GPT-5.1 Thinking (Reasoning)
by OpenAI
GPT-5.1 Thinking (Reasoning) is a reasoning model from OpenAI, released on November 12, 2025. It has a 400K-token context window and can generate up to 128K output tokens. API pricing is $1.25 per 1M input tokens and $10 per 1M output tokens. It ranks #54 of 220 models by Intelligence Score with a score of 36.8.
GPT-5.1 Thinking is the next iteration of GPT-5, designed with enhanced adaptive reasoning capabilities. Unlike GPT-5.1 Instant, GPT-5.1 Thinking adapts thinking time more precisely to each question, providing more thorough reasoning for complex queries. It offers improved conversational abilities with clearer and more engaging interactions, reducing jargon and enhancing user comprehension. GPT-5.1 Thinking demonstrates significant improvements in coding tasks and complex reasoning scenarios, making it valuable for developers and users who need deeper analysis.
Key specs
| Provider | OpenAI |
|---|---|
| Release date | 2025-11-12 |
| License | proprietary |
| Context window | 400K tokens |
| Max output | 128K tokens |
| Input price | $1.25 / 1M tokens |
| Output price | $10 / 1M tokens |
| Intelligence Score | 36.8 |
| Coding index | 21.4 |
Quick answers
What is the context window of GPT-5.1 Thinking (Reasoning)?
GPT-5.1 Thinking (Reasoning) has a context window of 400K tokens, with a maximum output of 128K tokens per response.
How much does GPT-5.1 Thinking (Reasoning) cost?
GPT-5.1 Thinking (Reasoning) costs $1.25 per 1M input tokens and $10 per 1M output tokens through the API.
Is GPT-5.1 Thinking (Reasoning) open source?
No. GPT-5.1 Thinking (Reasoning) is a proprietary model from OpenAI (proprietary license).
When was GPT-5.1 Thinking (Reasoning) released?
OpenAI released GPT-5.1 Thinking (Reasoning) on November 12, 2025.
How does GPT-5.1 Thinking (Reasoning) compare to Claude Opus 5.5 (Reasoning)?
GPT-5.1 Thinking (Reasoning) scores 36.8 on the Intelligence Score versus 60.5 for Claude Opus 5.5 (Reasoning), the current #1. Input pricing is $1.25 vs $4 per 1M tokens.
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