Chrome extension service worker fails to initialize native host connection (mcpConnected stays false)

Environment

• Claude Code: 2.1.92
• Chrome extension: v1.0.66
• macOS Darwin 25.4.0 (Apple Silicon)
• Claude Max subscription, OAuth token valid

Problem

The Chrome extension's service worker never initiates the native host connection or bridge WebSocket. mcpConnected stays false permanently. All mcp__claude-in-chrome__* tools return "Browser extension is not connected."

Diagnostic findings

What works

• Side panel chat functions normally
• Native host process runs (--chrome-native-host, creates UNIX socket)
• Manual connectNative('com.anthropic.claude_code_browser_extension') from service worker console returns {type: 'status_response', native_host_version: '1.0.0'} — native host is reachable
• chrome_ext_bridge_enabled: true in extension feature flags
• bridgeDeviceId exists in extension storage

What doesn't work

• chrome.storage.local shows mcpConnected: false, nativeHostInstalled: undefined
• Service worker DevTools shows zero network activity (no WebSocket to bridge.claudeusercontent.com)
• Service worker console shows zero messages (no errors, no warnings, no info)
• Disabling and re-enabling the extension does not trigger any service worker initialization
• No pairing prompt appears in the side panel
• --chrome flag confirmed in process args, "chrome": true in settings.json

Steps already taken

1. Disabled Claude Desktop's native messaging host (com.anthropic.claude_browser_extension.json → .disabled)
2. Removed extension from other devices
3. Killed all Claude Code sessions, quit Claude Desktop
4. Deleted bridge socket directory, restarted Chrome
5. Started single session with claude --chrome
6. Verified native host manifest points to correct extension ID (fcoeoabgfenejglbffodgkkbkcdhcgfn)

Root cause hypothesis

The extension's service worker startup/initialization code is not executing — it never calls connectNative() or opens a WebSocket to the bridge. The worker is registered and alive (responds to chrome.storage.local.get()) but its runtime.onStartup / runtime.onInstalled handlers appear to not fire or silently fail.

Related issues

• #20341, #20943, #23434 — Desktop/Code native host conflict
• #25551, #33813 — Multi-device routing
• #38533 — --chrome flag + Desktop coexistence

🤖 Generated with Claude Code