library

src/ is the mind. library/ is what it is built with: vectors and rotations, image arithmetic, fitting, codecs — code that would be the same in any mind.

library/
├── vec/
│   ├── vec.ts          # TypeScript half
│   └── vec.rs          # Rust half
├── image/
├── fit/
└── codec/

The test: could it be copied into another cognet unchanged? A function that halves an image passes. A constant naming this body's sensors doesn't — it stays in src/.

No world

Nothing here reads or writes components, or knows what a tick is. Values in, values out. That is what makes it testable on its own, and what keeps the systems that call it short.

Nothing here imports from src/.

Any language

A library can have halves in more than one language, side by side: vec/vec.ts, vec/vec.rs. Rust reaches it as crate::library::vec::vec, Python as library.vec.vec.

Where a computation exists in two languages, both give the same numbers, to the last digit — so a system ported from one to the other can be checked against itself.

One seam, one file

A dependency that might change is imported in exactly one place here. Change how frames are encoded, and one file in library/codec changes — nothing that sees.