Idempotency-Key: with vs without

Activity errors after the POST lands. Temporal retries. Watch what the receiver does.
Without Idempotency-Key
Activity attempt
POST /hooks
💥
Webhook receiver
Requests received
0
Recorded deliveries
0
duplicated
With Idempotency-Key
Activity attempt
POST /hooks (key=ABC)
💥
Webhook receiver
Requests received
0
Recorded deliveries
0
deduped by receiver
Same error. Same retry. The receiver uses the header to dedupe the effect.