ui: reconnect call (#7711)

* Update Call.hs * Update Internal.hs * add reconnecting string * Update WebRTC.kt * desktop: show reconnecting state, keep call duration * android keep connection time correct wiith adding reconnecting * Update CallTypes.swift add reconnecting status on IOS * Update WebRTC.swift add reconnecting * add reconnecting and make sure call duration is correct * Update call.ts * core: regenerate call.js from call.ts * Update Call.hs revert call status change minimization * Update Internal.hs rever to minimize changes * Update CallTypes.swift minimize changes * Update WebRTC.kt minimize changes * Update CallView.desktop.kt desktop shows reconnecting without sending to core * Update CallView.android.kt show reconnecting without sending it to the core * Update ActiveCallView.swift show reconnecting to ui without sending to core * Update CallView.desktop.kt add reconnecting sound on reconnect * Update CallView.android.kt add reconnecting sound * Update ActiveCallView.swift play reconnecting sound when reconnecting * Update RecAndPlay.desktop.kt * rebuild * refactor * build * android, desktop: restart ICE to reconnect calls * ios: restart ICE to reconnect calls * webrtc: add call reconnection e2e tests * android, desktop: fix lost call commands --------- Co-authored-by: GuavaGoat <320862384+GuavaGoat@users.noreply.github.com> Co-authored-by: Evgeny Poberezkin <evgeny@poberezkin.com> Co-authored-by: Evgeny @ SimpleX Chat <259188159+evgeny-simplex@users.noreply.github.com>
2026-10-22 10:12:25 +00:00 · 2026-10-19 12:17:16 +01:00
1 parent 634fa5ecff
commit 2ea1ec0d50
@@ -1850,8 +1850,8 @@ func apiSendCallAnswer(_ contact: Contact, _ rtcSession: String, _ rtcIceCandida
    try await sendCommandOkResp(.apiSendCallAnswer(contact: contact, answer: answer))
 }

-func apiSendCallExtraInfo(_ contact: Contact, _ rtcIceCandidates: String) async throws {
-    let extraInfo = WebRTCExtraInfo(rtcIceCandidates: rtcIceCandidates)
+func apiSendCallExtraInfo(_ contact: Contact, _ rtcSession: String?, _ rtcIceCandidates: String) async throws {
+    let extraInfo = WebRTCExtraInfo(rtcSession: rtcSession, rtcIceCandidates: rtcIceCandidates)
    try await sendCommandOkResp(.apiSendCallExtraInfo(contact: contact, extraInfo: extraInfo))
 }

