This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Al-Kafi became, and remains, the first and most authoritative of the Four Books, al-Kutub al-Arba'a, that together form the core hadith canon of Twelver Shi'a Islam, a documented standing distinct from being merely one collection among several of comparable weight. Later Shi'a jurisprudence has never stopped working directly from it, a documented continuity of use distinct from a foundational text that later scholarship cites mainly out of historical respect rather than active reliance.
That standing places al-Kulayni's own compilation ahead of three later works compiled by subsequent generations of Twelver scholars, each addressing gaps or refining method, yet none displacing Al-Kafi's own position as the first reference a jurist consults. That a tenth century compilation has kept that first-among-four ranking across roughly a millennium of subsequent Twelver legal scholarship is documented as evidence of Al-Kafi's own continuing authority rather than a purely historical honor.
That a single compiler's twenty-year project has remained the first-consulted of Twelver Islam's four core hadith collections for roughly a thousand years, still worked from directly rather than read as a historical artifact, marks Al-Kafi's place in the canon as a documented case where a founding text kept its working authority rather than being succeeded by what came after it.