Elon Musk announces completion of training for grok 4.8 model with 2.5 trillion parameters

On September 14, 2026, Elon Musk, CEO of xAI, announced on the X platform that the Grok 4.8 model has completed its training this week. The model features 2.5 trillion parameters and was trained using a new C++ software stack. Previously, Musk had stated that Grok 4.7 would be released on September 12, 2026, but later indicated the release might be delayed. The delay is attributed to the heavy penalty for response length in reinforcement learning, which caused the model to prematurely abandon difficult tasks and fail to thoroughly check its work. Musk’s comments highlight the challenges in refining large-scale AI models, emphasizing the balance between training efficiency and model accuracy.