GPT-5.3 Codex
ECI#21
157GPT-5.3 Codex is a closed-weights model from OpenAI, released February 5, 2026. It has an ECI score of 157 and ranks 21st of 260 tracked models. At the time of its release, it ranked 1st of 180 tracked models.
GPT-5.3 Codex vs select alternatives
| Domain | Benchmark | GPT-5.3 Codex | |||
|---|---|---|---|---|---|
ECI scoreBest score 167 | 157 | 156 | 155 | 153 | |
| Ranking | #21 | #29 | #33 | #46 | |
| Agent | Vending-Bench 2Best score $15,515 | $5,940 | — | $8,018 | $5,478 |
| Software engineering | METR Time HorizonsBest score 17 hr 25 min | 5 hr 50 min | — | 11 hr 59 min | 3 hr 44 min |
Text Arena (Coding)Best score 1820 | 1370 | — | 1556 | 1439 | |
ALE-BenchBest score 2951 | 1655 | — | 997 | 1177 | |
SWE-bench VerifiedBest score 83% | |||||
Terminal-Bench 2.0Best score 85% | |||||
WeirdML (v2)Best score 94% |
