[BUG] Claude crashes when loading .env/.env.local/.env.development on Linux 4.x kernels

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?

Environment:

• OS: Linux 4.4.0-146-generic (Ubuntu 16.04)
• Claude Version: 2.0.42
• Kernel: 4.4.0-146-generic

Issue:
Claude crashes with exit code 1 (no error message) when loading these files at startup:

• .env
• .env.local
• .env.development

Root Cause:
Claude calls syscall 332 (fsconfig) when loading these files, which returns ENOSYS on
Linux 4.x kernels. syscall 332 was added in Linux 5.1+.

Strace Log:

openat(AT_FDCWD, ".env", O_RDONLY|O_NOCTTY|O_CLOEXEC) = 13
syscall_332(0xd, ...) = -1 (errno 38: ENOSYS)
exit_group(1)

What Should Happen?

When .env/.env.local/.env.development files exist:

• Claude should detect that syscall 332 is unavailable (ENOSYS)
• Skip the fsconfig call and use standard file reading methods (open + read)
• Continue execution normally
• Display the help message when running claude -h

The program should work correctly regardless of kernel version, either by using fallback methods
or by gracefully handling unsupported syscalls.

Error Messages/Logs

Steps to Reproduce

1. Check your kernel version (must be Linux 4.x or earlier):

``bash
uname -r
# Output: 4.4.0-146-generic (or any 4.x kernel)
``

1. Create a test directory:

``bash
mkdir /tmp/claude-test
cd /tmp/claude-test
``

1. Create a .env file (content doesn't matter):

``bash
touch .env
# or with content:
echo "TEST=value" > .env
``

1. Try to run Claude Code:

``bash
claude -h
# Expected: Show help message
# Actual: No output, process exits with code 1
``

1. Verify with strace:

``bash
strace claude -h 2>&1 | tail -5
# You will see:
# openat(AT_FDCWD, ".env", O_RDONLY|O_NOCTTY|O_CLOEXEC) = 13
# syscall_332(...) = -1 (errno 38)
# exit_group(1)
``

1. Remove the .env file and verify Claude works:

``bash
rm .env
claude -h
# Now it works correctly and shows help message
``

Claude Model

None

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.0.42 (Claude Code)

Platform

Other

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Other

Additional Information

_No response_