Security guide: Keep coding agents from reading .env secrets

On November 1, 2026, a security guide by developer Eliran Kotzero for KitQuarry was published in DEV Community's AI section, titled "Don't let Claude Code, Cursor, and Codex read your .env." The article's opening argument is that .gitignore does not keep secrets away from a coding agent, and neither does a line in CLAUDE.md or AGENTS.md — each tool relies on its own dedicated controls rather than generic reminders.

For Claude Code, the guide prescribes Read deny rules combined with the sandbox. For Cursor, it recommends .cursorignore together with a hook for terminal commands. For Codex, it points to a permission profile with deny globs. The author stresses that no single one of these setups closes every gap, and lists the gaps that remain for each tool in turn. The fundamental remedy, according to the author, is to keep production keys out of the working tree altogether rather than trying to hide them from an agent after the fact.

So far this is the only coverage of the topic. No follow-up coverage or response from any of the vendors involved has appeared, so the situation currently stands at a single advisory with proposed mitigations for developers using Claude Code, Cursor, or Codex.