Comment on: FetchSandbox

We do something similar on a smaller scale in our own Stripe integration — coupon/pause mutations carry session-scoped idempotency keys so a double-click can't create two coupons, and webhook processing claims-then-deletes on failure so LS/Stripe can safely retry. The proof-gated regression capture here (reproduce → fix → rerun) is the piece we've been doing manually — would've saved some debugging early on. Following for the async/retry simulation angle, that's usually the first thing testing tools skip.