diff --git a/qt6-after/qt6-migrated-legatus/Lts/CMakeLists.txt b/qt6-after/qt6-migrated-legatus/Lts/CMakeLists.txt
index 78e512c74..5e97296c8 100644
--- a/qt6-after/qt6-migrated-legatus/Lts/CMakeLists.txt
+++ b/qt6-after/qt6-migrated-legatus/Lts/CMakeLists.txt
@@ -17,13 +17,20 @@ endif()
 
 # Add only existing subdirectories to allow partial checkouts / incremental migration
 if(RELEASE_BUILD)
-  # For first release: only build Lts/Common (excludes Tools, Application, DDS, Services, Proxies, Plugins, Viewer, Projects)
-  message(STATUS "RELEASE_BUILD=ON: Building only Lts/Common")
+  # For first release: only build Lts/Common and Lts/Proxies/TrainingAreaBase (tabTelegrams library)
+  # Excludes: Tools, Application, DDS, Services, most of Proxies, Plugins, Viewer, Projects
+  message(STATUS "RELEASE_BUILD=ON: Building Lts/Common and Lts/Proxies/TrainingAreaBase")
   if (EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/Common")
     NGL_ADD_SUBDIR_GUARDED(Common)
   else()
     message(STATUS "Skipping missing Lts subdirectory: Common")
   endif()
+  # TrainingAreaBase provides tabTelegrams library needed by TetraIF/CoPrtCnv
+  if (EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/Proxies/TrainingAreaBase")
+    NGL_ADD_SUBDIR_GUARDED(Proxies/TrainingAreaBase)
+  else()
+    message(STATUS "Skipping missing Lts subdirectory: Proxies/TrainingAreaBase")
+  endif()
 else()
   set(LTS_SUBDIRS Tools Application DDS Common Services Proxies Plugins Viewer Projects)
   foreach(dir IN LISTS LTS_SUBDIRS)