GPT-5.1 Brings Personality Presets to Voice AI, Now Live on Vapi

OpenAI's GPT-5.1 adds consistent personality presets — Default, Professional, Friendly, Candid, Quirky, Efficient, Nerdy, and Cynical — plus a more conversational GPT-5.1 Instant and fast adaptive reasoning that gives simple questions quick replies while complex ones get more thinking. Vapi says the model went live on its platform last week alongside OpenAI's announcement, letting voice agents adopt brand-consistent tones without prompt rewrites.