<p>{@code FormatContract} states each documented clause once - publish serves the exact bytes, a {@code HEAD} is answered from metadata without opening the blob, the shared traversal probe vectors are refused at both the request seam and the coordinate seam, a withheld version leaves every enumeration surface, a proxy leg holds an upstream body to the digest its protocol advertises and streams it, and a generated index is stable enough to revalidate - and {@code FormatFixture} is how one format ...