Autodetect of matrix server from MXID broken

[mvgorcum]

Steps to reproduce

1. Where are you starting? What can you see?
   I'm trying to log in to my (non-matrix.org) account.

2. What do you click?
   Sign in -> Continue -> fill in mxid and password

Outcome

What did you expect?

I expect element to use the client .well-known to find my server and log me in, based on my mxid.

What happened instead?

It tried to login to matrix.org sending my username and password to an unrelated server that should never have access to my account.

Operating system

Linux

Browser information

Firefox

URL for webapp

develop.element.io and app.element.io

Application version

No response

Homeserver

(not relevant here, but synapse 1.128.0)

Will you send logs?

No

[t3chguy]

Once you hit Continue you are no longer on Element so Element can do no such auto-detection. You are then on MAS which is scoped to a single homeserver. If you have suggestions for MAS then you'd need to make them at https://github.com/element-hq/matrix-authentication-service but keep in mind there's be zero way for MAS to log you into a different homeserver.

Screen.Recording.2025-04-28.at.09.17.43.mov

[Cadair]

Is there a way for element to pass the mxid off to MAS, so you could put your MXID into element and then it could detect which server to talk to and then pass that info over?

[t3chguy]

The UX could ask you for an MXID after you hit Sign In before showing you any server options but most users forget their MXID. If you wish to make any cross-platform UX suggestions the repo you want is https://github.com/element-hq/element-meta/discussions

[escix]

An alternative option is to make the homeserver editable (or blank) on page load, rather than need to click edit and then input the homeserver.

[mvgorcum]

The default of matrix.org caused me to trip up and accidentally supply my login to matrix.org rather than the homeserver I wanted. That seems like an issue worth solving to me.