Error text / 报错原文
failed to connect to browser via CDPCDP endpoint failedECONNREFUSED 127.0.0.1:9222
What it means
The agent cannot connect to the Chrome DevTools Protocol endpoint it was configured to use.
Most common causes
- Chrome not launched with remote debugging
- Port is blocked or already in use
- Endpoint is HTTP while client expects WebSocket
- Remote browser provider URL or token is wrong
Fastest fix
- Reproduce the smallest failing case outside the agent.
- Confirm auth, session, and transport before changing app code.
- Disable unrelated tools or servers and retry once.
- Capture the exact timestamp, client version, and raw error text.
Safe fix
- Keep secrets in environment variables or the platform secret store.
- Use least-privilege scopes and read-only tools by default.
- Add validation around manifests, schemas, and callback URLs.
- Document the working local and production configuration.
What not to do
- Do not paste OAuth tokens or session IDs into public logs.
- Do not bypass TLS, CSP, or permission prompts as a permanent fix.
- Do not enable every MCP tool globally just to make one task pass.
Diagnostic commands
node --version npx @playwright/mcp@latest --help curl http://127.0.0.1:9222/json/version