Messages (Anthropic)

POST /v1/messages

Accepts requests in the Anthropic Messages API format. Requests are translated to the internal OpenAI-compatible format, processed, and the response is translated back to the Anthropic format before returning.

This lets you use the Anthropic SDK with ai& without changing your code.

Note

This is a compatibility adapter. For the full set of request parameters, use Chat Completions directly.

Usage

Python

from anthropic import Anthropic

client = Anthropic(
    api_key="sk-your-api-key",
    base_url="https://api.aiand.com/v1",
)

message = client.messages.create(
    model="openai/gpt-oss-120b",
    max_tokens=1024,
    messages=[{"role": "user", "content": "Hello!"}],
)

print(message.content[0].text)

JavaScript

import Anthropic from "@anthropic-ai/sdk";

const client = new Anthropic({
  apiKey: "sk-your-api-key",
  baseURL: "https://api.aiand.com/v1",
});

const message = await client.messages.create({
  model: "openai/gpt-oss-120b",
  max_tokens: 1024,
  messages: [{ role: "user", content: "Hello!" }],
});

console.log(message.content[0].text);

How it works

1. Your request arrives in Anthropic Messages format
2. ai& translates it to OpenAI format and runs inference
3. The response is translated back to Anthropic format

Streaming is supported. Authentication uses the same Authorization: Bearer header as all other endpoints.

Supported parameters

Standard Anthropic Messages API parameters are accepted. Parameters with no equivalent in the underlying model are silently ignored.

Reasoning

The thinking block does not set the reasoning level — neither budget_tokens nor type maps onto our effort scale, so depth is left to the model’s own default. To control the level, send reasoning_effort with one of the model’s published reasoning_efforts. It is validated exactly as on /v1/chat/completions: an unsupported value is a 400 naming the values the model takes, and the applied level comes back in X-Reasoning-Effort.

What thinking does control is whether that reasoning is returned to you. Send thinking: { "type": "enabled" } — or "adaptive", which is accepted identically — and the reasoning comes back as a thinking content block ahead of the text block, streaming as thinking_delta events. Omit it and you get the answer alone.

The thinking blocks we return carry no signature — nothing upstream signs them, so one replayed to Anthropic’s own API is rejected. Echoing one back to ai& is safe: a thinking block on a request is dropped before it reaches the model.

Some reasoning models put their whole answer inside the reasoning and leave the message content empty. Those turns come back as an ordinary text block whether or not you asked for thinking, so a successful response always carries at least one content block.

Image input

Image content blocks are supported on vision-capable models. All three Anthropic source types work — base64, url, and file (referencing a file_id from POST /v1/files). See Anthropic’s content blocks docs for the wire format. Requests against models without the vision capability are rejected with 400 invalid_request_error before inference.