The expensive bugs in my SaaS never crashed — they just stayed quiet

Quick question before the story: how long is the gap between something breaking in your product and you actually noticing? For a long time mine was days, and I didn't realize how much it was costing me.

The bugs that hurt me weren't the ones that threw errors. Those I caught fast. It was the silent stuff:

• A payment failed and I found out Friday, when the customer emailed me annoyed — three days of a paying customer effectively churning while I had no idea.
• A trial expired without converting and I never got the nudge to reach out. By the time I looked, the moment to save it was gone.
• A background workflow had been failing on retries for most of a week. Nothing crashed. Nobody was watching that screen, so nobody noticed.

None of these showed up as a crash. They just quietly leaked money, and "check the dashboard more often" is not a real fix — nobody does it, least of all a solo or two-person team with a hundred other things on fire.

What actually worked was pushing the events that matter into the one place I already live all day: Slack. The non-obvious part was being ruthless about which events. My first instinct was "alert on everything," which is how you end up muting the channel in a week. The rule I landed on:

Only alert on things you'd want to act on within the hour. Payment failed, trial ending in ~3 days (not "expired" — too late by then), subscription canceled, a workflow that failed after exhausting retries. Everything else goes to a log I check on my own schedule.

I built this into BuildBase, the SDK I'm working on (auth + billing + workflows for React/Next SaaS), and I run it on my own products now. Paste a webhook, toggle the handful of events that matter, done. But the principle is portable — you can wire the same thing yourself with any webhook.

The honest state of things: I'm pre-revenue, ~100 people in the community, zero paying customers yet. Real bottleneck for me isn't this feature — it's activation, getting people to value before I ask them to commit. That's the thing I'm heads-down on. This alerting setup was one of those small wins that makes the day-to-day actually feel under control while I fight the bigger problem.

How do you all handle silent failures pre-scale? Slack/Discord alerts, a real monitoring setup, or honestly just vibes and customer emails? Genuinely curious where people draw the line.