subscription_provisioning_pending
A prior POST /v1/subscription has a durable operation but its first Stripe outcome is unknown. The API will not submit another order: wait for the signed customer.subscription.created webhook to reconcile it, then refresh billing. This refusal is what prevents a retry after Stripe's idempotency-retention window from creating a second base-fee subscription.
Problem shape
Every non-2xx response is an RFC 9457 application/problem+json body. The type URI below is stable and machine-matchable, so branch on the final path segment (the code) and treat the status as redundant confirmation. See the error-handling guide.
{
"type": "https://docs.vocapable.com/errors/subscription_provisioning_pending",
"title": "…",
"status": 409,
"detail": "…",
"instance": "/v1/…"
}