diff --git a/spack_repo/eic/packages/root/cling-cmake-external-llvm-include-order.patch b/spack_repo/eic/packages/root/cling-cmake-external-llvm-include-order.patch
new file mode 100644
index 00000000..208adfd4
--- /dev/null
+++ b/spack_repo/eic/packages/root/cling-cmake-external-llvm-include-order.patch
@@ -0,0 +1,15 @@
+--- a/interpreter/cling/CMakeLists.txt
++++ b/interpreter/cling/CMakeLists.txt
+@@ -284,7 +284,11 @@ endmacro()
+ endif()
+ endmacro()
+ 
+-include_directories(BEFORE SYSTEM ${LLVM_INCLUDE_DIRS} ${CLANG_INCLUDE_DIRS})
++if(builtin_llvm)
++  include_directories(BEFORE SYSTEM ${LLVM_INCLUDE_DIRS} ${CLANG_INCLUDE_DIRS})
++else()
++  include_directories(SYSTEM ${LLVM_INCLUDE_DIRS} ${CLANG_INCLUDE_DIRS})
++endif()
+ 
+ macro(add_cling_library name)
+   cmake_parse_arguments(ARG
diff --git a/spack_repo/eic/packages/root/package.py b/spack_repo/eic/packages/root/package.py
index b0ecca23..118ae0c0 100644
--- a/spack_repo/eic/packages/root/package.py
+++ b/spack_repo/eic/packages/root/package.py
@@ -13,6 +13,13 @@ class Root(BuiltinRoot):
     version("6.32.12", sha256="2e41968aeb0406ee31c30af9c046143099b251846e0839cb04f4e960c7893e19")
     version("6.32.10", sha256="5a896804ec153685e8561adaa4e546b708139c484280aa6713a0a178f5b7f98b")
 
+    # [cling] Guard BEFORE in include_directories for external LLVM to avoid
+    # cxxabi.h conflict between LLVM libc++abi and GCC runtime headers
+    patch(
+        "cling-cmake-external-llvm-include-order.patch",
+        sha256="f81e01aff35141cbbf1f34864c87dc570b410425a3bcc19b4ce53e6c1de78132",
+        when="@6.36: ~builtin_llvm",
+    )
     # [metacling] Add missing lock to TCling::Evaluate
     patch(
         "https://github.com/root-project/root/pull/18943.patch?full_index=1",