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GPT-5.3-Codex

OpenAI · 2026-02-05

GPT-5.3-Codex is OpenAI's reasoning model optimized for agentic coding tasks in Codex or similar environments. Released on February 5, 2026, it combines the frontier coding performance of GPT-5.2-Codex with GPT-5.2's reasoning and professional knowledge capabilities for long-running work involving research, tool use, and complex execution.

Benchmark scores

BenchmarkScore
AA-Briefcase Elo869
AA-LCR74.0
AA-Omniscience Index9.9
ALE-Bench1934
APEX (Mercor)13.5
APEX-Agents31.8
APEX-SWE41.5
APEX-v1-extended64.6
Arena Code WebDev — Brand & Marketing1387
Arena Code WebDev — Consumer Product1403
Arena Code WebDev — Content Creation Tools1449
Arena Code WebDev — Data & Analytics1399
Arena Code WebDev — Gaming1446
Arena Code WebDev — HTML1420
Arena Code WebDev — React1399
Arena Code WebDev — Reference-Based Design1416
Arena Code WebDev — Simulations1423
Artificial Analysis Intelligence Index44.3
Artificial Analysis Omniscience Accuracy51.8
Artificial Analysis Omniscience Hallucination Rate86.9
BLXBench77.7
BLXBench Coding category98.5
BLXBench Cost category92.7
BLXBench Debugging category79.6
BLXBench Hallucination category74.4
BLXBench pass rate61.2
BLXBench Reasoning category74.7
BLXBench Refactoring category67.1
BLXBench Security category73.0
BLXBench Speed category89.4
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