Claude in Chrome: native host crashes on Windows — ERR_INVALID_ARG_TYPE binding named pipe (claude.exe 2.1.143 / Bun 1.3.14)

Summary

Every mcp__claude-in-chrome__* tool call fails with Browser extension is not connected. Root cause is that claude.exe --chrome-native-host crashes immediately on startup when Chrome's extension spawns it, before any handshake. The extension is wired correctly and installed in the active Chrome profile.

Environment

• Claude Code: 2.1.143
• Runtime: Bun v1.3.14 (Windows x64 baseline)
• OS: Windows 11 Home 10.0.26200
• Chrome: Stable, active profile = "Profile 2"
• Claude in Chrome extension: fcoeoabgfenejglbffodgkkbkcdhcgfn version 1.0.70_0 (installed in active profile)

Reproduction

1. Have Claude in Chrome extension installed in the active Chrome profile.
2. From a Claude Code session, call any mcp__claude-in-chrome__* tool (e.g. tabs_context_mcp).
3. Receive: Browser extension is not connected. Please ensure the Claude browser extension is installed and running ...
4. Run claude.exe --chrome-native-host directly from a terminal to observe the underlying crash.

Observed behavior

claude.exe --chrome-native-host exits immediately. Stderr (Windows username replaced with <user>):

[Claude Chrome Native Host] Initializing...
[Claude Chrome Native Host] Creating socket listener: \.\pipe\claude-mcp-browser-bridge-<user>
[Claude Chrome Native Host] Socket server error: 9106 | ... <large minified source dump> ...

TypeError: Failed to listen at \.\pipe\claude-mcp-browser-bridge-<user>
 code: "ERR_INVALID_ARG_TYPE"

      at listen (unknown:1:1)
      at node:net:1339:30
      at listenInCluster (node:net:1423:24)
      at listen (node:net:1331:20)
      at B:/~BUN/root/src/entrypoints/cli.js:9111:1166
      at Promise (unknown:1:11)
      at start (B:/~BUN/root/src/entrypoints/cli.js:9111:1139)

Bun v1.3.14 (Windows x64 baseline)

The pipe path \.\pipe\claude-mcp-browser-bridge-<username> looks well-formed, so this appears to be a Bun-on-Windows regression in how net.Server.listen() validates Windows named-pipe paths. Suggest checking the argument shape passed to listen() for the named-pipe code path, or pinning a Bun version where this works on Windows.

Wiring verified intact

To save triage time, the native messaging plumbing is confirmed correct:

• Registry key HKCU\Software\Google\Chrome\NativeMessagingHosts\com.anthropic.claude_code_browser_extension exists and points to a valid manifest path.
• Manifest at %APPDATA%\Claude Code\ChromeNativeHost\com.anthropic.claude_code_browser_extension.json exists, names chrome-native-host.bat, and includes the extension's origin (fcoeoabgfenejglbffodgkkbkcdhcgfn) in allowed_origins.
• ~\.claude\chrome\chrome-native-host.bat exists and shells out to claude.exe --chrome-native-host.
• claude.exe runs fine for normal CLI use (claude --version → 2.1.143).
• Extension is installed in the active Chrome profile.

The failure is fully inside claude.exe --chrome-native-host, before any IPC.

Impact

Claude in Chrome is unusable on Windows in this version. There is no workaround from the user side — the native host binary itself crashes.

Suggested next step

Repro on a Windows machine with claude.exe --chrome-native-host from a shell. The crash is deterministic and instant; no Chrome needed to reproduce.