diff --git a/cmake/modules/RootTestDriver.cmake b/cmake/modules/RootTestDriver.cmake
index 0a549e688ff0c..4579acca8b1e5 100644
--- a/cmake/modules/RootTestDriver.cmake
+++ b/cmake/modules/RootTestDriver.cmake
@@ -72,12 +72,33 @@ endif()
 
 #---Set environment --------------------------------------------------------------------------------
 if(ENV)
-  string(REPLACE "#" ";" _env ${ENV})
+  # CMake treats ';' as a list separator. Since ENV values may legitimately
+  # contain semicolons (e.g. PATH-like variables), we must escape them here
+  # so they survive the upcoming list expansion in `foreach()`.
+  string(REPLACE ";" "\\;" _env "${ENV}")
+
+  # Deserialize the ENV string into a CMake list.
+  # This is the inverse operation of ROOT_ADD_TEST, which serializes the list
+  # by joining elements with '#'.
+  string(REPLACE "#" ";" _env "${_env}")
+
   foreach(pair ${_env})
-    string(REGEX REPLACE "^([^=]+)=(.*)$" "\\1;\\2" pair ${pair})
+
+    # During list expansion, CMake has already consumed any previous '\;'
+    # escaping. Re-escape semicolons so the key=value split below treats the
+    # value as a single string.
+    string(REPLACE ";" "\\;" pair "${pair}")
+
+    # Split KEY=VALUE into a 2-element CMake list: [KEY;VALUE]
+    string(REGEX REPLACE "^([^=]+)=(.*)$" "\\1;\\2" pair "${pair}")
+
     list(GET pair 0 var)
     list(GET pair 1 val)
-    set(ENV{${var}} ${val})
+
+    # As before, quoting is important here so the semicolons are not
+    # interpreted as list separators.
+    set(ENV{${var}} "${val}")
+
     if(DBG)
       message(STATUS "testdriver[ENV]:${var}==>${val}")
     endif()
diff --git a/core/clingutils/src/TClingUtils.cxx b/core/clingutils/src/TClingUtils.cxx
index 3c49f56bdf5d0..c534f82b28245 100644
--- a/core/clingutils/src/TClingUtils.cxx
+++ b/core/clingutils/src/TClingUtils.cxx
@@ -5219,9 +5219,16 @@ void ROOT::TMetaUtils::SetPathsForRelocatability(std::vector<std::string>& cling
 
    if (!envInclPath)
       return;
+
+#ifdef _WIN32
+   constexpr char kPathSep = ';';
+#else
+   constexpr char kPathSep = ':';
+#endif
+
    std::istringstream envInclPathsStream(envInclPath);
    std::string inclPath;
-   while (std::getline(envInclPathsStream, inclPath, ':')) {
+   while (std::getline(envInclPathsStream, inclPath, kPathSep)) {
       // Can't use TSystem in here; re-implement TSystem::ExpandPathName().
       replaceEnvVars("ROOT_INCLUDE_PATH", inclPath);
       if (!inclPath.empty()) {
diff --git a/roottest/root/io/transient/base/CMakeLists.txt b/roottest/root/io/transient/base/CMakeLists.txt
index c15e2ea07a457..c59bacde1dfa2 100644
--- a/roottest/root/io/transient/base/CMakeLists.txt
+++ b/roottest/root/io/transient/base/CMakeLists.txt
@@ -30,8 +30,18 @@ else()
   set(outref_suffix "ZLIB")
 endif()
 
+set(root_includepaths
+    ${CMAKE_CURRENT_SOURCE_DIR}
+    ${DEFAULT_ROOT_INCLUDE_PATH}
+)
+cmake_path(CONVERT "${root_includepaths}" TO_NATIVE_PATH_LIST root_includepaths_native)
+# Like in tutorials/CMakeLists.txt, we use this generator expression to make
+# sure the semicolon in Windows path separators doesn't get used up for list
+# parsing at configuration time in ROOTTEST_ADD_TEST.
+string(REPLACE ";" "$<SEMICOLON>" root_includepaths_escaped "${root_includepaths_native}")
+
 ROOTTEST_ADD_TEST(hadd_autoload
                   COMMAND hadd -f data_merge.root data1.root data2.root
                   OUTREF hadd_autoload${outref_suffix}.ref
                   FIXTURES_REQUIRED root-io-transient-base-WriteFile-fixture
-                  ENVIRONMENT ROOT_INCLUDE_PATH=${CMAKE_CURRENT_SOURCE_DIR}:${DEFAULT_ROOT_INCLUDE_PATH})
+                  ENVIRONMENT ROOT_INCLUDE_PATH=${root_includepaths_escaped})
diff --git a/tutorials/CMakeLists.txt b/tutorials/CMakeLists.txt
index 53ceffd1e4d9a..4035dfdafc322 100644
--- a/tutorials/CMakeLists.txt
+++ b/tutorials/CMakeLists.txt
@@ -18,15 +18,15 @@ set(root_includepaths
 )
 cmake_path(CONVERT "${root_includepaths}" TO_NATIVE_PATH_LIST root_includepaths_native)
 
-# The environment argument gets serialized in ROOT_ADD_TEST for the
-# RootTestDriver, and then deserialized in the latter with multiple steps of
-# string parsing. We have to escape the semicolon excessively, because in every
-# parsing step we lose one semicolon. Also we use the SEMICOLON generator
-# expression, so at least we don't have to worry about escaping for the initial
-# configuration stage.
-# TODO: consider improving ROOT_ADD_TEST and RootTestDriver.cmake so this is not necessary.
-string(REPLACE ";" "\\\\\\\\$<SEMICOLON>" pythonpaths_escaped "${pythonpaths_native}")
-string(REPLACE ";" "\\\\\\\\$<SEMICOLON>" root_includepaths_escaped "${root_includepaths_native}")
+# Use the $<SEMICOLON> generator expression to defer semicolon expansion until
+# generator-expression evaluation. This avoids CMake interpreting literal ';'
+# as list separators during argument handling.
+#
+# ROOT_ADD_TEST performs multiple string-to-list conversions when serializing
+# the test command, which makes it unsafe to pass literal semicolons in
+# arguments until this behavior is fixed.
+string(REPLACE ";" "$<SEMICOLON>" pythonpaths_escaped "${pythonpaths_native}")
+string(REPLACE ";" "$<SEMICOLON>" root_includepaths_escaped "${root_includepaths_native}")
 
 # - Set the environment for the tutorials, which also contains some environment
 # variables related to limiting the number of threads used by NumPy and