Localization in Pega Infinity '25 remains same on the surface but in fact the mechanics has changed fundamentaly under the hood...
Constellation App Static service is no longer required and Rule-UI-Localization is unified in a single instance per application...
And there are unexpected behaviors...This article aims to share some of those known issues and work-around...

known issue 1: App-specific language pack generation fails if "Re-translate all layers" checked.
work-around 1: Do not check "Re-translate all layers" when generating language pack.
solution 1: request (from my support portal) and install HFIX-C4425 into your 25.1.1 env.

known issue 2: OOTB translation texts are not displaying on the screen.
work-around 2: Remove all rows (from exported excel) which do not contain app-specific class names in the "Rule Key" column...make sure there are no rows has blank value in "Translated string" (column D)...if you want to override OOTB translations, then add them one by one in your excel.

known issue 3: Case type label is not translated in various places.
work-around 3: Update Case type label in the target language if users do not expect other language.

known issue 4: Assignment label is not translated in the table.
work-around 4: Unknown

known issue 5: Case type name, Stage name, Flow Action name is not translated in the case history (BUG-965401)
work-around 5: Unknown

known issue 6: Work status is not translated in table view (BUG-965299)
work-around 6: Unknown

known issue 7: Field values(e.x. Work status) are not translated in Field History view
work-around 7: Unknown

known issue 8: App specific field labels are not translated in Insight views
work-around 8: Add translation text with rule-key:INSIGHTS