ChatGPT plugin extensions: put your plugin in the sidebar, @ mentions, and file viewers (mentions are desktop-only)

#What changed

OpenAI Developers announced plugin extensions on Oct 7, 2026, with a video walkthrough by Corey Ching. Per OpenAI's Plugin Extensions docs, a plugin can now hook into ChatGPT surfaces beyond the chat reply: a sidebar entry that opens the app fullscreen, a side panel beside a conversation, product settings inside ChatGPT, file viewers and editors for chosen file types, composer @ mentions, deep links, richer forms with image choices, and an onboarding skill. OpenAI also says it rebuilt the plugin submission flow to give clearer review feedback. It names Adobe, Canva, Figma, Shopify, Instacart, Atlassian, tldraw and MagicPath as early adopters.

#Who is affected

Developers who build ChatGPT plugins (MCP servers with an MCP Apps UI). Users only see the new entry points once a plugin adopts them. Composer mentions work only in the ChatGPT desktop app, and extensions on the web are still coming to Free and Go users. Existing plugins keep working without changes.

#What to do now

• Install OpenAI's Bits & Bolts sample plugin first to see every extension in action.
• Pick the one surface that fits how people already use your product: a sidebar app for a workspace-style tool, a file viewer if you own a file format, or mentions if users need to point ChatGPT at a specific item.
• Declare it in your tool's _meta under openai/ui entrypoints: global for the sidebar, thread for the conversation side panel, or file with a list of extensions (for example stl) for a viewer. The TypeScript and Python SDKs are in the openai/mcp-extensions repo.
• If you use rich forms, note that OpenAI-registered MCP servers need multi-round-trip requests.
• Test mentions in the desktop app, since the web doesn't show them, then submit through the rebuilt submission flow.

#What is not confirmed

OpenAI hasn't given a date for web extensions on Free and Go. The clearer review feedback is OpenAI's own description; we haven't run a plugin through the new flow. The partner list comes from OpenAI's post, and not every partner feature may be live on every account.