We give a simple counterexample to the plausible conjecture that Adams-type maps of ring spectra are stable under composition. We then show that over a field, this failure is quite extreme, as any map to an E ∞ \mathbb {E}_{\infty } - k k -algebra is a transfinite composition of Adams-type maps.

We show that for a coconnective ring spectrum satisfying regularity and flatness assumptions, its algebraic K-theory agrees with that of its $$\pi _0$$ π 0 . We prove this as a consequence of a more general devissage result for stable infinity categories. Applications of our result include giving general conditions under which K-theory preserves pushouts, generalizations of $$\mathbb {A}^n$$ A n -invariance of K-theory, and an understanding of the K-theory of categories of unipotent local systems.