Threads are not visible to guests

[MadLittleMods]

Steps to reproduce

1. Setup a public room where you just sent a thread root and some replies to it
2. Visit the public room from a fresh incognito tab where you're not signed in
3. Notice how thread summaries below recent thread roots are not visible
4. Clicking on the threads action in the chat header see the list of threads available just shows a loading spinner forever
   • Behind the scenes /_matrix/client/v1/rooms/!aMzLHLvScQCGKDNqCB%3Agitter.im/threads just returns a 403 forbidden (no error state in the threads panel 😕)

Expected	Actual

Outcome

What did you expect?

Threads are visible

And the thread panel properly shows an error if it happens

What happened instead?

Threads aren't visible for recent messages. Threads do seem to appear in the scrollback (probably some difference of /messages) and they appear if you received the messages as they come in.

The thread panel doesn't show an error about fetching threads if it occurs.

Operating system

Windows 10

Browser information

Chrome Version 111.0.5563.65

URL for webapp

develop.element.io

Application version

Element version: c8b3f5d51211-react-a86a8e7f8eee-js-23837266fca5 Olm version: 3.2.12

Homeserver

matrix.org

Will you send logs?

Yes

[t3chguy]

@MadLittleMods I'm not seeing any logs having come through from you

[MadLittleMods]

@t3chguy Added some 👍 (also very easy to reproduce)

[t3chguy]

Behind the scenes /_matrix/client/v1/rooms/!aMzLHLvScQCGKDNqCB%3Agitter.im/threads just returns a 403 forbidden (no error state in the threads panel 😕)

So this looks like not a web specific issue, other than the lack of an error message. Looks like we might need to hide the threads panel for guest users

[MadLittleMods]

So this looks like not a web specific issue, other than the lack of an error message. Looks like we might need to hide the threads panel for guest users

It does seem like a server/Synapse thing but feels like we could have the same ACL's for /threads as we do for /messages. I think that guests could use /_matrix/client/v1/rooms/!xxx/threads?include=all just fine. We probably want to hide "My threads" (include=participated) though.

[t3chguy]

@MadLittleMods that would require a spec change, as /threads isn't allowed for guests - https://spec.matrix.org/v1.6/client-server-api/#client-behaviour-14

[t3chguy]

Going to pivot into a meta issue to decide what we want to do here
options being double down on guests not able to use /threads and fix the UI around that or allowing it via spec & synapse