diff --git a/interpreter/CMakeLists.txt b/interpreter/CMakeLists.txt
index 162235343e66c..52f8eb8439e4b 100644
--- a/interpreter/CMakeLists.txt
+++ b/interpreter/CMakeLists.txt
@@ -2,6 +2,10 @@
 set(CMAKE_MODULE_PATH "")
 
 #--- Check if we need to build llvm and clang ------------------------------------------------------
+if (builtin_llvm AND NOT builtin_clang)
+  message(FATAL_ERROR "Cannot enable builtin LLVM, but provide external Clang")
+endif()
+
 if (NOT builtin_clang)
   message(WARNING "Due to ROOT-specific patches you need a special version of clang. You cannot use vanilla clang.")
 endif()
@@ -52,7 +56,7 @@ set(LLVM_FORCE_USE_OLD_TOOLCHAIN ON CACHE BOOL "")
 set(CMAKE_DISABLE_FIND_PACKAGE_CUDA ON)
 
 # will be set again in case NOT builtin_llvm
-set(LLVM_DIR "${CMAKE_BINARY_DIR}/interpreter/llvm-project/llvm")
+set(LLVM_DIR "${CMAKE_CURRENT_BINARY_DIR}/llvm-project/llvm")
 if (clad)
   set(CLING_BUILD_PLUGINS ON)
 endif()
@@ -235,8 +239,8 @@ if(builtin_llvm)
     unset(CMAKE_MESSAGE_LOG_LEVEL)
   endif()
 
-  set(LLVM_INCLUDE_DIRS ${CMAKE_SOURCE_DIR}/interpreter/llvm-project/llvm/include
-    ${CMAKE_BINARY_DIR}/interpreter/llvm-project/llvm/include
+  set(LLVM_INCLUDE_DIRS ${CMAKE_CURRENT_SOURCE_DIR}/llvm-project/llvm/include
+    ${CMAKE_CURRENT_BINARY_DIR}/llvm-project/llvm/include
     CACHE STRING "LLVM include directories."
     )
   list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/llvm-project/llvm/cmake/modules")
@@ -458,18 +462,17 @@ endif(builtin_llvm)
 
 if (builtin_clang)
   if (builtin_llvm)
-    # For builtin LLVM this is set in interpreter/llvm-project/llvm/CMakeLists.txt
-    set(Clang_DIR "${LLVM_BINARY_DIR}/tools/clang/")
+    set(CLANG_BINARY_DIR "${LLVM_BINARY_DIR}/tools/clang/")
   else()
-    set(Clang_DIR "${CMAKE_BINARY_DIR}/interpreter/llvm-project/clang/")
-    set(Clang_Config_ExtraPathHints "${Clang_DIR}cmake/modules/CMakeFiles")
+    set(CLANG_BINARY_DIR "${CMAKE_CURRENT_BINARY_DIR}/llvm-project/clang/")
   endif()
   set(CLANG_INCLUDE_DIRS
-    ${CMAKE_SOURCE_DIR}/interpreter/llvm-project/clang/include
-    ${Clang_DIR}/include
+    ${CMAKE_CURRENT_SOURCE_DIR}/llvm-project/clang/include
+    ${CLANG_BINARY_DIR}/include
     CACHE STRING "Clang include directories.")
+  set(CLANG_CMAKE_DIR "${CMAKE_BINARY_DIR}/lib/cmake/clang/")
 else()
-  set(Clang_DIR "${LLVM_BINARY_DIR}/lib/cmake/clang/")
+  set(CLANG_CMAKE_DIR "${LLVM_BINARY_DIR}/lib/cmake/clang/")
 endif()
 
 # Reset the compiler flags after compiling LLVM and Clang
@@ -517,7 +520,7 @@ if (builtin_cling)
   add_subdirectory(cling EXCLUDE_FROM_ALL)
   add_dependencies(CLING ${CLING_LIBRARIES})
 
-  set(CLING_INCLUDE_DIRS ${CMAKE_SOURCE_DIR}/interpreter/cling/include CACHE STRING "")
+  set(CLING_INCLUDE_DIRS ${CMAKE_CURRENT_SOURCE_DIR}/cling/include CACHE STRING "")
 
 
 
diff --git a/interpreter/cling/CMakeLists.txt b/interpreter/cling/CMakeLists.txt
index 710de930b4ac4..c15ae096a30a6 100644
--- a/interpreter/cling/CMakeLists.txt
+++ b/interpreter/cling/CMakeLists.txt
@@ -23,7 +23,7 @@ if( CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR )
 
   find_package(Clang REQUIRED CONFIG)
   message(STATUS "Found supported version: Clang ${CLANG_PACKAGE_VERSION}")
-  message(STATUS "Using ClangConfig.cmake in: ${Clang_DIR}")
+  message(STATUS "Using ClangConfig.cmake in: ${CLANG_CMAKE_DIR}")
 
