How to make your email agent idempotent against duplicate webhooks

Nylas webhooks are at-least-once, meaning the same event can arrive up to three times, causing duplicate replies if not handled. The article explains how to use the webhook's `id` field as a dedup key, persist processed IDs atomically, and implement per-thread locks to prevent race conditions. These techniques ensure that an AI email agent sends only one reply per incoming message, even under retries.