  In this paper a multiparticle generalization of linearized ten-dimensional
super Yang--Mills superfields is proposed. Their equations of motions are shown
to take the same form as in the single-particle case, supplemented by contact
terms. A recursive construction of these superfields is inspired by the
iterated OPEs among massless vertex operators in the pure spinor formalism. An
enlarged set of BRST-covariant pure spinor blocks is then defined in a
streamlined fashion and combined to multiparticle vertex operators. The latter
can be used to universally describe tree-level subdiagrams in the perturbative
open and closed superstring, regardless of the loop order. The inherent
symmetries of the multiparticle superfields are reproduced by structure
constants of the gauge group, hinting a natural appearance of the BCJ-duality
between color and kinematics in the fundamentals of super Yang--Mills theory.
We present one-loop applications where known scalar cohomology objects are
systematically recomputed and a novel vector cohomology particularly relevant
to the closed string is constructed for arbitrary multiplicity.
