I have been working on my own "Digital Twins Universe" because 3rd-party SaaS tools often block the tight feedback loops required for long-horizon agentic coding. Unlike Stripe, which offers a full-featured environment usable in both development and staging, most B2B SaaS companies lack adequate fidelity (e.g., missing webhooks in local dev) or even a basic staging environment.

Taking the time to point a coding agent towards the public (or even private) API of a B2B SaaS app to generate a working (partial) clone is effectively "unblocking" the agent. I wouldn't be surprised if a "DTU-hub" eventually gains traction for publishing and sharing these digital twins.

I would love to hear more about your learnings from building these digital twins. How do you handle API drift? Also, how do you handle statefulness within the twins? Do you test for divergence? For example, do you compare responses from the live third-party service against the Digital Twin to check for parity?