diff --git a/lldb/cmake/modules/LLDBConfig.cmake b/lldb/cmake/modules/LLDBConfig.cmake
index a758261073ac5..93c8ffe4b7d8a 100644
--- a/lldb/cmake/modules/LLDBConfig.cmake
+++ b/lldb/cmake/modules/LLDBConfig.cmake
@@ -67,6 +67,8 @@ option(LLDB_SKIP_STRIP "Whether to skip stripping of binaries when installing ll
 option(LLDB_SKIP_DSYM "Whether to skip generating a dSYM when installing lldb." OFF)
 option(LLDB_ENFORCE_STRICT_TEST_REQUIREMENTS
   "Fail to configure if certain requirements are not met for testing." OFF)
+option(LLDB_TEST_USE_VENDOR_PACKAGES
+  "Use packages from lldb/third_party/Python/module instead of system deps." ON)
 
 set(LLDB_GLOBAL_INIT_DIRECTORY "" CACHE STRING
   "Path to the global lldbinit directory. Relative paths are resolved relative to the
diff --git a/lldb/test/API/lit.cfg.py b/lldb/test/API/lit.cfg.py
index 12675edc0fd3b..f9497b632fc50 100644
--- a/lldb/test/API/lit.cfg.py
+++ b/lldb/test/API/lit.cfg.py
@@ -309,3 +309,6 @@ def delete_module_cache(path):
 # Propagate XDG_CACHE_HOME
 if "XDG_CACHE_HOME" in os.environ:
     config.environment["XDG_CACHE_HOME"] = os.environ["XDG_CACHE_HOME"]
+
+if is_configured("use_vendor_packages"):
+    config.environment["LLDB_TEST_USE_VENDOR_PACKAGES"] = "1"
diff --git a/lldb/test/API/lit.site.cfg.py.in b/lldb/test/API/lit.site.cfg.py.in
index 053331dc4881f..c2602acd2ef85 100644
--- a/lldb/test/API/lit.site.cfg.py.in
+++ b/lldb/test/API/lit.site.cfg.py.in
@@ -38,6 +38,7 @@ config.libcxx_include_target_dir = "@LIBCXX_GENERATED_INCLUDE_TARGET_DIR@"
 # The API tests use their own module caches.
 config.lldb_module_cache = os.path.join("@LLDB_TEST_MODULE_CACHE_LLDB@", "lldb-api")
 config.clang_module_cache = os.path.join("@LLDB_TEST_MODULE_CACHE_CLANG@", "lldb-api")
+config.use_vendor_packages = @LLDB_TEST_USE_VENDOR_PACKAGES@
 
 # Plugins
 lldb_build_intel_pt = '@LLDB_BUILD_INTEL_PT@'
diff --git a/lldb/test/CMakeLists.txt b/lldb/test/CMakeLists.txt
index 1aa8843b6a2e7..d8cbb24b6c9b8 100644
--- a/lldb/test/CMakeLists.txt
+++ b/lldb/test/CMakeLists.txt
@@ -26,6 +26,20 @@ if(LLDB_ENFORCE_STRICT_TEST_REQUIREMENTS)
   endforeach()
 endif()
 
+# The "pexpect" package should come from the system environment, not from the
+# LLDB tree. However, we delay the deletion of it from the tree in case
+# users/buildbots don't have the package yet and need some time to install it.
+if (NOT LLDB_TEST_USE_VENDOR_PACKAGES)
+  lldb_find_python_module(pexpect)
+  if (NOT PY_pexpect_FOUND)
+    message(FATAL_ERROR
+      "Python module 'pexpect' not found. Please install it via pip or via "
+      "your operating system's package manager. For a temporary workaround, "
+      "use a version from the LLDB tree with "
+      "`LLDB_TEST_USE_VENDOR_PACKAGES=ON`")
+  endif()
+endif()
+
 if(LLDB_BUILT_STANDALONE)
   # In order to run check-lldb-* we need the correct map_config directives in
   # llvm-lit. Because this is a standalone build, LLVM doesn't know about LLDB,
@@ -240,7 +254,8 @@ llvm_canonicalize_cmake_booleans(
   LLDB_HAS_LIBCXX
   LLDB_TOOL_LLDB_SERVER_BUILD
   LLDB_USE_SYSTEM_DEBUGSERVER
-  LLDB_IS_64_BITS)
+  LLDB_IS_64_BITS
+  LLDB_TEST_USE_VENDOR_PACKAGES)
 
 # Configure the individual test suites.
 add_subdirectory(API)
diff --git a/lldb/use_lldb_suite_root.py b/lldb/use_lldb_suite_root.py
index fd42f63a3c7f3..b8f8acf5dd94a 100644
--- a/lldb/use_lldb_suite_root.py
+++ b/lldb/use_lldb_suite_root.py
@@ -21,5 +21,7 @@ def add_lldbsuite_packages_dir(lldb_root):
 
 lldb_root = os.path.dirname(inspect.getfile(inspect.currentframe()))
 
-add_third_party_module_dirs(lldb_root)
+# Use environment variables to avoid plumbing flags, lit configs, etc.
+if os.getenv("LLDB_TEST_USE_VENDOR_PACKAGES"):
+    add_third_party_module_dirs(lldb_root)
 add_lldbsuite_packages_dir(lldb_root)
diff --git a/lldb/utils/lldb-dotest/CMakeLists.txt b/lldb/utils/lldb-dotest/CMakeLists.txt
index 09f41dbce421e..2ba40f009cc92 100644
--- a/lldb/utils/lldb-dotest/CMakeLists.txt
+++ b/lldb/utils/lldb-dotest/CMakeLists.txt
@@ -10,6 +10,7 @@ set(LLDB_LIBS_DIR "${LLVM_LIBRARY_OUTPUT_INTDIR}")
 llvm_canonicalize_cmake_booleans(
   LLDB_BUILD_INTEL_PT
   LLDB_HAS_LIBCXX
+  LLDB_TEST_USE_VENDOR_PACKAGES
 )
 
 if ("libcxx" IN_LIST LLVM_ENABLE_RUNTIMES)
diff --git a/lldb/utils/lldb-dotest/lldb-dotest.in b/lldb/utils/lldb-dotest/lldb-dotest.in
index 5cd49d253b993..9291f59b41982 100755
--- a/lldb/utils/lldb-dotest/lldb-dotest.in
+++ b/lldb/utils/lldb-dotest/lldb-dotest.in
@@ -1,4 +1,5 @@
 #!@Python3_EXECUTABLE@
+import os
 import subprocess
 import sys
 
@@ -17,8 +18,12 @@ has_libcxx = @LLDB_HAS_LIBCXX@
 libcxx_libs_dir = "@LIBCXX_LIBRARY_DIR@"
 libcxx_include_dir = "@LIBCXX_GENERATED_INCLUDE_DIR@"
 libcxx_include_target_dir = "@LIBCXX_GENERATED_INCLUDE_TARGET_DIR@"
+use_vendor_packages = @LLDB_TEST_USE_VENDOR_PACKAGES@
 
 if __name__ == '__main__':
+    if use_vendor_packages:
+        os.putenv("LLDB_TEST_USE_VENDOR_PACKAGES", "1")
+
     wrapper_args = sys.argv[1:]
     dotest_args = []
     # split on an empty string will produce [''] and if you