Anthropic-compatible routes

Planck exposes an Anthropic SDK-compatible base URL at:

https://api.inquantum.ai/anthropic

The SDK appends /v1/messages, producing POST /anthropic/v1/messages. That Messages request is mapped through Planck’s standard chat pipeline, just like POST /v1/messages. Other paths under /anthropic/v1/* use native Anthropic passthrough.

Messages with the Anthropic SDK

import os
from anthropic import Anthropic

client = Anthropic(
    api_key=os.environ["PLANCK_API_KEY"],
    base_url="https://api.inquantum.ai/anthropic",
)

message = client.messages.create(
    model="claude-4.5-sonnet",
    max_tokens=256,
    messages=[{"role": "user", "content": "Say hello."}],
)

for block in message.content:
    if block.type == "text":
        print(block.text)

The Anthropic SDK calls the option api_key, but this value is your actual Planck API key. The SDK sends it in x-api-key, which Planck accepts. This field is not a compatibility label.

Messages with cURL

curl https://api.inquantum.ai/anthropic/v1/messages \
  -H "x-api-key: $PLANCK_API_KEY" \
  -H "anthropic-version: 2023-06-01" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-4.5-sonnet",
    "max_tokens": 256,
    "messages": [{ "role": "user", "content": "Say hello." }]
}'

max_tokens is required for Anthropic Messages. Planck does not add a default if it is omitted.

Explicit BYOK

If you want to provide an Anthropic key for this request, keep the Planck key in the SDK’s api_key option and send the provider key separately:

client = Anthropic(
    api_key=os.environ["PLANCK_API_KEY"],
    base_url="https://api.inquantum.ai/anthropic",
    default_headers={
        "X-Provider-Key": os.environ["ANTHROPIC_API_KEY"],
    },
)

For raw HTTP, POST /v1/messages remains available with Authorization: Bearer $PLANCK_API_KEY. See Native Anthropic streaming for SDK setup, the complete event lifecycle, tool-input deltas, and stream errors. See Reasoning and thinking for adaptive thinking and effort examples.

This endpoint uses the shared AI Gateway error envelope. See the Error Handling & Fallback guide for response examples, retry rules, fallback behavior, and streaming errors.

Gateway API

Observability API

Prompt API

Anthropic-compatible routes

Messages with the Anthropic SDK

Messages with cURL

Explicit BYOK

​Messages with the Anthropic SDK

​Messages with cURL

​Explicit BYOK

Messages with the Anthropic SDK

Messages with cURL

Explicit BYOK