ChatGPT Apps are the Apple move.

We're moving from tools that return outputs to tools that ship experiences. Once a tool can bring its own UI, the host is no longer just a chat window. It becomes an operating system for little applications.

You can think of @modelcontextprotocol/ext-apps as a way to turn "a tool result" into "a tool result plus an interactive micro-app UI" that renders inline inside a host. In MCP Apps, the UI is not generated by the model. It is a versioned HTML/JS artifact that the server advertises and the host renders in a sandboxed iframe.

If you control the host, you control distribution, policy, identity, and economics. You get an app store, a runtime, and a default surface area.

ChatGPT is trying to incentivize developers to "build on ChatGPT" – they want to be the Apple here.

Anthropic's MCP UI and MCP apps are a counter-move. They separate the app from the host. Same tool, same UI, many clients. The bet is that developers should not have to choose a single company's interface layer to reach users.