Verdict
Claude Fable 5 leads 5–4 across 10 shared benchmarks.
Claude Fable 5 5 · GPT-5.5 Pro 4 · 1 tied · higher isn't always better — check the caveats below.
Reported scores — protocols may differ. How we compare
Reasoning: Claude Fable 5 leads 3–1 across 4 shared reasoning benchmarks (largest gap: GPQA diamond, 91.9 vs 81.14 — single evaluator).
Math: Claude Fable 5 leads 1–0 across 2 shared math benchmarks (largest gap: FrontierMath-Tier-4-v2-Private, 87.8 vs 78.05 — 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.
Agentic / Tool Use
“The longer and more complex the task, the larger Fable 5's lead over our other models”
Coding
“It is state-of-the-art on nearly all tested benchmarks of AI capability, showing exceptional performance in software engineering, knowledge work, vision, scientific research, and many other areas”
General
“Fable 5's capabilities exceed those of any model we've ever made generally available”
Multimodal
“It can extract precise numbers from detailed scientific figures and can perform complex vision-based tasks like rebuilding a web app's source code from screenshots alone”
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 Fable 5 leads 5–4 across 10 shared benchmarks. Claude Fable 5 leads 5 benchmarks and GPT-5.5 Pro leads 4, with 1 tied. Higher isn't always better — see the integrity caveats on each benchmark.
Claude Fable 5 and GPT-5.5 Pro have 10 benchmarks in common in our data — those are the only rows where a direct, apples-to-apples comparison is drawn.
Claude Fable 5 leads reasoning 3–1. Claude Fable 5 leads math 1–0.