Answer

Can Claude Code read my .env file?

Yes. Claude Code runs as your own user account, and file reads require no approval by default, so it can open .env the same way any program you run can. Deny rules, ignore-style settings, and sandboxing reduce this, but researchers have reproduced gaps in each. Check what's actually exposed on your machine with blast.

Updated 2026-10-02 · Kloudle

Why can Claude Code read .env files by default?

Claude Code's own permissions documentation classifies file reads as a read-only tool type that needs no approval within your working directory and any additional directories you've added (code.claude.com/docs/en/permissions). That's a deliberate default for a coding agent that has to read source files constantly — but .env sits in the same filesystem as your code, with no special treatment unless you add one.

Under the hood, Claude Code is a program running under your OS user account. It inherits standard POSIX file permissions: if your shell can run cat .env, Claude Code's Read tool can open the same file.

What gaps have researchers found in the deny-rule protections?

The Register reproduced the issue directly: they created a test directory with secrets in .env, added blocking rules in .claudeignore, and found Claude still read and displayed the credentials, while separately warning the user about version-control risk for the same file (The Register). Claude also ignored .gitignore entries in some cases even with the "respect gitignore" setting enabled.

Knostic's research describes a related gap: Claude Code ingests .env-style files into its working context automatically, without explicit user permission, which matters because any later command that's already approved — even an innocuous one like echo — can then surface whatever secrets are already sitting in that loaded context (Knostic).

Security researcher Martin Paul Eve went further: he found .claudeignore wasn't actually enforced the way users expect, that instructions in CLAUDE.md or AGENTS.md telling Claude not to touch .env were simply not followed reliably, and that even an official deny rule can be sidestepped by having Claude write a small script or pipe chain that reads the file indirectly (eve.gd).

What does the official documentation say actually stops it?

Claude Code's current permissions model lets you write a deny rule like Read(./.env) to block a specific file, and deny rules for Bash commands can block invocations like Bash(rm *). But the documentation itself says plainly that a Bash rule "matches the command text Claude writes... isn't a security boundary around the program" — the same program invoked a different way, such as through its full path instead of the bare command Claude normally writes, isn't stopped by that rule (code.claude.com/docs/en/permissions). For enforcement that doesn't depend on matching command text, Claude Code points to its separate sandboxing feature, which can isolate filesystem and network access and mask credential files and variables.

How do you reduce your exposure?

Treat deny rules and ignore files as a speed bump, not a wall: add a Read(./.env*) deny rule, turn on sandboxing with credential masking where it's available, and keep actual secrets out of the working directory when you can — a secrets manager or a vaulted environment avoids the question entirely.

Whatever mitigations you run, check what's actually sitting in reach on your machine today. blast scans local .env files, SSH keys, cloud credential files, and MCP configs offline and read-only, reports where each one lives and its SHA-256 fingerprint without printing the value, and scores your overall exposure. See the Claude Code install guide for setup alongside it.

Check your own machine

Frequently asked

Does adding .env to .claudeignore stop Claude Code from reading it?

Not reliably. The Register reproduced Claude reading .env contents despite a .claudeignore blocking rule, and separately warning about the same file's exposure in version control.

Can I just tell Claude not to read .env in CLAUDE.md?

Don't rely on it. Testing found that instructions in CLAUDE.md or AGENTS.md didn't reliably stop access; permission rules enforced by Claude Code itself are different from instructions in a prompt file, which the model can disregard.

Is my .env data sent to Anthropic's servers?

Yes, as part of normal operation. Claude Code sends the context it has read — including a .env file Claude opened — back to Anthropic to run inference, and one researcher notes that content could be incorporated into future training runs.

Does blast stop Claude Code from reading my .env file?

No. blast only reports what's exposed on your machine; it doesn't sandbox or block any agent. Pair it with Claude Code's own deny rules and sandboxing.

Sources

1. Claude Code AI tool slurps up developers' secrets — The Register
2. Claude loads secrets without permission — Knostic
3. Claude Code can consume, transmit, and compromise your env files even if you tell it not to — eve.gd
4. Configure permissions — Claude Code docs

Related

• What is agent blast radius?
• What can an AI coding agent access on my machine?
• Can my MCP config leak hardcoded secrets?
• How do you sandbox Claude Code, and what does sandboxing not cover?