I tried again your sample app with Xcode beta 2 + macOS beta 2 whiteout success.
When start record, in console I see this message (note: I'm italian, so I forced language in "it_IT"):
loadRawPromptTemplateFromModelCatalog failed with Error Domain=NSCocoaErrorDomain Code=4099 "The connection to service named com.apple.modelcatalog.catalog was invalidated: failed at lookup with error 159 - Sandbox restriction." UserInfo={NSDebugDescription=The connection to service named com.apple.modelcatalog.catalog was invalidated: failed at lookup with error 159 - Sandbox restriction.}