Bundled Bun binary lacks AVX baseline support — crashes on non-AVX CPUs

Having the same issue on M2 Pro CPU, latest macOS.

I'm running Claude Code from homebrew installation.

Seeing:

warn: CPU lacks AVX support, strange crashes may occur. Reinstall Bun or use *-baseline build:
https://github.com/oven-sh/bun/releases/download/bun-v1.3.11/bun-darwin-x64-baseline.zip

Macbook M2 Pro CPU. The same issue

claude --warn: CPU lacks AVX support, strange crashes may occur. Reinstall Bun or use *-baseline build:
https://github.com/oven-sh/bun/releases/download/bun-v1.3.11/bun-darwin-x64-baseline.zip

Same issue here too.

============================================================
Bun v1.3.11 (a2743b6d) Windows x64 (baseline)
Windows v.win10_cu
Args:
Features: no_avx2 no_avx
Elapsed: 3ms | User: 15ms | Sys: 0ms
RSS: 16.20MB | Peak: 16.22MB | Commit: 54.23MB | Faults: 4538

CPU lacks AVX support. Please consider upgrading to a newer CPU.
panic (thread 476624): attempt to use null value
oh no Bun has crashed. This indicates a bug in Bun, not your code.

still seeing this problem with Claude Code v2.1.85

Claude Code v2.1.109

warn: CPU lacks AVX support, strange crashes may occur. Reinstall Bun or use *-baseline build:
https://github.com/oven-sh/bun/releases/download/bun-v1.3.13/bun-darwin-x64-baseline.zip

Fixed the issue for me.
Had x86 installed after migrating from older MacBook.
Replaced with arm homebrew. No warnings after that

From my chat w/ Claude app on Xubuntu-24.04:

Lol, the 'Code' section in this app is also running into same problem. I wonder if there's a way to pin it's version to 2.1.14 4:00 PM Claude responded: Ha, yes — the Claude Code integration built into claude. Ha, yes — the Claude Code integration built into claude.ai is a separate instance and will have the same AVX problem if it's also using the Bun-based runtime. For the claude.ai Code integration, that's unfortunately not something you can control directly — it's managed by Anthropic's servers. Your best bet there is to file a bug report through the thumbs-down button or feedback mechanism, specifically mentioning: AMD Phenom II X6 1100T (pre-AVX, bare metal) Illegal instruction (core dumped) on any version past 2.1.14 Request for either a no-AVX build or a way to pin versions The more people report it from bare metal (as opposed to VMs), the harder it is for Anthropic to dismiss it as a hypervisor configuration issue.

Btw, per Claude app's suggestion, I had to remove the write permission on both the claude-code binary, and the download folder to prevent auto-update from working as anything above 2.1.14 needs AVX and I, sadly, don't have that on my CPU. So now I've claude-code CLI working (it's pinned to v2.1.14), but the 'code' in Claude app doesn't work. I hope dependency on AVX is removed, or if it's needed then a fork or a version pinning mechanism is provided. Would be great to have 'code' work in both the Claude app and the CLI with feature parity. Thanks.

Edit: I heard that this is also seen in hypervisor mode, so want to make it clear that mine is bare metal usage

Hitting this on a 2013 Mac Pro (Xeon E5-2697 v2, Ivy Bridge-EP), bare metal.

CPU has AVX but not AVX2:

$ sysctl -n machdep.cpu.features | tr ' ' '\n' | grep AVX
AVX1.0

Since AVX is present, Bun's runtime check passes and no warning prints. SIGILL on the first AVX2 instruction (Illegal instruction: 4, exit 132, dies in dyld init before main).

Bisect:

• 2.1.112: works (Node-based cli.js)
• 2.1.113 through 2.1.150: crash on launch

bun build --compile bakes the runtime into the 200MB Mach-O, so installing bun-darwin-x64-baseline system-wide doesn't help. No JS fallback shipped since 2.1.113.

Could you publish @anthropic-ai/claude-code-darwin-x64-baseline (and linux/win equivalents) compiled against baseline Bun? Same optionalDependency layout as the current per-platform packages.

Pinned to 2.1.112 for now to keep things working, but locked out of newer releases.

Additional repro — Intel Ivy Bridge (i7-3520M), macOS Sonoma

Adding another confirmed affected environment to strengthen this report.

Environment

• OS: macOS Sonoma 14 (Darwin 23.6.0, x86_64)
• CPU: Intel Core i7-3520M @ 2.90GHz (Ivy Bridge, 2012) — supports AVX but NOT AVX2
• Node.js: v25.9.0 (x64)
• Claude Code: crashes on any version newer than 2.1.112
• Install method: npm install -g @anthropic-ai/claude-code

Error

zsh: illegal instruction: 4  claude

Root Cause (confirmed)

The bundled Bun binary starting from v2.1.113 requires AVX2 instructions. The i7-3520M is a pre-Haswell CPU (Ivy Bridge, 2012) that supports AVX but not AVX2. Any Claude Code version using Bun 1.3.14 or later compiled without the -baseline flag will SIGILL immediately on launch.

Workaround

Pinning to the last working version:

npm install -g @anthropic-ai/claude-code@2.1.112

Related issues

• #64378 — same crash on Intel i5-3470S / Ivy Bridge / macOS (marked duplicate)
• #63609 — Illegal Instruction crash on CPUs without AVX since v2.1.113
• #34481 — SIGILL on Intel Westmere (Xeon X5675)

Request

Please ship the Bun baseline binary (compiled without AVX2) for macOS x64, or auto-detect CPU capabilities at install time and select the appropriate binary. This affects all Intel Macs from 2012 and earlier (Ivy Bridge and older), which are still officially supported under macOS Sonoma.

Related: If you're affected by this, there's an active discussion on #55520 proposing a clean fix — shipping both AVX + baseline Bun builds with runtime auto-detection, so all users are covered with zero tradeoff. Drop a 👍 there to help get it prioritized: https://github.com/anthropics/claude-code/issues/55520#issuecomment-4763182570