diff --git a/packages/core-app-api/alpha-api-report.md b/packages/core-app-api/alpha-api-report.md
index 57a15f3894..f35adfdbaa 100644
--- a/packages/core-app-api/alpha-api-report.md
+++ b/packages/core-app-api/alpha-api-report.md
@@ -22,7 +22,10 @@ export class AppTranslationApiImpl implements AppTranslationApi {
   // (undocumented)
   addResources<Messages extends Record<string, string>>(
     translationRef: TranslationRef<Messages>,
-    initResources?: TranslationMessages<TranslationRef<Messages>>,
+    initResources?: Record<
+      string,
+      TranslationMessages<TranslationRef<Messages>>
+    >,
   ): void;
   // (undocumented)
   addResourcesByRef<Messages extends Record<string, string>>(
@@ -39,7 +42,7 @@ export class AppTranslationApiImpl implements AppTranslationApi {
 // @alpha (undocumented)
 export function createTranslationResource<T extends TranslationRef>(options: {
   ref: T;
-  messages?: TranslationMessages<T>;
+  messages?: Record<string, TranslationMessages<T>>;
   lazyMessages: Record<
     string,
     () => Promise<{
@@ -48,7 +51,7 @@ export function createTranslationResource<T extends TranslationRef>(options: {
   >;
 }): {
   ref: T;
-  messages?: TranslationMessages<T> | undefined;
+  messages?: Record<string, TranslationMessages<T>> | undefined;
   lazyMessages: Record<
     string,
     () => Promise<{
@@ -63,7 +66,7 @@ export type ExperimentalI18n = {
   fallbackLanguage?: string | string[];
   messages?: Array<{
     ref: TranslationRef;
-    messages?: TranslationMessages<TranslationRef>;
+    messages?: Record<string, TranslationMessages<TranslationRef>>;
     lazyMessages: Record<
       string,
       () => Promise<{
@@ -75,7 +78,7 @@ export type ExperimentalI18n = {
 
 // @alpha (undocumented)
 export type TranslationMessages<T> = T extends TranslationRef<infer R>
-  ? Record<string, Partial<R>>
+  ? Partial<R>
   : never;
 
 // (No @packageDocumentation comment for this package)
diff --git a/packages/core-app-api/api-report.md b/packages/core-app-api/api-report.md
index 2f6f02f37a..e53d2eed83 100644
--- a/packages/core-app-api/api-report.md
+++ b/packages/core-app-api/api-report.md
@@ -226,7 +226,7 @@ export type AppOptions = {
     fallbackLanguage?: string | string[];
     messages?: Array<{
       ref: TranslationRef;
-      messages?: TranslationMessages<TranslationRef>;
+      messages?: Record<string, TranslationMessages<TranslationRef>>;
       lazyMessages: Record<
         string,
         () => Promise<{
diff --git a/packages/core-app-api/src/apis/implementations/AppTranslationApi/AppTranslation.test.ts b/packages/core-app-api/src/apis/implementations/AppTranslationApi/AppTranslation.test.ts
index 85f8c5e3eb..b6eba8a1c7 100644
--- a/packages/core-app-api/src/apis/implementations/AppTranslationApi/AppTranslation.test.ts
+++ b/packages/core-app-api/src/apis/implementations/AppTranslationApi/AppTranslation.test.ts
@@ -33,6 +33,7 @@ jest.mock('i18next', () => ({
       },
       options: {
         fallbackLng: 'en',
+        supportedLngs: ['zh', 'en'],
       },
     })),
   })),
diff --git a/packages/core-app-api/src/apis/implementations/AppTranslationApi/AppTranslationImpl.ts b/packages/core-app-api/src/apis/implementations/AppTranslationApi/AppTranslationImpl.ts
index c65611fd9f..69820e7b67 100644
--- a/packages/core-app-api/src/apis/implementations/AppTranslationApi/AppTranslationImpl.ts
+++ b/packages/core-app-api/src/apis/implementations/AppTranslationApi/AppTranslationImpl.ts
@@ -30,7 +30,7 @@ export type ExperimentalI18n = {
   fallbackLanguage?: string | string[];
   messages?: Array<{
     ref: TranslationRef;
-    messages?: TranslationMessages<TranslationRef>;
+    messages?: Record<string, TranslationMessages<TranslationRef>>;
     lazyMessages: Record<
       string,
       () => Promise<{ messages: TranslationMessages<TranslationRef> }>
@@ -89,7 +89,10 @@ export class AppTranslationApiImpl implements AppTranslationApi {
 
