X changes recommendation algorithm to favor posts people actually read

Elon Musk announced two updates to X's recommendation algorithm: a new AI ranking model that better predicts how long users will view a post, and a retrieval model trained to surface posts people read to the end. The change could favor detailed posts and smaller accounts over viral ones.

• Ranking model predicts viewing time, not just likes and reposts
• Retrieval model is trained to find posts read in full
• Musk shared an unverified chart of rising daily user active seconds
• X did not disclose rollout timeline or weight of new signals