gist query parameter is being removed from a permalink

[heaths]

A colleague shared a permalink, but when I navigated to it the gist query parameter was removed, and I was shown a blank document but, oddly, progress in the right pane:

I found #884 that reported this behavior fixed, but that was closed so long ago I figured I'd open a new issue.

E.g., https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=6976bb9dceb45b9191e9002c000422fe