The "Target class [Post] does not exist" error in Laravel typically happens when Laravel can't find the Post class. To fix this, first make sure the Post model exists in the correct location, usually app/Models/Post.php (or just app/Post.php in older versions). Next, ensure that you're importing it correctly in your controller or wherever it's being used, with use App\Models\Post; at the top of the file. If you're using a custom namespace, double-check that it matches. Finally, try running php artisan config:cache and php artisan optimize:clear to clear any cached configurations that might be causing the issue.