Sub agents don't have much context and don't stay around for long, so misses in that case are trivial.

As of yesterday subagents were often getting the entire session copied to them. Happened to me when 2 turns with Claude spawned a subagent, caused 2 compactions, and burned 15% of my 5-hour limit (Max 5x).

how long they stay around after the cache miss is irrelevant if I am burning all the prior tokens again. also, how much context they have depends entirely on the task and your workflow. I you have a subagent implement a feature and use the compile + test loop to ensure it is implemented correctly before a supervisor agent reviews what was implemented vs asked then yes, subagents do have a lot of context.

I'd say it's next to impossible to have a subagent doing a compile+test loop where at least 1 call doesn't get made to the API over multiple 5-minute stretches to keep the cache warm. In such a case it may just be the same as doing the compile+test manually and then having the agent troubleshoot any issues before iterating.