xAI

xAI was founded in March 2023 by Elon Musk and 11 AI researchers from DeepMind, OpenAI, Google, and Microsoft Research. In February 2026, SpaceX acquired xAI at a combined $1.25T valuation. The company raised over $47B across multiple rounds, with investors including NVIDIA, Fidelity, Qatar Investment Authority, and MGX.

xAI's Grok model family progressed rapidly from Grok-1 (314B MoE, open-sourced with 51K stars) to Grok-4.20 (2026, multi-agent system, AA index 48, 2M context). Grok-3 (February 2025) was trained on 200K GPUs at the Colossus supercomputer in Memphis with 10x more compute than its predecessor. Grok-4 (July 2025) introduced native tool-calling and extended reasoning with an AA index of 42.

The Colossus supercomputer in Memphis, Tennessee was built in 122 days and houses 150K H100 + 50K H200 + 30K GB200 GPUs (~250MW). A second facility (Colossus 2) adds 110K GB200 GPUs toward a 1M GPU target. All co-founders except Musk have since departed, including Igor Babuschkin (DeepMind AlphaStar/AlphaCode) and Jimmy Ba (Adam optimizer, Layer Normalization co-author).