GPT-5.1
OpenAI·Nov 2025reasoningproprietary
59.6
modhub Index
GPT-5.1 introduced adaptive reasoning to the GPT-5 line: the model decides per request how much to think, which cut latency and cost on easy tasks without giving up performance on hard ones. It also brought a warmer default conversational style and better instruction following. It remains available in the API at the same price as GPT-5 and is a sensible pick where GPT-5.2's improvements aren't needed.
Benchmark results
- HLEReasoning · #3 of 14~26.5%
Where it shines
- Adaptive thinking keeps simple requests fast and cheap
- Solid all-round coding and reasoning performance
- 90% prompt-caching discount for repeated context
Alternatives to GPT-5.1
The budget coding-agent favorite of late 2025 — near-Sonnet coding utility with MIT weights and a $3/month plan.
The model that made 30-hour autonomous coding sessions real — 77.2% SWE-bench Verified and a 1M-token context beta at $3/$15.
A trillion-parameter open reasoning agent that can chain 200–300 tool calls — the open-weights agentic standout of late 2025.
The sparse-attention release that halved DeepSeek's already-lowest-in-class prices while keeping GPT-class quality.
Frequently asked questions
- How much does the GPT-5.1 API cost?
- GPT-5.1 costs $1.25 per million input tokens and $10 per million output tokens, with cached input at $0.13 per million. A workload of 10M input and 1.5M output tokens per month costs about $27.50.
- What is the context window of GPT-5.1?
- GPT-5.1 supports a context window of 400,000 tokens (400K), with up to 128K output tokens per response.
- Is GPT-5.1 open source?
- No — GPT-5.1 is a proprietary model available through OpenAI's API and partner platforms.
- What are the best alternatives to GPT-5.1?
- The closest alternatives by overall capability are GLM-4.6, Claude Sonnet 4.5, Kimi K2 Thinking, DeepSeek V3.2. See the comparison pages for detailed head-to-head breakdowns.