Sliding sync host name mismatch

[Daniel15]

Describe the bug
When I try to enable sliding sync in the Element web UI, I get this error:

proxyHealthCheck: client using https://matrix.example.com but server is as http://matrix-synapse:8008

and it doesn't let me continue.

If I hit https://matrix.example.com/sliding-sync/client/server.json, it returns:

{"server":"http://matrix-synapse:8008","version":"0.99.15 (bbb886e)"}

Do I need to somehow change that server field to match? How do I do that?

To Reproduce
My vars.yml file looks like this:

---
matrix_domain: staging.example.com

matrix_server_fqn_matrix: matrix.example.com
matrix_server_fqn_element: element.example.com
matrix_sliding_sync_enabled: true

matrix_homeserver_implementation: synapse
matrix_homeserver_generic_secret_key: '<removed>'

matrix_playbook_reverse_proxy_type: playbook-managed-traefik

devture_traefik_config_certificatesResolvers_acme_email: 'ssl@example.com'

devture_postgres_connection_password: '<removed>'

Expected behavior
Sliding sync should work

Matrix Server:

• OS: Debian 12.5
• Architecture amd64

[Daniel15]

If I modify /matrix/sliding-sync/env and change:

SYNCV3_SERVER=http://matrix-synapse:8008

to

SYNCV3_SERVER=https://matrix.example.com

it works fine. Looks like this is controlled by the matrix_sliding_sync_environment_variable_syncv3_server Ansible variable.

Does this mean it's set incorrectly out-of-the-box?

[EdGeraghty]

Does this mean it's set incorrectly out-of-the-box?

@spantaleev explains here: element-hq/element-web#26956

Regardless, I'm very close to finishing an upstream PR to fix Element-Web's behaviour to match the MSC - watch this space 😃

[bartvdbraak]

Anyone able to get this fixed?