OpenAI's GPT-5.5 is the new leading AI model

OpenAI's GPT-5.5 is the new leading model. GPT-5.5 tops the Artificial Analysis Intelligence Index by 3 points, breaking a three-way tie with Anthropic and Google

OpenAI gave us pre-release access to test all five reasoning effort levels: xhigh, high, medium, low and non-reasoning.

Key takeaways:

➤ OpenAI tops five headline evaluations: GPT-5.5 (xhigh) leads Terminal-Bench Hard, GDPval-AA and our newly hosted APEX-Agents-AA. The model trails only other OpenAI models in CritPt and AA-LCR, and comes second to Gemini 3.1 Pro Preview on three additional evaluations. The largest gains are on AA-Omniscience (+14 pts), our knowledge and hallucination benchmark, and τ²-Bench Telecom (+7 pts), a customer service agent benchmark.

➤ 20% more expensive to run our Index: Per-token pricing has doubled from GPT-5.4 to $5/$30 per 1M input/output tokens. However, a ~40% token use reduction largely absorbs the hike - resulting in a net ~+20% cost to run our Intelligence Index.

➤ Effort a clear ladder for balancing intelligence and cost: GPT-5.5 (medium) scores the same as Claude Opus 4.7 (max) on our Intelligence Index at one quarter of the cost (~$1,200 vs $4,800) - although Gemini 3.1 Pro Preview scores the same at a cost of ~$900. GPT-5.5 (low) approximates Claude Opus 4.7 (Non-reasoning, high) on our Intelligence Index at half the cost to run (~$500 vs ~$1,000).

➤ Number one in GDPval-AA with an Elo of 1785: GPT-5.5 (xhigh) leads Claude Opus 4.7 (max) by ~30 pts and Gemini 3.1 Pro Preview by ~470 pts. GDPval-AA is Artificial Analysis' benchmark that leverages OpenAI's GDPval dataset to evaluate models on real-world economically valuable tasks.

➤ Top AA-Omniscience accuracy, but trailing the frontier on hallucination: Our private AA-Omniscience benchmark rewards factual knowledge across diverse topics, but punishes hallucination. GPT-5.5 (xhigh) has the highest accuracy at 57% - meaning the model can recall facts in the Omniscience corpus more effectively than any other model. However, it has a hallucination rate of 86% - vs Opus 4.7 (max) at 36%, and Gemini 3.1 Pro Preview at 50%. This makes it more likely to answer a question when it does not 'know' the answer. The 14 pt gain in AA-Omniscience from GPT-5.4 (xhigh) was largely driven by knowledge, with a modest improvement in hallucination.

GPT-5.5 tops the Artificial Analysis Intelligence Index by 3 points, breaking a three-way tie with Anthropic and Google

OpenAI leads five of our headline evaluations and places second to Gemini 3.1 Pro Preview on three.

Effort variants provide a clear ladder to balance intelligence and cost. GPT-5.5 (xhigh) is ~20% more expensive to run our Index than its predecessor, but 30% cheaper than Claude Opus 4.7 (max)

GPT-5.5 (xhigh) uses ~40% fewer output tokens to run our Index than its predecessor

GPT-5.5 (xhigh) leads GDPval-AA with an Elo of 1785

GPT-5.5 (xhigh) records our highest ever AA-Omniscience accuracy score but trails the frontier on hallucination

See Artificial Analysis for further details and benchmarks of GPT-5.5: https://artificialanalysis.ai/models/gpt-5-5