Caught by TESTING the alert path instead of assuming it. Without an explicit
User-Agent, urllib sends 'Python-urllib/3.x' and Resend rejects it 403, while
the identical request via curl succeeds.
The failure mode this avoids is the worst one a canary has: it would have
detected every outage correctly and told nobody. Same bot-filtering trap as the
Gitea migrate call earlier today — worth recognising on sight.
Also prints the HTTP body on failure. '403 Forbidden' alone sends you hunting
for a bad key; the body names the real cause.
Verified: alert sent (200).
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Today's outage is the whole design brief: /health returned 200 for the entire
hour that login was dead. A canary watching /health would have stayed green
while nobody in the ecosystem could sign in. So the login probe is here and it
is the one that matters.
Three rules it obeys:
- never green for something it did not prove (I-8)
- alert on TRANSITIONS, not every run — a canary people filter is a dead
canary, which is how the last one sat 37 days dead unnoticed
- run where the watched thing cannot take it down: Veron 1, never Kit 0
Two independent signals, so losing one still leaves the other: an email via
Resend on state change, and a non-zero exit that turns the CI run red in the
forge itself.
Alerts say what broke in human terms — 'a human can actually sign in' — rather
than only naming an endpoint.
Verified against production: 7/7 green including login at 17.1s; a forced 404
reports DOWN; a 1s threshold reports SLOW at 23.3s.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
