OICD 'missing client id' when fetching access and ID token

Coz Twitch is weird at times.

Postman web or postman desktop.

Postman web can be weird
And postman might inject it’s own crap

You might want to compare what you are doing with this example server application

I don’t see anything obviously wrong with what you have written, so I don’t know if postman has done a weird or something else is going on.

I wonder if you turned on “oAuth” in the Postman settings and didn’t populate oAuth
So the clientID you specify in query string is being override by the unset one in postman oAuth settings.

Personally I use insomnia over postman and I don’t test oAuth stuff in the tester client I build my webcode for it instead.

As the documentation shows.

So it’s a POST submission, posting the items as query string or “normal” URL Encoded Post Form.