   find_program(LLVM_TABLEGEN_EXE "llvm-tblgen" ${LLVM_TOOLS_BINARY_DIR}
     NO_DEFAULT_PATH)
@@ -111,6 +111,7 @@ else()
     list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_PATH}")
     include(${LLVMCONFIG_FILE})
   endif()
+  set(CLANG_CMAKE_DIR "${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/clang")
   if (NOT CLANG_INCLUDE_DIRS)
     set (CLANG_INCLUDE_DIRS "${LLVM_MAIN_SRC_DIR}/tools/clang/include")
     if (NOT EXISTS ${CLANG_INCLUDE_DIRS})
diff --git a/interpreter/cling/cmake/modules/CMakeLists.txt b/interpreter/cling/cmake/modules/CMakeLists.txt
index e28220db6a06b..4de71a0994783 100644
--- a/interpreter/cling/cmake/modules/CMakeLists.txt
+++ b/interpreter/cling/cmake/modules/CMakeLists.txt
@@ -13,7 +13,7 @@ export(TARGETS ${CLING_EXPORTS} FILE ${cling_cmake_builddir}/ClingTargets.cmake)
 
 # Generate ClingConfig.cmake for the build tree.
 set(CLING_CONFIG_CMAKE_DIR "${cling_cmake_builddir}")
-set(CLING_CONFIG_CLANG_CMAKE_DIR "${clang_cmake_builddir}")
+set(CLING_CONFIG_CLANG_CMAKE_DIR "${CLANG_CMAKE_DIR}")
 set(CLING_CONFIG_EXPORTS_FILE "${cling_cmake_builddir}/ClingTargets.cmake")
 set(CLING_CONFIG_INCLUDE_DIRS
   "${CLING_SOURCE_DIR}/include"
diff --git a/interpreter/cling/tools/plugins/clad/CMakeLists.txt b/interpreter/cling/tools/plugins/clad/CMakeLists.txt
index 3c70d00a10f3b..6c5c145da40f9 100644
--- a/interpreter/cling/tools/plugins/clad/CMakeLists.txt
+++ b/interpreter/cling/tools/plugins/clad/CMakeLists.txt
@@ -46,10 +46,6 @@ if (CMAKE_CXX_STANDARD)
   list(APPEND _clad_extra_cmake_args -DCMAKE_CXX_STANDARD=${CMAKE_CXX_STANDARD})
 endif(CMAKE_CXX_STANDARD)
 
-if (Clang_DIR)
-  list(APPEND _clad_extra_cmake_args -DClang_DIR=${Clang_DIR} -DClang_CONFIG_EXTRA_PATH_HINTS=${Clang_Config_ExtraPathHints})
-endif(Clang_DIR)
-
 if (LLVM_FORCE_USE_OLD_TOOLCHAIN)
   list(APPEND _clad_extra_cmake_args -DLLVM_FORCE_USE_OLD_TOOLCHAIN=${LLVM_FORCE_USE_OLD_TOOLCHAIN})
 endif(LLVM_FORCE_USE_OLD_TOOLCHAIN)
@@ -94,7 +90,7 @@ ExternalProject_Add(
              -DCMAKE_CXX_FLAGS=${CLAD_CXX_FLAGS}
              -DCMAKE_INSTALL_PREFIX=${clad_install_dir}/plugins
              -DLLVM_DIR=${LLVM_BINARY_DIR}
-             -DCLANG_INCLUDE_DIRS=${CLANG_INCLUDE_DIRS}
+             -DClang_DIR=${CLANG_CMAKE_DIR}
              ${_clad_extra_cmake_args}
   # FIXME
   # Building with 1 core is a temporary workaround for #16654 and has to be 
diff --git a/interpreter/llvm-project/clang/cmake/modules/CMakeLists.txt b/interpreter/llvm-project/clang/cmake/modules/CMakeLists.txt
index 9a3ffb0ee624a..d2d68121371bf 100644
--- a/interpreter/llvm-project/clang/cmake/modules/CMakeLists.txt
+++ b/interpreter/llvm-project/clang/cmake/modules/CMakeLists.txt
@@ -9,7 +9,7 @@ include(FindPrefixFromConfig)
 set(CLANG_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/clang" CACHE STRING
   "Path for CMake subdirectory for Clang (defaults to '${CMAKE_INSTALL_PACKAGEDIR}/clang')")
 # CMAKE_INSTALL_PACKAGEDIR might be absolute, so don't reuse below.
-set(clang_cmake_builddir "${CLANG_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/clang")
+set(clang_cmake_builddir "${CMAKE_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/clang")
 
 # Keep this in sync with llvm/cmake/CMakeLists.txt!
 set(LLVM_INSTALL_PACKAGE_DIR "${CMAKE_INSTALL_PACKAGEDIR}/llvm" CACHE STRING
diff --git a/interpreter/llvm-project/llvm-project.tag b/interpreter/llvm-project/llvm-project.tag
index e06c311eb1fb0..b6c5cd7502d0a 100644
--- a/interpreter/llvm-project/llvm-project.tag
+++ b/interpreter/llvm-project/llvm-project.tag
@@ -1 +1 @@
-ROOT-llvm18-20250117-01
\ No newline at end of file
+ROOT-llvm18-20250121-01