GPT-5.1 Chat (also known as Instant) is the fast, lightweight member of the 5.1 family, optimized for low-latency chat while retaining strong general intelligence. It uses adaptive reasoning to selectively “think” on harder queries, improving accuracy on math, coding, and multi-step tasks without slowing down typical conversations. The model is warmer and more conversational by default, with better instruction following and more stable short-form reasoning. GPT-5.1 Chat is designed for high-throughput, interactive workloads where responsiveness and consistency matter more than deep deliberation.
Retired on Jul 23, 2026: requests to this model ID now return an error. These models are live and work with the same API key.
GPT-5.1 Chat (also known as Instant) is the fast, lightweight member of the 5.1 family, optimized for low-latency chat while retaining strong general intelligence.
No. GPT 5.1 Chat was retired on NagaAI on Jul 23, 2026, and requests to it now return an error. Live models you can use instead with the same API key: GPT-6.1 Terra, GPT-6.1 Sol and GPT-6 Luna.
It takes text, images and files as input and returns text.
