## The problem

Running FusionAuth in Docker with a port mapping like 2222:9011, the Identity Provider login redirect_uri contained the wrong (internal) port from FusionAuth 1.37 through 1.45.x, so the IdP callback went to an unreachable URL and login failed. The redirect_uri should have used the external mapped port (e.g. http://YOUR_HOST:2222/oauth2/callback). The bug persisted across every release from 1.37 until the 1.46.0 fix.

## What fixed it

Fixed in FusionAuth 1.46.0; the reporter verified the correct external port appears in redirect_uri and the redirect works on that image. Upgrade to 1.46.0 or newer if you run FusionAuth behind a Docker port mapping with Identity Provider login. The fix was verified against the exact Docker port-mapping setup from the report.