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ChatGPT (OpenAI account)

Table of contents

Use your ChatGPT subscription with Docker Agent by signing in with your OpenAI account. No API key needed.

Overview

The chatgpt provider authenticates with a ChatGPT account (the same "Sign in with ChatGPT" flow used by OpenAI's Codex CLI) instead of an OPENAI_API_KEY. Usage is billed against your ChatGPT Plus, Pro, or Business plan rather than pay-per-token API credits.

Under the hood, Docker Agent talks to the ChatGPT Codex backend (https://chatgpt.com/backend-api/codex), which serves the gpt-5 model family over the OpenAI Responses API. GPT-5.6 (Sol/Terra/Luna) is served there too; GPT-5.2 and GPT-5.3-Codex are deprecated for ChatGPT sign-in.

Prerequisites

  • A paid ChatGPT subscription (Plus, Pro, or Business).
  • A browser on the machine running the sign-in (the OAuth flow uses a fixed localhost:1455 callback).

Sign In 

docker agent setup

Pick chatgpt in the provider list: instead of asking for an API key, the wizard opens your browser on the ChatGPT sign-in page and stores the resulting OAuth credential in the Docker Agent config directory (~/.config/cagent/chatgpt-auth.json, owner-only permissions). The access token is refreshed automatically; you only need to sign in again if the refresh token is revoked.

Related commands:

docker agent doctor                        # the chatgpt row shows the credential state
rm ~/.config/cagent/chatgpt-auth.json      # sign out (remove the stored sign-in)

Configuration

Inline 

agents:
  root:
    model: chatgpt/gpt-5.6
    instruction: You are a helpful assistant.

Named model 

models:
  gpt:
    provider: chatgpt
    model: gpt-5.6
    thinking_budget: medium

agents:
  root:
    model: gpt

Available Models

The Codex backend serves the models available to your ChatGPT plan, typically:

Model Best For
gpt-5.6 Alias for gpt-5.6-sol; general purpose, strong reasoning
gpt-5.6-sol Frontier model, most capable
gpt-5.6-terra Everyday workhorse
gpt-5.6-luna High-volume, cost-efficient
gpt-5.2 Deprecated for ChatGPT sign-in
gpt-5.2-codex Deprecated for ChatGPT sign-in

The effort picker exposes Low/Medium/High/XHigh/Max on the GPT-5.6 family (no Minimal).

How It Works

  • Auth: the docker agent setup sign-in runs an OAuth 2.0 authorization-code + PKCE flow against auth.openai.com. The stored login is exposed to credential checks (doctor, first_available, auto model selection) as the virtual CHATGPT_OAUTH_TOKEN variable.
  • API: requests go to the Responses API only; the backend has no Chat Completions endpoint, so api_type is pinned automatically.
  • Request shape: the backend requires stateless requests (store: false) and a top-level instructions field, so Docker Agent moves system messages there. Client-side sampling parameters (temperature, top_p, max_tokens) are not supported by the backend and are dropped.

Setting the Token Explicitly

CHATGPT_OAUTH_TOKEN can also be set like any other credential (shell environment, --env-from-file, ...). An explicitly set value takes precedence over the stored sign-in. This is useful for short-lived CI runs with a pre-minted access token, but note that such a token expires and is not refreshed.

ChatGPT Subscription vs. OpenAI API Key

chatgpt openai
Credential ChatGPT account sign-in OPENAI_API_KEY
Billing Included in the ChatGPT plan (rate-limited) Pay per token
Models gpt-5 family served by the Codex backend Full OpenAI API catalog
Sampling controls (temperature, ...) Not supported Supported
Embeddings / reranking Not supported Supported

When both credentials are configured, automatic model selection prefers openai; pin --model chatgpt/gpt-5.6 (or use a named model) to use the subscription.

Note

Use of the Codex backend is governed by OpenAI's terms for ChatGPT and Codex. Sign-in is per user; do not share the stored credential.