Can't reproduce, with or without experimentalWorkspaceModule. Either way I don't think it's related to #36077. A log might help, but given how opaque the imports code is, I'm not sure :-/

Weird, can't repro in cache anymore because a honnef.co cache package is now outranking it.
Here's a log with source: https://gist.github.com/stamblerre/38f1589eec5c8a5758301835b125f7e3.
Sorry it's really unedited, so it may not be super useful.

The log doesn't include a completion request, so I'm not sure what I'm supposed to be looking at?

I must've messed it up when I was trying to truncate it. Just updated it.
The easiest thing will probably be to try reproducing yourself. Open up golang.org/x/tools/internal/lsp/source/rename_check.go, and in the first function, type source., and accept whatever the first completion is. This will add an import for golang.org/x/tools/internal/lsp/source.

I still can't reproduce the problem, but the logs were enough. These are typed completions from gopls, not the imports package, and it looks like I completely forgot to add a circular import check to those.