What is a reverse proxy?

A service that sits between you and an API and forwards your requests to the real provider on your behalf.

Do these third-party providers host their own Claude, GPT, or Gemini?

No.

Models like Claude, GPT, and Gemini are closed-weight. You cannot download them. You cannot run them on your own server. These models are only available through the companies that made them or their authorized cloud partners (AWS Bedrock, Azureetc). The model weights are not publicly available.

There is no alternative. A third-party provider cannot just spin up Claude on their own hardware.

So when a third-party provider offers you access to these models, they are not running anything themselves. They can't. They are forwarding your messages to the official provider using credentials they got from somewhere.

How does it actually work?

When you sign up with one of these providers, they give you an API key. You might think this is the key that connects you to Claude or Gemini.

It is not.

That key is just your login to the proxy's system. It is how they track and charge you.

Behind the scenes, the proxy has a separate key: the one that actually talks to Anthropic, Google, or OpenAI. That is the real key.

So the flow is:

1. You send your prompt to the proxy using the key they gave you
2. The proxy forwards it to the real provider using a different key
3. The response comes back through the proxy to you

Two different keys. The one you have is for the proxy. The one that matters is the one you never see.

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Where does that "real key" come from?

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Three place:-

Method 1: Stolen Keys (LLMJacking)