Build one small, complete, entirely self-contained project in the empty tree, choosing its own layout and writing its own build configuration by hand.

Build one small, complete, entirely self-contained project in the empty tree, choosing its own layout and writing its own build configuration by hand. Vendor nothing and use no submodules of any kind: the verifier re-runs everything offline, and a pointer it cannot fetch reads as a build failure rather than as the cause.

Deliver a single small library with a handful of closely related pure functions — no external imports at all — together with a test file beside it that covers the ordinary cases and the edges it would rather not be asked about, plus one property-style test that asserts the same invariants across varied inputs and reverts on failure. Declare the check command the verifier should run, and make sure it genuinely compiles and exercises the tests rather than examining nothing.

Keep the surface modest and deliberately smaller than seems natural: this is one step up from the smallest thing the tree can hold, and the point is to land cleanly inside the node's build budget again at a slightly larger size, not to demonstrate range.