Thank you, have updated and it works.

Probably better to set the last boolean parameter double_encode to false:

I think it was introduced in https://github.com/wikimedia/mediawiki-extensions-PageForms/commit/1b67fc6ced342237efe227af2ccab9a93272c88a which was related to T259433

I've tried this diff from the github mirror which seems to solve the issue. I'm not sure how to work on gerrit or if there is a gitlab transition planned for extension repos.

diff --git a/includes/PF_ValuesUtils.php b/includes/PF_ValuesUtils.php
index a372733..932b70d 100644
--- a/includes/PF_ValuesUtils.php
+++ b/includes/PF_ValuesUtils.php
@@ -425,7 +425,7 @@ class PFValuesUtils {
        }

Thank you Yaron. I've now used the #arraymap parser function to re-add the the namespace for my use case.

Is the differing behavior then on purpose in regards to the other autocompletes, like category and (SMW) property (I Did not check the behaviour here)? I.E if you are autocompleting on a category, you most likely want the namespace prepended, but if you autocomplete on namespace, there are other use cases?

Thank you @Aklapper, added to description.

Also applies to values from namespace