Segfault in claude.exe (Bun 1.4.0) when fetching large URLs - Claude Code 2.1.185 / Windows 11

Segfault in claude.exe (Bun 1.4.0) when fetching large URLs

Environment

• Claude Code: 2.1.185 (latest via npm install -g @anthropic-ai/claude-code@latest)
• Platform: win32-x64
• OS: Windows 11 (10.0.26200), single user install
• Bundled runtime: Bun v1.4.0 (324c5f012) — confirmed by extracting the version string from bin/claude.exe
• bun:ffi, node:* builtins all enabled (full Bun standalone)
• Install path: C:\Users\<user>\AppData\Roaming\npm\node_modules\@anthropic-ai\claude-code\bin\claude.exe (~225 MB)

What happens

claude runs normally for ~5 minutes, then crashes with a segmentation fault in Bun's main thread during a Fetch() operation. The crash is deterministic — any request that triggers a GitHub blob/raw fetch reproduces it.

Trigger command pattern (representative):

> please read https://github.com/<owner>/<repo>/blob/main/README.md

CLI output right before the crash:

Fetch(https://github.com/<owner>/<repo>/blob/main/README.md)
  ⎿  Fetching…

✶ Crunching… (30s · ↓ 854 tokens)
  ⎿  Tip: Double-tap esc to rewind the code and/or conversation to a previous point in time

Then the runtime banner and crash dump:

Bun v1.4.0 (324c5f012) Windows x64 (baseline)
Windows v10.26200t
CPU: sse42 avx avx2 avx512
Args: "C:\Users\<user>\AppData\Roaming\npm\node_modules\@anthropic-ai\claude-code\bin\claude.exe"
Features: Bun.stderr(2) Bun.stdin(2) Bun.stdout(2) abort_signal(28) fetch(84) http_server jsc spawn(35) standalone_executable yaml_parse(701) claude_code
Builtins: "bun:ffi" "bun:main" "node:assert" "node:async_hooks" "node:buffer" "node:child_process" "node:constants" "node:crypto" "node:dns" "node:events" "node:fs" "node:fs/promises" "node:http" "node:http2" "node:https" "node:module" "node:net" "node:os" "node:path" "node:path/posix" "node:path/win32" "node:perf_hooks" "node:process" "node:readline" "node:stream" "node:stream/consumers" "node:stream/promises" "node:string_decoder" "node:timers/promises" "node:tls" "node:tty" "node:url" "node:util" "node:vm" "node:zlib" "ws"

Elapsed: 293040ms | User: 14921ms | Sys: 4312ms
RSS: 0.57 GB | Peak: 0.59 GB | Commit: 1.24 GB | Faults: 315358 | Machine: 33.41 GB

panic(main thread): Segmentation fault at address 0x1D400000050
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/1.4.0/w_1324c5f0mgggkEuhooCs1x2xBkg61xBi6g2xBup57xBq0y7xB6n4kyBq92zzBk408xByv16xB8tntzBmj8hlB8opilBo0oilBm0ho6CA2odgF

What I've already tried

• npm install -g @anthropic-ai/claude-code@latest → resolves to 2.1.185, but the bundled binary still ships Bun 1.4.0. Verified by extracting the Bun vX.Y.Z string from bin/claude.exe.
• Confirmed the optional dependency @anthropic-ai/claude-code-win32-x64@2.1.185 is installed at claude-code/node_modules/@anthropic-ai/claude-code-win32-x64/claude.exe and the binary at the same path is also Bun 1.4.0.
• Killed any leftover claude/bun processes to release the EPERM on the old .exe during reinstall.

So this is not a stale install on the user's side — every 2.1.185 artifact on Windows includes Bun 1.4.0.

Workaround (not a fix)

Pasting content into the chat instead of letting claude fetch URLs avoids the segfault path entirely. This narrows it down to Bun.fetch / streaming-response handling under Windows, rather than anything in the Claude Code agent logic.

Request

Please rebuild the Windows claude.exe against a newer Bun (1.5+ has the relevant fetch/JSC fixes). Bun upstream has acknowledged this class of segfault — the bun.report link above is the canonical crash report for this trace.

Bun crash report

https://bun.report/1.4.0/w_1324c5f0mgggkEuhooCs1x2xBkg61xBi6g2xBup57xBq0y7xB6n4kyBq92zzBk408xByv16xB8tntzBmj8hlB8opilBo0oilBm0ho6CA2odgF