GPT-5.1 Chat 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.
Try NowLow-latency chat applications
Conversational tasks with occasional reasoning
Quick everyday interactions
128,000 tokens
16,384 tokens
$1.25
$10
$0.125
$15
$0.19