Gpt-4o-mini-tts-2025-12-15 still truncates final sentences; 2025-03-20 is being deprecated
OpenAI Developer Community
April 23, 2026
gpt-4o-mini-tts-2025-12-15 also ignores TTS instructions. So it is a worse model than gpt-4o-mini-tts-2025-03-20.
Discussion in the ATmosphere