[BUG] Bun has crashed

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?

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Title: crash: Bun Canary segfault when accepting edits on multiple files (50+ files)

Labels: bug, crash, platform:windows, area:core, has repro

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Description

Claude Code crashes with a Bun segmentation fault when accepting edits on a large number
of files (~50 files). The crash occurs with Bun Canary v1.3.9-canary.51 (bundled with
Claude Code) on Windows 11.

Environment

• Claude Code version: (Check with claude --version)
• Bun version (bundled): v1.3.9-canary.51 (d5628db2)
• OS: Windows 11 x64
• CPU features: sse42 avx avx2

Crash Details

⏵⏵ accept edits on (shift+tab to cycle) · 50 files +798 -159
============================================================
Bun Canary v1.3.9-canary.51 (d5628db2) Windows x64 (baseline)
Windows v.win11_zn
CPU: sse42 avx avx2
Args: "C:\Users\user\.local\bin\claude.exe"
Elapsed: 8306506ms | User: 337015ms | Sys: 300906ms
RSS: 1.74GB | Peak: 2.42GB | Commit: 3.13GB | Faults: 12241916

panic(main thread): Segmentation fault at address 0xFFFFFFFFFFFFFFFF
oh no: Bun has crashed. This indicates a bug in Bun, not your code.

Crash Report: https://bun.report/1.3.9/e_2d5628dbmgkgEuhogCgm+2W88outB4s+mqC49uiqC6ssiqCy
7sqXozg0U23wN2/tgUm17jOimsjOw0vxvDCYKERNEL32.DLLg+pFCSntdll.dll2lkBA2DD

Root Cause Analysis

1. Bun Canary Build: The bundled Bun is using an unstable canary build (v1.3.9-canary.51)

instead of stable (v1.3.8)

1. No File Batching: 50 files are processed concurrently without any backpressure or

batching

1. Memory Pressure: 12M+ page faults indicate severe memory pressure
2. Invalid Address: 0xFFFFFFFFFFFFFFFF suggests NULL pointer dereference or

use-after-free

Steps to Reproduce

1. Ask Claude Code to make edits across ~50 files (~800 line changes)
2. Accept the edits
3. Claude Code attempts to process all files concurrently
4. Crashes with segfault

Expected Behavior

Either:

• Files are edited successfully
• Graceful error handling with retry logic
• Files are processed in smaller batches automatically

Actual Behavior

Hard crash with segfault, all progress lost.

Related Issues

• https://github.com/anthropics/claude-code/issues/22632
• https://github.com/anthropics/claude-code/issues/21896
• https://github.com/anthropics/claude-code/issues/11201

Suggested Fixes

1. Switch to Stable Bun: Bundle Bun stable (v1.3.8) instead of canary builds
2. Implement File Batching: Automatically split large edit operations into smaller

batches (5-10 files at a time)

1. Adaptive Concurrency: Detect runtime type and adjust concurrency limits:

• Bun (Canary): 3-5 files
• Bun (Stable): 5-8 files
• Node.js: 10-15 files

1. Memory Awareness: Check available memory before batch operations
2. Checkpoint System: Save progress so failed operations can be resumed

What Should Happen?

Bun has crashed

Error Messages/Logs

============================================================
  Bun Canary v1.3.9-canary.51 (d5628db2) Windows x64 (baseline)
  Windows v.win11_zn
  CPU: sse42 avx avx2
  Args: "C:\Users\user\.local\bin\claude.exe"
  Features: Bun.stderr(2) Bun.stdin(2) Bun.stdout(2) abort_signal(325) fetch(1356) jsc
   spawn(11287) standalone_executable process_dlopen yaml_parse(1845)
  Builtins: "bun:main" "node:assert" "node:async_hooks" "node:buffer"
  "node:child_process" "node:constants" "node:crypto" "node:events" "node:fs"
  "node:fs/promises" "node:http" "node:https" "node:module" "node:net" "node:os"
  "node:path" "node:path/posix" "node:path/win32" "node:perf_hooks" "node:process"
  "node:querystring" "node:stream" "node:timers/promises" "node:tls" "node:tty"
  "node:url" "node:util" "node:zlib" "node:worker_threads" "undici" "ws" "node-fetch"
  "node:http2"
  Elapsed: 8306506ms | User: 337015ms | Sys: 300906ms
  RSS: 1.74GB | Peak: 2.42GB | Commit: 3.13GB | Faults: 12241916 | Machine: 68.30GB

  panic(main thread): Segmentation fault at address 0xFFFFFFFFFFFFFFFF
  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/1.3.9/e_2d5628dbmgkgEuhogCgm+2W88outB4s+mqC49uiqC6ssiqCy7sqXozg0
  U23wN2/tgUm17jOimsjOw0vxvDCYKERNEL32.DLLg+pFCSntdll.dll2lkBA2DD

Steps to Reproduce

-

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

-

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_