LIVE INTELLIGENCE · part of the Xentir AI Index

GPT-5.5 vs GPT-5.6 Terra

GPT-5.5 · OpenAI, released 2026-04-23
GPT-5.6 Terra · OpenAI, released 2026-07-09

“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 5 of 9 tracked benchmarks for both models — GPT-5.5 leads on 4, tied on 1.

Benchmark	GPT-5.5	GPT-5.6 Terra	Leads
Epoch Capabilities Index (ECI)	158.5	158.2	GPT-5.5
SWE-bench Verified	0.806 (xhigh-pre-release)	Not measured	Not measured on both
GPQA Diamond	0.940 (xhigh-pre-release)	0.933 (max)	GPT-5.5
MATH Level 5	Not measured	Not measured	Not measured on both
OTIS Mock AIME 2024-2025	1.000 (xhigh-pre-release)	0.997 (max)	GPT-5.5
FrontierMath	0.517 (xhigh-pre-release)	Not measured	Not measured on both
FrontierMath Tier 4	0.354 (xhigh-pre-release)	Not measured	Not measured on both
SimpleQA Verified	0.631 (xhigh-pre-release)	0.431 (max)	GPT-5.5
Chess Puzzles	0.540 (xhigh-pre-release)	0.540 (max)	Tied

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

GPT-5.5 → · GPT-5.6 Terra → · the full AI Model Rankings table