[BUG] Chrome native host crashes with Bun panic on Windows 11

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 Chrome native messaging host crashes immediately with a Bun runtime panic when attempting to
connect. The Chrome extension shows "Browser extension is not connected" for all
mcp__claude-in-chrome__ tool calls, even though the MCP server shows as "connected" in Claude Code.

What Should Happen?

The native messaging host should start without crashing and allow the Chrome extension to
communicate with Claude Code for browser automation.

Error Messages/Logs

& "C:\Users\newye\.local\bin\claude.exe" --chrome-native-host

  [Claude Chrome Native Host] Initializing...
  [Claude Chrome Native Host] Creating socket listener: \\.\pipe\claude-mcp-browser-bridge-newye
  ============================================================
  Bun v1.3.5 (1e86cebd) Windows x64 (baseline)
  Windows v.win11_dt
  CPU: sse42 avx avx2
  Args: "C:\Users\newye\.local\bin\claude.exe" "--chrome-native-host"
  Features: Bun.stderr(2) Bun.stdin(2) Bun.stdout(2) jsc standalone_executable
  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: 373ms | User: 375ms | Sys: 140ms
  RSS: 0.54GB | Peak: 0.54GB | Commit: 0.54GB | Faults: 133350 | Machine: 34.26GB

  panic(main thread): Internal assertion failure
  oh no: Bun has crashed. This indicates a bug in Bun, not your code.

  Bun crash report: https://bun.report/1.3.5/e_11e86cebEugggC++08F+mvBoxhkf0389e__0shkwCA0eNrzzCtJLcpL
  zFFILC5OLSrJzM9TSEvMzCktSgUAiSkKPg

Steps to Reproduce

1. Install Claude Code 2.1.27 on Windows 11
2. Install Chrome extension v1.0.41 from https://claude.ai/chrome
3. Start Claude Code with claude --chrome
4. Open Chrome and navigate to any website
5. In Claude Code, run /mcp - shows "Reconnected to claude-in-chrome"
6. Try any browser tool - returns "Browser extension is not connected"
7. To verify the root cause, run manually in PowerShell:

& "C:\Users\<username>\.local\bin\claude.exe" --chrome-native-host

1. Observe Bun crash with "panic(main thread): Internal assertion failure"

Verified that all configuration is correct:

• Registry key exists at

HKCU\Software\Google\Chrome\NativeMessagingHosts\com.anthropic.claude_code_browser_extension

• JSON manifest file exists and points to correct batch file
• Batch file exists and calls claude.exe --chrome-native-host
• Extension ID (fcoeoabgfenejglbffodgkkbkcdhcgfn) matches allowed_origins

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

2.1.19

Claude Code Version

2.1.27

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Chrome extension version: 1.0.41
Extension ID: fcoeoabgfenejglbffodgkkbkcdhcgfn
Windows 11

The native messaging host configuration is correct - the issue is that the Bun runtime crashes when
the native host process starts. This appears to be a Bun v1.3.5 bug affecting Claude Code on
Windows.

Claude Desktop was uninstalled to rule out conflicts with com.anthropic.claude_browser_extension.