When AVD won't connect: alerting on the failure before the tickets

When Azure Virtual Desktop stops letting people in, you usually find out the worst way: a wave of "I can't connect" tickets, twenty minutes after it started. But the session hosts already told you — the failure is sitting in the WVDErrors table in Log Analytics the moment it happens. This is a small, read-only Log Analytics alert that watches for the two errors that actually mean "sessions are failing" and emails the AVD admins the instant they appear. Call it version 1: deliberately simple, and shipped early.