> For the complete documentation index, see [llms.txt](https://angular-token.gitbook.io/docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://angular-token.gitbook.io/docs/common-problems.md).

# Common Problems

## CORS Configuration

If you are using CORS in your Rails API make sure that `Access-Control-Expose-Headers` includes `access-token`, `expiry`, `token-type`, `uid`, and `client`. For the rack-cors gem this can be done by adding the following to its config. More information can be found [here](https://github.com/lynndylanhurley/devise_token_auth#cors).

```ruby
:expose  => ['access-token', 'expiry', 'token-type', 'uid', 'client']
```

## Missing "@angular/core" and/or "rxjs"

I got the following error `You seem to not be depending on "@angular/core" and/or "rxjs". This is an error.`

To fix it `npm link` `ng serve`