payments-and-monetizationlisted

# Payments, subscriptions and metering **Read [`references/PAYMENTS-AND-MONETIZATION.md`](references/PAYMENTS-AND-MONETIZATION.md) before applying any of this.** That file is the standard; everything below it is a summary to help you decide whether this skill applies and to check your work afterwards. ## What this standard covers - The model in one paragraph - Merchant of record vs payment gateway - Mock-first - Webhooks - Subscription lifecycle - Quota and metering - Entitlement enforcement is layered - Tenant mode - Introducing paid tiers to an existing user base ## Failure modes | Symptom | Cause | |---|---| | Every production webhook rejected | Signature header name assumed, not confirmed; or webhook secret unset (correct behaviour — set the secret) | | Webhooks accepted in production without signatures | The mock-mode fallback was made symmetric; restore reject-in-production | | Subscription grants applied twice | No idempotency on provider event id; redelivery is normal, not exceptional | | Cancellations never take effect | Lifecycle events landing in the mapper's default branch; only payment events were handled | | Paying user loses days after early renewal | Extension computed from payment date instead of `max(expiry, payment date)` | | Renewal-day usage missing from the new period | Quota period reset from the extended expiry base, not the payment date | | Webhook dropped: "order not found" | Provider webhook beat your checkout write; synthesize from payload and