   addResources<Messages extends Record<string, string>>(
     translationRef: TranslationRef<Messages>,
-    initResources?: TranslationMessages<TranslationRef<Messages>>,
+    initResources?: Record<
+      string,
+      TranslationMessages<TranslationRef<Messages>>
+    >,
   ) {
     const resources = initResources || translationRef.getResources();
     if (!resources || this.cache.has(translationRef)) {
@@ -136,18 +139,13 @@ export class AppTranslationApiImpl implements AppTranslationApi {
     const namespace = translationRef.getId();
     const lazyResources = initResources || translationRef.getLazyResources();
 
-    const fallbackLanguages = services.languageUtils.getFallbackCodes(
-      options.fallbackLng,
-      currentLanguage,
-    ) as string[];
-
-    Promise.allSettled(
-      [...fallbackLanguages, currentLanguage].map(addLanguage),
-    ).then(results => {
-      if (results.some(result => result.status === 'fulfilled')) {
-        this.i18n.emit('loaded');
-      }
-    });
+    Promise.allSettled((options.supportedLngs || []).map(addLanguage)).then(
+      results => {
+        if (results.some(result => result.status === 'fulfilled')) {
+          this.i18n.emit('loaded');
+        }
+      },
+    );
 
     async function addLanguage(language: string) {
       if (cache!.has(language)) {
diff --git a/packages/core-app-api/src/app/TranslationResource.ts b/packages/core-app-api/src/app/TranslationResource.ts
index e5d34de587..65f1c4622c 100644
--- a/packages/core-app-api/src/app/TranslationResource.ts
+++ b/packages/core-app-api/src/app/TranslationResource.ts
@@ -18,13 +18,13 @@ import { TranslationRef } from '@backstage/core-plugin-api/alpha';
 
 /** @alpha */
 export type TranslationMessages<T> = T extends TranslationRef<infer R>
-  ? Record<string, Partial<R>>
+  ? Partial<R>
   : never;
 
 /** @alpha */
 export function createTranslationResource<T extends TranslationRef>(options: {
   ref: T;
-  messages?: TranslationMessages<T>;
+  messages?: Record<string, TranslationMessages<T>>;
   lazyMessages: Record<
     string,
     () => Promise<{ messages: TranslationMessages<T> }>
diff --git a/packages/core-app-api/src/app/types.ts b/packages/core-app-api/src/app/types.ts
index 89104ebf12..3d4b9cf8c5 100644
--- a/packages/core-app-api/src/app/types.ts
+++ b/packages/core-app-api/src/app/types.ts
@@ -185,7 +185,7 @@ export type AppRouteBinder = <
  * @ignore
  * */
 type TranslationMessages<T> = T extends TranslationRef<infer R>
-  ? Record<string, Partial<R>>
+  ? Partial<R>
   : never;
 
 /**
@@ -299,7 +299,7 @@ export type AppOptions = {
     fallbackLanguage?: string | string[];
     messages?: Array<{
       ref: TranslationRef;
-      messages?: TranslationMessages<TranslationRef>;
+      messages?: Record<string, TranslationMessages<TranslationRef>>;
       lazyMessages: Record<
         string,
         () => Promise<{ messages: TranslationMessages<TranslationRef> }>