How a Missing Config Line Cost Me 38x More for the Same Model

I'm building a custom coding agent harness that uses DeepSeek models through OpenRouter. The models offer a good price/performance balance (especially with the current Pro discount).

While editing the config, I accidentally removed the provider preference. My OpenRouter workspace had only two providers enabled: the Official and ProviderA. And, of course, OpenRouter picked ProviderA! My harness displays session cost in real time, and within about 30 minutes the session cost jumped up enough to catch my attention. I pulled the usage breakdown:

Model

Provider

Calls