Agreement involving T or v uniformly instantiates agreement with a subject or object. Clause-peripheral “C-agreement”, in contrast, is splintered, masking a slew of disparate phenomena which are seldom discussed in the same breath (but see Baker, To Appear): e.g. (West Germanic-style) downward complementizer agreement (DCA, see van Koppen, 2017), upward complementizer agreement (UCA, in many Bantu languages Diercks, 2013, a.o.), and so-called allocutive agreement (AA) in e.g. Basque, Japanese & Tamil (Oyharçabal, 1993; Miyagawa, 2017; McFadden, To appear). What causes this contrast and how can it be modelled? Here, we undertake one of the first detailed comparisons of these phenomena to show that the heterogeneity of C-agreement is epiphenomenal of two factors: (i) that it involves distinct C heads in DCA, UCA, and AA, all of which crucially also stand in different structural relations wrt. the embedded CP phase; (ii) that the structure of the CP itself is distinct in (D/U)CA vs. AA.