${moduleName} has already been loaded. Import Core modules i

Error message

${moduleName} has already been loaded. Import Core modules in the AppModule only.

What it means

Error "${moduleName} has already been loaded. Import Core modules in the AppModule only." thrown in akveo/ngx-admin.

Source

Thrown at src/app/@core/module-import-guard.ts:3

export function throwIfAlreadyLoaded(parentModule: any, moduleName: string) {
  if (parentModule) {
    throw new Error(`${moduleName} has already been loaded. Import Core modules in the AppModule only.`);
  }
}

View on GitHub (pinned to dc6a442704)

Solutions

Ensure CoreModule is imported only once, in AppModule (app.module.ts). Remove any CoreModule imports from lazy-loaded feature modules, SharedModule, or other modules.
Check that all imports of CoreModule in the codebase are removed except the single import in AppModule (e.g. grep for 'CoreModule' across src/app).
If CoreModule is imported in a module that is itself imported by AppModule twice (directly and transitively), break that cycle so it is loaded exactly once.
Verify the guard call: CoreModule's constructor should call throwIfAlreadyLoaded(parentModule, 'CoreModule') and AppModule must pass itself as parentModule; if parentModule is incorrectly truthy for a legitimate single load, fix the constructor signature/usage.
If CoreModule was intentionally imported twice (e.g. in tests), restructure so a single forRoot-style provider pattern is used instead of importing the whole module twice.

Defensive patterns

Strategy: validation

Validate before calling

// In any module other than AppModule, do not import CoreModule.
// Pre-check you can run before building/committing:
// grep -rn "CoreModule" src/app --include='*.ts' | grep -v 'core.module.ts'
// Ensure CoreModule appears only in app.module.ts imports.
import { CoreModule } from './@core/core.module';

function coreModuleImports(): string[] {
  // conceptual: verify only AppModule imports it
  return ['app.module.ts'];
}

Type guard

// The guard itself is a runtime check; a defensive wrapper:
export function ensureImportedInRootOnly(parentModule: unknown, moduleName: string): void {
  if (parentModule) {
    throw new Error(`${moduleName} has already been loaded. Import Core modules in the AppModule only.`);
  }
}

Try / catch

// Usually thrown during bootstrap (ngModule constructor) and not catchable in app code;
// catch is only useful in programmatic bootstrap scenarios:
try {
  platformBrowserDynamic().bootstrapModule(AppModule);
} catch (err) {
  if (err instanceof Error && err.message.includes('has already been loaded')) {
    console.error('CoreModule imported more than once: remove it from all modules except AppModule.');
  } else {
    throw err;
  }
}

Prevention

Import CoreModule only in AppModule; use SharedModule for reusable components/directives/pipes.
Provide singleton services via `@Injectable({ providedIn: 'root' })` so feature modules never need CoreModule.
Adopt a forRoot()/forChild() pattern for modules that must be configured once.
Run a lint/grep check in CI asserting CoreModule is imported only in app.module.ts.
Read the guard error's stack trace — it points to the second importing module.

When it happens

Trigger: Thrown at src/app/@core/module-import-guard.ts:3 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of akveo/ngx-admin@dc6a442704 (2026-08-30). Data as JSON: /api/errors/d17f520a39833dc7. Report an issue: GitHub.