X significantly expanded its open-source initiative by releasing the complete source code for its "For You" ranking engine and core filtering systems on GitHub under the Apache v2 license.
Simultaneously, the platform launched a new "Under the Hood" transparency tool within app settings, allowing users to download a JSON file revealing if their account or posts have been assigned visibility-limiting labels (often referred to as shadowbans) over the past month.
Thursday's release includes model configurations, filter logic, and ranking parameters, enabling developers to run the Phoenix scoring system independently to verify how content is suppressed or promoted.
The open-sourced code confirms that the "For You" feed relies on a Grok-based transformer model to rank content, blending roughly 50% in-network posts (from followed accounts) with 50% out-of-network recommendations.
The 2026 update reveals a strict engagement hierarchy where Replies carry the most weight, followed by Reposts, then Likes, while posts containing external links are systematically deprioritized to keep users on the platform. Additionally, the code exposes a visibility multiplier for X Premium subscribers, which boosts their distribution frequency and position in feeds compared to non-paying users.
The new shadowban detection feature is initially piloting with accounts older than one year that have posted at least 10 times in the last month, providing raw data that users can analyze via LLMs against the public codebase.
Elon Musk and X's VP of Product Keith Coleman framed this move as a method to let users verify fairness themselves, with Coleman noting that external researchers have already successfully trained and run the scoring system using the provided code. The repository allows for community pull requests to suggest improvements.
"In making š open source, we are actively seeking criticism to improve fairness and quality of algorithmic recommendations," Musk wrote on X.