Anthropic and OpenAI Release New Models

Anthropic and OpenAI released new large language models today: Opus 4.6 and GPT-5.3-Codex (the latter currently available only through OpenAI’s Codex app). The author had preview access and reports both models show incremental improvements over Opus 4.5 and Codex 5.2, with few clear new task breakthroughs; Anthropic highlights Opus 4.6's multi-agent C compiler work demonstrated by Nicholas Carlini.