Corpus: WikiText-103 — a sealed, fixed set of curated Wikipedia articles (the verified Good & Featured set), not all of Wikipedia, so most text won't be a member. 822,559 passages, Merkle-rooted over BLAKE3 and Sigstore-signed. Paste a sentence or paragraph for one honest answer: it's a verbatim passage in the corpus, or it isn't — and you can verify any match yourself with stock cosign, no Attestrum install. (Your paste is checked two ways: exact membership over the full sealed corpus, plus a real near-match computed in your browser — the same fingerprint kernel as the CLI, compiled to WebAssembly — against a small curated demo set. Paste a paraphrase of a showcase passage, or try a near-match chip.) New here? Try an example below.