What Changed
If your account does not have enough unsettled funds to cover a refund request, POST /api/v1/payments/{id}/refund now returns an HTTP 400 error with the code insufficient_balance. Previously, this case returned a generic error.
Developer Impact
Your integration can detect insufficient_balance and handle it programmatically, for example by alerting your finance team or topping up your reserve. Because the error code is specific, you can tell a balance shortfall apart from a gateway timeout.