With how easy it becomes to write software, I'd say that both the model and the harness are already being commoditized. I don't see a reason to believe there would be moat in any of them.
I anticipate that the harness (and memory) will evolve far more outside of engineering. Muse/Dots are an example of that.
I've been writing about this thesis for the past year or so and here is a bit of a summary of where I think it is going: https://zero2data.substack.com/p/the-future-of-consumer-ai