Verdict
GPT-5.5 leads 20–1 across 21 shared benchmarks.
Claude Opus 4.5 1 · GPT-5.5 20 · higher isn't always better — check the caveats below.
Reported scores — protocols may differ. How we compare
Unknown: GPT-5.5 leads 6–0 across 6 shared unknown benchmarks (largest gap: Mystery Game Puzzles, 51.53 vs 14.08 — protocols undisclosed).
Reasoning: GPT-5.5 leads 4–1 across 5 shared reasoning benchmarks (largest gap: SimpleQA Verified, 63 vs 45.7 — protocols undisclosed).
Math: GPT-5.5 leads 2–0 across 2 shared math benchmarks (largest gap: FrontierMath-Tier-4-v2-Private, 72.5 vs 4.88 — single evaluator).
Vendor claims — compare against the measured scores above. A claim is what a developer says about its own model, not an independent measurement.
No vendor claims on file for Claude Opus 4.5.
Agentic / Tool Use
“The gains are especially strong in agentic coding, computer use, knowledge work, and early scientific research”
Coding
“It excels at writing and debugging code, researching online, analyzing data, creating documents and spreadsheets, operating software, and moving across tools until a task is finished.”
General
“We're releasing GPT-5.5, our smartest and most intuitive to use model yet, and the next step toward a new way of getting work done on a computer.”
Speed / Latency
“GPT-5.5 matches GPT-5.4 per-token latency in real-world serving, while performing at a much higher level of intelligence.”
GPT-5.5 leads 20–1 across 21 shared benchmarks. Claude Opus 4.5 leads 1 benchmark and GPT-5.5 leads 20. Higher isn't always better — see the integrity caveats on each benchmark.
Claude Opus 4.5 and GPT-5.5 have 21 benchmarks in common in our data — those are the only rows where a direct, apples-to-apples comparison is drawn.
GPT-5.5 leads unknown 6–0. GPT-5.5 leads reasoning 4–1.