[BUG] Illegal instruction (core dumped) on install.sh

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?

When installing claude code on a fresh Ubuntu 26.04 server LTS, i get an illegal instruction error. Claude code cannot be installed on that machine.

What Should Happen?

I would expect claude code to be installed, as explained in the docs.

Error Messages/Logs

claude@peton:~$ curl -fsSL https://claude.ai/install.sh | bash
Setting up Claude Code...
bash: line 158:  3843 Illegal instruction        (core dumped) "$binary_path" install ${TARGET:+"$TARGET"}
claude@peton:~$ wget https://github.com/anthropics/claude-code/releases/download/v2.1.160/claude-linux-x64.tar.gz
[…]
claude@peton:~$ tar xf claude-linux-x64.tar.gz
claude@peton:~$ ./claude --help
Illegal instruction        (core dumped) ./claude --help

Note that the illegal instruction error happen when running the claude binary, not when downloading it.

Steps to Reproduce

Run curl -fsSL https://claude.ai/install.sh | bash

Claude Model

None

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Illegal instruction (core dumped) ./claude --version

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Xterm

Additional Information

claude@peton:~$ uname -a
Linux peton 7.0.0-22-generic #22-Ubuntu SMP PREEMPT_DYNAMIC Mon May 25 15:54:34 UTC 2026 x86_64 GNU/Linux
claude@peton:~$ cat /proc/cpuinfo
processor	: 0
vendor_id	: GenuineIntel
cpu family	: 6
model		: 23
model name	: Intel(R) Core(TM)2 Duo CPU     T6600  @ 2.20GHz
stepping	: 10
microcode	: 0xa0b
cpu MHz		: 2199.891
cache size	: 2048 KB
physical id	: 0
siblings	: 2
core id		: 0
cpu cores	: 2
apicid		: 0
initial apicid	: 0
fpu		: yes
fpu_exception	: yes
cpuid level	: 13
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl cpuid aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm pti dtherm
bugs		: cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds swapgs itlb_multihit spectre_v2_user
bogomips	: 4399.78
clflush size	: 64
cache_alignment	: 64
address sizes	: 36 bits physical, 48 bits virtual
power management:

processor	: 1
vendor_id	: GenuineIntel
cpu family	: 6
model		: 23
model name	: Intel(R) Core(TM)2 Duo CPU     T6600  @ 2.20GHz
stepping	: 10
microcode	: 0xa0b
cpu MHz		: 2199.843
cache size	: 2048 KB
physical id	: 0
siblings	: 2
core id		: 1
cpu cores	: 2
apicid		: 1
initial apicid	: 1
fpu		: yes
fpu_exception	: yes
cpuid level	: 13
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ht tm pbe syscall nx lm constant_tsc arch_perfmon pebs bts rep_good nopl cpuid aperfmperf pni dtes64 monitor ds_cpl est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm pti dtherm
bugs		: cpu_meltdown spectre_v1 spectre_v2 spec_store_bypass l1tf mds swapgs itlb_multihit spectre_v2_user
bogomips	: 4399.78
clflush size	: 64
cache_alignment	: 64
address sizes	: 36 bits physical, 48 bits virtual
power management:

claude@peton:~$ sudo apt update
Atteint : 1 http://fr.archive.ubuntu.com/ubuntu resolute InRelease
Atteint : 2 http://fr.archive.ubuntu.com/ubuntu resolute-updates InRelease
Atteint : 3 http://security.ubuntu.com/ubuntu resolute-security InRelease
Atteint : 4 http://fr.archive.ubuntu.com/ubuntu resolute-backports InRelease
Tous les paquets sont à jour.      

claude@peton:~$ df -h
Filesystem                         Size  Used Avail Use% Mounted on
tmpfs                              680M  1,5M  679M   1% /run
/dev/mapper/ubuntu--vg-ubuntu--lv   40G  6,7G   31G  19% /
tmpfs                              1,7G     0  1,7G   0% /dev/shm
none                               1,0M     0  1,0M   0% /run/credentials/systemd-journald.service
tmpfs                              1,7G     0  1,7G   0% /tmp
none                               1,0M     0  1,0M   0% /run/credentials/systemd-resolved.service
/dev/sda2                          2,0G  183M  1,7G  10% /boot
/dev/mapper/ubuntu--vg-lv--var      40G  367M   37G   1% /var
/dev/mapper/ubuntu--vg-lv--srv     196G  2,1M  186G   1% /srv
/dev/mapper/ubuntu--vg-lv--home     16G  583M   15G   4% /home
none                               1,0M     0  1,0M   0% /run/credentials/systemd-networkd.service
none                               1,0M     0  1,0M   0% /run/credentials/getty@tty1.service
tmpfs                              340M  8,0K  340M   1% /run/user/1000