gnus-refer-thread-use-nnir

gnus-refer-thread-use-nnir is a variable defined in `gnus-sum.el'.
Its value is

nil

Documentation:
*Use nnir to search an entire server when referring threads. A
nil value will only search for thread-related articles in the
current group.

You can customize this variable.

This variable was introduced, or its default value was changed, in version 24.1 of Emacs.