I've been in incident calls where every dashboard was green. Latency nominal. Error rate under 0.1%. CPU humming along at a comfortable 40%. And somewhere downstream, a critical workflow had been silently producing wrong results for six hours. Nobody had an alert for "the thing is doing something, just not the right thing." This is the gap most observability setups never close: they're watching the infrastructure, not the behavior. They'll tell you the system is alive. They won't tell you it's lying. The Three Dials Everyone Watches The default observability stack for most teams converges on the same three signals: uptime, latency, and error rate. These show up in every runbook, every SLA, every on-call rotation. They're not useless — a spike in error rate is real signal, a latency cliff is real signal — but they share a critical property: they're all lagging indicators of failure that's already happened. More importantly, they only fire when the system is explicitly misbehaving.…