GPT 5.1 Thinking is the reasoning-focused member of the GPT-5.1 family, applying extended chain-of-thought computation to produce more thorough and accurate responses on complex analytical, scientific, and multi-step problems.
import { streamText } from 'ai'
const result = streamText({ model: 'openai/gpt-5.1-thinking', prompt: 'Why is the sky blue?'})GPT 5.1 Thinking was released on November 12, 2025 as part of the GPT-5.1 model generation on AI Gateway. It occupies the reasoning-depth end of the GPT-5.1 spectrum, complementing the speed-optimized instant variant.
The model uses extended chain-of-thought computation, generating internal reasoning tokens that work through problems step by step before producing a visible response. This approach, proven effective in the o-series models, is here applied within the GPT-5.1 architecture to produce more accurate and thorough answers on complex problems.
The context window of 400K tokens supports the lengthy inputs that complex reasoning tasks often require, whether they are research papers, detailed problem statements, or extensive codebases that need architectural analysis. Longer response times come in exchange for deeper, more reliable reasoning.