To be sure I upgraded both softwares :
emacs-version 29.0.50 notmuch 0.34.2+35~ged03bab Maybe my first mail was a bit confuse ? To reproduce the issue : 1. In the *server* buffer, use `gnus-group-read-ephemeral-search-group' with the query "from:j...@gnu.org" 2. The first search succeed ; *in the ephemeral search buffer*, now use `gnus-summary-refer-thread' on an article. I get: (wrong-type-argument listp "")