LIVE INTELLIGENCE · part of the Xentir AI Index

Claude Fable 5 vs GPT-5.5 Pro

Claude Fable 5 · Anthropic, released 2026-06-09
GPT-5.5 Pro · OpenAI, released 2026-04-23

“Epoch AI, 'AI Benchmarking Hub'. Published online at epoch.ai. Retrieved from 'https://epoch.ai/benchmarks' [online resource].” · epoch.ai/benchmarks · Licensed CC BY 4.0 · data last verified 2026-07-26 · Methodology · Data Sources

Head-to-head

Measured on 4 of 9 tracked benchmarks for both models — Claude Fable 5 leads on 1, GPT-5.5 Pro leads on 3.

Benchmark	Claude Fable 5	GPT-5.5 Pro	Leads
Epoch Capabilities Index (ECI)	160.7	160.9	GPT-5.5 Pro
SWE-bench Verified	Not measured	Not measured	Not measured on both
GPQA Diamond	Not measured	0.939 (xhigh-pre-release)	Not measured on both
MATH Level 5	Not measured	Not measured	Not measured on both
OTIS Mock AIME 2024-2025	0.997 (max)	1.000 (xhigh-pre-release)	GPT-5.5 Pro
FrontierMath	Not measured	0.524 (high-pre-release)	Not measured on both
FrontierMath Tier 4	Not measured	0.396	Not measured on both
SimpleQA Verified	0.683 (xhigh)	0.645 (xhigh-pre-release)	Claude Fable 5
Chess Puzzles	0.410 (max)	0.640 (xhigh-pre-release)	GPT-5.5 Pro

Benchmark results measure specific tasks and should not be treated as a universal measure of model quality. A model with no row here for a benchmark has not been measured on it — that is left blank, never estimated.

Full profiles

Claude Fable 5 → · GPT-5.5 Pro → · the full AI Model Rankings table