Error: `Failed to set remote answer sdp: Called in wrong state: stable` triggers unexpected `unpublish` events

[fede987]

Description

When using the LiveKit Android SDK, an error is encountered intermittently, though often, when setting the remote description.

The LiveKit server is deployed on a custom machine, not using LiveKit Cloud.

The use case is always between 2 participants, A anb B.

Right after A and B enter the room their own audio and video tracks are published and subscribed by each other.
Then error encountered is the one that follows here:

RTCEngine$onAnswer: error setting remote description for answer: Failed to set remote answer sdp: Called in wrong state: stable

When this occurs for the user A, B participant client also receives an unexpected unpublish event from the remote participant. The behavior appears random and is difficult to reproduce reliably.

Expected Behavior

• setRemoteDescription succeeds when negotiation flow is correct.
• No unexpected unpublish events are emitted as a side effect.
• Some API to recover from the error by allowing the re-publish of the tracks

Actual Behavior

• During join or track negotiation, the SDK logs the error above.
• Immediately after, the SDK emits an unpublish event for tracks that were previously published/visible.

Steps to Reproduce

This is intermittent; examples of flows where it has occurred:

1. A and B join a room.
2. A and B publish their own audio and video and the audio and video are then subscrbed correctly.
3. Few seconds after, the local A participant SDK logs the error and the B participants receives an unpublish event.

Environment

• SDK: LiveKit Android SDK
• SDK Version: v2.20.1
• Android Version: Occurring on all versions from 11 to 15
• Devices: Oppo X3 neo, Xiaomi Pocophone f5 pro, various Android emulators
• Network Conditions: stable wi-fi connection

Logs / Stacktrace (from user A)

2025-09-05 15:30:59.765 23421-14241 RTCModule$...ialization com.xxxx.xxxx V webrtc_sdp.cc: (line 3335): Ignoring send_rids without simulcast
2025-09-05 15:30:59.765 23421-14798 RTCModule$...ialization com.xxxx.xxxx E sdp_offer_answer.cc: (line 3759): Called in wrong state: stable (INVALID_STATE)
2025-09-05 15:30:59.765 23421-14798 RTCModule$...ialization com.xxxx.xxxx E sdp_offer_answer.cc: (line 993): Failed to set remote answer sdp: Called in wrong state: stable
2025-09-05 15:30:59.766 23421-14134 RTCEngine com.xxxx.xxxx V received ice candidate from peer: 0:0:candidate:2363694099 1 tcp 1671430143 172.31.120.190 7881 typ host tcptype passive ufrag dOjamyXyvoyHKouk::UNKNOWN, PUBLISHER
2025-09-05 15:30:59.766 23421-14916 SignalClient com.xxxx.xxxx V response: # livekit.LivekitRtc$SignalResponse@eb1a8d1d
trickle {
candidate_init: "{"candidate":"candidate:2371725571 1 udp 2130706431 54.194.75.113 59410 typ host ufrag GLTaUtjrPxKmaysS","sdpMid":"1","sdpMLineIndex":0,"usernameFragment":null}"
}
2025-09-05 15:30:59.767 23421-14330 RTCEngine$onAnswer com.xxxx.xxxx E error setting remote description for answer: Failed to set remote answer sdp: Called in wrong state: stable

[davidliu]

Fixed by #813