How do you catch silent user churn before it shows up in your revenue?

The scariest form of churn isn't when someone cancels their account it's when they slowly stop opening your app over three months while still paying. By the time the cancellation comes it's already too late to fix things. We used to rely heavily on monthly active users until we realized half of them were passive.

Now we look at feature usage depth and response time to key workflows.

I'm curious how other founders measure this what early warning signs tell you a customer is losing interest before they actually leave?