September 19, 2026
X now reveals the country behind post visibility restrictions: Under the Hood is widely available
On September 19, 2026, Under the Hood became widely available: reports show whether a post's visibility was limited by legal requirements and which country they came from. The xai-org/x-algorithm repository reveals how the For You feed works: it combines posts from followed and unfollowed accounts, filters them, and ranks them with a transformer model. On August 13, 2026, X added model weights, visibility filtering, training, the Phoenix launch, synthetic data generation, and SimClusters.
Elon Musk
@elonmusk
Transparency builds trust.
Under The Hood is now widely available - appreciate the patience of those who've been waiting and asking about it. It already delivered unprecedented transparency, but we wanted to add more. Now you can see if legal demands from a country are causing your visibility to be limited, and which country.
· 4.3M views
On March 31, 2023, X open-sourced its recommendation code, but did not publish training data or model weights, inviting issues and pull requests instead. On September 18, 2026, X added information to its reports about legal visibility restrictions and the country where each restriction was applied.
What is available to run. Quickstart requires Linux with an NVIDIA GPU and CUDA 12, uv, Python 3.11+, Rust, and protoc 3.15+; installation begins with `uv sync --extra engine` and `export PYTHONPATH=$PWD`, while verification uses `uv run python xrex/inference/oss_bench/bench.py --smoke --service_type ranking`. On synthetic data, Quickstart can train, save, resume, and run nano ranking and retrieval models, but it is not a production system: it lacks production traffic data, saved model states, deployment management, and scale. Phoenix has a Cargo workspace, pyproject.toml, and Quickstart, but other components may lack build files, deployment files, and internal dependencies.
X plans to publish changes for experiments affecting a substantial share of traffic, such as 10% or more, and synchronize production configurations with the repository using cron scripts.
Source
