This often fixes issues caused by your ISP, VPN, or proxy
Other things to check:
Do you have MCP servers enabled? Settings → MCP → disable any enabled servers
Are you on a VPN or corporate network? Try without VPN
Does it work in a fresh new chat?
Try restarting your router and computer
Many users with similar “stuck at planning/responding” issues fixed it by disabling HTTP/2 or by talking to their ISP about possible connection interference. Let me know what the diagnostics show.