diff --git a/python/helpers/generator3.py b/python/helpers/generator3.py
index 0aaeb91bd81b..508dadc3c207 100644
--- a/python/helpers/generator3.py
+++ b/python/helpers/generator3.py
@@ -31,6 +31,14 @@ def is_test_mode():
     return ENV_TEST_MODE_FLAG in os.environ
 
 
+# Future generator mode where all the checks will be performed on Python side.
+# Now it works in transitional mode where validity of existing SDK skeletons is checked on
+# Java side (see PySkeletonRefresher), and generator itself inspects only the cache.
+@cached
+def is_standalone_mode():
+    return ENV_STANDALONE_MODE_FLAG in os.environ
+
+
 _helpers_dir = os.path.dirname(os.path.abspath(__file__))
 
 
@@ -529,7 +537,7 @@ def process_one(name, mod_file_name, doing_builtins, sdk_skeletons_dir):
         global_cache_dir = os.path.join(python_stubs_dir, CACHE_DIR_NAME)
         mod_cache_dir = build_cache_dir_path(global_cache_dir, name, mod_file_name)
         # At the moment this is actually enforced on Java-side
-        if not should_update_skeleton(sdk_skeletons_dir, name, mod_file_name):
+        if is_standalone_mode() and not should_update_skeleton(sdk_skeletons_dir, name, mod_file_name):
             return True
 
         if should_update_skeleton(mod_cache_dir, name, mod_file_name):
diff --git a/python/helpers/pycharm_generator_utils/constants.py b/python/helpers/pycharm_generator_utils/constants.py
index 7d573d56a632..3c6af7e0741b 100644
--- a/python/helpers/pycharm_generator_utils/constants.py
+++ b/python/helpers/pycharm_generator_utils/constants.py
@@ -811,6 +811,7 @@ REQUIRED_GEN_VERSION_LINE = re.compile(r'(?P<name>\S+)\s+(?P<version>\d+\.\d+)')
 BLACKLIST_VERSION_LINE = re.compile(r'(?P<path>{mod_path}|[^=]+) = (?P<version>\d+\.\d+) (?P<mtime>{mod_mtime}|\d+)')
 
 ENV_TEST_MODE_FLAG = 'GENERATOR3_TEST_MODE'
+ENV_STANDALONE_MODE_FLAG = 'GENERATOR3_STANDALONE_MODE'
 ENV_VERSION = 'GENERATOR3_VERSION'
 ENV_REQUIRED_GEN_VERSION_FILE = 'GENERATOR3_REQUIRED_GEN_VERSION_FILE'
 
diff --git a/python/helpers/pycharm_generator_utils/test/test_generation.py b/python/helpers/pycharm_generator_utils/test/test_generation.py
index 154a6a5f7767..1b4657b1a847 100644
--- a/python/helpers/pycharm_generator_utils/test/test_generation.py
+++ b/python/helpers/pycharm_generator_utils/test/test_generation.py
@@ -12,6 +12,7 @@ from pycharm_generator_utils.constants import (
     ENV_VERSION,
     ENV_REQUIRED_GEN_VERSION_FILE,
     CACHE_DIR_NAME,
+    ENV_STANDALONE_MODE_FLAG,
 )
 from pycharm_generator_utils.test import GeneratorTestCase
 
@@ -34,7 +35,8 @@ class SkeletonCachingTest(GeneratorTestCase):
     def run_generator(self, mod_qname=None, mod_path=None, builtins=False,
                       extra_syspath_entry=None,
                       gen_version=None,
-                      required_gen_version_file_path=None):
+                      required_gen_version_file_path=None,
+                      extra_env=None):
         output_dir = self.temp_skeletons_dir
 
         if not extra_syspath_entry:
@@ -50,6 +52,9 @@ class SkeletonCachingTest(GeneratorTestCase):
         if required_gen_version_file_path:
             env[ENV_REQUIRED_GEN_VERSION_FILE] = required_gen_version_file_path
 
+        if extra_env:
+            env.update(extra_env)
+
         if _run_generator_in_separate_process:
             generator3_path = os.path.abspath(generator3.__file__)
             base, ext = os.path.splitext(generator3_path)
@@ -190,7 +195,8 @@ class SkeletonCachingTest(GeneratorTestCase):
         # We can't safely updated cache from SDK skeletons (backwards) because of binaries declaring
         # multiple modules. Skeletons for them are scattered across SDK skeletons directory, and we can't
         # collect them reliably.
-        self.check_generator_output('mod', mod_path='mod.py', gen_version='0.2', custom_required_gen=True)
+        self.check_generator_output('mod', mod_path='mod.py', gen_version='0.2', custom_required_gen=True,
+                                    standalone_mode=True)
 
     def test_cache_skeleton_reused_when_sdk_skeleton_is_missing(self):
         self.check_generator_output('mod', mod_path='mod.py', gen_version='0.2', custom_required_gen=True)
@@ -208,7 +214,8 @@ class SkeletonCachingTest(GeneratorTestCase):
         self.check_generator_output('mod', mod_path='mod.py', gen_version='0.3', custom_required_gen=True)
 
     def test_cache_skeleton_not_regenerated_when_sdk_skeleton_generation_failed_for_same_version_and_same_binary(self):
-        self.check_generator_output('mod', mod_path='mod.py', gen_version='0.1', custom_required_gen=True)
+        self.check_generator_output('mod', mod_path='mod.py', gen_version='0.1', custom_required_gen=True,
+                                    standalone_mode=True)
 
     def test_cache_skeleton_regenerated_when_sdk_skeleton_generation_failed_for_modified_binary(self):
         self.check_generator_output('mod', mod_path='mod.py', gen_version='0.1', custom_required_gen=True)
@@ -227,10 +234,13 @@ class SkeletonCachingTest(GeneratorTestCase):
     def test_binary_declares_extra_module_that_fails(self):
         self.check_generator_output('mod', mod_path='mod.py')
 
-    def check_generator_output(self, mod_name, mod_path=None, mod_root=None, custom_required_gen=False, **kwargs):
+    def check_generator_output(self, mod_name, mod_path=None, mod_root=None,
+                               custom_required_gen=False, standalone_mode=False, **kwargs):
         if custom_required_gen:
             kwargs.setdefault('required_gen_version_file_path',
                               os.path.join(self.test_data_dir, 'required_gen_version'))
+        if standalone_mode:
+            kwargs.setdefault('extra_env', {})[ENV_STANDALONE_MODE_FLAG] = 'True'
 
         if not mod_root:
             mod_root = self.test_data_dir