fix(config): reject malformed YAML before saving configuration

agent_reach/config.py

@@ -144,9 +144,13 @@ def load(self):
             self.data = {}
             return
 
-        loaded = yaml.safe_load(payload) or {}
+        loaded = yaml.safe_load(payload)
+        if loaded is None:
+            loaded = {}
         if not isinstance(loaded, dict):
             raise ConfigError("配置文件顶层必须是对象")
+        if not all(isinstance(key, str) for key in loaded):
+            raise ConfigError("配置文件的键必须是字符串")
         self.data = loaded
 
     def save(self):

tests/test_config_shape.py

@@ -0,0 +1,30 @@
+"""Malformed config shapes fail before they can be mistaken for empty settings."""
+
+import pytest
+
+from agent_reach.config import Config, ConfigError
+
+
+@pytest.mark.parametrize("payload", ["[]", "false", "0", "''"])
+def test_falsy_non_mapping_config_is_rejected_without_changing_file(tmp_path, payload):
+    path = tmp_path / "config.yaml"
+    path.write_text(payload, encoding="utf-8")
+    with pytest.raises(ConfigError):
+        Config(path)
+    assert path.read_text(encoding="utf-8") == payload
+
+
+@pytest.mark.parametrize("payload", ["1: value", "true: value", "null: value"])
+def test_non_string_config_keys_are_rejected_at_load(tmp_path, payload):
+    path = tmp_path / "config.yaml"
+    path.write_text(payload, encoding="utf-8")
+    with pytest.raises(ConfigError):
+        Config(path)
+    assert path.read_text(encoding="utf-8") == payload
+
+
+@pytest.mark.parametrize("payload", ["", "# only a comment\n", "null", "{}"])
+def test_empty_config_still_loads_as_an_empty_mapping(tmp_path, payload):
+    path = tmp_path / "config.yaml"
+    path.write_text(payload, encoding="utf-8")
+    assert Config(path).data == {}