@Majardom the problem you will run into is the OIDC "allow" page.

The flow is:

1. Hit https://deployment.coder.com/api/v2/users/oauth2/github/callback. This returns a 307 redirect to the OIDC/oauth provider
2. Follow redirect to https://github.com/login/oauth/authorize?...
3. This is where you hit the "allow" page

4. After allow, you get a 302 redirect back to https://deployment.coder.com/api/v2/users/oauth2/github/callback?coder=..... The code works, and you get a 307 to /workspaces with a cookie that contains the session token.

So a headless auth flow for OIDC can only work if the IDP can do so headless. Which probably will not work for initial auth flows, but you can sometimes do it with subsequent auth flows if everything has been approved before.

I think what would work best for you is not implemented yet, but described in this issue: #11901