GPT-5.1
Pinned snapshot gpt-5.1-2025-11-13. Our most intelligent model yet, with faster responses and increased steerability.
About GPT-5.1
GPT-5.1 earns its place through adaptive reasoning — a system that genuinely calibrates effort to the task, running roughly twice as fast on straightforward queries and digging deeper on complex ones. That mechanical intelligence shows up in the benchmarks: 94% on AIME 2025, 88.1% on GPQA Diamond, and a 76.3% solve rate on SWE-Bench Verified, making it one of the more capable off-the-shelf options for serious coding and research-level math. Users consistently praise how much cleaner the code output is — fewer logic errors, better edge-case handling — and the improved tool-calling reliability makes it a practical choice for production agentic pipelines. The catch is that the Auto-routing variant has frustrated users who found it silently redirecting requests through stricter safety filters without explanation, a criticism that turned OpenAI's own Reddit launch AMA into a notable PR setback. For teams willing to pick the right variant (Instant, Thinking, or Auto) and work within a September 2024 knowledge cutoff, GPT-5.1 offers strong price-to-capability value at $1.25 per million input tokens — cheaper than its GPT-5.2 successor while covering most production needs.
Best for
- Autonomous software engineering — bug fixes, patch generation, and algorithmic problem-solving backed by a 76.3% SWE-Bench Verified solve rate
- Research-level math and science — step-by-step reasoning on AIME, GPQA, and graduate-level problems, especially in Thinking mode
- Production API and agentic workflows — reliable structured output and improved instruction-following for chatbots and automated pipelines
- Long-document and codebase analysis — a 400k token context window handles full repositories, lengthy contracts, and extended conversation histories
- Cost-conscious multimodal workloads — text and image input at $1.25/M input tokens for teams that need solid capability without GPT-5.2 pricing
Specs & capabilities
How GPT-5.1 stacks up — intelligence, speed, context, and modalities.
Intelligence
High
Speed
Medium
Context window
400,000 tokens
Max output
128,000 tokens
Knowledge cutoff
September 30, 2024
Frequently asked questions
What does GPT-5.1 cost?
Input tokens are priced at $1.25 per million, output at $10.00 per million, and cached input at $0.125 per million.
How large is the context window?
OpenAI documents a 400,000-token context window, with a maximum output of 128,000 tokens per response.
What are the three variants and when should I use each?
GPT-5.1 Instant prioritizes speed for simpler tasks, Thinking applies deeper compute for math and complex reasoning, and Auto attempts to route between them based on query complexity — though the Auto router has drawn user complaints for opaque behavior.
What is GPT-5.1 best at?
Coding (especially multi-step algorithmic tasks), research-level mathematics, and agentic tool-use pipelines where structured output and reliable instruction-following matter.
What are its known limitations?
The model still produces hallucinations, has a knowledge cutoff of September 2024, and the Auto variant has frustrated users by silently redirecting requests through stricter safety filters.
How does GPT-5.1 compare to GPT-5.2?
GPT-5.2 (released December 2025) outperforms it on harder reasoning and competitive programming benchmarks, but GPT-5.1 costs less and covers the majority of production use cases adequately.