Note
This addresses the concern of "how to get Xcode's agent support to reach outside of itself without asking for permission" but does not address the reverse of "how to get a terminal agent to talk to Xcode without prompting."
This is basically the equivalent of running something like claude --dangerously-skip-permissions, so... probably this is a bad idea.
defaults write com.apple.dt.Xcode IDEChatAgenticChatSkipPermissions -bool YES
When you set this flag, after you initiate a session with Claude Agent in Xcode, if you go to terminal and run ps -ax | grep danger you will see the claude agent process has --dangerously-skip-permissions passed directly to it from Xcode.