Composer 2.5 finetuned Kimi K2.5[0].
In the blog post, it is unclear whether Grok 4.5 is also a finetune on top of Kimi; they do imply it is also a finetune.
> Training included trillions of tokens of Cursor data… We used reinforcement learning on difficult problems
If xAI pivoted from a frontier base model company, to a finetuning company, it does mark a stark change to their relevance in the industry.