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

### 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 should install.

### Error Messages/Logs

```shell

```

### Steps to Reproduce

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

```bash
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

```bash
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

```bash
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.

```bash
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

Reproduce the installation using the Debian 13 amd64 cloud image and the reported QEMU x86 configurations, comparing KVM with non-KVM and the working arm64 case. Start with the curl install.sh flow around curl, sha256sum, and the binary_path install command; done means the installer completes without a hang or illegal-instruction crash.

Written by the indexing model from the issue text.