[BUG] Bun binaries crash on ARM Neoverse-V2 (Python SDK + native installer)

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?

Summary

All Bun 1.2.8 binaries crash with SIGABRT on ARM Neoverse-V2 processors. Affects:

• Python SDK bundled binary (v2.0.62)
• Native installer from GCS (v2.0.64)

Root cause: Binary compiled for Neoverse-N1, incompatible with V2.

Reproduction

# Python SDK
pip install claude-agent-sdk==0.1.14
/usr/local/lib/python3.12/dist-packages/claude_agent_sdk/_bundled/claude --version
# Result: Aborted (core dumped)

# Native installer
curl -fsSL <bootstrap.sh URL> | bash
~/.claude/downloads/claude-2.0.64-linux-arm64 --version
# Result: Aborted (core dumped)

Confirmed on 2 different V2 machines (CPU part 0xd4f, different variants/kernels).

Root Cause

Binary compiled for Neoverse-N1 (CPU part 0xd0c, 15 features) but V2 has 30+ additional features:

• bti (Branch Target Identification)
• paca/pacg (Pointer Authentication)
• sve/sve2 (Scalable Vector Extensions)
• Plus i8mm, bf16, enhanced crypto, etc.

Binary's startup validation detects unexpected V2 features → calls abort().

Analysis confirms:

• ✅ 0 LSE atomic instructions (not LSE issue)
• ✅ Minimal SVE code (not SVE issue)
• ✅ No runtime CPU detection
• ✅ Intentional abort, not illegal instruction

The Fix

Recompile Bun with generic ARM flags:

# Current (broken on V2)
-march=neoverse-n1

# Fix (works N1/N2/V1/V2)
CFLAGS="-march=armv8-a+crc"
CXXFLAGS="-march=armv8-a+crc"
RUSTFLAGS="-C target-cpu=generic"

Workaround

NPM package works (uses Node.js v18, not Bun):

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

Impact

• Severity: CRITICAL
• Official installer broken on all V2 hardware (Graviton4, Ampere Altra Max)
• 100% reproducible
• Both distribution methods affected (pip + GCS bucket)

Action Items

1. 🔴 URGENT: Update GCS bucket binaries
2. 🔴 Release new Python SDK with V2-compatible binary
3. 🟡 Add V2 to CI/CD testing

Full technical analysis available if needed.

What Should Happen?

Nvidia Grace CPU (GH200, GB200) uses Neoverse-V2. We should let the binary work there.

While I don't have concrete evidence, our CI started seeing such failures around 12/3 2:30 pm PT

Error Messages/Logs

see above

Steps to Reproduce

claude

the binary itself crashes on Neoverse-V2 ARM

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

While I don't have concrete evidence, our CI started seeing such failures around 12/3 2:30 pm PT

Claude Code Version

2.0.64

Platform

Other

Operating System

Ubuntu/Debian Linux

Terminal/Shell

Other

Additional Information

Nvidia Grace CPU (GH200, GB200) uses Neoverse-V2. We should let the binary work there.

While I don't have concrete evidence, our CI started seeing such failures around 12/3 2:30 pm PT