### Preflight Checklist - [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) 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 does not install in Qemu x86+KVM, or Qemu x86 without KVM with Debian 13 Trixie or Ubuntu 20.04 Focal ### What Should Happen? Claude code

[BUG] Qemu VM : arm64 OK, x86+KVM+AVX2 OK , x86+KVM KO (hangs forever 100% CPU) , x86 KO (crashes)

Status Open

Reported on v2.1.240

Maintainer reply None cached

Workaround ✓ Mentioned in thread ↓

Activity 3 comments · opened Aug 22, 2026

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 does not install in Qemu x86+KVM, or Qemu x86 without KVM with Debian 13 Trixie or Ubuntu 20.04 Focal

What Should Happen?

Claude code should install.

Error Messages/Logs

Steps to Reproduce

Download Debian stable (13 Trixie) cloud generic image for x86_64

wget https://cloud.debian.org/images/cloud/trixie/latest/debian-13-generic-amd64.qcow2

resize qemu img, configure ssh, run qemu x86 + KVM, ssh login

debian@localhost:~$ curl -fsSL https://claude.ai/install.sh | bash
Setting up Claude Code...

CPU 100% hangs forever (after the curl+sha256sum in the script), I have to send SIGTERM (contrary to #83624 that says it's irresponsive to SIGTERM)

if I do with qemu x86 without KVM, it's worse

debian@localhost:~$ curl -fsSL https://claude.ai/install.sh | bash
Setting up Claude Code...
bash: line 183:   946 Illegal instruction     "$binary_path" install ${TARGET:+"$TARGET"}
Installation was killed before it could finish (exit code 132).

if I run with arm64 (take the same Debian 13 Trixie Stable but for arm64), I can install Claude Code.

debian@localhost:~$ curl -fsSL https://claude.ai/install.sh | bash
Setting up Claude Code...

✔ Claude Code successfully installed!

  Version: 2.1.240

  Location: ~/.local/bin/claude


  Next: Run claude --help to get started

⚠ Setup notes:
  ● Native installation exists but ~/.local/bin is not in your PATH. Run:

    echo 'export PATH="$HOME/.local/bin:$PATH"' >> ~/.bashrc && source ~/.bashrc


✅ Installation complete!

Claude Model

_No response_

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.240

Platform

Other

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Other

Additional Information

sorry if its already known / you are working on it...

there are tons of Issues (14370...), several CPU 100% in virtualized env issues have already been opened, closed, ...

it's my first time ever with vibe-blabla-agentic-blabla-AI so it's a bit disappointing...

tell me how I can help

View original on GitHub ↗

3 Comments

Rehan-MALAK · 1 month ago

Running an old claude code installer : 2.1.100 made me realize that AVX2 is needed for Bun

debian@localhost:~$ ./claude-2.1.100-linux-x64 install
============================================================
Bun v1.3.11 (87b3dff3) Linux x64 (baseline)
Linux Kernel v6.12.101 | glibc v2.41
Args: "./claude-2.1.100-linux-x64" "install"
Features: jsc no_avx2 no_avx standalone_executable 
Builtins: "bun:main" 
Elapsed: 21557ms | User: 12790ms | Sys: 8743ms
RSS: 15.96GB | Peak: 8.63GB | Commit: 15.96GB | Faults: 227 | Machine: 16.78GB

CPU lacks AVX support. Please consider upgrading to a newer CPU.
panic(main thread): Segmentation fault at address 0x50532000000
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/1.3.11/B_187b3dffEggggigD4ovilF+++Pg2p5hDmp3wuDk7jvuD+rnv6Do26uzE24/twE0sgghG_2i1hvE2i1hvE2i1hvE2i1hvE2i1hvE2i1hvE2i1hvE2i1hvE2i1hvE2i1hvEA2qwCgggggyB

Illegal instruction

so the solutions consists of launching qemu x86 + KVM with `-cpu host` .... and most probably in that case, you are exposing AVX2 registers from host

qemu-system-x86_64 \
    -enable-kvm \
    -cpu host \
    -m 16G \
    -smp 4 \
    ...

I am not closing. I let maintainers chose if this AVX2 requirement is sufficiently documented.

genose · 1 month ago

The -cpu host workaround works if you control the QEMU flags, but there is a zero-config alternative if you cannot expose AVX or just want something that works out of the box:

Claudius — a community rebuild of Claude Code using Node.js + esbuild instead of the bundled Bun binary. No AVX/AVX2 required, runs on any x86_64 CPU (including bare QEMU without -cpu host).

# Linux / macOS
curl -fsSL https://raw.githubusercontent.com/genose/claude-code-source-build-community-edition-noAVX-foroldtimer/noavx_esbuild/install.sh | bash

Works as claudius (and symlinks claude so existing scripts/extensions do not need changes).

Repo: https://github.com/genose/claude-code-source-build-community-edition-noAVX-foroldtimer (branch: noavx_esbuild)

Your x86+KVM case (hangs at 100% CPU) is the Bun JIT spinning on a missing instruction — the Node.js build avoids this entirely.

genose · 16 days ago

If you are hitting this because Bun requires AVX and your CPU / VM does not have it, the Claude Code Community Edition no-AVX fork exists for exactly this situation.

It rebuilds Claude Code using Node.js + esbuild instead of Bun, so it runs on any CPU without AVX/AVX2 — bare metal, VMs, VPS, OpenStack, Proxmox KVM, Hyper-V, VirtualBox, QEMU, old Xeons, AMD pre-Bulldozer, all of it. One-line install:

curl -fsSL https://raw.githubusercontent.com/genose/claude-code-source-build-community-edition-noAVX-foroldtimer/noavx_esbuild/install.sh | bash

Currently at v2.1.283. The binary is called claudius (with a claude symlink for IDE/VS Code compat).

Honest note: the version number tracks upstream so the API gate passes, but the underlying app code is frozen at the v2.1.88 era — upstream switched to Bun-compiled bytecode at v2.1.126 and source maps are no longer obtainable. What you get: a working Node.js build that runs on your hardware, with fresh npm dependency packages at build time.