Matthew Lear <matt@bubblegen.co.uk> writes:

> (setq notmuch-mua-compose-in 'new-frame)
> (setq notmuch-multipart/alternative-discouraged '("text/plain"))


Using devel/try-emacs-mua in the source tree, only these last two lines
are needed. But yes agree, after discouraging text/plain, multipart
messages can also duplicate this bug

> ...and load it using 'emacs-25 -q --load ~/.emacs.d/tiny-init.el',
> searching for any mimetype:text/html and replying to it triggers the bug
> for me.
>
> Commenting out the setting of notmuch-mua-compose-in is enough to
> prevent the problem from occurring.
> Cheers,
> --  Matt