[BUG] Illegal instruction - CPU lacks AVX support (Linux)

[Francoshum95]

Preflight Checklist

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

What's Wrong?

The latest version of Claude can’t run on my old CPU. It shows:
CPU lacks AVX support. Please consider upgrading to a newer CPU.

It was working fine on v2.1.34.

What Should Happen?

it should not crash

Error Messages/Logs

claude --version
============================================================
Bun Canary v1.3.9-canary.51 (d5628db2) Linux x64 (baseline)
Linux Kernel v5.4.0 | glibc v2.31
Args: "claude" "--version"
Features: jsc no_avx2 no_avx standalone_executable 
Builtins: "bun:main" 
Elapsed: 14548ms | User: 7548ms | Sys: 7000ms
RSS: 14.45GB | Peak: 5.24GB | Commit: 14.45GB | Faults: 0 | Machine: 65.85GB

CPU lacks AVX support. Please consider upgrading to a newer CPU.
panic(main thread): Segmentation fault at address 0x5D6E7800000
oh no: Bun has crashed. This indicates a bug in Bun, not your code.

To send a redacted crash report to Bun's team,
please file a GitHub issue using the link below:

 https://bun.report/1.3.9/B_2d5628dbEggggigD4skkwE+o4Qgpjt9Cstg4pDkgt2pD+2+k1Di1jhmE0os1sEwj6vtF_6muvhE6muvhE6muvhE6muvhE6muvhE6muvhE6muvhE6muvhE6muvhE6muvhEA2s9ChgggwY

Illegal instruction (core dumped)

Steps to Reproduce

Run any claude command

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.34

Claude Code Version

2.1.37

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Warp

Additional Information

No response

[github-actions]

Found 3 possible duplicate issues:

1. v2.1.15 crashes on CPUs without AVX (regression from 2.1.14) #19907
2. [BUG] Bun crashes with "CPU lacks AVX support. Please consider upgrading to a newer CPU." #19904
3. Bun 1.3.6 in Claude Code 2.1.15 crashes with SIGILL on CPUs without AVX support #20116

This issue will be automatically closed as a duplicate in 3 days.

• If your issue is a duplicate, please close it and 👍 the existing issue instead
• To prevent auto-closure, add a comment or 👎 this comment

🤖 Generated with Claude Code

[Francoshum95]

Found 3 possible duplicate issues:

1. [v2.1.15 crashes on CPUs without AVX (regression from 2.1.14) #19907](https://github.com/anthropics/claude-code/issues/19907)

2. [[BUG] Bun crashes with "CPU lacks AVX support. Please consider upgrading to a newer CPU." #19904](https://github.com/anthropics/claude-code/issues/19904)

3. [Bun 1.3.6 in Claude Code 2.1.15 crashes with SIGILL on CPUs without AVX support #20116](https://github.com/anthropics/claude-code/issues/20116)

This issue will be automatically closed as a duplicate in 3 days.

* If your issue is a duplicate, please close it and 👍 the existing issue instead

* To prevent auto-closure, add a comment or 👎 this comment

🤖 Generated with Claude Code

above three issues were related to version 2.1.1x, but this one happens on the latest Claude Code version (2.1.37).It’s possible there’s a regression in the latest version

[Junxiao-Liao]

It's ridiculous to deprecate npm when this kind of problem happening again and again

[briankelley]

Workaround for AVX/CPU Crash on Linux

The crash is caused by the bundled Bun runtime (Bun Canary v1.3.9) attempting to use AVX instructions despite being compiled as "baseline" (no_avx). This affects VMs and older CPUs that don't expose AVX.

Affected versions: 2.1.37+ (including current latest 2.1.39)
Working versions: 2.1.29 (current stable), 2.1.7 (haven't fully tested others)

---

Step 1: Get a working version

Stop using the installer - it downloads the broken latest build first, so you can't even downgrade. Grab a working version directly:

curl -fsSL -o ~/.local/share/claude/versions/2.1.29 "https://storage.googleapis.com/claude-code-dist-86c565f3-f756-42ad-8dfa-d59b1c096819/claude-code-releases/2.1.29/linux-x64/claude"

chmod +x ~/.local/share/claude/versions/2.1.29

Delete the symlink and use an alias instead (the installer keeps recreating that symlink pointing to latest):

rm ~/.local/bin/claude

Add to ~/.bashrc
alias claude='/home/YOUR_USER/.local/share/claude/versions/2.1.29'

---

Step 2: Lock it down before you launch

Don't run the working version yet. If your release channel is still set to "latest", it'll auto-update and pull the broken build the moment it starts.

Lock the versions directory first:
chmod 500 ~/.local/share/claude/versions/

This prevents Claude from writing new binaries. The environment variables below are supposed to help, but they didn't fully work for me:
export CLAUDE_CODE_DISABLE_AUTOUPDATE=1
export CLAUDE_AUTO_UPDATE=0

---

Step 3: Launch and switch to stable

Now you can safely run your working version. Switch from latest to stable so future updates don't pull broken builds:

Run /config inside Claude and change your release channel, or edit the config directly:

Edit ~/.claude/settings.json or ~/.claude/settings.local.json

{
"releaseChannel": "stable"
}

When you want to update later, unlock the directory temporarily (chmod 700), download the version you want, then lock it again.

---

All of the above instructions were the result of me screwing around with this all day. I can appreciate a high velocity CI/CD pipeline that forces EVERY SINGLE USER TO BE BETA TESTERS (e.g. 'latest'), but when you release a breaking version where it's not clear how to revert because the installation process downloads the broken version in order to downgrade, that's an incredibly myopic approach.

[Francoshum95]

tested 2.1.45. latest version, the issue still exists. well, we basically can’t use the Sonnet 4.6 model because of this bug…