Chrome native host crashes on Windows: Bun v1.3.11 internal assertion failure

Environment

• OS: Windows 11 Pro (10.0.26100)
• Claude Code: v2.1.77
• Chrome extension: v1.0.62 (fcoeoabgfenejglbffodgkkbkcdhcgfn)
• Bun: v1.3.11 (a2743b6d), Windows x64 (baseline)

Problem

All claude-in-chrome MCP tools fail with "Browser extension is not connected." The Chrome native messaging host process crashes immediately on startup.

Reproduction

Run the native host directly:

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

Output:

[Claude Chrome Native Host] Initializing...
[Claude Chrome Native Host] Creating socket listener: \.\pipe\claude-mcp-browser-bridge-Daniel
============================================================
Bun v1.3.11 (a2743b6d) Windows x64 (baseline)
Windows v.win11_dt
CPU: sse42 avx avx2
Args: "C:\Users\Daniel\.local\bin\claude.exe" "--chrome-native-host"
Features: Bun.stdin(2) jsc standalone_executable
Builtins: "bun:main" "node:async_hooks" "node:buffer" "node:child_process" "node:crypto" "node:fs" "node:fs/promises" "node:net" "node:os" "node:path" "node:process" "node:stream" "node:timers/promises" "node:url" "node:util"
Elapsed: 91ms | User: 31ms | Sys: 109ms
RSS: 0.32GB | Peak: 0.32GB | Commit: 0.47GB | Faults: 77592 | Machine: 0.14TB

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/1.3.11/e_1a2743b6EkgggC+zxlG+zwB6uvohB0xoihB__64rp3CA0eNrzzCtJLcpLzFFILC5OLSrJzM9TSEvMzCktSgUAiSkKPg

Root Cause

The process successfully initializes and creates the named pipe \.\pipe\claude-mcp-browser-bridge-{username}, then immediately panics with a Bun internal assertion failure. The crash occurs within ~91ms of startup.

Native Host Configuration

Manifest: %APPDATA%\Claude Code\ChromeNativeHost\com.anthropic.claude_code_browser_extension.json

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

Bat wrapper: C:\Users\Daniel\.claude\chrome\chrome-native-host.bat

@echo off
"C:\Users\Daniel\.local\bin\claude.exe" --chrome-native-host

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

Note

Claude Desktop's native host (chrome-native-host.exe at %APPDATA%\Claude\ChromeNativeHost\) works fine — it's a standalone binary, not Bun-based. Only the Claude Code Bun-based host is affected.