Yes, custom GPTs are going away. OpenAI will retire them on December 11, 2026 across all ChatGPT plans, and is moving them to plugins. Most GPTs move over with a few clicks. The part that breaks is custom actions: any GPT that looks things up or makes changes in another system, such as your CRM, online store or an internal tool, will lose that connection and needs it rebuilt. If your team relies on GPTs for real work, you have about ten weeks. Below is what moves, what breaks, and a week-by-week plan to get through it without a scramble.
What is happening to custom GPTs?
On September 11, 2026, OpenAI announced it will retire custom GPTs, the build-your-own assistants it launched in late 2023. Their replacement is plugins. A plugin does the same job as a GPT, packaged differently:
- Skills hold the instructions: "you are our proposal writer, always use this format."
- Apps connect ChatGPT to other tools, such as Google Drive, Slack or Zendesk.
- A plugin bundles skills and apps into one thing people install and use.
So the idea of a custom assistant isn't going away. The container is changing, and some things don't survive the move.
When do custom GPTs stop working?
Dates as of September 27, 2026, from OpenAI's migration FAQ:
| Date | What happens | Who it applies to |
|---|---|---|
| Sep 11, 2026 | Retirement announced; admins notified | All plans |
| Sep 22, 2026 | Target date for the migration option to appear | Enterprise (other plans roll out at different times) |
| Oct 26, 2026 (planned) | Nobody can create new custom GPTs | Enterprise workspaces |
| Dec 11, 2026 | Custom GPTs and their pages stop working | All plans |
| Feb 11, 2027 | Later retirement date | Only Enterprise workspaces with an approved extension |
What moves to the plugin, and what doesn't?
| Part of your GPT | After migration |
|---|---|
| Instructions | Moves. Becomes a skill in the new plugin |
| Uploaded knowledge files | Moves. Copied in as reference files |
| Connected apps (Google Drive, Slack and similar) | Moves. People may need to connect their own accounts again |
| Custom actions | Does not move. Must be rebuilt |
| The model you picked for it | Does not move |
| Past conversations | Do not move. You can still open them in the old GPT until retirement |
| Who it was shared with | Does not move. The plugin starts private |
| Unpublished draft edits | Do not move. Migration uses the last published version |
Two details catch people out. First, once you migrate a GPT, the original becomes read-only. Finish any edits before you press the button. Second, migration doesn't give anyone else access. You have to share the plugin, and each person has to install it.
Which of your GPTs will actually break?
Sort every GPT your team uses into one of these rows. The row tells you how much work it needs.
| What the GPT does | What happens on December 11 | Effort to fix |
|---|---|---|
| Instructions only, like a saved prompt with a name | Migrates cleanly | Minutes, plus a quick test |
| Instructions plus uploaded files (price lists, policies, templates) | Migrates cleanly | An hour of testing against real tasks |
| Uses built-in apps like Google Drive or Slack | Migrates, but people may need to reconnect | Test with a real user before switching |
| Uses custom actions to reach your CRM, store, booking system, database or internal tools | Breaks | A small technical project, plus a security review |
| Is public, used by customers or linked from your website | The page goes dark | Plan a replacement and update every link |
A custom action is a connection someone set up so the GPT could reach into another system: check an order status, create a lead in your CRM, pull a customer record. These are usually the GPTs that do the most useful work, which is why they're the ones to worry about.
What if the person who built the GPT has left?
This is the problem most guides skip. Only a GPT's creator can migrate it. In Enterprise workspaces, a workspace admin can too. Being allowed to use a GPT doesn't let you migrate it, and someone who only uses a GPT can't open its settings to see the instructions or files behind it.
So a GPT built by a former employee, a contractor or an agency can quietly become impossible to move. If that GPT matters, get its instructions and files out now, through its creator or your admin, while it still works. Rebuilding from scratch later means guessing at instructions nobody can see anymore.
How do you replace a custom action?
You have two options, and it's worth checking them in this order:
- Use a ready-made app. ChatGPT's plugin directory keeps growing, and covers popular tools such as Google Drive, SharePoint, Dropbox, Box and Zendesk. If an app does what your action did, you connect it and you're done.
- Rebuild it as an MCP server. For your own systems, or anything the directory doesn't cover, the connection gets rebuilt as an MCP server: a small connector that lets AI assistants use your system with permissions you control. MCP is an open standard, so the same connector also works with Claude and other assistants. We explain the difference from a regular integration in MCP server vs API.
Either way, test it before switching people over. OpenAI says plainly that a rebuilt connection shouldn't be assumed to do everything the old action did. Have someone check what data it can read and what it's allowed to change. Anything that can create, update or delete records should ask for approval before acting.
A week-by-week plan to be done before December 11
Work backward from the deadline, and leave the last two weeks as a buffer. The hard parts always take longer than expected.
| When | What to do |
|---|---|
| This week | List every GPT your team relies on. For each one, note who built it, who uses it, whether it has custom actions, and whether customers can reach it |
| Early October | Get the instructions and files out of any GPT whose creator has left or is hard to reach. Publish any unfinished edits you want to keep |
| October | Migrate the simple GPTs (instructions and files only). Test each one with 3 to 5 tasks people really use it for, plus one hard case |
| By Oct 26 | Enterprise only: publish any drafts you still need, since creating new GPTs is planned to end then |
| October to mid-November | Rebuild custom actions, starting with the GPT that would hurt most if it stopped. Include time for a security review |
| Mid to late November | Share the plugins, have users install and test them, and update links on your website, emails and help docs |
| December 1 to 11 | Buffer. Fix what testing turned up. Tell people the old GPTs are going away |
When you test, compare the plugin's answers with the old GPT's on the same tasks. Check that it follows your instructions, uses the right files, returns answers in the format you need, and that every connection works.
Should you stay on ChatGPT or move to Claude or Gemini?
Our rule of thumb:
- Your GPTs are instructions and files, and your team lives in ChatGPT. Migrate to plugins. It's the least work.
- The real value was a custom action. You're rebuilding that connection no matter where you go. Build it as an MCP server, so it works with ChatGPT today and other assistants tomorrow.
- You were already unhappy with ChatGPT. This is a natural moment to switch. Instructions and files copy into a Claude Project or a Gemini Gem in an afternoon. Connections need the same rebuild as above.
If you're weighing the switch for the whole company, our Claude vs ChatGPT for business comparison covers seat prices, data terms and where Copilot fits.
Whichever you pick, keep a copy of every GPT's instructions and files somewhere you own, such as a shared drive. This retirement is a reminder that anything you build on someone else's platform can change on their schedule.
What does this cost?
The migration itself is a built-in option in ChatGPT. On Enterprise, OpenAI says using a migrated GPT without apps in regular chat has no extra cost. Building and editing plugins happens in ChatGPT Work, where actions use credits.
The real costs are time and help:
- Your team's time to list, migrate and test each GPT. Budget an hour or so per simple GPT.
- Developer time to rebuild each custom action, including a security check. For one connection to a well-documented system, that's usually days of work, not months.
- The cost of missing the date: whatever that GPT was doing gets done by hand again from December 12.
Our take
For most businesses, this is an afternoon of housekeeping for the simple GPTs and a real project for the one or two that connect to your systems. The companies that get caught out won't be the ones with complicated GPTs. They'll be the ones who find out on December 11 that the GPT their sales or support team used every day was built by someone who left last year.
Start with the list. If it turns up GPTs with custom actions, ask us: send the list of what each one connects to, and an engineer will reply within 24 hours with which ones will break and what it takes to fix them. If you have several, our fixed-price Metad Diagnostic can map them, rank them by risk and scope the rebuild in five days.