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Guide · Custom GPT migration

Custom GPT to plugin

What OpenAI’s migration moves into a plugin, what it leaves behind, and how to rebuild Actions so the plugin still does the job. Updated 5 Oct 2026.

Custom GPTs retire on every ChatGPT plan on 11 December 2026. OpenAI’s migration turns each one into a plugin, not a project or an agent. A ChatGPT plugin is a set of skills, at most one MCP server, and an optional app interface, published as one listing that ChatGPT and Codex share. The Plugin Directory replaced the App Directory on 9 July 2026.

What moves, and what does not

In the GPTIn the pluginState
InstructionsA skill inside the pluginCarries over
Knowledge filesReference files for the skillCarries over
Connected appsApps in the pluginCarries over
Custom ActionsDo not transfer: rebuild as an MCP server or connectorAction needed
Conversations, starters, model choice, sharing settings and draftsDo not carry overCheck

The new plugin starts private. Conversations with the GPT, its conversation starters, its selected model, its sharing settings and any drafts stay behind.

Custom Actions are the work

Actions do not transfer. Every GPT whose value lived in its Actions needs them rebuilt as an MCP server or connector: each OpenAPI operation becomes a tool, sign-in moves to OAuth, and every tool declares whether it reads, writes or deletes. How an Action becomes an MCP tool walks through the mapping.

Step by step

  1. Inventory the GPT. Its instructions, knowledge files, Actions and their authentication, and the conversations it is used for.
  2. Instructions become a skill. Rewrite them as a skill whose description says when to use it, with the knowledge files as its references.
  3. Actions become an MCP server. One tool per operation, honest annotations, OAuth sign-in instead of a shared key.
  4. Write test cases. Requests the plugin should handle and requests it should leave alone, run on a test account.
  5. Go public if you need to. A public listing takes the normal plugin submission: verified identity, a domain challenge, test cases and a video.
  6. Check it still wins the requests the GPT served. A plugin among other plugins is chosen by an agent, not opened by name. Measure whether agents pick it.

Check your GPT, free

Paste the GPT’s configuration and its OpenAPI Action schema. The checker shows what breaks, then builds the plugin package with an MCP server that replaces every Action.

Check your GPT The retirement dates

Sources