Single Peer Connection

.changes/single-pc

@@ -0,0 +1 @@
+minor type="added" "Single peer connection mode via `RoomOptions.singlePeerConnection`. Requires LiveKit Cloud or LiveKit OSS >= 1.9.2."

.github/workflows/ci.yaml

@@ -57,38 +57,38 @@ jobs:
 
           # https://github.com/actions/runner-images/blob/main/images/macos/macos-26-arm64-Readme.md
           - os: macos-26
-            xcode: 26.1
-            platform: "iOS Simulator,name=iPhone 17 Pro,OS=26.1"
+            xcode: 26.3
+            platform: "iOS Simulator,name=iPhone 17 Pro,OS=26.2"
             symbol-graph: true
           - os: macos-26
-            xcode: 26.1
-            platform: "iOS Simulator,name=iPhone 17 Pro,OS=26.1"
+            xcode: 26.3
+            platform: "iOS Simulator,name=iPhone 17 Pro,OS=26.2"
             extension-api-only: true
           - os: macos-26
-            xcode: 26.1
+            xcode: 26.3
             platform: "macOS"
             symbol-graph: true
           - os: macos-26
-            xcode: 26.1
+            xcode: 26.3
             platform: "macOS"
             asan: true
           - os: macos-26
-            xcode: 26.1
+            xcode: 26.3
             platform: "macOS"
             tsan: true
           - os: macos-26
-            xcode: 26.1
+            xcode: 26.3
             platform: "macOS"
             strict-concurrency-env: true
           - os: macos-26
-            xcode: 26.1
+            xcode: 26.3
             platform: "macOS,variant=Mac Catalyst"
           - os: macos-26
-            xcode: 26.1
-            platform: "visionOS Simulator,name=Apple Vision Pro,OS=26.1"
+            xcode: 26.3
+            platform: "visionOS Simulator,name=Apple Vision Pro,OS=26.2"
           - os: macos-26
-            xcode: 26.1
-            platform: "tvOS Simulator,name=Apple TV,OS=26.1"
+            xcode: 26.3
+            platform: "tvOS Simulator,name=Apple TV,OS=26.2"
 
     runs-on: ${{ matrix.os }}
     timeout-minutes: 60
@@ -102,7 +102,8 @@ jobs:
         run: brew install livekit
 
       - name: Run LiveKit Server
-        run: livekit-server --dev &
+        run: |
+          livekit-server --dev --config-body '{"room":{"departure_timeout":1}}' &
 
       - uses: maxim-lobanov/setup-xcode@v1
         with:
@@ -127,7 +128,7 @@ jobs:
       - name: Run Tests
         uses: nick-fields/retry@v3
         env:
-          LIBDISPATCH_COOPERATIVE_POOL_STRICT: ${{ matrix.strict-concurrency-env == true && '1' || '' }}
+          LIBDISPATCH_COOPERATIVE_POOL_STRICT: ${{ matrix.strict-concurrency-env == true && '1' || '0' }}
         with:
           timeout_minutes: ${{ env.TEST_TIMEOUT_MINUTES }}
           max_attempts: ${{ env.TEST_RETRY_ATTEMPTS }}

.github/workflows/cocoapods-lint.yaml

@@ -19,7 +19,7 @@ jobs:
           - os: macos-15
             xcode: 16.4
           - os: macos-26
-            xcode: 26.1
+            xcode: 26.3
     runs-on: ${{ matrix.os }}
     timeout-minutes: 30
     steps:

.github/workflows/publish-docs.yaml

@@ -23,7 +23,7 @@ jobs:
     strategy:
       matrix:
         include:
-          - platform: "iOS Simulator,name=iPhone 17 Pro,OS=26.1"
+          - platform: "iOS Simulator,name=iPhone 17 Pro,OS=26.2"
             artifact_name: symbol-graph-ios
           - platform: "macOS"
             artifact_name: symbol-graph-macos
@@ -38,7 +38,7 @@ jobs:
       - name: Set up Xcode
         uses: maxim-lobanov/setup-xcode@v1
         with:
-          xcode-version: "26.1"
+          xcode-version: "26.3"
 
       - name: Build for Release - Symbol Graph
         run: |
@@ -72,7 +72,7 @@ jobs:
       - name: Set up Xcode
         uses: maxim-lobanov/setup-xcode@v1
         with:
-          xcode-version: "26.1"
+          xcode-version: "26.3"
 
       - name: Download Symbol Graphs
         uses: actions/download-artifact@v4

.gitignore

@@ -1,5 +1,6 @@
 .DS_Store
-/.build
+.build
+.claude
 /Packages
 /*.xcodeproj
 .swiftpm/

Sources/LiveKit/Core/Room+Engine.swift

@@ -44,16 +44,11 @@ extension Room {
         publisherDataChannel.reset()
         subscriberDataChannel.reset()
 
