Verdict
Claude Opus 5.5 leads 7–1 across 9 shared benchmarks.
Claude Opus 5.5 7 · GPT-5.5 Pro 1 · 1 tied · higher isn't always better — check the caveats below.
Reported scores — protocols may differ. How we compare
Math: Claude Opus 5.5 leads 1–0 across 2 shared math benchmarks (largest gap: FrontierMath-Tier-4-v2-Private, 95 vs 78.05 — protocols undisclosed).
Reasoning: Evenly split 1–1 across 2 shared reasoning benchmarks (largest gap: GPQA diamond, 91.9 vs 87.46 — protocols undisclosed).
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 5.5.
General
“In GPT-5.5 Pro, early testers are seeing a significant step up in both the difficulty and quality of work ChatGPT can take on”
Reasoning
“GPT-5.5 Pro, designed for even harder questions and higher-accuracy work, is available to Pro, Business, and Enterprise users.”
Writing
“testers found GPT-5.5 Pro's responses significantly more comprehensive, well-structured, accurate, relevant, and useful”
Claude Opus 5.5 leads 7–1 across 9 shared benchmarks. Claude Opus 5.5 leads 7 benchmarks and GPT-5.5 Pro leads 1, with 1 tied. Higher isn't always better — see the integrity caveats on each benchmark.
Claude Opus 5.5 and GPT-5.5 Pro have 9 benchmarks in common in our data — those are the only rows where a direct, apples-to-apples comparison is drawn.
Claude Opus 5.5 leads unknown 2–0. Claude Opus 5.5 leads math 1–0.