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GPT-5.3-Codex: Top-Tier Agentic Model for Software Engineering

GPT-5.3-Codex was released in February 2026 as a successor to GPT-5.2 and GPT-5.2-Codex.

As a member of the Codex family it's OpenAI's latest agentic coding model that combines top-tier software engineering ability with strong general reasoning and professional knowledge work skills. GPT-5.3-Codex is designed as a general work agent that merges coding, reasoning, and computer-use into one model rather than separating "coding model" and "chat model".

Key Capabilities & Performance Highlights of GPT-5.3-Codex

GPT-5.3-Codex excels at handling complex reasoning and coding tasks. It stands out for the following capabilities:

• State-of-the-art performance on coding and software engineering benchmarks like SWE-Bench Pro and strong results on Terminal-Bench and OSWorld, which test terminal use and full-computer interaction.
• Handles end-to-end software lifecycle tasks: generating and refactoring code, debugging, writing tests, updating documentation, and interacting with tools like terminals, browsers, and GUIs.
• Strong at general “knowledge work”: drafting documents, slide decks, spreadsheets, analyses, and other professional outputs measured by the GDPval benchmark.
• Roughly 25% faster than the previous Codex model while using fewer tokens for many tasks, making long, multi-step workflows more efficient.

Comparison of GPT-5.3-Codex and Other Leading Models