OpenAI: GPT-5.1 Chat API
A dynamic snapshot of the GPT-5.1 series released in November 2025. It points to the GPT-5.1 Instant variant, designed for a more "personable" interaction. Introducing a "warmer" conversational tone and lightweight Adaptive Reasoning, it autonomously decides whether to engage in minimal thinking based on instruction complexity, delivering high-speed responses with significantly improved instruction following.
- Context window: 128,000 tokens
- Max output: 16,384 tokens
- Input: text, image
- Output: text
- Reasoning: Supported
- Tool calling: Supported
- File input: Supported
- Released: 2025-11-12
- Knowledge cutoff: 2024-09-30
Frequently Asked Questions
What is the context window of GPT-5.1 Chat?
GPT-5.1 Chat supports a context window of up to 128,000 tokens.
Does GPT-5.1 Chat support function calling?
Yes. GPT-5.1 Chat supports tool / function calling.
Does GPT-5.1 Chat support reasoning?
Yes. GPT-5.1 Chat is a reasoning-capable model.
What is the knowledge cutoff of GPT-5.1 Chat?
The knowledge cutoff of GPT-5.1 Chat is 2024-09-30.