Gemini Shifts from Gems to Skills, While OpenAI Phases Out Custom GPTs for Enterprise Users
The AI agent skills marketplace sees significant platform shifts this week, with Google evolving its custom instructions and OpenAI initiating a GPT retirement.
New here? The 60-second primer
Skills are packaged expertise you install into an AI assistant: Claude Code has skills and plugins (from Anthropic's directory and open git marketplaces), ChatGPT has custom GPTs (the GPT Store), and Google's Gemini has Gems (shareable custom experts). Every rank below comes from captured data — official install counts, GitHub star growth, and the GPT Store's own trending list — not from opinion.
The week
This week brought notable structural changes to how users customize AI agents. Google announced that its Gemini Gems will transition to "Skills" starting November 17, 2026, with existing Gems automatically migrating.
The new Skills offer stackable functionality and easier in-chat access, replacing the previous Gems interface. Simultaneously, OpenAI began phasing out Custom GPTs, recommending a move to plugins.
New Custom GPT creation for Enterprise workspaces ended on September 25, 2026, with full retirement planned for December 11, 2026. This shift also highlighted security concerns, as a ClickFix campaign used malicious Custom GPTs to trick users into executing PowerShell commands, leading to OpenAI taking down compromised instances.
In the Claude ecosystem, Anthropic released a broad reliability and UX update for Claude Code around October 4, 2026, enhancing recovery flows and plugin handling. The Claude Marketplace also launched on September 23rd, featuring over 2,000 connectors and plugins.
Pattern watch
A clear pattern of platform evolution and consolidation is visible this week. Both Google and OpenAI are streamlining their custom AI instruction offerings, moving from discrete "Gems" and "Custom GPTs" towards more integrated "Skills" and "plugins." This indicates a push towards more robust, developer-centric, and potentially more secure methods of extending AI capabilities, as highlighted by the security incidents involving malicious Custom GPTs. The shift also suggests a desire for greater interoperability and stackable functionality within their respective ecosystems.
Try this week
With Anthropic's Claude Marketplace now live, a practical step this week is to explore its plugin offerings. You can install a Claude plugin by accessing the "Customize" menu in Claude's left sidebar, navigating to the "Plugins" tab, and selecting from the "Discover" options, then clicking "Add."
Reporting + analyst voices: grounded via Google Search at publish time.