What it requires. An action that is not safe to run twice, on a path that can run it twice - a retry, a re-planned step, or a user repeating themselves.
Why it matters. Planners retry, and users repeat themselves. Where the action creates, sends or moves money, the second run is a second real-world effect. The remedy is an idempotency key derived from the run itself, so a retry cannot double-charge or double-refund; without one the failure is silent and expensive.
How to fix it. Give the action an idempotency key derived from the request rather than the attempt, or gate it behind a confirmation the planner cannot repeat.
Source. Our refund model implementation
Is this rule worth checking?
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