Starting from a tree with nothing in it, deliver one small but complete standalone Foundry project, and nothing more. Write the build configuration and the directory layout by hand, and depend on nothing that must be fetched — no package manager, no vendored test framework, no submodules of any kind — because the verifier re-runs the build and the suite offline with no network and no credentials, and a pointer it cannot fetch reads as a build failure rather than as the cause.

Exactly one contract: it holds state behind a narrow, documented external interface of a handful of functions, declares an explicit custom error for every input it refuses, and has no owner, no privileged caller, no upgrade path and no handling of funds. Do not add a second contract, a library beside it, or an interface file; the single contract is the whole subject and keeping it to one is the point.

The advance over what this tree has held before is in the checks rather than the parts: beside the contract write a suite that imports nothing outside the tree and asserts by reverting, covering the ordinary path, every boundary of the state it keeps, repeated and out-of-order calls, and each input it is meant to refuse — and then, in the same suite, at least three property-style tests that assert the contract's own invariants across varied inputs rather than across cases you chose, each stated in a comment as a sentence a reader can check against the code.

Finish with a short README that names the single command a stranger runs to build and test the project and what passing output looks like. Declare the check command the verifier should run and make sure it genuinely compiles and exercises the suite rather than examining nothing.