Fix empty tool selection persistence

hermes_cli/tools_config.py

@@ -308,7 +308,7 @@ def _get_platform_tools(config: dict, platform: str) -> Set[str]:
     platform_toolsets = config.get("platform_toolsets", {})
     toolset_names = platform_toolsets.get(platform)
 
-    if not toolset_names or not isinstance(toolset_names, list):
+    if toolset_names is None or not isinstance(toolset_names, list):
         default_ts = PLATFORMS[platform]["default_toolset"]
         toolset_names = [default_ts]
 

tests/hermes_cli/test_tools_config.py

@@ -0,0 +1,19 @@
+"""Tests for hermes_cli.tools_config platform tool persistence."""
+
+from hermes_cli.tools_config import _get_platform_tools
+
+
+def test_get_platform_tools_uses_default_when_platform_not_configured():
+    config = {}
+
+    enabled = _get_platform_tools(config, "cli")
+
+    assert enabled
+
+
+def test_get_platform_tools_preserves_explicit_empty_selection():
+    config = {"platform_toolsets": {"cli": []}}
+
+    enabled = _get_platform_tools(config, "cli")
+
+    assert enabled == set()