GPT-5.1 Chat (AKA Instant 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…
Model details →OpenAI: GPT-5.1 Chat vs Anthropic: Claude Fable Latest
OpenAI: GPT-5.1 Chat and Anthropic: Claude Fable Latest are evenly matched on 6 axes — pick the one whose provider, latency, or licensing fits your stack.
This model always redirects to the latest model in the Claude Fable family.
Model details →Side-by-side comparison
| Capability | OpenAI: GPT-5.1 Chat | Anthropic: Claude Fable Latest | Winner |
|---|---|---|---|
| Context window Maximum number of input tokens the model can attend to in a single request. | 128K | 1M | 🏆 Anthropic: Claude Fable Latest |
| Input price (per 1M) Cost per million input tokens billed by the provider. | $1.25 | $10.00 | 🏆 OpenAI: GPT-5.1 Chat |
| Output price (per 1M) Cost per million output tokens billed by the provider. | $10.00 | $50.00 | 🏆 OpenAI: GPT-5.1 Chat |
| Tool / function calling First-class support for emitting structured tool calls. | Yes | Yes | Tie |
| Vision input Accepts image inputs alongside text. | Yes | Yes | Tie |
| Reasoning mode Internal chain-of-thought / extended-thinking support. | — | Yes | 🏆 Anthropic: Claude Fable Latest |
Frequently asked questions
Is OpenAI: GPT-5.1 Chat better than Anthropic: Claude Fable Latest?
OpenAI: GPT-5.1 Chat and Anthropic: Claude Fable Latest are evenly matched on 6 axes — pick the one whose provider, latency, or licensing fits your stack.
What's the price difference between OpenAI: GPT-5.1 Chat and Anthropic: Claude Fable Latest?
Input: $1.25 vs $10.00 per 1M tokens. Output: $10.00 vs $50.00 per 1M tokens.
What context windows do OpenAI: GPT-5.1 Chat and Anthropic: Claude Fable Latest support?
OpenAI: GPT-5.1 Chat supports up to 128K tokens. Anthropic: Claude Fable Latest supports up to 1M tokens.
Do both OpenAI: GPT-5.1 Chat and Anthropic: Claude Fable Latest support tool calling?
OpenAI: GPT-5.1 Chat: yes. Anthropic: Claude Fable Latest: yes.
Compare OpenAI: GPT-5.1 Chat with other models
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