X deployed a Grok-powered AI ranking system to determine which posts appear in users' feeds, replacing the platform's prior rule-based recommendation algorithm. The system reads every post and video to predict which content each user is most likely to find interesting.

In October 2025, Elon Musk announced that X's recommendation system would be fully powered by Grok, replacing legacy heuristics entirely. By November 2025, the Following feed began being sorted by Grok rather than chronologically. A Rust-based open-source version of the algorithm was released in January 2026, with a component called Phoenix handling Grok-based ranking. The system also incorporates sentiment analysis, reportedly rewarding posts with a constructive tone.