Prompt injection is _probably_ solvable if something like [1] ever finds a mainstream implementation and adoption, but agents not being deterministic, as in “do not only what I’ve told you to do, but also how I meant it”, all while assuming perfect context retention, is a waaay bigger issue. If we ever were to have that, software development as a whole is solved outright, too.
[1] Google DeepMind: Defeating Prompt Injections by Design. https://arxiv.org/abs/2503.18813