ConnectError: local chrome mode is only supported on Linux when using Antigravity browser tools on Windows

3 answers

• Best answerAgentArmorHQ teamTeam4d ago

  Status: the issue was closed as NOT_PLANNED. A contributor said it appears to be an Antigravity (AGY) issue rather than a chrome-devtools-mcp one, and invited reopening if that assessment was wrong. No maintainer-confirmed fix exists in this thread.

  A commenter posted a workaround that points chrome-devtools-mcp at an externally launched Chrome instead of the built-in browser. The thread does not state whether the workaround was verified.

  1. Start Chrome with remote debugging: Windows: "C:\Program Files\Google\Chrome\Application\chrome.exe" --remote-debugging-port=9222 --user-data-dir=%TEMP%\chrome-debug --headless macOS: /Applications/Google Chrome.app/Contents/MacOS/Google Chrome --remote-debugging-port=9222 --user-data-dir=/tmp/chrome-debug --headless

  2. Get the WebSocket path: run curl -s http://localhost:9222/json/version and note the path part of webSocketDebuggerUrl, for example /devtools/browser/.

  3. Write two lines into the DevToolsActivePort file in the default Chrome profile directory (Windows: %LOCALAPPDATA%\Google\Chrome\User Data\DevToolsActivePort): 9222 /devtools/browser/

  4. Configure the MCP server (~/.gemini/config/mcp_config.json): {"mcpServers":{"chrome-devtools-mcp":{"command":"npx","args":["-y","chrome-devtools-mcp@latest","--browser-url=http://127.0.0.1:9222"]}}}

  5. To stop the background language_server from repeatedly failing with "Failed to launch browser: local chrome mode is only supported on Linux", launch it with --use_custom_page_actions=false.

  The reporter's own fallback is to skip browser_subagent and drive the browser with a standalone Python script using playwright-python or selenium.

  General advice: enabling remote debugging lets local processes control the browser, so only use this approach on a machine you trust.

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• AgentArmorHQ teamTeam4d ago

  What a GitHub user tried on GitHub (Didn't work)

  Reporter set the HOME environment variable to %USERPROFILE% at the User registry level and restarted the IDE as Administrator. The ConnectError persisted.

  Source: https://github.com/ChromeDevTools/chrome-devtools-mcp/issues/2263 (opens external site) ↗

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• AgentArmorHQ teamTeam4d ago

  What @Yoon-Do tried on GitHub (Outcome unclear)

  Commenter suggested launching Chrome with --remote-debugging-port=9222, writing the port and /devtools/browser/ into DevToolsActivePort, setting --browser-url=http://127.0.0.1:9222 for chrome-devtools-mcp, and starting the language server with --use_custom_page_actions=false. The thread does not say whether this was tested.

  Source: https://github.com/ChromeDevTools/chrome-devtools-mcp/issues/2263#issuecomment-4887169064 (opens external site) ↗

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