LIVE INTELLIGENCE · part of the Xentir AI Index

Claude Fable 5 vs GPT-5.5 Pro

Name: Claude Fable 5 vs GPT-5.5 Pro — benchmark results
Creator: Epoch AI
License: https://creativecommons.org/licenses/by/4.0/

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 2026-09-09 · Methodology · Data Sources

GPT-5.5 Pro leads on more of the 4 benchmarks where both are measured — Claude Fable 5 on 1, GPT-5.5 Pro on 2, tied on 1. The remaining 5 of 9 tracked benchmarks cannot be compared: 3 have a result for only one of the two models, 2 for neither. Nothing on this page is estimated to fill those in.

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 2, tied on 1.

Benchmark	Claude Fable 5	GPT-5.5 Pro	Leads
Epoch Capabilities Index (ECI)	163.4	162.3	Claude Fable 5
SWE-bench Verified	Not measured	Not measured	Not measured on both
GPQA Diamond	0.859 (max)	0.939 (xhigh-pre-release)	GPT-5.5 Pro
MATH Level 5	Not measured	Not measured	Not measured on both
OTIS Mock AIME 2024-2025	1.000 (high)	1.000 (xhigh-pre-release)	Tied
FrontierMath	Not measured	0.524 (high-pre-release)	Comparison unavailable — Claude Fable 5 has no published result
FrontierMath Tier 4	Not measured	0.396	Comparison unavailable — Claude Fable 5 has no published result
SimpleQA Verified	0.707 (xhigh)	Not measured	Comparison unavailable — GPT-5.5 Pro has no published result
Chess Puzzles	0.410 (high)	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.

What remains uncertain

Claude Fable 5 has no published result on FrontierMath, FrontierMath Tier 4.
GPT-5.5 Pro has no published result on SimpleQA Verified.
2 tracked benchmarks have no published result for either model.

A missing result means Xentir has not found one published by the source it cites, not that the model performs badly. See Data Sources.

Reference price

Per 1M tokens	Claude Fable 5	GPT-5.5 Pro
Output	$50.00 stale	$180.00

List price as published by the vendor. Xentir does not verify negotiated or enterprise rates, and price is not a measure of capability — see Data Sources.

Full profiles

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