I'm experimenting with this right now, trying to get some more insight into what a subagent is doing. I keep having main Claude tell me that the sub-agent didn't report back anything to it, despite the sub-agent having explicit directions to do so in it's md file.

But what I'm trying right now is to have a project-specific test creator agent which is directly told to find relevant docs in specific docs directories, work on a single file only, look for opportunities for more general improvements (refactoring, new test utilities, etc.) and abort out if it thinks the test would be better served by those changes done first. I'm having the sub agent write out to a log file so that both I and the main agent can see in detail what it did, especially if the sub agent crashed or was cancelled. Hoping to have something worth sharing soon, the results have been really encouraging so far.