Chrome native host crashes on Windows with Bun assertion failure

Summary

The Chrome native host (claude.exe --chrome-native-host) crashes immediately on startup with a Bun internal assertion failure, preventing the Claude in Chrome browser automation feature from working.

Environment

• OS: Windows 11
• Claude Code version: Latest (claude.exe dated Feb 3, 2025)
• Bun version: 1.3.5

Symptoms

• Chrome extension reports: Unchecked runtime.lastError: Could not establish connection. Receiving end does not exist.
• tabs_context_mcp tool returns: "Browser extension is not connected"

Diagnostic Steps

1. Verified registry entry exists

Get-ItemProperty -Path "HKCU:\Software\Google\Chrome\NativeMessagingHosts\*"

Found entry for com.anthropic.claude_code_browser_extension pointing to:
C:\Users\<username>\AppData\Roaming\Claude Code\ChromeNativeHost\com.anthropic.claude_code_browser_extension.json

2. Verified manifest file

{
  "name": "com.anthropic.claude_code_browser_extension",
  "description": "Claude Code Browser Extension Native Host",
  "path": "C:\Users\<username>\.claude\chrome\chrome-native-host.bat",
  "type": "stdio",
  "allowed_origins": [
    "chrome-extension://fcoeoabgfenejglbffodgkkbkcdhcgfn/"
  ]
}

3. Verified batch file

@echo off
REM Chrome native host wrapper script
REM Generated by Claude Code - do not edit manually
"C:\Users\<username>\.local\bin\claude.exe" --chrome-native-host

4. Verified claude.exe exists

-rwxr-xr-x 1 <username> 197609 232423072 Feb  3 18:27 C:\Users\<username>\.local\bin\claude.exe

5. Invoked native host directly - crash observed

timeout 3 cmd //c "C:\Users\<username>\.claude\chrome\chrome-native-host.bat"

Output:

[Claude Chrome Native Host] Initializing...
[Claude Chrome Native Host] Creating socket listener: \.\pipe\claude-mcp-browser-bridge-<username>
============================================================
Bun v1.3.5 (1e86cebd) Windows x64 (baseline)
Windows v.win11_dt
CPU: sse42 avx avx2
Args: "C:\Users\<username>\.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" ... [truncated]
Elapsed: 490ms | User: 687ms | Sys: 171ms
RSS: 0.63GB | Peak: 0.63GB | Commit: 0.66GB | Faults: 153618 | Machine: 68.64GB

panic(main thread): Internal assertion failure
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/1.3.5/e_11e86cebEugggC++08F+mvBoxhkf0389e__0shkwCA0eNrzzCtJLcpLzFFILC5OLSrJzM9TSEvMzCktSgUAiSkKPg

Root Cause

The native host process crashes with a Bun internal assertion failure before it can respond to the Chrome extension, causing the "Receiving end does not exist" error.

Bun Crash Report

https://bun.report/1.3.5/e_11e86cebEugggC++08F+mvBoxhkf0389e__0shkwCA0eNrzzCtJLcpLzFFILC5OLSrJzM9TSEvMzCktSgUAiSkKPg

Additional Context

• Windows Smart App Control was disabled during troubleshooting (not the cause)
• All file paths and registry entries are correctly configured
• The crash occurs consistently on every invocation