Does one frustrated message trigger an alert?

No: one flagged message writes a detection, not an alert, and a case opens only when a call site’s rate of frustrated conversations rises above the rate it learned as its own normal.

The unit is the conversation, not the message. A conversation counts as frustrated once one of its messages is flagged, and scoring of that conversation stops there, so a user who complains five times still counts once. That’s what keeps one unhappy person from looking like a trend.

Each call site learns its own normal rate from its own traffic and is compared with its own past, not with a shipped number. When its rate rises above that normal, the finding and the case open together. There’s no triage step in between, because the rate on the finding is the claim. The case is what alert rules route to people.

The limit is the baseline itself: a call site that frustrates users from its first day learns that as normal, and is flagged only if it gets worse.