Every AI Agent Failure I've Debugged in 2026 was an Idempotency Problem

Short summary

AI agents generate millions of tool calls with built-in retry semantics, but underlying tools aren't idempotent—causing duplicate emails, charges, and orders in production. Every major failure this author debugged in 2026 traces to non-idempotent operations retried by agent frameworks. The fix remains unchanged from 2010: idempotency keys plus deduplication stores at tool boundaries, but frameworks don't enforce this by default.

• •Agent frameworks retry tool calls at massive scale, exposing non-idempotent operations downstream
• •Real incidents: duplicate emails (14×), double charges, duplicate orders—all trace to the same root cause
• •Solution: deterministic idempotency keys + deduplication stores at every state-mutating tool, currently unenforced

Generated with AI, which can make mistakes.