I developed a conversational agent using Gradium and it worked fine using the iPhone's built-in speaker on iOS 18.7 and iOS 26.6. I developed similar conversational agent using the Gemini stack and it also worked fine using the iPhone's built-in speaker on iOS 18.7 and iOS 26.6. Now on iOS 27.0, we hear crackling in the transcripts and responses, with both stacks.