The debugger has a pause button in the top left. Clicking it does nothing.

Here’s the rendering of the button:

https://github.com/elm/browser/blob/1.0.2/src/Debugger/Main.elm#L689-L694

It uses if playing to switch between a pause and play icon. But the button always has onClick Resume. And when handling Resume it explicitly does nothing when model.state is already Running:

https://github.com/elm/browser/blob/1.0.2/src/Debugger/Main.elm#L237-L249

The workaround is to drag the slider to the left (causing the app to be paused), and then all the way to the right (to stay at the latest message).