Anthropic

Add the credential

Open Settings > Model Providers, click Add Model Provider and select Anthropic. Give the row a name, pick the organization, team or project it belongs to, and fill in:

Field	Value
`ANTHROPIC_API_KEY`	Your Anthropic API key. Required unless you set a base URL.
`ANTHROPIC_BASE_URL`	Optional. An Anthropic-compatible endpoint to call instead of `api.anthropic.com`.

Save the row. Every virtual key whose scope can see the row can now dispatch to it, unless the key restricts its providers. See Virtual keys.

The Anthropic model provider drawer with ANTHROPIC_API_KEY filled in, ANTHROPIC_BASE_URL empty and the routing handle anthropic — The Anthropic row: name, scope, ANTHROPIC_API_KEY, the optional base URL and the routing handle.

Model names

Write anthropic/<model>, for example anthropic/claude-sonnet-4-5 or anthropic/claude-haiku-4-5. A bare name that starts with claude- resolves to Anthropic when the key reaches an Anthropic row.

Send a request

The Anthropic SDK sends the virtual key in the X-Api-Key header. Set the base URL to https://gateway.langwatch.ai without /v1; the SDK adds /v1/messages.

curl https://gateway.langwatch.ai/v1/messages \
  -H "Authorization: Bearer $LANGWATCH_VIRTUAL_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "anthropic/claude-haiku-4-5",
    "max_tokens": 64,
    "messages": [{"role": "user", "content": "Say hi in one word"}]
  }'

import anthropic

client = anthropic.Anthropic(
    base_url="https://gateway.langwatch.ai",
    api_key="vk-lw-...",
)
message = client.messages.create(
    model="anthropic/claude-haiku-4-5",
    max_tokens=64,
    messages=[{"role": "user", "content": "Say hi in one word"}],
)
print(message.content[0].text)

An OpenAI SDK call to /v1/chat/completions with an Anthropic model also works: the gateway translates the request to the Messages API and the answer back to a chat completion.

Endpoints

Endpoint	Served
`POST /v1/messages`	Yes, forwarded as is
`POST /v1/chat/completions`	Yes, translated to Messages
`POST /v1/embeddings`	No. Anthropic has no embeddings API; the gateway returns Anthropic’s rejection
`GET /v1/models`	Yes, from the Anthropic catalog

cache_control blocks pass through unchanged and the cache read and write token counts come back in usage. See Cache control.

Last modified on September 6, 2026

Get Started

SDK Integration

Virtual Keys & Budgets

Billing & Metering

Governance

Providers

Features

API Reference

Self-Hosting

Cookbooks

Add the credential

Model names

Send a request

Endpoints

​Add the credential

​Model names

​Send a request

​Endpoints

Add the credential

Model names

Send a request

Endpoints