OpenAI adds ChatGPT plugin extensions and MCP event automations

OpenAI’s September 29 DevDay recap announced plugin extensions and MCP Events for developers building connected experiences in ChatGPT. The current developer documentation describes how extensions add user-interface surfaces and how an MCP server can expose event subscriptions for supported automations.

Build plugin interfaces inside ChatGPT

OpenAI MCP Extensions let a plugin connect to ChatGPT surfaces beyond a tool call. The extension documentation describes sidebar apps, conversation panels, plugin settings, file viewers and editors, display modes, deep links, context sharing, composer mentions, rich forms, and onboarding.

For example, a plugin can open an app beside a conversation or provide an interface for a supported file type. Composer mentions are available only in the ChatGPT desktop app. The documentation says plugin extensions on the web are coming soon to ChatGPT Free and Go users; check current rollout details for other surfaces before planning an install.

Start automations from MCP events

MCP Events lets ChatGPT subscribe to updates from an MCP server, such as new messages, content changes, or status updates, and respond according to the user’s instructions. A server advertises event support and implements events/list, events/subscribe, and events/unsubscribe; ChatGPT then delivers matching events to a callback URL using webhooks.

The integration requires MCP 2.0 protocol version 2026-07-28, persistent subscription storage, and outbound HTTPS access. The documentation lists availability in Work chats on ChatGPT web, Work chats in the desktop app with Cloud selected, and with dots. It supports webhook delivery and callback verification, not polling or streaming.

Treat an event subscription as an authenticated integration, not as a generic notification hook. The server must authorize the user, validate subscription filters and callback destinations, and verify signed deliveries before acting on an event.

Sources

• OpenAI — “DevDay 2026 Recap” (September 29, 2026): https://openai.com/index/devday-2026-recap
• OpenAI Developers — “Plugin Extensions”: https://developers.openai.com/plugins/build/extensions
• OpenAI Developers — “MCP Events”: https://developers.openai.com/plugins/build/mcp-events