LIVE INTELLIGENCE · part of the Xentir AI Index

Claude Opus 4.6 vs GPT-5.3 Codex

Claude Opus 4.6 · Anthropic, released 2026-02-05
GPT-5.3 Codex · OpenAI, released 2026-02-05

“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 2 of 9 tracked benchmarks for both models — Claude Opus 4.6 leads on 1, GPT-5.3 Codex leads on 1.

Benchmark	Claude Opus 4.6	GPT-5.3 Codex	Leads
Epoch Capabilities Index (ECI)	155.4	155.6	GPT-5.3 Codex
SWE-bench Verified	0.772	0.748 (high)	Claude Opus 4.6
GPQA Diamond	0.905 (32k)	Not measured	Not measured on both
MATH Level 5	Not measured	Not measured	Not measured on both
OTIS Mock AIME 2024-2025	0.944 (64k)	Not measured	Not measured on both
FrontierMath	0.407 (max)	Not measured	Not measured on both
FrontierMath Tier 4	0.229 (max)	Not measured	Not measured on both
SimpleQA Verified	0.465 (32k)	Not measured	Not measured on both
Chess Puzzles	0.170 (32k)	Not measured	Not measured on both

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 Opus 4.6 → · GPT-5.3 Codex → · the full AI Model Rankings table