Reading through the System Prompts / Hints that Xcode 26.3 injects into the agents is fascinating..and honestly is just helpful documentation to read…essentially concise examples of best practices and implementations recommendations.
Reminds me of the old programming "Guides" which apple used to publish alongside the main documentation which were more focused on how to use the API, than what it was.
There're in: Xcode.app/Contents/PlugIns/IDEIntelligenceChat.framework/Versions/A/Resources

