Engineering deep-dives, design decisions, and notes from building atrium.
A full audit of all 2,053 files in X’s open-sourced recommendation stack — the 23 published ranking coefficients, what the code proves, and what it cannot.
The most upvoted complaint about AI coding isn't that it's wrong — it's that the work stopped feeling like anything. The research says the flow tax is real. But it's not the model's fault. It's the pile of terminals you bolted it onto.
The Google OAuth wall that forced an engine swap, the punchout trick that makes the embed look native, and the hit-test layering that makes clicks land.