Acknowledge an escalation alert

Confirms that a human has taken the alert and STOPS its escalation chain: no further step runs, nobody else is woken. This is the outcome the product exists for, and the only way to end an escalation other than letting it run out.

This endpoint requires an API key with the notifications.send ability — acknowledging decides the fate of a notification, so it sits with sending rather than with reading. It is not public: the UUID is an identifier, not a credential, and anything that could read one out of a log would otherwise be able to silence a live incident.

It is also NOT the endpoint behind the acknowledge button in an email or a Telegram message. Those links point at GET /ack/{uuid}?t=…&sig=… on the web surface, which authenticates the HMAC signature baked into the link and expires 24 hours after the alert was sent. That path needs no key precisely because the signature is the credential. Nothing has to be configured for it — it is attached to outgoing alerts automatically.

Use this endpoint when the acknowledgement comes from your own system: a chat bot, an incident tool, or an operator console that already holds an API key. Send it once; a second call answers 409 and changes nothing.