Its not even a POC at this point, just a readme and a sandbox for testing it while I work on it. But you might find the readme interesting:

https://github.com/MatrixManAtYrService/poag

I'm especially pleased with how explicit it makes the inner dependency graph. Today I'm tinkering with pact (https://docs.pact.io/). I like that I'm forced to add the pact contracts generated during consumer testing as flake outputs (so they can then be inputs to whichever flake does provider testing). It's potentially a bit more work than it would be under other schemes, but it also makes the directionality of the dependency into a first class citizen and not an implementation detail. Otherwise it would be easy to forget which batch of tests depends on artifacts generated by the other.

I suppose there's things like Bazel for that sort of thing also but I don't think you can drop an agent into a bazel... thingy... and expect it to feel at home.