Sign in with ChatGPT: Run Coding Agents on Your Plan (2026)

Last updated: October 7, 2026. Google Trends shows "sign in with chatgpt" holding a steady 3-17 on a 0-100 scale over the past month, with a spike on September 30, the day after DevDay (Trends, past month, worldwide; for scale, "claude code skills" mostly sat between 25 and 60 in the same window).

Sign in with ChatGPT is OpenAI's way to let an app bill model calls to a user's existing ChatGPT plan instead of an API key. Per OpenAI's cookbook guide, eligible Plus and Pro users "can try your tool with the account and plan they already have, without creating or configuring an API key." For anyone running a coding agent outside OpenAI's own apps, that changes where the bill lands and who controls the meter.

What OpenAI actually shipped#

The feature has two separate permissions, and mixing them up is the most common misreading.

Identity proves who the user is so they can sign in. Neither permission gives the app access to ChatGPT conversations, per OpenAI's docs.
ChatGPT plan usage is an optional second grant that lets the app complete eligible requests against the allowance included in the user's plan, or against their available credits. The user chooses whether to grant it and manages it in ChatGPT settings.

The reporting from The New Stack names 16 launch partners for plan usage: OpenCode, OpenClaw, Pi, T3, Hyperagent, Hermes Agent, Vorflux, Amp, Dactyl, Kilo Code, Warp, Conductor, Devin, Notion and Vercel, with Lovable coming soon. Third-party requests draw from the same Work and Codex allowance the plan already includes, users can set weekly caps for individual apps, and once a limit is hit, included usage stops rather than rolling over to the partner's own billing.

The catch is who gets the plan-usage grant. At launch it covers open-source projects, personal projects that run locally, and selected private apps. OpenAI's overview of plan usage says a paid or remotely hosted app has to complete an interest form first. So an open-source terminal agent can ship this today, while a hosted SaaS cannot just switch it on.

How the flow works under the hood#

The cookbook walks through an open-source Electron app, and the mechanics apply to any local agent harness:

The app generates a stable host ID (a urn:uuid: value) once per install and saves it.
It opens the system browser, with a listener on 127.0.0.1 and fresh state, nonce and PKCE values. The user picks a workspace and approves permissions.
The scopes requested include offline_access for a refresh token and resource.invoke with chatgpt.tokens.use.direct, against the resource https://api.openai.com/v1.
OpenAI issues a client_id, the app exchanges the code for tokens, verifies the ID token, and checks a sharing flag. Identity alone does not set it.
Requests go to the public Responses API with the profile's access token, per OpenAI's docs with store: false and stream: true.

No client secret and no API key are involved. That is the whole pitch, and also the constraint: it is the Responses API only. Kilo Code's docs say the subscription route supports the Responses API, not Chat Completions, and Docker Agent's docs add that sampling parameters such as temperature, top_p and max_tokens are dropped because the backend does not support them.

The strategic angle: who wins, who loses#

This is a distribution move disguised as an auth feature. A coding agent that used to need "paste an API key and set up billing" now needs one browser click, and the token cost lands on the user's flat-rate plan. For open-source harnesses, that removes their biggest onboarding hurdle, and it quietly pulls the whole OpenAI-compatible ecosystem toward OpenAI's models. The loser is any harness vendor whose margin depended on reselling tokens.

The second-order effect is the interesting part. All of that third-party traffic draws from the shared Work and Codex pool, and OpenAI's help center says new Pro 200 subscriptions already include a lower allowance than before, with existing subscribers moving to the lower allowance after October 29, 2026. More places to spend the allowance, a smaller allowance to spend: expect "why did my weekly limit vanish" threads that turn out to be a background agent. We covered the plan math in Codex Usage Limits and Pricing in 2026, and the launch context in the OpenAI DevDay 2026 recap.

