The Strangler Fig in Production: Running AngularJS and Next.js Side by Side

This is the second article in a series about migrating a production healthcare platform from AngularJS to Next.js. The first article covered how we got here — 10 years of technical debt, ecosystem decay, and a failed AI migration attempt. This one is about the approach that actually works. Why Big-Bang Rewrites Were Never an Option When you run a healthcare SaaS platform used by clinical staff daily, you can't just flip a switch and hope for the best. You can't take the system down for a migration weekend. You can't risk broken workflows for users who are tracking quality events in hospitals. And you definitely can't pause feature development for months while you rewrite everything. We knew this from experience. Our designer attempted a Metronic UI framework upgrade twice over the years. Both times followed the same pattern: months of isolated work, then an attempt to merge against a codebase that had moved on without him. The first time, weeks of merge conflicts. The second time — yea