  We investigate Eisenstein congruences between the so-called Euler systems of
Garrett--Rankin--Selberg type. This includes the cohomology classes of
Beilinson--Kato, Beilinson--Flach and diagonal cycles. The proofs crucially
rely on different known versions of the Bloch--Kato conjecture, and are based
on the study of the Perrin-Riou formalism and the comparison between the
different $p$-adic $L$-functions.
