Chat Completions

POST /v1/chat/completions accepts the OpenAI request shape and returns the OpenAI response shape. The model id is the only required swap from your current OpenAI code.

Request

POST https://api.oneprovider.dev/v1/chat/completions
Authorization: Bearer sk-...
content-type: application/json
{
"model": "claude-sonnet-5-5",
"messages": [
{ "role": "system", "content": "You are concise." },
{ "role": "user", "content": "Why is the sky blue?" }
],
"max_tokens": 256,
"stream": false
}

Response

Shape matches OpenAI 1:1 — id, choices[].message, usage.

{
"id": "chatcmpl_01...",
"object": "chat.completion",
"created": 1715472000,
"model": "claude-sonnet-5-5",
"choices": [
{
"index": 0,
"message": { "role": "assistant", "content": "Rayleigh scattering..." },
"finish_reason": "stop"
}
],
"usage": {
"prompt_tokens": 48,
"completion_tokens": 92,
"total_tokens": 140
}
}

OpenAI SDK (Python)

from openai import OpenAI
client = OpenAI(
api_key="<OPENAI_API_KEY>",
base_url="https://api.oneprovider.dev/v1",
)
r = client.chat.completions.create(
model="claude-sonnet-5-5",
messages=[{"role": "user", "content": "Say hi."}],
)
print(r.choices[0].message.content)

OpenAI SDK (Node)

import OpenAI from "openai";
const client = new OpenAI({
apiKey: process.env.OPENAI_API_KEY,
baseURL: "https://api.oneprovider.dev/v1",
});
const r = await client.chat.completions.create({
model: "claude-sonnet-5-5",
messages: [{ role: "user", content: "Say hi." }],
});
console.log(r.choices[0].message?.content);

Field mapping

Quick answers

Which base URL do I use?

Claude Code and Anthropic SDKs use https://api.oneprovider.dev. OpenAI SDKs and OpenAI-compatible clients use https://api.oneprovider.dev/v1. One key works behind both; the model list is on the models page ; rates are on the pricing page .

How do I authenticate?

Send the raw sk-… key in x-api-key or Authorization: Bearer: one of them, never both. Keep the key in an environment variable, not in a file that gets committed. More on authentication .

Where do I get a key?

Open your cabinet in the Telegram bot @oneprovider_robot or at app.oneprovider.dev, top up the balance and press “Issue a key”. Each key can carry its own spend limit. Cabinet & API keys .

What do 401, 404 and 429 mean?

401: the key is missing, mistyped or sent in the wrong header; paste the whole key without quotes or spaces. 404: usually a wrong base URL, for example a missing or doubled /v1. 429 with “Insufficient balance”: the cabinet balance or the key’s spend limit is used up, so top up instead of retrying; any other 429 is a rate limit, so wait for Retry-After. Details: error codes and troubleshooting .

Why do streams cut off or reset?

VPN and VLESS proxies often buffer SSE or break HTTP/2 negotiation. OneProvider has no regional restrictions and does not buffer streams, so turn the proxy off and retry.

Where do I ask if this is not enough?

Message @Oneproviderhelpbot on Telegram or open “Support” in the web cabinet, with the HTTP status code and the exact error message. How support works .