OpenAI opened Sign in with ChatGPT to 16 third-party developer tools so users can spend their ChatGPT allowance instead of a new bill

The hardest step in getting a developer to try a new AI-powered tool has been the second credit card and the API key. OpenAI announced Sign in with ChatGPT for third-party developer tools at Dev Day on 29 September 2026, with 16 launch partners, letting ChatGPT Plus and Pro subscribers use their existing plan allowance inside those tools instead of paying the tool's own credits or standing up a separate API key. The New Stack reported the details from OpenAI's own stage session.

What the 16 launch partners get

The full list, as OpenAI stated: OpenCode, OpenClaw, Pi, T3, Hyperagent, Hermes Agent, Vorflux, Amp, Dactyl, Kilo Code, Warp, Conductor, Devin, Notion and Vercel are live today, with Lovable "coming soon." OpenAI's own line, quoted by The New Stack: "We're starting with these 16 launch partners today, and we'll expand quickly." The set spans open-source developer tools and commercial coding platforms and includes tools that had already run their own version of plan-sharing, notably Dactyl.

The mechanics, and where the money moves

Sign in with ChatGPT had already existed as an identity flow, giving partners a user's name, email address and profile picture with any additional permissions approved separately. What is new today is the plan-usage side. A ChatGPT Plus or Pro subscriber signs in with their OpenAI account inside a partner tool, and OpenAI-powered usage inside that tool now draws from the ChatGPT Work and Codex allowance already included in their subscription, rather than from the tool's own credits or an API key. Users can set weekly caps for each partner app, and once the relevant limit is reached, included usage stops rather than automatically switching to the third party's own billing.

OpenAI CEO Sam Altman said on stage, quoted by The New Stack: "This makes it easier for people to try your product. They're already paying for an AI subscription, and now you don't have to cover their token costs to get them going." The economic point Altman is making is that model cost has been a real line on a tool builder's P&L for a first-time user, and Sign in with ChatGPT lets that cost draw from a bucket the user is already paying for. OpenAI has not published the settlement mechanics on the tool-builder side in the announcement.

What a team shipping an AI feature has to decide this week

There are two decisions here, and they are separate. The first is whether to join the program: for a tool whose free-trial funnel is losing users at the API-key step, the answer is likely yes and the operational cost is low. The second is what to do about users who already sit on the tool's own credit or subscription model, because Sign in with ChatGPT gives them a same-account way to route model calls through their ChatGPT allowance instead. That is not automatically a loss for the tool, since Altman's point is that the user who now shows up is the one who would not have signed up at all before, but the accounting on active-paid users needs to be watched from the first month rather than the third.

Source

• The New Stack, OpenAI makes 'Sign in with ChatGPT' a way to use your subscription in third-party developer tools, by Frederic Lardinois, 2026-09-29.