After your agent approves a plan, how often does it actually follow it?

Building multi-step agent workflows and I keep hitting the same wall. I get the agent to write a plan, I review it, I approve it, and then during execution it quietly does something else. Adds an abstraction I didn't ask for, "fixes" a file that wasn't in scope, or solves it a different way than the plan said. I've started clearing context between steps and breaking tasks smaller, which helps some. But the gap between "agreed on the plan" and "followed the plan" is still what costs me the most time. For people running real multi-step setups: what actually closed that gap? Tests or hooks it can't skip? Smaller steps? Something structural? Or did you just accept you have to watch every step?