Roel

Sorry, the supplied code can be a little confusing. `clientSecret` **or** `clientCertificate` is defined, not both. The other will be `undefined`. I will probably be able to do some more...

@Robbie-Microsoft I did some more testing and found something interesting. This works: ```js auth: { authority: '', clientId: '', clientSecret: '', } ``` This throws the error mentioned: ```js auth:...

> I believe you would have prevented this error on your end if you typed your config as Configuration, the type from msal-node that ConfidentialClientApplication expects to be passed into...

So this method should transform `Configuration` to `NodeConfiguration`, but it's not guaranteed: https://github.com/AzureAD/microsoft-authentication-library-for-js/blob/22651b30bce9244cce2d7ffcfa1a81e4c44be133/lib/msal-node/src/config/Configuration.ts#L210-L243 In my case this line: ```js auth: { ...DEFAULT_AUTH_OPTIONS, ...auth }, ``` Actually does this: ```js auth:...