Limits of Laravel mass assignment protection when teams mix $fillable and $guarded conventions

Laravel Eloquent provides mass-assignment protection through either a $fillable whitelist or a $guarded blacklist, but the framework does not enforce a single default strategy. Teams that allow both patterns across models may face inconsistent protection as new columns are added or new developers contribute code. The choice affects whether newly added database attributes are assignable by default or protected by default, and Laravel 9 introduced Model::preventSilentlyDiscardingAttributes() to change how non-fillable attributes are handled, making the exception behavior version-sensitive.

Global state toggles such as Model::unguard() and Model::reguard() add further uncertainty because they can alter mass-assignment behavior beyond a single model boundary. Nested relationship writes also do not automatically inherit the parent model's fillable or guarded configuration, which complicates enforcement when arrays are passed to create or update methods.

What factors determine whether a codebase should standardize on a single mass-assignment guard strategy or permit both $fillable and $guarded with explicit boundaries? What approach should teams take to account for the changed exception behavior introduced around Laravel 9 when auditing existing models? Where is the safest scope for global unguard calls so they do not leak into unrelated requests, seeders, or queued jobs?