Xcode is using the Claude Agent SDK, which means that you
"get the full power of Claude Code directly in Xcode—including subagents, background tasks, and plugins—all without leaving the IDE¹". I assume that means iOS development plug-ins like Axiom² should work as well.
¹ https://www.anthropic.com/news/apple-xcode-claude-agent-sdk ² https://charleswiltgen.github.io/Axiom/