diff --git a/tests/config/test_config_save_paths.py b/tests/config/test_config_save_paths.py
new file mode 100644
index 00000000..1f3a59b0
--- /dev/null
+++ b/tests/config/test_config_save_paths.py
@@ -0,0 +1,119 @@
+import logging
+from typing import Dict, Iterable, List
+
+import pytest
+
+from py import config as config_module
+from py.services import settings_manager as settings_manager_module
+
+
+def _setup_config_environment(monkeypatch: pytest.MonkeyPatch, tmp_path) -> Dict[str, List[str]]:
+    loras_dir = tmp_path / "loras"
+    checkpoints_dir = tmp_path / "checkpoints"
+    embeddings_dir = tmp_path / "embeddings"
+
+    for directory in (loras_dir, checkpoints_dir, embeddings_dir):
+        directory.mkdir()
+
+    folder_paths: Dict[str, List[str]] = {
+        "loras": [str(loras_dir)],
+        "checkpoints": [str(checkpoints_dir)],
+        "unet": [],
+        "embeddings": [str(embeddings_dir)],
+    }
+
+    def fake_get_folder_paths(kind: str) -> Iterable[str]:
+        return folder_paths.get(kind, [])
+
+    monkeypatch.setattr(config_module.folder_paths, "get_folder_paths", fake_get_folder_paths)
+    monkeypatch.setattr(config_module, "standalone_mode", False)
+    monkeypatch.setattr(
+        config_module,
+        "ensure_settings_file",
+        lambda logger=None: str(tmp_path / "settings.json"),
+    )
+
+    return folder_paths
+
+
+def test_save_paths_renames_default_library(monkeypatch: pytest.MonkeyPatch, tmp_path):
+    folder_paths = _setup_config_environment(monkeypatch, tmp_path)
+
+    class FakeSettingsService:
+        def __init__(self, default_paths: Dict[str, List[str]]):
+            self._default_paths = default_paths
+            self.rename_calls = []
+            self.upsert_calls = []
+            self._renamed = False
+
+        def get_libraries(self):
+            if self._renamed:
+                return {"comfyui": {}}
+            return {
+                "default": {
+                    "folder_paths": {key: list(value) for key, value in self._default_paths.items()},
+                    "default_lora_root": "",
+                    "default_checkpoint_root": "",
+                    "default_embedding_root": "",
+                }
+            }
+
+        def rename_library(self, old_name: str, new_name: str):
+            self.rename_calls.append((old_name, new_name))
+            self._renamed = True
+
+        def upsert_library(self, name: str, **payload):
+            self.upsert_calls.append((name, payload))
+
+    fake_settings = FakeSettingsService(folder_paths)
+    monkeypatch.setattr(settings_manager_module, "settings", fake_settings)
+
+    config_instance = config_module.Config()
+
+    assert isinstance(config_instance, config_module.Config)
+    assert fake_settings.rename_calls == [("default", "comfyui")]
+    assert len(fake_settings.upsert_calls) == 1
+
+    name, payload = fake_settings.upsert_calls[0]
+    assert name == "comfyui"
+    assert payload["folder_paths"] == folder_paths
+    assert payload["default_lora_root"] == folder_paths["loras"][0]
+    assert payload["default_checkpoint_root"] == folder_paths["checkpoints"][0]
+    assert payload["default_embedding_root"] == folder_paths["embeddings"][0]
+    assert payload["metadata"] == {"display_name": "ComfyUI", "source": "comfyui"}
+    assert payload["activate"] is True
+
+
+def test_save_paths_logs_warning_when_upsert_fails(
+    monkeypatch: pytest.MonkeyPatch, tmp_path, caplog
+):
+    folder_paths = _setup_config_environment(monkeypatch, tmp_path)
+
+    class RaisingSettingsService:
+        def __init__(self):
+            self.upsert_attempts = []
+
+        def get_libraries(self):
+            return {
+                "comfyui": {
+                    "folder_paths": {key: list(value) for key, value in folder_paths.items()},
+                    "default_lora_root": "existing",
+                }
+            }
+
+        def rename_library(self, *_):
+            raise AssertionError("rename_library should not be invoked")
+
+        def upsert_library(self, name: str, **payload):
+            self.upsert_attempts.append((name, payload))
+            raise RuntimeError("boom")
+
+    fake_settings = RaisingSettingsService()
+    monkeypatch.setattr(settings_manager_module, "settings", fake_settings)
+
+    with caplog.at_level(logging.WARNING, logger=config_module.logger.name):
+        config_instance = config_module.Config()
+
+    assert isinstance(config_instance, config_module.Config)
+    assert fake_settings.upsert_attempts and fake_settings.upsert_attempts[0][0] == "comfyui"
+    assert "Failed to save folder paths: boom" in caplog.text