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GPT-5.3 Codex

A new Codex-branded GPT-5.3 model intended for code-centric use cases, listed as newly added on OpenRouter with a large context window.

code-generationreasoning

Overview

A new Codex-branded GPT-5.3 model intended for code-centric use cases, listed as newly added on OpenRouter with a large context window.

Key Capabilities

  • Code Generation — suited for tasks requiring code generation proficiency
  • Reasoning — suited for tasks requiring reasoning proficiency

Recommended Use Cases

  • Software Engineering
  • Code Assistance
  • Large Codebase Context

Technical Specifications

  • Context Window: 400K tokens
  • Open Weight: No
  • Release Date: February 24, 2026

Provider

GPT-5.3 Codex is developed by OpenAI. For the latest information, visit the official documentation.