I tried the three provider types with xcodes current agent integration pane and just trying to use them crashed xcode itself so badly that the ide couldn’t even be launched.

FTA: “In addition to these built-in integrations, Xcode 26.3 makes its capabilities available through the Model Context Protocol, an open standard that gives developers the flexibility to use any compatible agent or tool with Xcode.”

There may be other improvements.

I came here to ask this question. I find the existing agentic coding integraton to be clunky and slow. I've had much better luck with my Xcode projects just using my agentic coding tool of choice in the CLI.