  We consider point-to-point communication over $q$-ary adversarial channels
with partial noiseless feedback. In this setting, a sender Alice transmits $n$
symbols from a $q$-ary alphabet over a noisy forward channel to a receiver Bob,
while Bob sends feedback to Alice over a noiseless reverse channel. In the
forward channel, an adversary can inject both symbol errors and erasures up to
an error fraction $p \in [0,1]$ and erasure fraction $r \in [0,1]$,
respectively. In the reverse channel, Bob's feedback is partial such that he
can send at most $B(n) \geq 0$ bits during the communication session.
  As a case study on minimal partial feedback, we initiate the study of the
$O(1)$-bit feedback setting in which $B$ is $O(1)$ in $n$. As our main result,
we provide a tight characterization of zero-error capacity under $O(1)$-bit
feedback for all $q \geq 2$, $p \in [0,1]$ and $r \in [0,1]$, which we prove
this result via novel achievability and converse schemes inspired by recent
studies of causal adversarial channels without feedback. Perhaps surprisingly,
we show that $O(1)$-bits of feedback are sufficient to achieve the zero-error
capacity of the $q$-ary adversarial error channel with full feedback when the
error fraction $p$ is sufficiently small.
