VS Code extension native binary crashes (SIGSEGV) on CPU with AVX but no AVX2

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?

The Claude Code extension crashes immediately on startup in VSCodium on Linux.
The bundled native binary appears to be the standard (non-baseline) Bun build,
which requires AVX2. My CPU supports AVX but not AVX2.

CPU: Intel Core i7-2820QM (Sandy Bridge) — AVX, no AVX2
OS: Linux, kernel 6.12.111, glibc 2.41
Editor: VSCodium
Crashing extension version: 2.1.283

Version 2.1.283 worked normally for about 43 minutes, then crashed mid-session with a segfault. Since that first crash, every launch crashes within milliseconds of startup.

What Should Happen?

The Claude Code extension should start normally and let me chat with Claude in VSCodium, as it did in earlier versions. On CPUs without AVX2, the extension should use a compatible (baseline) build instead of crashing.

Error Messages/Logs

FIRST CRASH: mid-session, after ~43 minutes of normal use on 2.1.283:

Bun v1.4.3 (7c1d0ed28) Linux x64
Linux Kernel v6.12.111 | glibc v2.41
CPU: sse42 popcnt avx
Features: jsc no_avx2 spawn(369) standalone_executable yaml_parse(22) claude_code
Elapsed: 2559299ms | User: 42419ms | Sys: 5013ms
RSS: 0.29 GB | Peak: 0.36 GB | Commit: 2.80 GB | Faults: 241 | Machine: 12.49 GB
panic(main thread): Segmentation fault at address 0x37A495748A0
https://bun.report/1.4.3/l_17c1d0edmgggkQuhogigBkm7o1Euq8nwE2+5nwE8jsl6D____67lr6D67lr6Dms4i6D20uutEq9mjwC0lwx9B2kvn+Bs47oqCowwnqC48lnqCggm4/B6t2k7BA203Bgqk9qpC

EVERY LAUNCH SINCE THEN: crashes 4–7 ms after startup:

Error: Claude Code process terminated by signal SIGSEGV.
Bun v1.4.3 (7c1d0ed28) Linux x64
Linux Kernel v6.12.111 | glibc v2.41
CPU: sse42 popcnt avx
Features: jsc no_avx2 standalone_executable claude_code
Elapsed: 4ms | User: 7ms | Sys: 0ms
RSS: 18.72 MB | Peak: 47.67 MB | Commit: 33.82 MB | Faults: 0 | Machine: 12.49 GB
panic(main thread): Segmentation fault at address 0x4E223
https://bun.report/1.4.3/l_17c1d0edkggggQggggigB_A2AmixT

Steps to Reproduce

1. Use a Linux machine with a CPU that supports AVX but not AVX2 (mine: Intel Core i7-2820QM, Sandy Bridge, Linux kernel 6.12.111, glibc 2.41).
2. Install the Claude Code extension version 2.1.283 in VSCodium.
3. Open a project folder and start a Claude Code session in the extension panel.
4. Work normally. In my case, it ran fine for about 43 minutes (a long session with many file reads, edits and shell commands) before the process crashed with a segfault mid-session.
5. After that first crash, open the Claude Code panel again or start a new session.
6. The native binary now crashes with SIGSEGV within 4–7 ms of every launch, before any message can be sent. This happens on every attempt, including after reloading VSCodium.

I don't know what triggered the first crash, so step 4 may not reproduce reliably. Steps 5–6 happen 100% of the time on my machine.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.283 worked normally for about 43 minutes before the first crash. I was on 2.1.282 before that with no problems.

Claude Code Version

2.1.283 (VSCodium extension, linux-x64 native binary)

Platform

Anthropic API

Operating System

Ubuntu/Debian Linux

Terminal/Shell

VS Code integrated terminal

Additional Information

• Editor: VSCodium (not Microsoft VS Code), running locally (no Remote/SSH/WSL).
• CPU: Intel Core i7-2820QM (Sandy Bridge, 2011). Flags reported by Bun: sse42 popcnt avx, no AVX2.
• The crash banner says "Bun v1.4.3 Linux x64", not "(baseline)", so the extension seems to ship the non-baseline Bun build. That build may assume AVX2, which could be related.
• RAM: 12.5 GB. The crash isn't memory-related at startup (RSS ~18 MB when it crashes).
• Every launch path crashes the same way: resuming the previous session, starting a new session, and the extension's own background "config cache" launch.
• Telemetry is turned off in my settings, in case that affects crash reporting on your side.
• I can provide the full extension output log privately if needed (it contains private project details, so I haven't posted it publicly).
• Possibly related: #79359 (SIGSEGV in the linux-x64 native binary on a CPU without usable AVX2), though my case is a physical machine with no AVX2 at all, and the same version worked for 43 minutes before crashing.