diff --git a/.docker/selfhost/schema.json b/.docker/selfhost/schema.json
index 579dad67f0..b066dfbdec 100644
--- a/.docker/selfhost/schema.json
+++ b/.docker/selfhost/schema.json
@@ -507,8 +507,7 @@
       "properties": {
         "name": {
           "type": "string",
-          "description": "A recognizable name for the server. Will be shown when connected with AFFiNE Desktop.\n@default \"AFFiNE Cloud\"",
-          "default": "AFFiNE Cloud"
+          "description": "A recognizable name for the server. Will be shown when connected with AFFiNE Desktop.\n@default undefined"
         },
         "externalUrl": {
           "type": "string",
@@ -532,7 +531,7 @@
         },
         "path": {
           "type": "string",
-          "description": "Subpath where the server get deployed if there is.\n@default \"\"\n@environment `AFFINE_SERVER_SUB_PATH`",
+          "description": "Subpath where the server get deployed if there is one.(e.g. /affine)\n@default \"\"\n@environment `AFFINE_SERVER_SUB_PATH`",
           "default": ""
         }
       }
diff --git a/packages/backend/server/src/base/config/__tests__/config.spec.ts b/packages/backend/server/src/base/config/__tests__/config.spec.ts
index c90dfe9cb5..cd13a1f8b7 100644
--- a/packages/backend/server/src/base/config/__tests__/config.spec.ts
+++ b/packages/backend/server/src/base/config/__tests__/config.spec.ts
@@ -185,3 +185,28 @@ test('should clone from original config without modifications', t => {
 
   t.not(newConfig.auth.allowSignup, config.auth.allowSignup);
 });
+
+test('should override with undefined fields', async t => {
+  await using module = await createModule({
+    imports: [ConfigModule],
+  });
+
+  const config = module.get(Config);
+  const configFactory = module.get(ConfigFactory);
+
+  configFactory.override({
+    copilot: {
+      providers: {
+        // @ts-expect-error undefined field
+        unknown: {
+          apiKey: '123',
+        },
+      },
+    },
+  });
+
+  // @ts-expect-error undefined field
+  t.deepEqual(config.copilot.providers.unknown, {
+    apiKey: '123',
+  });
+});
diff --git a/packages/backend/server/src/base/config/factory.ts b/packages/backend/server/src/base/config/factory.ts
index 2443f13bcb..952582241c 100644
--- a/packages/backend/server/src/base/config/factory.ts
+++ b/packages/backend/server/src/base/config/factory.ts
@@ -7,7 +7,7 @@ export const OVERRIDE_CONFIG_TOKEN = Symbol('OVERRIDE_CONFIG_TOKEN');
 
 @Injectable()
 export class ConfigFactory {
-  #original: AppConfig;
+  readonly #original: AppConfig;
   readonly #config: AppConfig;
   get config() {
     return this.#config;
@@ -18,8 +18,8 @@ export class ConfigFactory {
     @Optional()
     private readonly overrides: DeepPartial<AppConfig> = {}
   ) {
-    this.#config = this.loadDefault();
-    this.#original = structuredClone(this.#config);
+    this.#original = this.loadDefault();
+    this.#config = structuredClone(this.#original);
   }
 
   clone() {
@@ -28,8 +28,8 @@ export class ConfigFactory {
   }
 
   override(updates: DeepPartial<AppConfig>) {
+    override(this.#original, updates);
     override(this.#config, updates);
-    this.#original = structuredClone(this.#config);
   }
 
   validate(updates: Array<{ module: string; key: string; value: any }>) {
diff --git a/packages/backend/server/src/base/config/register.ts b/packages/backend/server/src/base/config/register.ts
index 28a329804b..9dfa905394 100644
--- a/packages/backend/server/src/base/config/register.ts
+++ b/packages/backend/server/src/base/config/register.ts
@@ -57,6 +57,10 @@ function typeFromShape(shape: z.ZodType<any>): ConfigType {
       return 'array';
     case z.ZodObject:
       return 'object';
+    case z.ZodOptional:
+    case z.ZodNullable:
+      // @ts-expect-error checked
+      return typeFromShape(shape.unwrap());
     default:
       return 'any';
   }
@@ -251,6 +255,14 @@ export function override(config: AppConfig, update: DeepPartial<AppConfig>) {
         return right;
       }
 
+      // EDGE CASE:
+      //   the right value is primitive and we're still not finding the key in descriptors,
+      //   which means the overrides has keys not defined
+      //   that's where we should return
+      if (typeof right !== 'object') {
+        return left;
+      }
+
       // go deeper
       return mergeWith(left, right, (left, right, key) => {
         return merge(left, right, path === '' ? key : `${path}.${key}`);
diff --git a/packages/backend/server/src/core/config/config.ts b/packages/backend/server/src/core/config/config.ts
index 2b901b68d0..b84515c3f2 100644
--- a/packages/backend/server/src/core/config/config.ts
+++ b/packages/backend/server/src/core/config/config.ts
@@ -23,7 +23,8 @@ declare global {
 defineModuleConfig('server', {
   name: {
     desc: 'A recognizable name for the server. Will be shown when connected with AFFiNE Desktop.',
-    default: '',
+    default: undefined,
+    shape: z.string().optional(),
   },
   externalUrl: {
     desc: `Base url of AFFiNE server, used for generating external urls.
diff --git a/packages/frontend/admin/src/config.json b/packages/frontend/admin/src/config.json
index df6c0224ef..cae75fa051 100644
--- a/packages/frontend/admin/src/config.json
+++ b/packages/frontend/admin/src/config.json
@@ -174,7 +174,7 @@
     },
     "path": {
       "type": "String",
-      "desc": "Subpath where the server get deployed if there is.",
+      "desc": "Subpath where the server get deployed if there is one.(e.g. /affine)",
       "env": "AFFINE_SERVER_SUB_PATH"
     }
   },