protecting it means separating what the agent can read, what enters the repository and what is sent to the provider.
Three different places to protect a secret
Excluding a file from Git helps keep it from being accidentally added to the repository in normal workflows. It does not prevent a tool from reading it, or filter prompt text and command output on its own.
A credential may appear in configuration, logs or a tool response. A rule for .env is only part of the picture: also review how the assistant builds and transmits its context.
Start by reducing exposure
Give the assistant a .env.example containing variable names and fictional values. Keep real credentials out of examples, issues and conversations. If the task only needs the structure of a configuration, there is no need to share its sensitive contents.
Review the documented permissions and exclusions for the assistant version your team uses. Check file reads as well as tools that can print values. Do not use production credentials to test these controls.
Masking before transmission serves a different purpose
In a supported workflow, TigerMole replaces the sensitive values it detects before sending the request to the AI provider. The remaining content can still leave the device. This does not stop the agent from reading the file or turn a remote model into a local one.
Coverage depends on the integration, version, format and detection rules. An unknown value or an unsupported workflow may fall outside it. Review the security coverage matrix and verify that protection is active before using real data.
A practical check for your team
Prepare a test project using synthetic data and a documented example pattern. Never use a valid key to demonstrate filtering.
- Record the client version, integration and protection status.
- Reproduce a file read and a command output containing the example as separate cases.
- Follow the verification guide to check substitution in the supported workflow. Do not rely solely on an icon or the model's response as proof.
- Document formats or paths you have not validated and repeat the check after relevant changes.
If a credential has already been sent
Masking later requests does not retrieve information already shared. Follow your organization's response procedure: revoke or rotate the credential as appropriate, review its use and check for copies in logs or conversations.
For team adoption, assign owners for configuration and review. Combine minimal access, repository scanning and verification of supported traffic; no single control replaces the others.