A key says "I already sent this call", not "this is what the object is". The
catalogue calls sent metadata that the key knew nothing about, so adding the
tax_treatment field in 9da1358 poisoned yesterday's key for a day — and
AddonPrices::ensure() runs inside a customer's module booking, not only in the
sweep.
createPrice and createProduct now fold a fingerprint of their parameters into
the key. refund, cancelSubscription, addSubscriptionItem and the checkout
deliberately do not: there a second object is the customer's money taken twice,
and Stripe's refusal is the thing worth keeping.
The fake could not see any of this. Its ledger replayed the first id for a
repeated key without ever comparing what the second call asked for.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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