diff --git a/app/application/system.py b/app/application/system.py
index f990eed74..007707005 100644
--- a/app/application/system.py
+++ b/app/application/system.py
@@ -317,7 +317,8 @@ class SystemService:
                     success = await self._system_config.async_set(key, value)
                 if success:
                     await self._events.publish(key, event_value)
-                return SystemOperationResult(True)
+                # None 表示值未变化，仍是成功完成；只有明确 False 才代表持久化失败。
+                return SystemOperationResult(success is not False)
         except PluginMutationRejectedError as error:
             return SystemOperationResult(False, str(error))
 
diff --git a/tests/test_plugin_system_setting_admission.py b/tests/test_plugin_system_setting_admission.py
index 7d291e96b..ddb5fbb6a 100644
--- a/tests/test_plugin_system_setting_admission.py
+++ b/tests/test_plugin_system_setting_admission.py
@@ -216,6 +216,28 @@ async def test_non_plugin_system_config_does_not_resolve_plugin_runtime(
     config.async_set.assert_awaited_once_with(SystemConfigKey.Directories.value, None)
 
 
+@pytest.mark.asyncio
+async def test_system_http_reports_persistent_write_failure(monkeypatch) -> None:
+    """通用系统配置持久化失败时 HTTP 响应和事件均不得伪造成功。"""
+    config = MagicMock()
+    config.async_set = AsyncMock(return_value=False)
+    send_event = AsyncMock()
+    monkeypatch.setattr(
+        "app.startup.composition.system.eventmanager.async_send_event", send_event
+    )
+
+    response = await system_endpoint.set_setting(
+        SystemConfigKey.Directories.value,
+        [],
+        None,
+        runtime=_runtime(config),
+    )
+
+    assert response.success is False
+    config.async_set.assert_awaited_once_with(SystemConfigKey.Directories.value, None)
+    send_event.assert_not_awaited()
+
+
 @pytest.mark.asyncio
 async def test_rule_group_setting_reconciles_stale_references_when_unchanged(
     monkeypatch,
diff --git a/tests/test_system_application.py b/tests/test_system_application.py
index 55ec16acb..b3112ebd1 100644
--- a/tests/test_system_application.py
+++ b/tests/test_system_application.py
@@ -221,6 +221,34 @@ async def test_update_setting_routes_runtime_and_persistent_values() -> None:
     )
 
 
+@pytest.mark.anyio
+@pytest.mark.parametrize(
+    ("persisted_result", "expected_success", "publishes_event"),
+    [(True, True, True), (None, True, False), (False, False, False)],
+)
+async def test_update_setting_preserves_persistent_write_result(
+    persisted_result: bool | None,
+    expected_success: bool,
+    publishes_event: bool,
+) -> None:
+    """通用系统配置写入只把明确 False 映射为失败并抑制失败事件。"""
+    service, dependencies = _build_service()
+    dependencies.settings.contains.return_value = False
+    dependencies.system_config.async_set.return_value = persisted_result
+
+    result = await service.update_setting(
+        SystemConfigKey.IndexerSites.value, [1, None, 2]
+    )
+
+    assert result.success is expected_success
+    if publishes_event:
+        dependencies.events.publish.assert_awaited_once_with(
+            SystemConfigKey.IndexerSites.value, [1, 2]
+        )
+    else:
+        dependencies.events.publish.assert_not_awaited()
+
+
 @pytest.mark.anyio
 async def test_update_setting_applies_rule_groups_and_reports_mutation_rejection() -> None:
     """规则组使用原子 mutation，插件写入拒绝应转换为稳定结果。"""