How do you keep frontend moving when one backend route is still missing?

I kept running into the same local dev problem: 90% of the backend was usable, but one unfinished or unstable route would break the whole UI flow or make QA hard to reproduce consistently.

I tried MSW, Mockoon, Postman mock servers, and custom scripts. They all helped, but I kept wanting a faster workflow for one specific situation:

- mock the blocked route

- passthrough the routes that are already ready

- turn a route off entirely when I want strict 404 behavior

- see exactly what served the response

- simulate delay/failure without rebuilding the setup

That frustration is what pushed me to build Mockphine, a macOS app for running a local mock API server with per-route mock / passthrough / disabled modes, strict 404 or passthrough fallback, and a Live View that shows served-by, status, and duration.

Not claiming this is the only way to solve it. I’m mostly curious how other frontend teams here handle the "backend is mostly ready, but the last 1-2 routes keep blocking local work" problem.

Are you using MSW in-app, Mockoon/Postman, proxy scripts, or something else?