Claude in Chrome: Browser extension not connected after Claude Code auto-update (Windows)

Update: narrowed this to a server-side 405 on /v1/toolbox/shttp/mcp/

I worked the local layer all the way through; the failure is now isolated to MCP
session creation, server-side. Details in case they help triage.

Eliminated the Desktop/Code native-host collision (this machine also hits #58201)

• Disabled Claude Desktop's native host: renamed

com.anthropic.claude_browser_extension.json → .json.disabled and removed its
HKCU\...\NativeMessagingHosts keys, leaving only
com.anthropic.claude_code_browser_extension registered.

• Killed cowork-svc.exe, the Desktop chrome-native-host.exe, and a stale

claude.exe --chrome-native-host, which freed the held named pipe
claude-mcp-browser-bridge-<HOST>.

• Verified a fresh claude.exe --chrome-native-host then spawns and recreates the

pipe cleanly.

MCP server ↔ Claude Code link is healthy

From mcp-logs-claude-in-chrome:

Successfully connected (transport: stdio) in 12ms
Connection established ... serverVersion: {"name":"Claude in Chrome","version":"1.0.0"}
Calling MCP tool: tabs_context_mcp
Tool 'tabs_context_mcp' completed successfully in 414ms   <- payload is the "not connected" error

Failure is isolated to browser session creation

Terminal: Remote Control failed to connect: Session creation failed — see debug log

Reproducible root cause

The session-creation request to claude.ai returns 405 on every attempt:

/v1/toolbox/shttp/mcp/<uuid>  → 405 (Method Not Allowed)
/v1/toolbox/shttp/mcp/<uuid>  → 405 (Method Not Allowed)   (new UUID each retry)

A 405 means the request reached the server and the method was rejected — so this is
server-side, not a local native-host/config issue.

Environment / timing

Windows 11, Claude Code 2.1.150, Chrome 148, extension 1.0.72. Last worked 2026-05-22;
broke after CC auto-updated to 2.1.150 on 2026-05-25 — consistent with the 2.1.150
client using a handshake the toolbox/shttp/mcp endpoint rejects with 405.

Questions for maintainers

1. Is the 405 on /v1/toolbox/shttp/mcp/ a known server-side regression / method or

protocol-version mismatch with the 2.1.150 client?

1. Is there a client version compatible with the currently-deployed endpoint (i.e.,

would pinning to a pre-2.1.150 build restore connectivity)?

Bumping this — still broken as of today (2026-06-05).

Claude Code desktop app updated today but the Chrome extension bridge is still returning "Browser extension is not connected." Same 405 on v1/toolbox/shttp/mcp/ endpoint.

• Claude Code: latest (updated 2026-06-05)
• Chrome: up to date
• Extension: latest from Chrome Web Store

No changes on our end. The native host binary still appears to be the same one from May 22. Is there any timeline on a fix, or any workaround we might be missing?

Same for me