Messages API

xmAI natively supports the Anthropic Messages API (/v1/messages). Point the official Anthropic SDK at xmAI with zero code changes.

Endpoint

POST https://api.xmai.sg/v1/messages

Authentication matches /v1/chat/completions — send Authorization: Bearer <xmAI-API-Key>.

Minimal example (curl)

curl -X POST https://api.xmai.sg/v1/messages \
  -H "Authorization: Bearer $XMAI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "claude-sonnet-4-6",
    "messages": [{"role": "user", "content": "Hello!"}],
    "max_tokens": 1024
  }'

SDK integration (zero code changes)

Use the official @anthropic-ai/sdk and override baseURL:

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

const client = new Anthropic({
  baseURL: "https://api.xmai.sg",
  apiKey: process.env.XMAI_API_KEY,
});

const message = await client.messages.create({
  model: "claude-sonnet-4-6",
  max_tokens: 1024,
  messages: [{ role: "user", content: "Hello, Claude!" }],
});

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

Billing details (x_billing_details)

The response includes a usage._billing field and a top-level x_billing_details mirror that carry the billing snapshot for the request:

{
  "usage": {
    "input_tokens": 10,
    "output_tokens": 5,
    "_billing": {
      "dimensions": {
        "input": 10,
        "output": 5
      },
      "cost_micro_usd": 120,
      "saved_micro_usd": 0
    }
  },
  "x_billing_details": {
    "dimensions": { "input": 10, "output": 5 },
    "cost_micro_usd": 120,
    "saved_micro_usd": 0
  }
}

• usage._billing — follows the Anthropic unofficial-extension convention (underscore prefix).
• x_billing_details — top-level mirror, same object reference as usage._billing.
• cost_micro_usd — request cost in micro-USD (1 / 1,000,000 USD).
• saved_micro_usd — amount saved versus official provider pricing.

Supported fields

Fully compatible with the Anthropic Messages API, including:

• model, messages, max_tokens (required)
• system (string or array, with cache_control)
• temperature, top_p, top_k, stop_sequences
• stream, tools, tool_choice
• thinking, metadata.user_id

Unsupported endpoints

The following endpoints are not yet available (tracked in future stories):

• POST /v1/messages/count_tokens
• POST /v1/messages/batches