Elon Musk Calls Claude Opus 5.5 a ‘Masterpiece’, Admits Grok 4.8 Won’t Match It

Elon Musk said xAI’s forthcoming Grok 4.8 would not match Anthropic’s Claude Opus 5.5, which he called “a masterpiece”. The admission highlights the gap xAI is trying to close with rivals, while Musk said a later model, Grok 5, should surpass Opus 5.5.

Musk said Grok 4.8 had completed pretraining and was still undergoing reinforcement learning and data clean-up, with a limited rollout to some users expected later this week. He said xAI had rewritten parts of its training and inference systems in C and C++, but gave no performance figures. Anthropic reported Opus 5.5 scored 66.4% on Terminal-Bench 4.0, compared with 57.9% for OpenAI’s GPT-6 Astra; Musk has not published comparable Grok 4.8 results and estimated Grok 5 could arrive in two or three months.