GPT-5 Thinking

GPT-5 Thinking is the deep reasoning variant within the unified GPT-5 system released by OpenAI on August 7, 2025. The GPT-5 system consists of a fast model answering most queries, a deeper reasoning model (GPT-5 Thinking), and a real-time router that selects the path based on conversation type, complexity, tool needs, and user intent. In ChatGPT, GPT-5 Thinking is explicitly selectable from the model picker for paid users, or can be triggered by phrases such as "think hard about this". In the API, the same GPT-5 model (identifier gpt-5, snapshot gpt-5-2025-08-07) exposes a reasoning_effort parameter with values minimal/low/medium/high that controls the depth of the chain-of-thought. The context window is 400,000 tokens, maximum output is 128,000 tokens. Knowledge cutoff: September 30, 2024. Input modalities are text and image, output is text. API pricing: USD 1.25 per 1M input tokens (USD 0.125 cached) and USD 10 per 1M output tokens. The model was trained on Microsoft Azure AI supercomputers.