Anthropic compatibility

/v1/infer also speaks the Anthropic Messages API, on the same model as the OpenAI routes. The Anthropic SDKs work with two changes: the base URL, and your B3OS key as the credential.

The SDKs add /v1/messages, so requests go to /v1/infer/v1/messages. The key works as a bearer token (ANTHROPIC_AUTH_TOKEN, authToken, auth_token) and as x-api-key (ANTHROPIC_API_KEY), so SDK releases that send either header authenticate.

bash
export ANTHROPIC_BASE_URL="https://beta-api.b3os.org/v1/infer"export ANTHROPIC_AUTH_TOKEN="$B3OS_API_KEY"export B3OS_MODEL=$(curl -s https://beta-api.b3os.org/v1/infer/models \  -H "Authorization: Bearer $B3OS_API_KEY" | jq -r '[.data[] | select(.b3os.kind == "chat")][0].id')

bash
curl -s https://beta-api.b3os.org/v1/infer/v1/messages \  -H "Authorization: Bearer $B3OS_API_KEY" \  -H "anthropic-version: 2023-06-01" \  -H "Content-Type: application/json" \  -d "{\"model\": \"$B3OS_MODEL\", \"max_tokens\": 256, \"messages\": [{\"role\": \"user\", \"content\": \"Name one river in Oregon.\"}]}"

ts
import Anthropic from "@anthropic-ai/sdk";const client = new Anthropic({  authToken: process.env.B3OS_API_KEY,  baseURL: "https://beta-api.b3os.org/v1/infer",});const message = await client.messages.create({  model: process.env.B3OS_MODEL!,  max_tokens: 256,  messages: [{ role: "user", content: "Name one river in Oregon." }],});console.log(message.content, message.usage);

python
import osimport anthropicclient = anthropic.Anthropic(    auth_token=os.environ["B3OS_API_KEY"],    base_url="https://beta-api.b3os.org/v1/infer",)message = client.messages.create(    model=os.environ["B3OS_MODEL"],    max_tokens=256,    messages=[{"role": "user", "content": "Name one river in Oregon."}],)print(message.content, message.usage)

Messages shows streaming, tools and thinking with both SDKs.

Request fields

Supported

POST /v1/infer/v1/messages/count_tokens counts a request's input tokens with the model's own chat template, for free.

Accepted and ignored

Refused with 400 and the B3OS code unsupported_parameter, naming the field

A system message inside messages is refused too (400, invalid_request): instructions go in the top-level system.

Errors

Errors use Anthropic's shape, {"type": "error", "error": {"type", "message"}}, with the B3OS code and the offending field under b3os. That holds for errors raised before the request reaches the model service too (authentication, scopes, body size), on the node and at the edge, so the SDKs raise the same exception classes they raise for Anthropic's API. Nothing maps another provider's model name to the node's model, so code that names a Claude model gets a 404:

bash
curl -s -X POST 'https://beta-api.b3os.org/v1/infer/v1/messages' \  -H "Authorization: Bearer $B3OS_API_KEY" \  -H 'content-type: application/json' \  -H 'anthropic-version: 2023-06-01' \  -d '{"model":"claude-sonnet-4-5","max_tokens":256,"messages":[{"role":"user","content":"Name one river in Oregon."}]}'

json
{  "b3os": {    "code": "model_not_available",    "param": "model"  },  "error": {    "message": "claude-sonnet-4-5 is not served on this node; GET /v1/infer/models lists the models that are",    "type": "not_found_error"  },  "request_id": "req_01m69wb38zspekwybkv2gfz3ey",  "type": "error"}

http
server-timing: total;dur=0.280x-request-id: req_01m69wb38zspekwybkv2gfz3ey

Per-model token and request limits are on Infer limits.

json
{  "model": "b3os/qwen3.5-9b",  "max_tokens": 256,  "messages": [{ "role": "user", "content": "Name one river in Oregon." }]}