The field of Islamic studies has fostered pioneers in the computational analysis of prosopographical sources. As a function of the extent of this genre, individual studies posit narrow frames of inquiry: a single city (Bulliet 1972; Petry 1981); a single source (Günther 1991; Romanov 2012); or a single group of actors (Nawas and Bernards 1998; ?entürk 2005; Haider 2012). Further progress is possible through extending computational analysis of prosopographical sources to multiple cities, sources, and groups of actors. This paper describes cooperation between tenth-century Sufis and Shafi?is through a network analysis of relational data in relevant (quasi-)prosopographical works. Sufis in Nishapur almost uniquely identified with the Shafi?i law school by the middle of the eleventh century (Bulliet 1972; Halm 1974; Chabbi 1976). This arrangement is known in the field of organizational theory as "corporate interlock" (e.g. Hunter 1953). In the case of the Sufi-Shafi?i interlock, however, major elements of this cooperative agreement remain poorly understood: none of the aforementioned studies proposes a date for the onset of the "Sufi-Shafi?i interlock"; Melchert (2001) has suggested a single Nishapuri figure who achieved prominence in both groups. These results are attributable to two factors: (1) reliance on Nishapuri histories of Sufism and Shafi?ism (al-Sulami, [1953/1960]; al-?Abb?d? [1964]; al-Farisi [1965]); (2) restriction of the pool of prospective cooperators by analyzing only figures who are the subject of a full notice (_tarjamah_) in the aforementioned works. Recourse to alternative sources and data provides more extensive historical and geographical data on the Sufi-Shafi?i interlock. A number of Sufi prosopographies predate or are co-eval with al-Sulami's (al-Malini, ed. 1997; al-Naqqash, ed. 1991; al-Khuldi, [forthcoming]; there are several early lists of Shafi?is (El Shamsy 2013). Temporal and relational about the teachers and students of thefigures in these non-Nishapuri works exist in non-Nishapuri local histories (e.g. _Tarikh Baghdad_), or "universal" sources (e.g. _Siyar a?lam al-nubala?_). The resulting dataset can be used to study the temporal dynamics of Sufi-Shafi?i cooperation, comprising ~450 figures, sharing ~3,000 relational ties. The date at which this cooperation reached an "interlock" level can be ascertained through network analysis, specifically the identification of instances of "triadic closure" – i.e., when a Sufi and Shafi?i figure share a connection with a third figure (teacher or student) (Jasny 2007; Opsahl 2015). This analysis shows that "saturation point" of triadic closure between Sufis and Shafi?is occurred in the first half of the tenth century, amongst figures associated with Baghdad.