Building a unified OpenAI-compatible gateway for 16 Chinese LLMs: architecture notes on routing, payments and ops

A developer built HOUJIAYAN API, an OpenAI-compatible gateway that routes requests across 16 Chinese LLMs including DeepSeek, Kimi, Qwen, MiniMax, and Doubao. The gateway handles authentication, billing, and automatic routing with three tiers (quality, balanced, cost), and supports WeChat Pay and USDT-TRC20 payments. The developer noted that WeChat's new 'platform public key' mode causes callback signature verification failures for new merchant accounts.

Why we built this If you want to use Chinese frontier models — DeepSeek, Kimi, Qwen, MiniMax, Doubao — as an international developer, you quickly hit friction: every provider has its own auth scheme, its own billing quirks, and several require mainland-China payment methods or business verification. We run these models in production ourselves, so we built the gateway we wanted to have: one OpenAI-compatible endpoint, one API key, and automatic routing across 16 Chinese LLMs. The result is HOUJIAYAN API https://api.houjiayan.com https://api.houjiayan.com . These are our architecture notes. Architecture Client any OpenAI SDK │ https://api.houjiayan.com/v1 ▼ Cloudflare WAF / rate limiting / TLS ▼ NewAPI forked — channels, API keys, quota, billing │ │ ▼ ▼ Custom smart Custom payment bridge standalone service router ├─ WeChat Native Pay APIv3 quality / └─ NOWPayments USDT-TRC20 balanced / cost tiers │ ▼ 16 upstream model channels 11 enrolled in auto-routing Gateway: a fork of NewAPI.NewAPI is a mature open-source API gateway popular in the Chinese LLM ecosystem. We kept its channel abstraction, token management and quota accounting, and customized pricing so that rates stay exactly at upstream official pricing — no markup — with a live price table in the console. Rates go as low as ¥1.00 / 1M tokens. Smart router: a custom stateless service.Beyond the standard /v1/chat/completions where you can pin any of the 16 models directly , we expose POST /v1/auto/chat/completions with three routing tiers: - quality default : pick the highest-quality model for the task class; - balanced : the quality/cost sweet spot; - cost : cheapest adequate model, for batch workloads. The router scores candidate channels by task features context length, code vs. prose, expected output length against a curated quality-tier table. Fourteen of the sixteen models participate in the auto pool. On upstream failure it degrades to the next-best channel. Payment bridge: the hardest part.NewAPI doesn't handle payments, so we built a standalone pay\ bridge service: - WeChat Native Pay APIv3 for domestic users QR-code Native orders → signed callback → signed epay-style notify into the gateway ; - NOWPayments for USDT-TRC20 for users outside mainland China IPN callback → FX conversion → credit . The bridge talks to the gateway through a signed callback protocol so the gateway credits accounts natively — no double-entry writes. Lessons learned 1. WeChat's new "platform public key" mode.New merchant accounts are forced onto public-key verification key IDs prefixed with PUB KEY ID instead of the old platform-certificate chain. Nearly all tutorials and SDK examples still assume certificate mode. If your callback signature verification fails on a new merchant account, this is why. 2. base url must end with /v1 .The OpenAI SDK concatenates paths onto base url , so https://api.houjiayan.com alone 404s. We added a gentle redirect at the edge, and put the correct snippet at the top of the docs: python from openai import OpenAI client = OpenAI api key="sk-...", base url=" https://api.houjiayan.com/v1" https://api.houjiayan.com/v1%22 3. Usage accounting across providers.Upstreams report token usage inconsistently some only at the end of a stream . We normalize accounting to gateway-parsed usage with a local estimation fallback for streams that never report it, and keep per-request audit detail. Access & pricing full disclosure - Endpoint: https://api.houjiayan.com/v1 OpenAI-compatible ; auto-routing at POST /v1/auto/chat/completions - Models: 16 Chinese LLMs directly addressable DeepSeek V4 Pro/Flash, Kimi K3, MiniMax M3, Qwen3.6/3.7 series, Doubao Seed Code, etc. ; 11 in the auto-routing pool - Pricing: identical to upstream official pricing, no markup; live table in the console; from ¥1.00 / 1M tokens - Sign-up credit: ¥6.6 ~$1 free trial credit; stays valid with ongoing usage; reclaimed only after 7 consecutive days with no API calls and no logins - Top-up: WeChat Pay min ¥50, 5.5% service fee ; USDT-TRC20 min $25, 5% service fee, non-mainland-China residents only - Refunds: WeChat top-ups refundable within 24h if unused service fee excluded ; crypto top-ups are non-refundable - Docs: https://houjiayan.com/docs/ - Operator: Inner Mongolia Huozhong Intelligent Technology Co., Ltd.; support@houjiayan.com What's next Routing tiers are currently static + task-feature scoring. We plan to fold historical success rate, latency and user feedback into dynamic channel weights.Support more models and payment methods. Happy to compare notes with anyone running multi-upstream LLM gateways. ---