What a builder does Monday#

If you run any of the partner harnesses, do this before you point it at a repo:

Set the per-app cap. Kilo's docs note that OpenAI applies a per-app usage quota to apps signed in with ChatGPT, defaulting to 100% of your allowance per app, adjustable under Settings, Usage & Billing, App Limits in the ChatGPT or Codex app. Lower it for any agent you leave running unattended.
Know what the sign-in command looks like. Docker Agent's documented flow is docker agent setup, then pick the chatgpt provider; its stored login lives at ~/.config/cagent/chatgpt-auth.json, and the docs say to pin the model, because with both credentials configured, automatic selection prefers the API key. OpenClaw's docs list openclaw models auth login --provider openai --method siwc for the new flow (beta), separate from its earlier Codex OAuth route. I did not run either; both are copied from the vendors' own docs.
Expect a hard stop, not a fallback. Kilo's docs say that when you reach your ChatGPT limit the request errors and is not retried against a saved API key or credits. If you want a fallback, build it yourself.
Check where your code goes. Kilo's BYOK route passes requests and code context through the Kilo Gateway before reaching OpenAI, while its direct VS Code and CLI route does not. That is a data-handling decision, not just a billing one.
Treat the token like a credential. Docker's docs say sign-in is per user and the stored credential must not be shared. Do not bake a personal token into CI.

If you are choosing a harness rather than configuring one, the Claude Code vs Codex vs Cursor vs OpenCode comparison covers the differences that matter more than which login button it has, and Codex custom model providers covers the API-key route that remains the right choice for hosted or multi-user setups.

What people are actually saying#

Reaction splits along one line: is this a gift to users or a lever for OpenAI?

The enthusiast case. On r/SillyTavernAI, a poster argues that a $20 Plus plan is now worth far more than $20 once apps can spend it directly, describing it as roughly $200 of API usage for roleplay (thread). That figure is the poster's estimate, not an OpenAI number.
The skeptical case. A r/ClaudeCode thread, "Openai Dev day proved one thing," treats Sign in with ChatGPT as the highlight but says it landed the same day OpenAI cut the $200 plan's allowance (thread). The Hacker News thread on the Pro 500 plan runs the same argument from the cost side: commenters note that the old 20x plan now buys 10x, and that 25x costs $500 (thread).
The builder case. A r/OpenAI post argues the feature could let users bring their own plan into SaaS products and undercut apps that resell tokens (thread). A commenter in an r/ChatGPT thread about the plan changes adds that hosted SaaS has to apply and so far it is mostly big names (thread), which matches OpenAI's own docs.
The policy case. In an r/codex thread about merging Chat and Work, a commenter points out that OpenAI supports Sign in with ChatGPT and codex exec for third-party apps while others debate banning "sub to api" use (thread). My read, not a claim from the thread: if partner traffic gets expensive, the terms are the lever OpenAI can still pull.

Most of this is opinion, and none of it measures real consumption by partner tools. Read it as a map of the arguments, not as data.

FAQ#

An OAuth flow from OpenAI that lets an app sign users in with their ChatGPT account and, with a separate permission, spend the user's Plus or Pro plan allowance on eligible AI requests instead of an API key.

Which coding agents support it?#

Per The New Stack, the launch partners include OpenCode, OpenClaw, Pi, Amp, Kilo Code, Warp, Conductor and Devin, among 16 total, with more promised.

Does it cost extra?#

OpenAI's docs describe the usage as coming from the allowance or credits already attached to your plan. Hosted partners may still charge for their own compute, as Kilo's docs note for Cloud Agents.

Can I use it in my own paid app?#

Not yet by default. OpenAI's docs say plan usage at launch is for open-source projects, personal local projects and selected private apps, and paid or hosted apps must request access.

Continue Reading#

OpenAI DevDay 2026 Recap - everything else announced alongside this feature
Codex Usage Limits and Pricing in 2026 - the allowance this feature spends from
Claude Code vs Codex vs Cursor vs OpenCode - choosing the harness
Codex Custom Model Providers - the API-key route for hosted setups
Codex Exec in CI - headless runs and why credentials need care

Sources#