Claude in Chrome: extension not connecting (native messaging silent failure)

[surendrab-bhtpl]

Description

mcp__claude-in-chrome__* tools consistently fail with:

Browser extension is not connected. Please ensure the Claude browser extension is installed and running (https://claude.ai/chrome), and that you are logged into claude.ai with the same account as Claude Code.

This happens despite the extension being installed, enabled, and working correctly with the Claude Desktop app (and having previously worked with Claude Code in past sessions).

Environment

• Claude Code version: 2.1.209
• OS: macOS (Darwin 25.5.0)
• Chrome version: 150.0.7871.49
• Claude in Chrome extension version: 1.0.80 (ID fcoeoabgfenejglbffodgkkbkcdhcgfn)

Troubleshooting already performed

• Verified native messaging host manifest exists and is correct: ~/Library/Application Support/Google/Chrome/NativeMessagingHosts/com.anthropic.claude_code_browser_extension.json, pointing to a valid, executable wrapper script that execs the currently-running Claude Code binary (~/.local/share/claude/versions/2.1.209 --chrome-native-host)
• Confirmed extension is installed in the correct (Default) Chrome profile and matches the allowed_origins extension ID in the manifest
• Confirmed logged into claude.ai in Chrome with the same account used by Claude Code CLI
• Fully quit (Cmd+Q) and restarted Chrome — confirmed via new PID/start time — issue persists
• Ran /chrome → "Reconnect extension" in Claude Code — opens a claude.ai/new tab that closes almost instantly with no visible error or status update
• Opened the extension's service worker DevTools console (chrome://extensions → Developer mode → "service worker") and watched it during a reconnect attempt — no errors or log output appear at all, on either the extension side or in Claude Code's tool response
• Fully uninstalled and reinstalled the extension — issue persists
• Extension works correctly with Claude Desktop app using the same claude.ai account

Expected behavior

The extension should connect to Claude Code CLI (as it has in prior sessions on this same machine), or the reconnect/pairing flow should surface a visible error explaining the failure instead of silently opening and closing a tab.

Actual behavior

Connection silently fails with no diagnostic information in either the extension's console or Claude Code's output, despite all local configuration appearing correct.

[surendrab-bhtpl]

Update: found the actual underlying error

Using /chrome → "Select browser…" in Claude Code surfaces a concrete error (this is more specific than the generic "extension not connected" message reported above):

Couldn't list connected browsers: JSON Parse error: Unexpected identifier "Browser"

On a colleague's machine, the same "Select browser…" flow correctly lists a connected browser entry (labeled with the Mac's hostname). On my machine it lists nothing and immediately surfaces the JSON parse error instead — so this isn't a timeout/discovery-failure, it's a malformed-response parsing bug in the "list connected browsers" call.

Additional detail ruling out a Claude Desktop conflict: Claude Desktop app was not running at all when this was reproduced, so it isn't Desktop holding an exclusive connection to the extension and returning a non-JSON response for that reason.

This strongly suggests whatever local process/response Claude Code's CLI reads to enumerate connected browsers is returning non-JSON content (literal text containing the word "Browser") instead of a JSON array/object, causing JSON.parse() to throw on the CLI side.

Environment is otherwise unchanged from the original report (Claude Code 2.1.209, macOS Darwin 25.5.0, Chrome 150.0.7871.49, extension 1.0.80).

[surendrab-bhtpl]

Update: reinstall attempted, no change

Ran the official install script again (`curl -fsSL https://claude.ai/install.sh | bash`) to rule out a corrupted local install. It reported "Claude Code successfully installed! Version: 2.1.209" — same version as before, since it was already latest. The native messaging manifest and wrapper script (`~/.claude/chrome/chrome-native-host`) were unchanged (same content/mtime), and the connection issue persists identically after reinstall.

At this point I believe local troubleshooting is exhausted:

• Manifest/binary/extension all verified correct and matching
• Full Chrome restart done
• Extension fully uninstalled/reinstalled
• Claude Desktop confirmed not running (rules out a Desktop connection conflict)
• Full Claude Code reinstall done (no-op since already latest)
• Concrete error reproduced: `Couldn't list connected browsers: JSON Parse error: Unexpected identifier "Browser"` (see comment above)

This looks like it needs investigation from the Claude Code team into what's producing non-JSON output for the "list connected browsers" call on this machine specifically, since a colleague's machine on the same setup works fine.

[ES-Bristol]

Confirming this on my machine — same silent native-messaging failure.

• Claude Code 2.1.202 (also reproduced on 2.1.197)
• macOS 26.5.2 (Darwin 25.5.0)
• Chrome 150.0.7871.125
• Extension ID fcoeoabgfenejglbffodgkkbkcdhcgfn, installed + enabled, same account as Claude Code

Same symptom: /chrome → "Reconnect extension" opens a Chrome window that closes after ~1 second, and every browser tool returns "Browser extension is not connected." Native-messaging host manifest is present and correct, its wrapper execs the current binary (/opt/homebrew/Caskroom/claude-code/2.1.202/claude --chrome-native-host, exists + executable), correct Chrome profile, same account. Already tried full Chrome restart, extension remove + reinstall, and a complete machine power-cycle. Reproduces identically across two Claude Code versions and a reboot.