How to save your brand voice GPT before custom GPTs retire

OpenAI says custom GPTs are scheduled to retire on December 11, 2026. Some workspaces get February 11, 2027: FedRAMP workspaces and affected Enterprise workspaces with an approved delay. OpenAI also says to follow the notice for your own account, which can give a different date. So dates can change. Check OpenAI's retirement FAQ for yours. I read it on 1 November 2026.

I am Vedran. I build brands for B2B tech teams, and I set up the files that keep their AI on-brand. Here is what I would do this week if your brand voice lived in a GPT.

This is what OpenAI's FAQ says happens if you use its move to a plugin:

Two more things to know. After you move a GPT, the original still works until the retirement date, but it becomes read-only. You also cannot delete it. So finish your edits and publish them before you move. Publishing does not mean making it public.

Your old chats do not move, but OpenAI says they stay open to you after retirement. You do not need to do anything to keep them.

The sharing part matters for a team. Your GPT can move and still stop working for everyone else, because nobody but you can see it. Plan to share it again on the same day.

Do this even if you plan to use the move tool. It takes 10 minutes.

1. Open GPTs, then My GPTs.
2. Click Edit on your brand voice GPT, then open Configure.
3. Copy the instructions into a plain text file.
4. Copy your best conversation starters into the same file.
5. Download every knowledge file.
6. Put it all in one folder with today's date.

Menu names can change, so look for the closest match. Now you own the real source. Keep it here from now on. ChatGPT gets a copy, not the master.

Most old voice GPTs grew by accident. Someone added a line after every bad draft. So fix the file now. Use this shape and copy it:

WHO WE WRITE FOR
[One line. Job, company type, what they care about.]

HOW WE WRITE
- [Rule you can check. Example: Sentences under 20 words.]
- [Rule you can check. Example: Numbers before adjectives.]
- [Rule you can check. Example: No exclamation marks.]

WORDS WE USE
[List]

WORDS WE NEVER USE
[List]

RIGHT AND WRONG
Right: [A real line from your best work.]
Wrong: [A line that sounds off.]
Why: [One short reason.]
(Add 3 to 5 pairs.)

FACTS YOU CAN USE
- [Product names, numbers, dates, customers you may name.]

NEVER SAY
- [Guarantees, unreleased features, legal claims, prices.]

BEFORE YOU ANSWER
Check your draft against every rule above. Fix what breaks.
If a fact is not on this list, ask me. Do not guess.

Delete rules like "be friendly and professional." A model cannot check that. A person cannot check it either.

You have two good choices.

My pick for a team under 20 people is a Project. It is simple, and you can see what is in it. OpenAI's own path is the plugin, so use that if you need its apps.

To set up a Project, based on OpenAI's Projects page:

1. Pick New project in the sidebar. Give it your old GPT's name.
2. Open the three dots, then Project settings. Paste your instructions.
3. Add your files to the Project sources. How many depends on your plan.
4. Save your best starter lines in a shared note.
5. Pick Share and invite your team.

One trap: OpenAI says chats made with a GPT cannot be moved into a Project. So copy what you need from them and start new chats there.

OpenAI's FAQ warns: "A migrated plugin may respond differently." It tells you to compare familiar prompts and at least one harder case. Your picked model does not move, so the answers can change. A Project can change them too. So test it.

Use this quick test. It takes about 30 minutes.

1. Pick 5 real jobs: a LinkedIn post, a sales email, a reply to a hard question, a product update and a case study intro.
2. Run each job in the old GPT and in the new home. Save both answers.
3. Ask one extra question that tempts it to lie: "Can we promise 100% uptime?"
4. Hand the answers to a teammate with no labels on them.
5. Score each one with this table.

A made-up fact or promise is a fail, even if the draft sounds great. Wrong facts cost more than a wrong tone. I wrote up a real test like this in my blind test on a client's brand.

Fix the file, not the chat. Run the test again. Then share the new home with your team and tell them the date you will stop using the old one.

This move is a pain because the brand lived inside one tool. Tools change. Your brand should not have to move every time they do.

Keep one master file and copy it into each tool. The same text can feed a Claude Project or skill and a ChatGPT Project. Then when a fact changes, you change it once and copy it out. Give one person the job. Put their name at the top of the file.

Now your words are safe. But your team still has a few problems the file cannot fix:

• People still paste old versions.
• Nobody checks new drafts unless you do.
• The file covers words. It does not make the post, the banner or the slide.

That is why I build Brand OS Portal. It is one online place made for your brand. Your team logs in and makes on-brand posts, banners, signatures and slides. It also has an AI Kit for ChatGPT and Claude and a Voice Check for drafts. So your rules live in one place, and the tools stay in step.

Jeremy Murray, Founder of KORDIN and Stack8s, said it like this: "the guidelines are so clear our team just uses them without asking questions."

One fixed price to build it. A small monthly Care fee keeps it running. Or book 15 minutes and I will tell you what to do next.

When do custom GPTs stop working? OpenAI's FAQ gives December 11, 2026. FedRAMP workspaces and affected Enterprise workspaces with an approved delay have until February 11, 2027. Follow the notice for your own account, because dates can change.

What happens to the original GPT after I move it? It still works until the retirement date, but it becomes read-only and you cannot delete it. On the retirement date, custom GPTs and their pages close.

Will my chats move too? No. OpenAI says your old chats stay open to you after retirement. Chats made with a GPT cannot be moved into a Project, so start new ones there.

Do I have to use a plugin? No. A plugin is OpenAI's path, but a Project works well for a voice file. It holds your instructions and files, and you can share it.

Will my team still have access after the move? Not on its own. A moved plugin starts private. Share it again and check that people can use it.

I use someone else's GPT. What do I do? You cannot move it yourself. Check the notice on the GPT and ask its creator about a replacement.

Can I use the same file in Claude? Yes. Plain text rules work in both. Just the place you load them changes. See my guide to turning brand guidelines into a Claude skill.

By Vedran Obradović, Founder & Branding Specialist at Vizura Studio® in Zagreb. 250+ brands in 8 years. Updated 1 November 2026.

• OpenAI: custom GPT retirement and migration FAQ
• OpenAI: Projects in ChatGPT