Most ChatGPT Plus subscribers are paying twice without noticing. They pay OpenAI for the plan, then pay Notion, a coding agent or an app builder separately for AI credits that often run on the same OpenAI models. Since 29 September 2026, a lot of that second bill is optional.
At DevDay 2026, OpenAI turned "Sign in with ChatGPT" from a login button into a way to spend your existing plan inside other apps. The catch is that the default settings are loose, the caps work differently from what most people assume, and one wrong toggle can let an app quietly eat the allowance you need for your own work. This guide shows you how to set it up properly.
What is Sign in with ChatGPT and what changed at DevDay?
Sign in with ChatGPT lets you log in to partner apps with your ChatGPT account. Since 29 September 2026, Plus and Pro subscribers can also let those apps use their plan for AI requests. Eligible requests count toward the ChatGPT Work and Codex usage already in your plan, with no API key needed.
According to OpenAI's help article, there are two separate permissions. Signing in shares your name, email address and profile picture. Sharing your plan is a second, optional choice that the app asks for during sign-in. You can say yes to the first and no to the second.
Two details matter before you start. First, this does not add any new allowance. It lets other apps draw from the pool you already pay for. Second, Free and Go users can still sign in with ChatGPT, but only Plus and Pro can share their plan with commercial apps.
Which apps can use your ChatGPT plan, and what do they get?
OpenAI launched with 16 plan-usage partners, including Notion, Devin, Vercel, Warp, Amp, Kilo Code, Dactyl, Hermes Agent and open-source tools such as OpenClaw, OpenCode, Pi and T3. Lovable is listed as coming soon. The apps get your basic profile and, if you allow it, your usage, but not your chats or memories.
The New Stack's launch report lists the current partners, and Nerd's Chalk notes that Airtable, Canva, GitLab, HubSpot and Supabase support sign-in only. You can log in to those with ChatGPT, but they will not draw on your plan.
For most practitioners, the useful split looks like this:
- Everyday knowledge work: Notion Agent is the obvious one for marketers, project managers and anyone who lives in docs and databases.
- Building things: Vercel, Dactyl and Lovable (when it arrives) cover websites and apps. These can burn usage quickly because each build runs many requests.
- Agents and coding: Devin, Warp, Amp and Hermes Agent are heavier users by design, since they run long, multi-step tasks.
The partner app can still charge you for its own subscription or premium features. Sharing your plan replaces the OpenAI-powered part of the bill, not the whole thing.
How do you connect Notion and set a weekly cap?
Connect from the partner app, allow plan use, then go to ChatGPT Settings, Usage, App limits and set a weekly percentage cap for that app. In Notion, you must pick a specific GPT model in Notion Agent. If you leave the model on Auto, Notion bills your workspace's Notion credits instead.
Here is the full sequence, using Notion as the example because it is the partner most practitioners already use. Per Notion's help page, your workspace must be on the Business or Enterprise plan, and it works with Notion Agent but not with Custom Agents.
- Connect in Notion. Go to Settings, Notion AI, Usage. Under Connected subscriptions, select Connect next to ChatGPT. You can also do it from the model picker inside Notion Agent.
- Allow plan use when asked. Sign in to the ChatGPT account you actually pay for. If you run several accounts or workspaces, check which one is active first.
- Pick a GPT model, not Auto. The model picker shows which plan will pay before you send a message. This is the step people miss.
- Set the cap in ChatGPT. Go to Settings, Usage. Under App limits, find Notion, select Manage limits, enter a weekly percentage and select Save. Check the saved value, because OpenAI says a failed change should not be assumed to have taken effect.
- Leave credit use off. The option that lets apps continue on ChatGPT credits after your plan runs out is off by default. Keep it that way until you know how fast the app spends.
When you hit your ChatGPT limit, Notion Agent asks whether to switch to your workspace's Notion credits and switches back automatically when your ChatGPT usage resets.
How should you split your weekly allowance across apps?
Treat app caps as ceilings, not reservations. A cap never sets usage aside for an app, so a heavy agent can still drain the pool your own ChatGPT work needs. A practical rule is to keep total app caps at or below 60 percent, with light apps at 10 to 20 percent and heavy agents at 20 to 30 percent.
The three-bucket cap plan is a simple way to decide the numbers:
- Protected bucket (at least 40 percent): your own work inside ChatGPT, such as research, drafting, voice briefs and the Work tab. Nothing else touches this.
