diff --git a/packages/cli-module-build/src/lib/runner/runBackend.test.ts b/packages/cli-module-build/src/lib/runner/runBackend.test.ts
index 1bf2ef1568..0cf2b6bd4c 100644
--- a/packages/cli-module-build/src/lib/runner/runBackend.test.ts
+++ b/packages/cli-module-build/src/lib/runner/runBackend.test.ts
@@ -87,6 +87,7 @@ describe('runBackend', () => {
 
     mockToConfig.mockResolvedValue({
       close: jest.fn(),
+      getOptional: () => undefined,
       getOptionalString: () => undefined,
       getOptionalNumber: () => undefined,
     });
@@ -184,6 +185,7 @@ describe('runBackend', () => {
     it('should start embedded DB and inject all defaults when no user connection config is provided', async () => {
       mockToConfig.mockResolvedValue({
         close: jest.fn(),
+        getOptional: () => undefined,
         getOptionalString: (key: string) =>
           key === 'backend.database.client' ? 'embedded-postgres' : undefined,
         getOptionalNumber: () => undefined,
@@ -232,6 +234,7 @@ describe('runBackend', () => {
       };
       mockToConfig.mockResolvedValue({
         close: jest.fn(),
+        getOptional: () => ({ host: '0.0.0.0', port: 15432 }),
         getOptionalString: (key: string) => {
           const val = configValues[key];
           return typeof val === 'string' ? val : undefined;
@@ -288,6 +291,12 @@ describe('runBackend', () => {
       };
       mockToConfig.mockResolvedValue({
         close: jest.fn(),
+        getOptional: () => ({
+          host: '0.0.0.0',
+          port: 15432,
+          user: 'myuser',
+          password: 'mypass',
+        }),
         getOptionalString: (key: string) => {
           const val = configValues[key];
           return typeof val === 'string' ? val : undefined;
@@ -328,6 +337,7 @@ describe('runBackend', () => {
     it('should resolve config paths relative to targetDir', async () => {
       mockToConfig.mockResolvedValue({
         close: jest.fn(),
+        getOptional: () => undefined,
         getOptionalString: () => undefined,
         getOptionalNumber: () => undefined,
       });
@@ -346,9 +356,10 @@ describe('runBackend', () => {
       );
     });
 
-    it('should not start embedded DB for other database clients', async () => {
+    it('should not start embedded DB for other database clients with a string connection', async () => {
       mockToConfig.mockResolvedValue({
         close: jest.fn(),
+        getOptional: () => ':memory:',
         getOptionalString: (key: string) =>
           key === 'backend.database.client' ? 'better-sqlite3' : undefined,
         getOptionalNumber: () => undefined,
diff --git a/packages/cli-module-build/src/lib/runner/runBackend.ts b/packages/cli-module-build/src/lib/runner/runBackend.ts
index 1046235d35..9e872fed38 100644
--- a/packages/cli-module-build/src/lib/runner/runBackend.ts
+++ b/packages/cli-module-build/src/lib/runner/runBackend.ts
@@ -252,6 +252,13 @@ async function readDatabaseConfig(
       return undefined;
     }
 
+    // Only read structured connection config if the value is an object;
+    // it can also be a plain string (e.g. ':memory:' for better-sqlite3).
+    const rawConnection = config.getOptional('backend.database.connection');
+    if (typeof rawConnection === 'string' || rawConnection === undefined) {
+      return { client };
+    }
+
     const host = config.getOptionalString('backend.database.connection.host');
     const port = config.getOptionalNumber('backend.database.connection.port');
     const user = config.getOptionalString('backend.database.connection.user');