Claude Opus 4.6 vs GPT-5 Codex

Claude Opus 4.6

Anthropic

Claude Opus 4.6, released by Anthropic in February 2026, is a large language model from the Claude 4 family designed for complex agent orchestration, extended reasoning, and long-form code generation. It features a 200K token context window (extendable to 1M tokens in beta), 128K maximum output tokens, native image understanding, and extended thinking with both standard and adaptive effort modes. Opus 4.6 targets multi-step agentic workflows, parallel tool use, and applications requiring sustained reasoning over large contexts.

GPT-5 Codex

OpenAI

GPT-5 Codex, released by OpenAI in August 2025, is a coding-specialized large language model from the GPT-5 family engineered for software engineering, code generation, and agentic development workflows. It builds on GPT-5's architecture with optimizations targeting multi-file code editing, test generation, and automated debugging. GPT-5 Codex targets developers and agentic coding tools requiring a model tuned specifically for programming tasks.