-        let (subscriber, publisher) = _state.read { ($0.subscriber, $0.publisher) }
-
-        // Close transports
-        await publisher?.close()
-        await subscriber?.close()
+        await _state.transport?.close()
 
         // Reset publish state
         _state.mutate {
-            $0.subscriber = nil
-            $0.publisher = nil
+            $0.transport = nil
             $0.hasPublished = false
         }
     }
@@ -75,7 +70,10 @@ extension Room {
 
     func send(dataPacket packet: Livekit_DataPacket) async throws {
         func ensurePublisherConnected() async throws {
-            guard _state.isSubscriberPrimary else { return }
+            // Only needed when subscriber is primary in dual PC mode
+            guard case .subscriberPrimary = _state.transport else {
+                return
+            }
 
             let publisher = try requirePublisher()
 
@@ -91,7 +89,7 @@ extension Room {
         try await ensurePublisherConnected()
 
         // At this point publisher should be .connected and dc should be .open
-        if await !(_state.publisher?.isConnected ?? false) {
+        if await !(_state.transport?.publisher.isConnected ?? false) {
             log("publisher is not .connected", .error)
         }
 
@@ -116,7 +114,7 @@ extension Room {
 
 extension Room {
     // swiftlint:disable:next function_body_length
-    func configureTransports(connectResponse: SignalClient.ConnectResponse) async throws {
+    func configureTransports(connectResponse: SignalClient.ConnectResponse, singlePeerConnection: Bool) async throws {
         func makeConfiguration() -> LKRTCConfiguration {
             let connectOptions = _state.connectOptions
 
@@ -147,23 +145,20 @@ extension Room {
         if case let .join(joinResponse) = connectResponse {
             log("Configuring transports with JOIN response...")
 
-            guard _state.subscriber == nil, _state.publisher == nil else {
+            guard _state.transport == nil else {
                 log("Transports are already configured")
                 return
             }
 
-            // protocol v3
-            let isSubscriberPrimary = joinResponse.subscriberPrimary
-            log("subscriberPrimary: \(joinResponse.subscriberPrimary)")
-
-            let subscriber = try Transport(config: rtcConfiguration,
-                                           target: .subscriber,
-                                           primary: isSubscriberPrimary,
-                                           delegate: self)
+            let isSinglePC = singlePeerConnection
+            let isSubscriberPrimary = isSinglePC ? false : joinResponse.subscriberPrimary
+            log("subscriberPrimary: \(isSubscriberPrimary), singlePeerConnection: \(isSinglePC)")
 
+            // Publisher always created; is primary in single PC mode
             let publisher = try Transport(config: rtcConfiguration,
                                           target: .publisher,
-                                          primary: !isSubscriberPrimary,
+                                          primary: isSinglePC || !isSubscriberPrimary,
+                                          singlePCMode: isSinglePC,
                                           delegate: self)
 
             await publisher.set { [weak self] offer, offerId in
@@ -186,23 +181,29 @@ extension Room {
             log("dataChannel.\(String(describing: reliableDataChannel?.label)) : \(String(describing: reliableDataChannel?.channelId))")
             log("dataChannel.\(String(describing: lossyDataChannel?.label)) : \(String(describing: lossyDataChannel?.channelId))")
 
-            _state.mutate {
-                $0.subscriber = subscriber
-                $0.publisher = publisher
-                $0.isSubscriberPrimary = isSubscriberPrimary
+            let subscriber = isSinglePC ? nil : try Transport(config: rtcConfiguration,
+                                                              target: .subscriber,
+                                                              primary: isSubscriberPrimary,
+                                                              delegate: self)
+
+            let transport: TransportMode = if let subscriber, isSubscriberPrimary {
+                .subscriberPrimary(publisher: publisher, subscriber: subscriber)
+            } else if let subscriber {
+                .publisherPrimary(publisher: publisher, subscriber: subscriber)
+            } else {
+                .publisherOnly(publisher: publisher)
             }
+            _state.mutate { $0.transport = transport }
 
             log("[Connect] Fast publish enabled: \(joinResponse.fastPublish ? "true" : "false")")
-            if !isSubscriberPrimary || joinResponse.fastPublish {
-                // lazy negotiation for protocol v3+
+            if isSinglePC || !isSubscriberPrimary || joinResponse.fastPublish {
+                // In single PC mode or when publisher is primary, negotiate immediately
                 try await publisherShouldNegotiate()
             }
 
