GPT-5.3 Codex
Coding-optimized GPT model for repository edits, reviews, and agentic software work
ECI STANDING#15 of 266
SCORE156.58153.91–159.73 CI
FRONTIER LAGLaunched in the leadNothing released before it had scored higher.
SCORES LIKE THESE MODELSQwen 3.8 MaxAlibaba · Aug 2026156.62Gemini 3.8 FlashGoogle DeepMind · Sep 2026156.54Grok 4.6xAI · Aug 2026156.35Claude Opus 4.7Anthropic · Apr 2026156.34
Full Epoch Capabilities Index ranking ↗From the lab
Launch announcement · Feb 5, 2026Introducing GPT-5.3-CodexRELEASE DATEFeb 5, 2026
WEIGHTSClosed weights
CONTEXT WINDOW400K
MAX OUTPUT128K
REASONINGYes
TOOL CALLINGYes
INPUTStext, image, pdf
OUTPUTStext
Specifications from Models.dev. Availability and limits may differ by provider. Benchmark scores come from Epoch AI under CC BY 4.0.