Building production agents? The hard part is idempotent writes across apps, not model reasoning
anishfish · reddit · 2026-09-04
Reddit user anishfish, building an iMessage agent that acts across Gmail, Calendar, Slack and Notion, found that deciding what to do is easy for the model — the hard part is ensuring external side effects actually happened correctly.
Core problems:
- sendemail() times out: did the send fail, or did Gmail commit it while the response got lost? Retrying risks duplicates.
- In multi-step tasks, Calendar and Slack succeed but Notion's state is unknown — what is the task's real state?
- Agents report "done" because the tool call returned success, yet the external app may not be in the right state.
He lists candidate solutions: explicit UNKNOWN/PARTIAL states, read-after-write verification, idempotency keys and side-effect ledgers, per-integration retry policies, Temporal/LangGraph/n8n or custom durable state machines, and per-integration reconciliation.
What he really wants is an "execution layer": the agent states intent ("move the meeting to Friday, keep attendees, tell Sarah on Slack, update Notion"), and the layer handles app-specific calls, retries, partial failures and verification, returning a clean machine-readable receipt. He asks whether such a product exists or everyone rebuilds this per integration.
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