So Grok 4.5 was developed based on the 1.5 tn param V9 foundation model by xAI and using Cursor data.
Rohan Paul Twitter · Rohan Paul (@rohanpaul_ai) · 2026-06-28
xAI's Grok 4.5 is built on a 1.5 trillion parameter V9 foundation model — roughly three times larger than the December-trained 0.5 trillion parameter V8 base — and was trained using data from Cursor, marking a significant generational upgrade.
Extraction
Topics: grokxaifoundation-modelsmodel-architecturetraining-data
Claims
- Grok 4.5 is built on xAI's V9 foundation model with approximately 1.5 trillion parameters.
- The V9 model is approximately three times larger than the V8 foundation model used for Grok 4.3.
- Cursor data was used in training Grok 4.5.
- The V8 foundation model finished training in December and contains fundamental flaws, making the V9-based upgrade feel substantial.
- xAI's model improvement cadence is accelerating as top Starlink and Starship engineers shift significant time to AI work.
Key quotes
the v8 foundation (Grok 4.3) model is a 0.5T model that finished training all the way back in December and has many fundamental flaws, so Grok 4.5 will feel like a gigantic upgrade!
I'm not saying the Grok v9 foundation model will be mind-blowingly better than anything, but it will be a solid workhorse in the same league as Opus.