codex-backend-sdk 0.2.0

Unofficial Python SDK for the ChatGPT Codex backend API

codex-backend-sdk

Unofficial Python SDK for the ChatGPT Codex backend API (chatgpt.com/backend-api/codex).

This package mirrors the official OpenAI Python SDK shape for the API surface that the Codex backend exposes. Use OpenAI, client.responses.create(...), and client.models.list() just as you would with openai-python, with Codex-specific authentication and backend limitations under the hood.

Requirements: a ChatGPT Plus, Pro, or Enterprise subscription. Authentication goes through ChatGPT OAuth and stores tokens in ~/.codex/auth.json.

Disclaimer: This is an independent, community-maintained library that reverse-engineers undocumented endpoints of chatgpt.com. It is not affiliated with, endorsed by, or supported by OpenAI.

Installation

git clone https://github.com/B4PT0R/codex-backend-sdk.git
cd codex-backend-sdk
pip install -e .

Basic Usage

from codex_backend_sdk import OpenAI

client = OpenAI().authenticate()

response = client.responses.create(
    model="gpt-5.4",
    input="Explain quicksort in one paragraph.",
)

print(response.output_text)

Streaming

stream = client.responses.create(
    model="gpt-5.4",
    input="Say 'hi' five times.",
    stream=True,
)

for event in stream:
    if event.type in {"response.output_text.delta", "response.content_part.delta"}:
        delta = event.delta
        print(delta if isinstance(delta, str) else delta.get("text", ""), end="")

Models

models = client.models.list()
for model in models:
    print(model.id, model.display_name, model.context_window)

info = client.models.retrieve("gpt-5.4")

Multi-Turn Input

The Codex backend does not expose previous_response_id, so pass prior input/output items explicitly.

history = [
    {"role": "user", "content": "My name is Alice. Say OK."},
]

reply1 = client.responses.create(input=history).output_text
history.append({"role": "assistant", "content": reply1})
history.append({"role": "user", "content": "What is my name?"})

reply2 = client.responses.create(input=history).output_text
print(reply2)

Function Calling

import json

tools = [{
    "type": "function",
    "name": "get_weather",
    "description": "Get the current weather for a city.",
    "parameters": {
        "type": "object",
        "properties": {"city": {"type": "string"}},
        "required": ["city"],
        "additionalProperties": False,
    },
}]

first = client.responses.create(
    input="What's the weather in Paris?",
    tools=tools,
)

call = next(item for item in first.output if item["type"] == "function_call")
result = {"temperature": 18, "unit": "celsius", "condition": "cloudy"}

second = client.responses.create(
    input=[
        call,
        {
            "type": "function_call_output",
            "call_id": call["call_id"],
            "output": json.dumps(result),
        },
    ],
    tools=tools,
)

print(second.output_text)

Structured Output

schema = {
    "title": "person",
    "type": "object",
    "properties": {
        "name": {"type": "string"},
        "age": {"type": "integer"},
    },
    "required": ["name", "age"],
    "additionalProperties": False,
}

response = client.responses.create(
    input="Extract: Bob is 42 years old.",
    text={
        "format": {
            "type": "json_schema",
            "name": "person",
            "schema": schema,
            "strict": True,
        }
    },
)

Codex-Specific Endpoints

Codex-only operations live under client.codex.

quota = client.codex.usage()

The backend currently rejects some official Responses parameters, including temperature, top_p, max_output_tokens, metadata, user, safety_identifier, truncation, and previous_response_id. The SDK raises CodexBackendUnsupportedParameterError for those instead of silently dropping them.