Strange think happened to me last night. I have the latest Antigravity with AI Ultra subscription. Since yesterday evening, I have been unable to create any new chats! I type text in the chat window, press Enter, a new chat is created, and then nothing happens. I tried to restart everything, uninstall, reinstall, and sign out, sign in, no difference. Interesting is that i cannot even submit bug report, it just says Submitting and nothing 
It happened since i started testing Claude Code in parallel, CC adds worktree and this is not supported by Antigravity and everything stops working for that repo:
Quick summary of what fixed it, in case it happens again:
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Your repo had
extensions.worktreeConfig = trueset (enabled automatically by some worktree operations) -
Antigravity’s language server doesn’t support that extension and errors out, which silently breaks agent responses
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Unsetting it with
git config --unset extensions.worktreeConfigresolves it — worktrees keep working fine