The brief
- Bought by SpaceX on 2 February 2026, in a deal valuing SpaceX at $1T and xAI at $250B.
- Colossus went from empty building to 100,000 H100 GPUs in about four months in 2024.
- Grok 4 (July 2025) and Grok 4.1 (November 2025) ranked near the top on reasoning tests.
Technical approach
Speed
Build compute fast
xAI turned an old factory into Colossus, using mobile gas turbines and Tesla batteries before the grid hookup.
RL scale
Heavy practice training
For Grok 4, xAI says it spent about as much compute on reward-based practice as on the initial training.
Data
Live posts from X
Grok reads X posts and the web in real time. That keeps it current but exposes it to junk and manipulation.
Programs
xAI, two programs
Updated 19d agoGrokxAI's AI models, in the Grok app, on X and for developers, with reasoning, image generation and live search.ScalingNextGrok 5 releaseUpdated 19d agoView program →ColossusxAI's AI supercomputers in Memphis, Tennessee. Colossus 1 reached 100,000 NVIDIA H100 GPUs in 2024, then about 200,000. Colossus 2 aims to be the first gigawatt-scale training cluster.DeployNextColossus 2 gigawatt-scale buildUpdated 5 Jun 2026View program →
Research · Proto · Pilot · Deploy · Scaling
Research & demos
Open technical problems
- Controlling behaviourOpen
In July 2025 a prompt change made Grok post antisemitic content on X. Keeping a public bot in line is still hard.
- Local pollutionOpen
Gas turbines powering Colossus drew complaints and permit fights in Memphis over air emissions.
Peers
Company & funding
- Valuation
- $250BSpaceX-owned
- Raised
- $32Bdisclosed private rounds
- Last round
- Series EJan 2026
- Parent
- SpaceX
- HQ
- US
- Founded
- 2023
- Website
- x.ai (opens x.ai)
| Date | Round | Amount | Post-money | Lead |
|---|---|---|---|---|
| Jan 2026 | Series E | $20B | — | — |
| Dec 2024 | Series C | $6B | — | — |
| May 2024 | Series B | $6B | $24B | — |