How the X algorithm works now

The live, open-source For You system — Phoenix, Thunder, Grox, and Home Mixer — explained from the code.

• How does the For You feed actually get built?
• What is Phoenix, the Grok-based ranker?
• What is Thunder vs Phoenix retrieval?
• Does X still use engagement weights like "replies = 13.5x"?
• What signals does the X algorithm learn from?
• What is Grox and what does it classify?
• How do ads get blended into the For You feed?
• What does X know about you before ranking a single post?
• Does X infer my demographics or gender for ranking?