[BUG] Prevent Claude Code from loading .env.local into environment

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Claude code is sourcing .env* files on start and reading project defaults into the shell which then overrides settings defined in files like .env.test or .env.test.local which would normally be picked up when running unit tests but are now ignored because there's a shell environment set. This causes unit tests to run against local dev resources like databases.

What Should Happen?

Claude should not source industry standard .env files when starting - instead it should source .claude.env or some other namespaced .env files to prevent reading project defaults into claude's shell environment. People wanting values from .env can port those specific values into those files.

Error Messages/Logs

None.

Steps to Reproduce

Check shell env before loading clause

1. set | grep -i "database"
2. witness no DATABASE_URL is set
3. start claude code
4. as claude to run set and tell you what database_url is set to
5. witness that it is now set to the same value as in your .env file(s)

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

NA

Claude Code Version

v2.0.54

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

iTerm2

Additional Information

Have checked in iterm2 as well as terminal on mac and both behave the same.

Current workaround is to rename .env to ._env then start claude code then rename back. This works but it's a pain and if you forget this step you're at risk.