OpenAI and Anthropic go to war: Claude Opus 4.6 vs GPT 5.3 Codex

**OpenAI** launched **GPT-5.3-Codex**, emphasizing **token efficiency**, **inference speed**, and hardware/software co-design with **GB200-NVL72** and **NVIDIA** collaboration. The new **Frontier** agent platform supports business-context agents with execution environments and learning capabilities. **Anthropic** showcased **Opus 4.6** agent teams autonomously building a clean-room C compiler booting Linux, highlighting advances in agentic coding and long-context capabilities. Community benchmarks report **2.93× faster** inference and significant efficiency gains, signaling a shift away from infinite compute budgets in 2026.