POST /v1/chat/completions

OpenAI-compatible protocol with fields matching the official API. Intended for:

Official OpenAI SDKs (openai-python / openai npm)
Any OpenAI-compatible client that supports configuring base_url
IDE plugins such as Cursor, Cline, and Continue
Frameworks such as LangChain and LlamaIndex

Endpoint

POST https://relay.4aicode.com/v1/chat/completions

Request

POST /v1/chat/completions HTTP/1.1
Host: relay.4aicode.com
Authorization: Bearer sk-4ai-xxxxxxxxxxxxxxxx
content-type: application/json

{
  "model": "gpt-5.6-terra",
  "stream": true,
  "messages": [
    { "role": "system", "content": "You are helpful." },
    { "role": "user",   "content": "Write fizzbuzz in Go." }
  ]
}

Supported Models

GPT-6:

Model	Best for
`gpt-6-astra`	New-generation flagship; short-context input $1.50/M and output $7.50/M (15% of official price)
`gpt-6.1-sol`	GPT-6.1 flagship for complex coding and long-running tasks; $0.30/M input and $1.50/M output (15% of list price)
`gpt-6-sol`	GPT-6 flagship for complex coding and long-running tasks; $0.30/M input and $1.50/M output (15% of list price)
`gpt-6-luna`	Lightweight GPT-6 model for fast everyday tasks; $0.015/M input and $0.075/M output (15% of list price)

GPT-5 series:

Model	Best for
`gpt-5.6-sol`	Flagship model, prioritized for complex coding and long-running tasks; supports `max` reasoning effort
`gpt-5.6-terra`	Balanced tier with excellent value
`gpt-5.6-luna`	Fast and affordable; sufficient for everyday use
`gpt-5.5`	Previous-generation general-purpose model
`gpt-5.4`	General-purpose use
`gpt-5.4-mini`	Fast and affordable
`gpt-5.3-codex`	Code optimization

Google Gemini:

Model	Best for
`google/gemini-3.1-pro-preview`	Google Gemini Pro preview
`google/gemini-3-flash-preview`	Google Gemini Flash preview
`google/gemini-2.5-flash`	Stable Google Gemini Flash model
`google/gemini-2.5-pro`	Stable Google Gemini Pro model

GPT-5.2 and earlier models have been deprecated upstream. Other models, such as gpt-4o and gpt-4, will be rejected with a 400 response whose error message includes a list of available models.

Model availability depends on upstream support and service status. If the upstream service reports that a model is unsupported, the relay returns an explicit 400 response directly.

Ignored Parameters

The following parameters are accepted but have no effect, ensuring SDK compatibility without errors:

logit_bias
user
functions (use the newer tools instead)

Response

Matches the official OpenAI response format:

choices[].message.content
choices[].finish_reason
usage (prompt_tokens / completion_tokens / total_tokens)

Streaming format:

data: {"choices":[{"delta":{"content":"Hello"}}]}
data: {"choices":[{"delta":{"content":", world"}}]}
data: [DONE]

Complete Examples

Python

from openai import OpenAI

client = OpenAI(
    base_url="https://relay.4aicode.com/v1",
    api_key="sk-4ai-xxxxxxxxxxxxxxxx",
)

resp = client.chat.completions.create(
    model="gpt-5.4",
    messages=[
        {"role": "system", "content": "You are a helpful assistant."},
        {"role": "user", "content": "Introduce yourself in one sentence"},
    ],
)
print(resp.choices[0].message.content)

TypeScript

import OpenAI from "openai";

const client = new OpenAI({
  baseURL: "https://relay.4aicode.com/v1",
  apiKey: process.env.OPENAI_API_KEY,
});

const resp = await client.chat.completions.create({
  model: "gpt-5.4-mini",
  messages: [{ role: "user", content: "hi" }],
});
console.log(resp.choices[0].message.content);

Errors

HTTP	Meaning
400	Invalid field / model not in the allowlist
401	Invalid token
403	Team suspended
429	Rate limit or quota exceeded
502	Upstream OpenAI service instability
503	Upstream services are temporarily unavailable; see Service Cooldowns and Retries

Differences from `/v1/messages`

Aspect	`/v1/messages`	`/v1/chat/completions`
Protocol	Anthropic	OpenAI
Available models	All Claude models	`gpt-5` / `google/gemini-`
Required fields	`max_tokens`	—
Usage fields	`input_tokens` / `output_tokens`	`prompt_tokens` / `completion_tokens`