Claude Code 2.1.149 crashes on launch — Bun v1.3.14 SIGILL/segfault on Intel macOS (x64)

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

Claude Code crashes immediately on launch with a Bun panic (segmentation
The bundled Bun runtime exits with code 132 (SIGILL) roughly 474ms after
starting,
before any work is done. This happens on an Intel x64 Mac.

The crash reports itself as a Bun-level bug ("This indicates a bug in Bun, not
your
code"), and since Bun is bundled inside the Claude Code binary, the version
can't be
updated independently of Claude Code.

## Environment

• Claude Code: 2.1.149 (launched via Claude Desktop)
• Bundled Bun: v1.3.14 (521eedd6)
• OS: macOS 15.7.5
• Arch: x86_64 (genuine Intel Mac, not Rosetta — sysctl.proc_translated =

n/a)

• CPU: Intel Core i9-9900K (CPU features: sse42 popcnt avx avx2 — no AVX-512)
• Memory at crash: RSS 0.23GB / Peak 0.23GB (not an OOM)

## What happened

On launch, the Claude Code process exits with code 132 (128 + 4 → SIGILL).
Bun's own crash handler reports a segmentation fault. The CPU features Bun
detected (avx2, no avx512) match the i9-9900K exactly, so this does not look
like an unsupported-instruction mismatch — it appears to be a genuine crash in
the x64 macOS build of the bundled Bun runtime.

## Reproducibility

[à compléter : est-ce que ça crashe à CHAQUE lancement, ou est-ce arrivé une
seule fois ?]

## Already tried

[à compléter : ex. "Updated Claude Desktop to the latest version — still
crashes" /
"Haven't updated yet"]

## Crash log

Claude Code process exited with code 132

Bun v1.3.14 (521eedd6) macOS x64
macOS v15.7.5
CPU: sse42 popcnt avx avx2
Args: "/Library/Application
Support/Claude/claude-code/2.1.149/claude.app/Contents/MacOS/claude"
"--output-format" "stream-json" "--verbose" "--input-format" "stream-json"
"--effort" "xhigh" "--model" "claude-opus-4-7[1"...
Features: Bun.stderr(2) Bun.stdin(2) Bun.stdout(2) fetch(2) jsc spawn(4)
standalone_executable yaml_parse(3) claude_code
Elapsed: 474ms | User: 323ms | Sys: 75ms
RSS: 0.23GB | Peak: 0.23GB | Commit: 29.29MB | Faults: 204 | Machine: 0.07TB
panic(main thread): Segmentation fault at address 0x3411A85F01
oh no: Bun has crashed. This indicates a bug in Bun, not your code.
To send a redacted crash report to Bun's team,
please file a GitHub issue using the link below:
https://bun.report/1.3.14/

> Note: the bun.report URL above was truncated when copied — the full link
(with
> the encoded crash blob) can be provided if useful for cross-filing with the
Bun team.

What Should Happen?

Claude Code should launch normally on Intel (x86_64) macOS without the bundled
Bun
runtime crashing. The process should start up and reach an interactive/ready
state
instead of dying with EXC_BAD_INSTRUCTION/SIGILL ~474ms after launch.

At minimum, if the runtime hits an unrecoverable error, it should fail
gracefully
with an actionable message rather than crash-looping on every launch (25
crashes in
~11 minutes here).

Si le template attend plutôt un libellé du type « Expected behavior », la même
chose en une phrase :

Claude Code launches and runs normally on Intel macOS; the bundled Bun runtime
does
not crash on startup.

Error Messages/Logs

### Bun crash output (stderr)
  Claude Code process exited with code 132

  Bun v1.3.14 (521eedd6) macOS x64
  macOS v15.7.5
  CPU: sse42 popcnt avx avx2
  Args: ".../claude.app/Contents/MacOS/claude" "--output-format" "stream-json"
  "--verbose" "--input-format" "stream-json" "--effort" "xhigh" "--model"
  "claude-opus-4-7[1"...
  Features: Bun.stderr(2) Bun.stdin(2) Bun.stdout(2) fetch(2) jsc spawn(4)
  standalone_executable yaml_parse(3) claude_code
  Elapsed: 474ms | User: 323ms | Sys: 75ms
  RSS: 0.23GB | Peak: 0.23GB | Commit: 29.29MB | Faults: 204 | Machine: 0.07TB
  panic(main thread): Segmentation fault at address 0x3411A85F01
  oh no: Bun has crashed. This indicates a bug in Bun, not your code.
  To send a redacted crash report to Bun's team,
  please file a GitHub issue using the link below:
   https://bun.report/1.3.14/
  (Note: Bun printed the literal placeholder `<blob>` instead of an encoded
  trace, so
  there is no valid bun.report link to share — its crash reporter failed to
  run.) 
  
  ### macOS crash report (.ips)
  - Exception type: EXC_BAD_INSTRUCTION (SIGILL), codes 0x1, 0x0
  - Parent exit code: 132 (128 + 4 = SIGILL)
  - 25 .ips reports generated today between 07:48 and 07:59 (crash loop)
  - Faulting thread (top frames):
  claude+0x3b52c5d        (Bun panic handler)
  claude+0x3b426db        
  claude+0x1202a98
  libsystem_platform.dylib  _sigtramp
  None+0x0                 <-- execution jumped to an unmapped address (actual
  fault)
  claude+0x363c980
  Full .ips file attached: claude-2026-05-27-075954.ips

Steps to Reproduce

## Steps to Reproduce

Environment: Intel Mac (Core i9-9900K), macOS 15.7.5, Claude Desktop running
Claude Code 2.1.149 (bundled Bun v1.3.14).

1. Open Claude Desktop.
2. Start a Cowork session [à préciser : depuis tel projet / tel bouton], which

spawns
the bundled Claude Code binary.

1. Claude Code is launched with (from the crash log):

--output-format stream-json --verbose --input-format stream-json
--effort xhigh --model claude-opus-4-7[1m]

1. The Claude Code process crashes ~474ms after launch with SIGILL before

reaching a
ready state, and exits with code 132.

1. It crash-loops: every (re)launch produces the same crash (25 .ips reports

in ~11 min).

Reproducibility: 100% on this machine.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.152 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_