Yes, that's agile software development.

No, not quite. The specifications we use for agents make any ticket written before them pale in comparison. That enables a hybrid workflow that is both spec-driven and "agile", in the sense that you're doing very rapid development cycles.

Until the agents start touching things that already worked well before and break them.

They do need a competent developer operating them. That has nothing to do with whether nor not specs have value.