GPT-5.3 Codex

Published

Feb 5, 2026

GPT-5.3 Codex is an AI model developed by OpenAI (United States), first published in February 2026. It works in the language domain, on tasks such as language modeling/generation.

Epoch AI has no training-compute estimate for this model.

Access: API access. Its weights are not openly released. Epoch AI rates the confidence of this record as likely.

Full record

Organization: OpenAI
Country of organization: United States
Domain: Language
Task: Language modeling/generation
Model accessibility: API access
Open weights: No
Epoch confidence: Likely

Benchmark results

01	Vending-Bench 2	Score	5940.1
02	WebDev Arena	Arena Score	1406.7
03	Epoch Capabilities Index	ECI Score	155.6
04	WeirdML	Accuracy	0.79
05	Terminal-Bench	Accuracy mean	0.78
06	METR Time Horizons	average_score	0.75
07	Posttrainbench	Average (%)	0.14