fix(proxy): fail fast when general_settings is not a mapping

A non-dict general_settings (e.g. a bare string from a malformed YAML
block) reached general_settings.get(...) in run_server and crashed at
startup with an opaque AttributeError: 'str' object has no attribute
'get' (see #38190). Guard the value: None still coerces to {}, and any
other non-mapping now raises a ValueError that points at the config block.

Adds regression tests covering the None (tolerated) and string (fails
fast) cases.

litellm/proxy/proxy_cli.py

@@ -1151,6 +1151,16 @@ def run_server(
             general_settings = _config.get("general_settings", {})
             if general_settings is None:
                 general_settings = {}
+            elif not isinstance(general_settings, dict):
+                # A non-dict `general_settings` (e.g. a bare string from a
+                # malformed YAML block) otherwise surfaces as a cryptic
+                # `AttributeError: 'str' object has no attribute 'get'` deep in
+                # startup. Fail fast with a message that points at the config.
+                raise ValueError(
+                    "`general_settings` in the proxy config must be a mapping "
+                    f"(got {type(general_settings).__name__}). Check the "
+                    "`general_settings:` block in your config file."
+                )
             ### LOAD KEY MANAGEMENT SETTINGS FIRST (needed for custom secret manager) ###
             key_management_settings: Final = general_settings.get("key_management_settings", None)
             if key_management_settings is not None:

tests/test_litellm/proxy/test_proxy_cli.py

@@ -2532,3 +2532,31 @@ class TestTokenAuthCliFlags:
         assert result.exit_code == 0, f"exit_code={result.exit_code}, output={result.output}"
         assert "ENTRA_TOKEN" not in (database_url or "")
         assert toggle is None
+
+
+@pytest.mark.xdist_group("proxy_cli")
+class TestGeneralSettingsShape:
+    """`general_settings` is read straight from user YAML. A non-mapping value
+    (a bare string when the block is malformed, or `null` from an empty block)
+    used to reach `general_settings.get(...)` and blow up at startup with an
+    opaque `AttributeError: 'str' object has no attribute 'get'`. Startup must
+    either tolerate it (None -> {}) or fail with a message pointing at the config.
+    """
+
+    def test_null_general_settings_is_tolerated(self, tmp_path):
+        """An empty `general_settings:` block parses as None and must not crash."""
+        config_path = tmp_path / "config.yaml"
+        config_path.write_text(yaml.dump({"model_list": [], "general_settings": None}))
+
+        captured = _run_server_and_capture_urls(str(config_path))
+        assert captured["DATABASE_URL"].startswith("postgresql://t:t@localhost:5432/t")
+
+    def test_string_general_settings_fails_with_actionable_error(self, tmp_path):
+        """A non-mapping value must fail fast, not as a cryptic AttributeError."""
+        config_path = tmp_path / "config.yaml"
+        config_path.write_text(
+            yaml.dump({"model_list": [], "general_settings": "database_url"})
+        )
+
+        with pytest.raises(ValueError, match=r"general_settings.*must be a mapping"):
+            _run_server_and_capture_urls(str(config_path))