This is the tenth post in the Meet Horizon UI series, and the first of Act 3 — operate it . The earlier posts were about seeing your data — dashboards, topology, traces, logs, profiles. This one is about the moment something breaks, and Horizon’s answer to the only two questions that matter then: what is on fire right now, and why? The alarm surface is built around two ideas: incidents, not a wall of events , and replaying the exact metric snapshot that fired the rule .