For builders shipping this week
Test a Replit app signup on the public URL, not the preview.
The Replit webview is logged in as you. Your users are not. FirstUser signs up on the deployed URL with a fresh browser.
Replit previews hide a class of bugs: cookies that only work on the dev host, a database that was never migrated in production, and a sign-up button that points at localhost. FirstUser refuses to be impressed by the preview. You give it the public URL.
The run opens that URL, finds the account form, and submits a new email and password. If production returns a database error or an empty body, the landing or sign-up step fails with a screenshot and a fix prompt aimed at the Replit agent. You paste it, redeploy, and run again.
Add the optional first action if the app is more than a login wall. “Create a note” or “Save a project” tells the test user what a real session should be able to do. Leave it blank and that step is skipped, not failed.
Scheduled runs need a FirstUser plan because they watch an app you own. The free test does not. It is the right first run against a Replit deployment you are about to share.