Idempotency Lessons From an Email Agent

Short summary

Email agents teach idempotency through visceral duplicate failures landing in inboxes. Build a defense stack of cheap checks—atomic dedup by message ID, per-thread locks, and state verification—to handle webhook redeliveries at different layers. Architectural partitioning into per-agent inboxes eliminates coordination problems; circuit breakers prevent reply loops.

• •Webhook systems guarantee at-least-once delivery, so deduplication is essential, not optional
• •Layer defense: atomic dedup by message ID, locking for concurrency, verification against ground truth
• •Architectural partitioning (one agent per inbox) beats distributed locking; circuit breakers catch reply loops

Generated with AI, which can make mistakes.