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Field Guide · level 3 · Power features

What happened to custom GPTs and Gems, and what replaces them?

Know the dates. Split each old assistant into its new homes, and test it.

5 min · try it 10 min · as of Oct 2026
Bring this to your team · AI implementationMove and test your team's custom GPTs and Gems before the dates. Get in touch
01

Your custom GPT has a date

Custom GPTs retire on 11 Dec 2026. Personal Gems become skills from November 2026.

02

What was in the box

A custom GPT or a Gem was saved instructions plus files. Some also had actions in other apps.

03

Each part gets a new home

Files and rules for one job: a project. A how-to used in many chats: a skill. Actions in another app: a connector.

04

Each assistant moves it differently

In Claude, you rebuild by hand. ChatGPT: Migrate to plugin, but custom actions stay behind. Gemini turns Gems into skills as they retire; review each.

05

Test it on three requests

Save three requests you know, with the old answers. Ask the new one the same three. Fix the instructions until they match.

06

Move it before the date

Testing takes time, and custom actions need rebuilding. Then tell its users, share the new one, and name an owner.

Try it · 10 minutes · on your own work

Rebuild one as a skill

Made-up instructions only.

  1. List the GPTs or Gems you use, and who made them.3 min
  2. Sort each part: project, skill or connector.2 min
  3. Rebuild one as a skill. Skip Migrate to plugin for now: it locks the original.4 min
  4. Test one familiar request.1 min

A skill made from a GPT's instructions (made up for this lesson)

---
name: supplier-replies
description: Drafts a first reply to a supplier in our tone. Use when I paste a supplier's email. Drafts only.
---
1. Read the email I paste. Use only what it says.
2. Reply in our tone: warm, short, no promises on dates.
3. Missing something? Ask me. Do not guess.
4. Draft only. Never send.

Good looks likeThe same requests get answers as good as the old ones.

In your assistant · as of Oct 2026 · Claude, ChatGPT, Gemini

Move one, in your assistant

Menus move often. Missing something? A rollout, your plan, your country or an admin setting may be why.

  • CheckYour company approves the tool
  • CheckThree requests saved
  • CheckAn owner named

My pickClaude first, ChatGPT second, Gemini third. I'd rebuild in Claude: a project for the files, a skill for the how-to, and the same SKILL.md then works in the other two. Made the GPT yourself? Migrate to plugin does the moving. Your company's approved tool comes before my pick.

Read a shared skill before you turn it on: Anthropic doesn't review them. Keep passwords and customer details out of instructions.

Claude

Nothing retires. Rebuild it as a project and a skill.

Files

A project for one job: add its files and instructions (the lesson on projects).

Skill
CustomizethenSkillsthen+thenCreate skill

Upload the skill's .zip, then turn it on.

Test
/

Type / and pick the skill.

Projects on every plan (Free: up to five). Skills on every plan, including Free, say Anthropic's help centre and plans page (its skills docs still list Pro and up), with Code execution and file creation on.

ChatGPT

Custom GPTs move to plugins.

First

Publish the edits you need. Drafts don't move.

Move
My GPTsthenCreated by methenMigrate to plugin

Instructions become a skill; files come along. Custom actions don't: replace them with an app.

Test
@

Test it with @, then share it: it starts private.

Every plan; the button appears when migration reaches your account. Only its creator, or an Enterprise workspace admin, can migrate a GPT, and migrating makes the original read-only. Enterprise: no new custom GPTs from 26 Oct 2026 (planned); with an approved deferral, they retire on 11 Feb 2027.

Gemini

Google turns Gems into skills when they go away. Review each one.

Save
SidebarthenGemsthenEdit

On gemini.google.com. Download each file under Knowledge.

Move
CustomizethenSkillsthenCreatethenCreate manually

Paste the Gem's name, description and instructions, then click Create.

Files

Download the skill's .zip, put its SKILL.md and your files in a folder named like the skill, then Replace skill.

18 or over, Keep Activity on; personal accounts now, and Google's post of 13 Oct 2026 says work and school accounts by mid-November. No Word or Excel files. Work and school: Gems move to Settings on 17 Nov 2026 and stay usable; they stop on 1 Mar 2027 (work) and 1 Jun 2027 (school) at the earliest.

Quick check · three questions

Did it stick?

  1. 1When do custom GPTs retire, with no approved deferral?

    The answer: B That's OpenAI's date. 26 Oct is only the planned end of new GPTs on Enterprise, and 11 Feb 2027 is for Enterprise workspaces with an approved deferral.

  2. 2An old Gem held one monthly report's files and rules. Where does that go in Claude?

    The answer: C One job's files and rules belong in a project.

  3. 3Your team uses a colleague's custom GPT. Who can migrate it?

    The answer: A OpenAI says permission to use someone else's GPT doesn't give you permission to migrate it.
0 of 3 answered
A made-up exampleSide note
A supplier-replies GPT becomes a tone skill, a project holding the product sheet, and an email connector.
Dates can moveSide note
OpenAI says its dates are subject to change, and Google's 2027 dates are the earliest. Follow the notice on your own account.
One giant skillSide note
Three jobs make three skills, each with a description that says when it applies.
Sources, checked 16 Oct 2026Source

Product details as of Oct 2026, each checked on the vendor's own page on 16 Oct 2026. Recheck on 26 Oct, mid-November, 17 Nov and 11 Dec 2026. The examples in the pictures are made up for this lesson.

Free kitThe Agent PlaybookBring this to your teamAI implementation · Get in touchBack to level 3, Power features

Move it early. Test it on what you know.

Next lesson · 15 minWhat is a skill, and why is it replacing the prompt pack?