Which credential type fits an endpoint that charges per call?

The AI nodes in n8n's LangChain package each sit beside a credential that holds a key, and OpenRouter shows the whole shape in two files. The node itself is built on the OpenAI client, and packages/@n8n/nodes-langchain/credentials/OpenRouterApi.credentials.ts is what stands behind it: an API Key marked required and stored as a password, a base URL that stays hidden, and an authenticate block that turns that key into a bearer header before a request leaves. The test a user runs when saving the credential then proves it against the vendor. Pointing that plumbing at an OpenAI-compatible endpoint is where it gets rough, and your tracker is carrying the reports. There is an open thread about OpenAI credentials routed through compatible gateways coming apart, with the model prefix stripped and header fields dropped (#39227), another about the Gemini compatible endpoint in the assistant, and a third where a five word question ran to about 137k input tokens and $0.42 (#38130). BlockRun …