- Light bucket (10 to 20 percent per app): apps that run short requests, like Notion Agent summarising pages or drafting database entries.
- Heavy bucket (20 to 30 percent per app): apps that run long chains of requests, like coding agents and app builders. Start low and raise the cap only after a week of real data.
Because caps are percentages of your whole weekly pool, they can add up to more than 100 percent. That is exactly the trap. Three apps capped at 40 percent each can, in a busy week, leave you with nothing. OpenAI also notes that usage rates can differ between an app and ChatGPT, so one Notion request is not the same cost as one ChatGPT message.
This matters more for Pro 200 subscribers. The Next Web reports that from 30 October, Pro 200's included Work and Codex usage falls from 20 times to 10 times the Plus allowance. Third-party apps draw from exactly that pool.
To set your first caps without guessing, give ChatGPT your real week and let it do the sorting:
Try this prompt:
You are helping me plan how my ChatGPT Plus weekly usage is shared with other apps through Sign in with ChatGPT.
My connected apps: [e.g. Notion Agent, Vercel]
My recurring weekly AI tasks: [list 5 to 10 tasks, e.g. "summarise 3 client meeting pages in Notion", "draft weekly report in ChatGPT", "build one landing page draft in Vercel"]
Rules:
1. Keep at least 40% of weekly usage protected for tasks I do inside ChatGPT itself.
2. Classify each task as LIGHT (short, single request) or HEAVY (multi-step, builds, agents).
3. Suggest a weekly cap percentage for each app. Light apps 10 to 20%, heavy apps 20 to 30%. Total app caps must not exceed 60%.
4. For Notion tasks, remind me to choose a specific GPT model, not Auto.
5. Flag any task that is better done inside ChatGPT to save usage.
Output a table with columns: Task | App | Light or Heavy | Suggested cap | Reason. Then give me a 3-line Friday check I can run to see if the caps need adjusting.
The prompt works because it forces a classification before a number. Most bad caps come from treating every app the same.
What are the most common mistakes with shared ChatGPT plans?
The five common mistakes are leaving Notion on Auto, assuming a cap reserves usage, turning on credit use with automatic purchases enabled, thinking that signing out disconnects an app, and expecting every ChatGPT feature to work inside partner apps. Each one costs money or usage without any warning message.
- Auto model in Notion: your Notion credits pay, not ChatGPT. Check the model picker every time you start a session.
- Caps as reservations: an app can hit its own cap while ChatGPT still has usage left, and your ChatGPT work can run dry while an app is still under its cap.
- Credit spill: only an app capped at 100 percent can use credits after your plan runs out, and only if you opt in. If automatic credit purchases are also on, continued use can create charges, and OpenAI says you may not get a separate notice.
- Signing out is not disconnecting: logging out of the app does not stop it using your plan. Go to Settings, Security and login, Sign in with ChatGPT, pick the app and choose Disconnect. Disconnecting does not undo usage already recorded.
- Missing features: some ChatGPT or API capabilities are not available when an app runs on your plan, and usage settings show totals, not a log of what the app actually did. Keep task notes if you ever need to query unexpected usage.
Also check availability for your own account and region before you build a team workflow on this. Participating apps may offer plan sharing only on certain plans of their own, as Notion does with Business and Enterprise.
What can you try in the next 20 minutes?
Connect one partner app you already use, set its cap to 15 percent, run three real tasks, then open ChatGPT Settings, Usage and read how much of the app's limit those tasks consumed. That single number tells you more about the right cap than any guide, including this one.
If three light tasks used 5 percent of the app's cap, you can safely leave it. If they used half, the app is heavier than it looks, and you should move some of that work back into ChatGPT or lower the cap. Run the Friday check from the prompt above for two weeks, then adjust once. After that, the setup runs itself.
For more on getting value from the ChatGPT side of the pool, see our guides to voice briefs for the ChatGPT Work tab and ChatGPT dots, which also launched at DevDay.
The bigger shift is that your AI subscription is starting to behave like a budget you allocate, not a chat window you open. The practitioners who treat it that way will get more out of the same subscription. We understand AI. We understand you better. With UD by your side, AI doesn't feel cold.
Reviewed by the UD AI team. Sources: OpenAI DevDay 2026 recap (29 September 2026), OpenAI Help Center, Notion Help Center, The New Stack.
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