Element X on iOS and Android doesn't send Authorization header for MSC4143 endpoint → MISSING_MATRIX_RTC_TRANSPORT

[Yason24]

Steps to reproduce

I'm experiencing the same issue as described in this thread. Element X fails to start calls with error MISSING_MATRIX_RTC_TRANSPORT, even though the server is fully and correctly configured.

Environment:

• App: Element X (both iOS and Android)
• Version: 26.03.3
• Devices: iPhone 15 Plus (iOS 26.3.1) and Samsung SM-A725F (Android 14)
• Homeserver: matrix.rdk-invest.ru:8450 (Synapse 1.150.0)
• SFU: LiveKit 1.10.0 with JWT service (lk-jwt-service 0.4.1)
• Reverse proxy: Nginx Proxy Manager
• TURN/STUN: Coturn (works fine for classic Element)

What works correctly:

• ✅ Login and authentication (MAS works)
• ✅ Text messages
• ✅ .well-known/matrix/client returns correct JSON with rtc_foci
• ✅ LiveKit accessible: https://matrix.rdk-invest.ru:8450/livekit/ -> OK
• ✅ JWT service accessible: https://matrix.rdk-invest.ru:8450/livekit/jwt/healthz -> empty response
• ✅ All other authenticated endpoints work (sync, messages, profile, etc.)

.well-known/matrix/client:
json

{
  "m.homeserver": {
    "base_url": "https://matrix.rdk-invest.ru:8450"
  },
  "org.matrix.msc2965.authentication": {
    "issuer": "https://auth.rdk-invest.ru:8450",
    "account": "https://auth.rdk-invest.ru:8450/account/"
  },
  "org.matrix.msc4143.rtc_foci": [
    {
      "type": "livekit",
      "livekit_service_url": "https://matrix.rdk-invest.ru:8450/livekit/jwt"
    }
  ]
}

What doesn't work:

• ❌ Element X cannot start calls
• ❌ Error: MISSING_MATRIX_RTC_TRANSPORT

Server logs (captured request):
text

GET /_matrix/client/unstable/org.matrix.msc4143/rtc/transports HTTP/1.1
Host: matrix.rdk-invest.ru:8450
User-Agent: Element X/26.03.3 (iPhone 15 Plus; iOS 26.3.1; Scale/3.00)
// No Authorization header present

Server response:
text

401 Missing access token

Manual verification (with token):
bash

curl -X GET "https://matrix.rdk-invest.ru:8450/_matrix/client/unstable/org.matrix.msc4143/rtc/transports" \
  -H "Authorization: Bearer <valid_token>"

-> Returns {} (200 OK)

What I've tried:

• Clearing app cache
• Reinstalling Element X
• Rebooting devices
• Restarting Synapse and LiveKit
• Verified .well-known is correct
• Verified LiveKit and JWT service are accessible
• Verified all other endpoints work with authentication

Conclusion:
This is a client-side bug. Element X does not send the Authorization: Bearer ... header specifically for the MSC4143 rtc/transports endpoint, while it correctly sends it for other authenticated endpoints (e.g., /profile, /sync, /messages). Because of this, Synapse returns 401, and the app shows MISSING_MATRIX_RTC_TRANSPORT.

The server is fully configured according to the official Element Call documentation and works perfectly with classic Element for calls (using TURN/Coturn). This issue only affects Element X.

Please fix this bug so Element X can work with self-hosted servers!

Server info for developers:

• .well-known: https://matrix.rdk-invest.ru:8450/.well-known/matrix/client
• LiveKit: https://matrix.rdk-invest.ru:8450/livekit/
• JWT service: https://matrix.rdk-invest.ru:8450/livekit/jwt/healthz

Thank you! 🚀

[pixlwave]

@Yason24: I've transferred this to the Element Call project so that the right team will see it.

[Yason24]

Thank you for getting back to me! 🙏

A quick clarification: the classic Element client does NOT work on this server -- and that's expected, because this server uses MAS (Matrix Authentication Service) with OIDC, which classic Element does not support. That's why we're trying to use Element X in the first place.

