Solo SaaS dev uses automated arch tests to stop AI from corrupting codebase

A solo developer building a SaaS product found that AI coding assistants consistently ignored architecture guidelines, defaulting to imitation of existing patterns rather than enforcing documented standards. An internal audit revealed 89 instances of a prohibited coding pattern versus only 6 correct ones, meaning the wrong approach had become the de facto norm that the AI kept replicating. The developer concluded that text-based documentation like CLAUDE.md and ADRs acts merely as a suggestion, while a failing CI test is the only constraint AI cannot bypass. Using Laravel's Pest architecture testing library, rules such as keeping database queries out of controllers are encoded as automated tests that break the build on violation. To handle pre-existing violations without disabling the guardrail entirely, a shrink-only baseline list was introduced, blocking new infractions while gradually forcing cleanup of legacy ones.