         } else if case let .reconnect(reconnectResponse) = connectResponse {
             log("[Connect] Configuring transports with RECONNECT response...")
-            let (subscriber, publisher) = _state.read { ($0.subscriber, $0.publisher) }
-            try await subscriber?.set(configuration: rtcConfiguration)
-            try await publisher?.set(configuration: rtcConfiguration)
+            try await _state.transport?.set(configuration: rtcConfiguration)
             publisherDataChannel.retryReliable(lastSequence: reconnectResponse.lastMessageSeq)
         }
     }
@@ -249,16 +250,32 @@ public enum StartReconnectReason: Sendable {
 extension Room {
     // full connect sequence, doesn't update connection state
     func fullConnectSequence(_ url: URL, _ token: String) async throws {
-        let connectResponse = try await signalClient.connect(url,
+        var singlePC = _state.roomOptions.singlePeerConnection
+
+        let connectResponse: SignalClient.ConnectResponse
+        do {
+            connectResponse = try await signalClient.connect(url,
                                                              token,
                                                              connectOptions: _state.connectOptions,
                                                              reconnectMode: _state.isReconnectingWithMode,
-                                                             adaptiveStream: _state.roomOptions.adaptiveStream)
+                                                             adaptiveStream: _state.roomOptions.adaptiveStream,
+                                                             singlePeerConnection: singlePC)
+        } catch let error as LiveKitError where error.type == .serviceNotFound && singlePC {
+            log("v1 RTC path not supported, retrying with legacy path", .warning)
+            singlePC = false
+            connectResponse = try await signalClient.connect(url,
+                                                             token,
+                                                             connectOptions: _state.connectOptions,
+                                                             reconnectMode: _state.isReconnectingWithMode,
+                                                             adaptiveStream: _state.roomOptions.adaptiveStream,
+                                                             singlePeerConnection: false)
+        }
+
         // Check cancellation after WebSocket connected
         try Task.checkCancellation()
 
         _state.mutate { $0.connectStopwatch.split(label: "signal") }
-        try await configureTransports(connectResponse: connectResponse)
+        try await configureTransports(connectResponse: connectResponse, singlePeerConnection: singlePC)
         // Check cancellation after configuring transports
         try Task.checkCancellation()
 
@@ -288,8 +305,8 @@ extension Room {
             throw LiveKitError(.invalidState)
         }
 
-        guard _state.subscriber != nil, _state.publisher != nil else {
-            log("[Connect] Publisher or subscriber is nil", .error)
+        guard _state.transport != nil else {
+            log("[Connect] Transport is nil", .error)
             throw LiveKitError(.invalidState)
         }
 
@@ -308,16 +325,19 @@ extension Room {
         @Sendable func quickReconnectSequence() async throws {
             log("[Connect] Starting .quick reconnect sequence...")
 
+            let singlePC = await !signalClient.useV0SignalPath
             let connectResponse = try await signalClient.connect(url,
                                                                  token,
                                                                  connectOptions: _state.connectOptions,
                                                                  reconnectMode: _state.isReconnectingWithMode,
                                                                  participantSid: localParticipant.sid,
-                                                                 adaptiveStream: _state.roomOptions.adaptiveStream)
+                                                                 adaptiveStream: _state.roomOptions.adaptiveStream,
+                                                                 singlePeerConnection: singlePC)
             try Task.checkCancellation()
 
             // Update configuration
-            try await configureTransports(connectResponse: connectResponse)
+            try await configureTransports(connectResponse: connectResponse,
+                                          singlePeerConnection: singlePC)
             try Task.checkCancellation()
 
             // Resume after configuring transports...
@@ -337,9 +357,9 @@ extension Room {
             // send SyncState before offer
             try await sendSyncState()
 
-            await _state.subscriber?.setIsRestartingIce()
+            await _state.transport?.setSubscriberRestartingIce()
 
-            if let publisher = _state.publisher, _state.hasPublished {
+            if let publisher = _state.transport?.publisher, _state.hasPublished {
                 // Only if published, wait for publisher to connect...
                 log("[Connect] Waiting for publisher to connect...")
                 try await publisher.createAndSendOffer(iceRestart: true)
@@ -473,13 +493,12 @@ extension Room {
 
 extension Room {
     func sendSyncState() async throws {
-        guard let subscriber = _state.subscriber else {
-            log("Subscriber is nil", .error)
+        guard let transport = _state.transport else {
+            log("Transport is nil", .error)
             return
         }
 
-        let previousAnswer = await subscriber.localDescription
-        let previousOffer = await subscriber.remoteDescription
+        let (previousAnswer, previousOffer) = await transport.syncStateDescriptions()
 
         // 1. autosubscribe on, so subscribed tracks = all tracks - unsub tracks,
         //    in this case, we send unsub tracks, so server add all tracks to this
@@ -517,7 +536,7 @@ extension Room {
 
 extension Room {
     func requirePublisher() throws -> Transport {
-        guard let publisher = _state.publisher else {
+        guard let publisher = _state.transport?.publisher else {
             log("Publisher is nil", .error)
             throw LiveKitError(.invalidState, message: "Publisher is nil")
         }