xAI has said on the record that Grok 5 is training on Colossus 2, its ~550K GB200/GB300 cluster. Everything beyond that statement sits on a spectrum from plausible to promotional, and it is worth separating the two.

What is actually known

Confirmed: the training run exists, and xAI wants Grok 5 to be a step-change rather than another 4.x point release. Grok 4.7 (September 21) already moved to a new, larger base at the same $2/$6 pricing, which reads like a bridge release while the big run cooks.

Rumored: a ~6-trillion-parameter mixture-of-experts, the largest announced figure in the industry, with native multimodal input including video temporal reasoning, and a context window around 1.5M tokens. Those numbers come via Musk posts and trade-press repetition, not from any xAI model card.

Treat 6T as a headline, not a spec sheet. xAI has published no architecture document for Grok 5.

The slipping window

Earlier public-beta estimates pointed at March–April 2026. That window passed quietly, and trade-press expectations have converged on Q1 2027. Our Grok 5 roundup scores the overall picture 68/100: the direction is well supported, the date and the spec sheet are not.

Until then, Grok 4.7 carries an Adopt Now badge in our Model Guide, there is no confirmed reason to hold a migration for a model at least a quarter away.