[Bug] Native Claude Code build crashes on non-AVX CPU with SIGILL

Bug Description
Here’s a draft you can paste into /bug (und bei Bedarf leicht anpassen):

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Title: Claude Code native build crashes on non‑AVX CPU; v2.0.62 via npm works

Body:

Hi Claude team,

I’m running Claude Code on a Linux machine with an older Intel CPU that does not support AVX:

• CPU: Intel(R) Celeron(R) G5920 (2) @ 3.50GHz (no AVX, only SSE4.2/POPCNT)
• OS: CachyOS x86_64 (Arch-based), Btrfs root, up-to-date kernel and userspace

Until a recent update, Claude Code was working fine on this machine. After updating, the native Claude Code build started to fail immediately on startup with messages like:

• CPU lacks AVX support. Please consider upgrading to a newer CPU.
• panic(main thread): Illegal instruction (SIGILL)

Because of this, even claude uninstall fails with the same SIGILL error (the Bun runtime crashes before it can do anything). I had to remove the native Claude binary and its files manually.

As a workaround, I installed Claude Code v2.0.62 explicitly via npm:

npm install -g @anthropic-ai/claude-code@2.0.62

When I run that version, Claude Code works normally again on this CPU with no AVX/SIGILL errors. This strongly suggests that newer native builds (and possibly newer npm versions as well) are being compiled with AVX/AVX2 assumptions that break on non‑AVX hardware, while 2.0.62 still works.

What I’d like to ask for:

1. Please provide a CPU-baseline build of Claude Code that does not require AVX/AVX2 (similar in spirit to Bun “baseline” builds), so users with slightly older but still capable CPUs can continue to use Claude Code.

1. Document clearly which CPU features the native and npm builds require (AVX, AVX2, etc.), and ideally fail gracefully with a clear message instead of crashing with SIGILL.

1. If possible, restore the ability to run claude uninstall or similar on non‑AVX CPUs even when newer builds are installed, so users are not stuck with an unremovable crashing binary.

If you need more details (e.g. lscpu output, exact kernel/glibc versions, or logs), I’m happy to provide them.

Thanks a lot for looking into this!

Environment Info

• Platform: linux
• Terminal: konsole
• Version: 2.0.62
• Feedback ID: 40116f42-d51d-47f8-8471-885060b9f88f

Errors

[{"error":"AxiosError: Request failed with status code 403\n    at sS (file:///home/josi/.npm-global/lib/node_modules/@anthropic-ai/claude-code/cli.js:186:1137)\n    at IncomingMessage.<anonymous> (file:///home/josi/.npm-global/lib/node_modules/@anthropic-ai/claude-code/cli.js:187:9852)\n    at IncomingMessage.emit (node:events:520:35)\n    at IncomingMessage.emit (node:domain:489:12)\n    at endReadableNT (node:internal/streams/readable:1701:12)\n    at process.processTicksAndRejections (node:internal/process/task_queues:89:21)\n    at dHA.request (file:///home/josi/.npm-global/lib/node_modules/@anthropic-ai/claude-code/cli.js:189:2130)\n    at process.processTicksAndRejections (node:internal/process/task_queues:103:5)\n    at async JE0 (file:///home/josi/.npm-global/lib/node_modules/@anthropic-ai/claude-code/cli.js:4675:3924)","timestamp":"2026-01-24T16:50:33.335Z"}]