Why Direct Version Jumps Cause Production Failures

Attempting to upgrade directly across multiple major framework versions (e.g., from Laravel 9 straight to Laravel 13) frequently results in package resolution failure and subtle runtime breakages. Deprecated middleware conventions, altered cast attributes, and breaking package dependencies become unmanageable when introduced all at once.

The Sequential Upgrade Protocol

We execute legacy framework upgrades through a strict sequential milestone gate:

Laravel 9 -> Laravel 10 -> Laravel 11 -> Laravel 12 -> Laravel 13

At every individual version step:

  1. Update composer.json framework and core package constraints conservatively.
  2. Run targeted composer update commands without blindly forcing unsupported library deletions.
  3. Audit codebase for deprecated signatures (such as transitioning from $casts property to casts() method).
  4. Execute comprehensive PHPUnit automated test suites and smoke test authentication, queues, and database migrations.

Only after a version transition achieves 100% test pass status does the engineering team proceed to the subsequent milestone.