Claude Opus 5.5 Overtakes OpenAI's GPT-6 Astra on Speed and Cost, Setting New Efficiency Benchmark

Anthropic's Claude Opus 5.5, launched September 22, 2026, has established itself as the leading cost-efficient alternative to OpenAI's GPT-6 Astra, released three weeks earlier on September 3. The two models represent the most consequential release cycle in large language models this year, arriving within weeks of each other and immediately becoming the focus of developer comparisons.