Verdict
Claude Sonnet 5.5 leads 8–2 across 11 shared benchmarks.
Claude Sonnet 5.5 8 · GPT-5.5 2 · 1 tied · higher isn't always better — check the caveats below.
Reported scores — protocols may differ. How we compare
Unknown: Claude Sonnet 5.5 leads 3–0 across 3 shared unknown benchmarks (largest gap: ProofBench, 100 vs 50 — single evaluator).
Math: Claude Sonnet 5.5 leads 1–0 across 2 shared math benchmarks (largest gap: FrontierMath-Tier-4-v2-Private, 80.49 vs 72.5 — protocols undisclosed).
Reasoning: Evenly split 1–1 across 2 shared reasoning benchmarks (largest gap: SimpleQA Verified, 63 vs 46.5 — 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 Sonnet 5.5.
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.”
Claude Sonnet 5.5 leads 8–2 across 11 shared benchmarks. Claude Sonnet 5.5 leads 8 benchmarks and GPT-5.5 leads 2, with 1 tied. Higher isn't always better — see the integrity caveats on each benchmark.
Claude Sonnet 5.5 and GPT-5.5 have 11 benchmarks in common in our data — those are the only rows where a direct, apples-to-apples comparison is drawn.
Claude Sonnet 5.5 leads unknown 3–0. Claude Sonnet 5.5 leads math 1–0.