Migration

Make a new Laravel 9 project and follow the instructions for installing Breeze w/ Inertia nad Vue.

• https://laravel.com/docs/9.x/starter-kits#breeze-and-inertia

You will then move the *.vue files over to the new project and parse them appropriately.

For instance, you may get data via Axios calls in your Spa. With Inertia, you pass data directly from the controllers.

Furthermore, you will have to import your controllers and all related PHP files into the new project and parse them to align with the Inertia design structure.

Testing

If you haven’t already, I highly suggest you get into testing with PHPUnit. Properly tested code can make migrating files from one repository to another less nerve-wracking.

• https://laravel.com/docs/9.x/testing

Conclusion

Overall, this would be a massive project that could possibly take months. But if you intend to combine two completely different projects into one, that complexity will require it, especially if neither is tested.