xAI released Grok-4, which Musk called 'the most intelligent model in the world,' with native tool use and stronger reasoning. Alongside it came Grok-4 Heavy, which runs multi-agent ensembles on hard problems, sold through a $300-per-month SuperGrok Heavy tier.

Grok-4 Heavy's ensemble approach — spawning multiple agents to work a problem in parallel — previewed the multi-agent patterns the whole industry adopted in 2026. The $300 tier was the priciest consumer AI subscription to date.

Grok-4 held xAI's frontier position through the second half of 2025, with the 4.1 refresh arriving in November.