Anthropic

proxium calls Anthropic with your own Anthropic key. Your applications send their requests to proxium with a proxium virtual key. They never hold the Anthropic key.

Setting	Value
Preset id	anthropic
Base URL	https://api.anthropic.com/v1
How proxium sends the key	an x-api-key header
Request format	the Anthropic Messages format. proxium translates an OpenAI chat request into it
Request type	chat

Add Anthropic to a project

1. Get a key from Anthropic at console.anthropic.com/settings/keys.
2. In the console, open Providers and select Add a vendor.
3. In What are you adding, select Anthropic. proxium fills in the base URL and the models.
4. Paste the key into API key, and select Add Anthropic.

proxium stores the key encrypted with AES-256-GCM. The console does not show the key again.

Models

A new Anthropic vendor starts with these models. You can change the list on the Providers screen.

• claude-sonnet-4-5
• claude-opus-4-1
• claude-haiku-4-5

Call a model

A vendor that you add has the provider id t.<project>.anthropic, where <project> is the project slug. Send GET /v1/models to get the exact ids that your key can use.

curl https://proxium.tech/v1/chat/completions \
  -H "Authorization: Bearer $PROXIUM_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "t.<project>.anthropic/claude-sonnet-4-5", "messages": [{"role": "user", "content": "Hello"}]}'

You can also send a tier name, such as trial, in model. proxium then picks the model from the routing policy of the project. Refer to Routing.