diff --git a/Lts/CMakeLists.txt b/Lts/CMakeLists.txt
index f75cff26c..b6b350b04 100644
--- a/Lts/CMakeLists.txt
+++ b/Lts/CMakeLists.txt
@@ -7,19 +7,24 @@
 cmake_minimum_required(VERSION 3.16)
 project(LtsPlaceholder)
 SET(DOXYGEN_OUT_DIR ${CMAKE_CURRENT_BINARY_DIR}/doxygen_Lts)
-ADD_DOXYGEN_TARGET(Lts ${CMAKE_SOURCE_DIR}/doxygen/DoxyfileLts.in ${CMAKE_BINARY_DIR}/DoxyfileLts
-                           ${CMAKE_SOURCE_DIR}/doxygen/rheinmetall_defence_logo.jpg
-                                                      ${DOXYGEN_OUT_DIR})
+if (EXISTS "${CMAKE_SOURCE_DIR}/doxygen/DoxyfileLts.in")
+  ADD_DOXYGEN_TARGET(Lts ${CMAKE_SOURCE_DIR}/doxygen/DoxyfileLts.in ${CMAKE_BINARY_DIR}/DoxyfileLts
+                             ${CMAKE_SOURCE_DIR}/doxygen/rheinmetall_defence_logo.jpg
+                                                        ${DOXYGEN_OUT_DIR})
+else()
+  message(WARNING "Doxygen config ${CMAKE_SOURCE_DIR}/doxygen/DoxyfileLts.in not found; skipping ADD_DOXYGEN_TARGET(Lts)")
+endif()
 
-ADD_SUBDIRECTORY(Tools)
-ADD_SUBDIRECTORY(Application)
-ADD_SUBDIRECTORY(Common)
-ADD_SUBDIRECTORY(DDS)
-ADD_SUBDIRECTORY(Plugins)
-ADD_SUBDIRECTORY(Projects)
-ADD_SUBDIRECTORY(Proxies)
-ADD_SUBDIRECTORY(Services)
-ADD_SUBDIRECTORY(Viewer)
+# Add only existing subdirectories to allow partial checkouts / incremental migration
+set(LTS_SUBDIRS Tools Application Common DDS Plugins Projects Proxies Services Viewer)
+foreach(dir IN LISTS LTS_SUBDIRS)
+  if (EXISTS "${CMAKE_CURRENT_SOURCE_DIR}/${dir}")
+    ADD_SUBDIRECTORY(${dir})
+  else()
+    message(STATUS "Skipping missing Lts subdirectory: ${dir}")
+  endif()
+
+endforeach()
 
 IF (BUILD_TESTING)
   ADD_SUBDIRECTORY(Tests)
diff --git a/Lts/Common/CodeGen/CMakeLists.txt b/Lts/Common/CodeGen/CMakeLists.txt
index a08b3948c..efab5366d 100755
--- a/Lts/Common/CodeGen/CMakeLists.txt
+++ b/Lts/Common/CodeGen/CMakeLists.txt
@@ -4,7 +4,7 @@
 # $Author$
 #
 
-FIND_PACKAGE(RTI REQUIRED)
+FIND_PACKAGE(RTI)
 FIND_PACKAGE(Grantlee5 REQUIRED)
 
 NGL_ADD_LIBRARY(ALL codegen_base SHARED
@@ -27,12 +27,20 @@ NGL_TARGET_LINK_LIBRARIES(codegen_base
 NGL_TARGET_INCLUDE_DIRECTORIES(codegen_base
   PUBLIC
     ${CMAKE_CURRENT_SOURCE_DIR}/../
-    $<TARGET_PROPERTY:RTI::nddscpp2,INTERFACE_INCLUDE_DIRECTORIES>
-)
-NGL_TARGET_COMPILE_DEFINITIONS(codegen_base
-  PUBLIC
-    $<TARGET_PROPERTY:RTI::nddscpp2,INTERFACE_COMPILE_DEFINITIONS>
 )
+# If RTI target is available, propagate its include dirs/compile defs
+if (TARGET RTI::nddscpp2)
+  NGL_TARGET_INCLUDE_DIRECTORIES(codegen_base
+    PUBLIC
+      $<TARGET_PROPERTY:RTI::nddscpp2,INTERFACE_INCLUDE_DIRECTORIES>
+  )
+  NGL_TARGET_COMPILE_DEFINITIONS(codegen_base
+    PUBLIC
+      $<TARGET_PROPERTY:RTI::nddscpp2,INTERFACE_COMPILE_DEFINITIONS>
+  )
+else()
+  message(STATUS "RTI not found; building codegen_base without RTI include/compile definitions")
+endif()
 NGL_INSTALL_TARGET(codegen_base)
 
 NGL_ADD_LIBRARY(ALL codegen_grantlee STATIC