WeChat Pay APIv3 (Service Provider / Partner)
WeChat Pay's APIv3 in "service provider" mode, used by payment platforms and ISVs to onboard and operate sub-merchants. Adds combined-order JSAPI/Native/App payments, sub-merchant onboarding ("特约商户进件"), sub-merchant settlement and bill journals, partner-mode refunds, profit sharing across sub-merchants, marketing tooling, and consumer complaint handling on behalf of sub-merchants.