GPT-5.3-Codex

GPT-5.3-Codex is OpenAI's flagship agentic coding model, designed for long-horizon software engineering tasks including multi-step code generation, debugging, repository work, and tool-using agent workflows. OpenAI describes it as 25% faster than its predecessor and its most capable agentic coding model to date, with benchmark leadership claims on SWE-Bench Pro and Terminal-Bench. Source: supabase.