2026-06-19

[MtkN1]

Today I Learned ...

[MtkN1]

ChatGPT Codex OAuth で Responses API を呼ぶ最小サンプル

• Codex が認証済み (~/.codex/auth.json がある) 前提.
• Web search | OpenAI API を例を実行します.
• 所感:
  • access_token をそのまま API キーにする.
  • account_id を ChatGPT アカウント ID をして headers に入れる.
  • ベース URL は https://chatgpt.com/backend-api/codex.
• 落とし穴:
  • client.responses.create() は幾つかのオプションを明示しないと Bad Request になる.
    • instructions でロールの指定が必須.　Codex の実物は恐らく ~/.codex/models_cache.json にある.
    • store=False, stream=True (Streaming 限定).
    • with client.responses.stream(...): ... はバグる時があるらしい (responses.stream crashes with TypeError: 'NoneType' object is not iterable when server emits response.completed with output=None openai/openai-python#3312).

from pathlib import Path

from openai import OpenAI
from openai.types.responses import ResponseTextDeltaEvent
from pydantic import BaseModel


class Tokens(BaseModel):
    access_token: str
    account_id: str


class Auth(BaseModel):
    tokens: Tokens


path = Path.home().joinpath(".codex", "auth.json")
auth = Auth.model_validate_json(path.read_bytes())

client = OpenAI(
    api_key=auth.tokens.access_token,
    base_url="https://chatgpt.com/backend-api/codex",
    default_headers={
        "ChatGPT-Account-ID": auth.tokens.account_id,
    },
)

stream = client.responses.create(
    model="gpt-5.5",
    reasoning={"effort": "low"},
    instructions="You are a helpful assistant.",
    input=[
        {
            "role": "user",
            "content": "What was a positive news story from today?",
        },
    ],
    tools=[{"type": "web_search"}],
    store=False,
    stream=True,
)

for event in stream:
    match event:
        case ResponseTextDeltaEvent():
            print(event.delta, end="", flush=True)
        case _:
            pass
else:
    print()