I Built a SaaS in 2 Hours with Replit Agent—Then the "Silent 500s" Started (Here's How I Fixed It)

If you haven’t tried Replit Agent yet, you’re missing out on the pure dopamine hit of "vibecoding."

I literally typed "Build me a subscription-based habit tracker," watched the AI spin up a Postgres DB, handle auth, and deploy the whole thing, and 2 hours later, I was live. I felt like a god.

Then i asked my friend to try it out (dev friend btw). And that’s when the vibe died lol .

i realized that vibecoding is great until it isn't. When you build an app with an AI agent, you don't always know exactly how the error handling is structured. You just know it "works" on your machine.

But in production? Replit apps can be a black box.

I got a dm from my friend saying : "Hey, the app just spins forever when I try to save a habit."

I checked the Replit Console. Nothing. Standard POST /api/habits 500. No stack trace. No reason. No clue why the AI-generated code was failing for that specific user. i was in confusion honestly
If you’re trying to build a "ShipFast" style micro-SaaS, your biggest enemy isn't competition it's trust.
If a user hits a white screen on their first try, they aren't going to email you for support. They’re just going to close the tab and never come back. ive been here trust me
so i knew i need a way to track errors in production,
some users(most users wont come back ) they'd just leave , so i needed a way to find out the bug they hit and how they hit the bug (and the users context , so i can circle back )

needed something that took 0 effort to set up (because if I'm vibecoding, I'm not in the mood for a 4-hour Sentry configuration).

That’s when I dropped BugMail into my Replit project.

It took me exactly 60 seconds to set up. I didn't even have to understand the code the Agent wrote. I just told the Agent: "Add BugMail error tracking to every API route and send me an email if anything breaks."

Here is the prompt I used:

"Install @bugmail-js/next. Wrap all existing try/catch blocks in my API routes to report errors using BugMail. Use my API Key and Project ID from secrets. If a crash happens, I want the full stack trace in my inbox immediately."

The Result: Real-Time Debugging

The next time a "Silent 500" happened, I didn't have to hunt through messy streaming logs.

I got an instant notification. I opened the BugMail dashboard which is literally an inbox and there it was.

The Bug: A missing database constraint that the AI forgot to add.
The Context: The exact user ID and the data they were trying to save.
The Fix: BugMail’s AI summarized the error in plain English: "Hey, your Postgres table 'habits' is missing a 'user_id' column for this specific query."

I fixed it in 30 seconds, pushed the update, and the "vibes" were back.