The classic Element works fine on my other server (which uses legacy password auth), but on this new server, only Element X is able to log in.

The issue remains:

When Element X tries to start a call, it requests

GET /_matrix/client/unstable/org.matrix.msc4143/rtc/transports

without the Authorization: Bearer ... header.

Synapse responds with 401 Missing access token, and Element X shows MISSING_MATRIX_RTC_TRANSPORT.

I've confirmed that:

• ✅ The endpoint works correctly when called manually with a valid token
• ✅ .well-known/matrix/client is correct and contains rtc_foci
• ✅ LiveKit and JWT service are accessible
• ✅ All other authenticated endpoints (like /sync, /profile, /messages) work fine in Element X -- they include the Authorization header and return 200

So this really seems to be a specific issue with how Element X handles this particular MSC4143 endpoint. If this is a known glitch, I'll wait for the fix -- just wanted to provide as much detail as possible.

Let me know if you need logs, configs, or anything else to help debug.

[BillCarsonFr]

Thanks this is a known issue.
/rtc/transport is not yet supported on embeded, but this should not be a problem because it will fallback to check the well-known.

Related/Duplicate of #3790

We are adding more logs to understand what is happening, but I cannot reproduce yet

[Yason24]

Thank you for the update! I see this is a known issue and related to #3790 🙏

Just to add more context — in my case, the error is MISSING_MATRIX_RTC_TRANSPORT, and the root cause (from server logs) is that Element X does NOT send the Authorization: Bearer ... header when calling the MSC4143 endpoint. All other authenticated endpoints work fine and include the header.

I've already shared the full Nginx configuration, .well-known, and server setup in the thread. Let me know if you need any additional logs or details to help reproduce.

I'll wait for the fix — thanks again for your work on this! 🚀

[BillCarsonFr]

and the root cause (from server logs) is that Element X does NOT send the Authorization: Bearer ...

No this is not the root cause.
This is just fine if this API fails, EC will just then fallback to the well-known.
Nonetheless I created a PR to stop calling this API because it is creating red heerings

Your well-known foci is 404

"org.matrix.msc4143.rtc_foci": [
    {
      "type": "livekit",
      "livekit_service_url": "https://matrix.rdk-invest.ru/livekit/jwt"
    }
  ]

GET https://matrix.rdk-invest.ru/livekit/jwt/
404 page not found

[Yason24]

Update:

I've now fully configured the server with:

• Valid SSL certificate for matrix.rdk-invest.ru
• .well-known/matrix/client correctly served with rtc_foci
• LiveKit accessible at https://matrix.rdk-invest.ru/livekit/sfu/ -> OK
• JWT Service accessible at https://matrix.rdk-invest.ru/livekit/jwt/sfu/get -> 405 Method Not Allowed (expected)
• All experimental flags enabled in Synapse
• livekit_jwt_sso correctly configured

The issue persists. When I try to make a call in Element X:

• No requests appear in JWT Service logs
• No "livekit" or "rtc" mentions in Element X logs
• The app shows MISSING_MATRIX_RTC_TRANSPORT

Conclusion: This is a client-side bug. Element X does not attempt to use LiveKit at all, despite the server being fully configured according to the official documentation.

Please prioritize fixing this so Element X can work with self-hosted servers.

[BillCarsonFr]

@Yason24 Can you provide some logs from EC.
I cannot reproduce your issue

[Yason24]

@BillCarsonFr Thank you for your response!

I've submitted debug logs from Element X on iOS:

• Debug logs ID: console.2026-04-01-22.log

Server is fully configured:

• LiveKit accessible: https://matrix.rdk-invest.ru/livekit/sfu/ → OK
• JWT Service accessible: https://matrix.rdk-invest.ru/livekit/jwt/sfu/get → 405 Method Not Allowed (expected)
• .well-known/matrix/client contains rtc_foci

Let me know if you need any additional information or server logs.

Thank you for your help!