These are the names in the public code. A codename, then the job.
| Name | Job |
|---|---|
| Home Mixer | Builds the page you see. Conductor. Not a ranker. |
| Thunder | Short-term store of posts from accounts you follow. About two days. Recency only — no model. |
| Phoenix | The ranking model. Predicts like, reply, copy-link, report, and more. Also has a retrieval side that finds strangers’ posts. |
| SimClusters | Community map (~145,000 groups). At request time: more like tweets you just engaged with. Cap 800. Empty if you did nothing recently. |
| Visibility Filtering | Last gate after the score: show, blur, or hide. A hide cannot be ranked back in. |
| Grox | Grok-based labels (spam replies, adult, graphic…). Plan names are public. The prompts are not. |
| Scarecrow | Simple rules on the tweet. Twenty files are public (copy-paste, bad URLs, NSFW…). |
| Agatha | Models that score a tweet or an account for NSFW, spam, abuse. |
| Night Owl | Search. Powers Following Latest. Not Phoenix. |
In-network — they follow you.
Out-of-network / stranger — they don’t. Score × 0.75, plus extra safety rules.
Weight — the price of a guessed action. Copy-link +20. Like +0.5. Report −234.
Mutual-follow original — you follow each other, and it is not a reply or repost. Reply becomes +20.
Author diversity — your extra posts on the same page are cut (62.5%, then 43.75%, never below 25%).
Cold-start — one small, new original can be lifted toward slot 16.
For You — follows + strangers, then extras. About 35 real posts.
Ranked Following — same scorer as For You, follows only.
Following Latest — newest first. Score 0. No Phoenix.
Your own labels: Under the Hood.
<aside> →
Back to How X decides what you see.
</aside>