HeimWall

HeimWall is a free Mac menu-bar application designed for individual developers to prevent accidental exposure of sensitive information in AI prompts. It operates entirely on-device, ensuring that no data or prompts are sent off the user's machine at any point. The app is tailored to catch secrets and personally identifiable information (PII) before they are included in prompts for AI tools such as Cursor, Claude Code, and Copilot.

The application continuously monitors prompts as they are composed, flagging content that matches over 25 hand-written rules for credentials with distinct formats. This includes detection of AWS access keys, GitHub tokens, private keys, JWTs, database URLs, and other sensitive credentials. It also identifies PII such as Social Security Numbers, credit card numbers, and email addresses that may be inadvertently pasted from logs or stack traces. HeimWall's detection and alerting occur instantly and locally, even if the machine is disconnected from the internet, as there is no server communication or account required.

HeimWall is delivered as a Mac menu-bar agent that integrates directly with the prompt composer of supported AI tools. It does not require per-tool setup, as it reads the prompt at the point of composition regardless of how the AI tool communicates with its cloud services. The focus on privacy and local processing means that nothing typed or detected by the app ever leaves the user's Mac.

The tool is available at no cost and is specifically aimed at individual developers who use AI coding assistants and want to safeguard against unintentional data leaks. Its approach emphasizes privacy, simplicity, and immediate feedback, providing a layer of protection without the need for organizational infrastructure or user accounts.