Alertmanager was configured as an alerting target but never scraped, so its own
metrics were absent: a silently breaking alert chain could not report itself —
the same blind spot as a missing series, now at the end of the chain. Adds the
operating_alertmanager scrape job and AlertDeliveryFailing on
alertmanager_notifications_failed_total.
The README still claimed alert delivery was deliberately muted via a
room=security null receiver. That route is gone; alertmanager.yml routes
everything to the matrix receiver, so the backup alerts added yesterday do get
delivered. Documentation asserting the opposite is dangerous in both directions,
so it now states the current wiring and keeps the alert-storm history as
background.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
sorbandClaude Opus 4.8
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