@@ -2987,7 +2987,7 @@ func processReceivedMsg(_ res: ChatEvent) async {
        }
    case let .callExtraInfo(_, contact, extraInfo):
        await withCall(contact) { _ in
-            await m.callCommand.processCommand(.ice(iceCandidates: extraInfo.rtcIceCandidates))
+            await m.callCommand.processCommand(.ice(iceCandidates: extraInfo.rtcIceCandidates, session: extraInfo.rtcSession))
        }
    case let .callEnded(_, contact):
        if let invitation = await MainActor.run(body: { m.callInvitations.removeValue(forKey: contact.id) }) {
@@ -161,10 +161,10 @@ struct ActiveCallView: View {
                        CallSoundsPlayer.shared.stop()
                    }
                }
-            case let .ice(iceCandidates):
+            case let .ice(iceCandidates, session):
                Task {
                    do {
-                        try await apiSendCallExtraInfo(call.contact, iceCandidates)
+                        try await apiSendCallExtraInfo(call.contact, session, iceCandidates)
                    } catch {
                        logger.error("apiSendCallExtraInfo \(responseError(error))")
                    }
@@ -172,15 +172,24 @@ struct ActiveCallView: View {
            case let .connection(state):
                if let callStatus = WebRTCCallStatus.init(rawValue: state.connectionState),
                   case .connected = callStatus {
-                    call.direction == .outgoing
-                    ? CallController.shared.reportOutgoingCall(call: call, connectedAt: nil)
-                    : CallController.shared.reportIncomingCall(call: call, connectedAt: nil)
+                    // connectedAt is kept on reconnection, so that call duration is not reset
+                    if call.connectedAt == nil {
+                        call.direction == .outgoing
+                        ? CallController.shared.reportOutgoingCall(call: call, connectedAt: nil)
+                        : CallController.shared.reportIncomingCall(call: call, connectedAt: nil)
+                        call.connectedAt = .now
+                    }
                    call.callState = .connected
-                    call.connectedAt = .now
+                    CallSoundsPlayer.shared.stop()
                    if !wasConnected {
                        CallSoundsPlayer.shared.vibrate(long: false)
                        wasConnected = true
                    }
+                } else if state.connectionState == "reconnecting" {
+                    if call.callState != .reconnecting {
+                        CallSoundsPlayer.shared.startConnectingCallSound()
+                    }
+                    call.callState = .reconnecting
                }
                if state.connectionState == "closed" {
                    closeCallView(client)
@@ -190,17 +199,22 @@ struct ActiveCallView: View {
                    m.activeCall = nil
                    m.activeCallViewIsCollapsed = false
                }
-                Task {
-                    do {
-                        try await apiCallStatus(call.contact, state.connectionState)
-                    } catch {
-                        logger.error("apiCallStatus \(responseError(error))")
+                // "reconnecting" is not a core call status
+                if state.connectionState != "reconnecting" {
+                    Task {
+                        do {
+                            try await apiCallStatus(call.contact, state.connectionState)
+                        } catch {
+                            logger.error("apiCallStatus \(responseError(error))")
+                        }
                    }
                }
            case let .connected(connectionInfo):
                call.callState = .connected
                call.connectionInfo = connectionInfo
-                call.connectedAt = .now
+                if call.connectedAt == nil {
+                    call.connectedAt = .now
+                }
                if !wasConnected {
                    CallSoundsPlayer.shared.vibrate(long: false)
                    wasConnected = true
@@ -77,6 +77,7 @@ enum CallState {
    case answerReceived     // incoming - webrtc answer received via API
    case negotiated         // outgoing - webrtc offer processed and answer sent, incoming - webrtc answer processed
    case connected
+    case reconnecting
    case ended

    var text: LocalizedStringKey {
@@ -89,6 +90,7 @@ enum CallState {
        case .answerReceived: return "received confirmation…"
        case .negotiated: return "connecting…"
        case .connected: return "connected"
+        case .reconnecting: return "reconnecting…"
        case .ended: return "ended"
        }
    }
@@ -119,7 +121,7 @@ enum WCallCommand: Equatable, Encodable, Decodable {
    case start(media: CallMediaType, aesKey: String? = nil, iceServers: [RTCIceServer]? = nil, relay: Bool? = nil)
    case offer(offer: String, iceCandidates: String, media: CallMediaType, aesKey: String? = nil, iceServers: [RTCIceServer]? = nil, relay: Bool? = nil)
    case answer(answer: String, iceCandidates: String)
-    case ice(iceCandidates: String)
+    case ice(iceCandidates: String, session: String? = nil)
    case media(source: CallMediaSource, enable: Bool)
    case end

@@ -131,6 +133,7 @@ enum WCallCommand: Equatable, Encodable, Decodable {
        case offer
        case answer
        case iceCandidates
+        case session
        case enable
        case iceServers
        case relay
@@ -174,9 +177,10 @@ enum WCallCommand: Equatable, Encodable, Decodable {
            try container.encode("answer", forKey: .type)
            try container.encode(answer, forKey: .answer)
            try container.encode(iceCandidates, forKey: .iceCandidates)
-        case let .ice(iceCandidates):
+        case let .ice(iceCandidates, session):
            try container.encode("ice", forKey: .type)
            try container.encode(iceCandidates, forKey: .iceCandidates)
+            try container.encodeIfPresent(session, forKey: .session)
        case let .media(source, enable):
            try container.encode("media", forKey: .type)
            try container.encode(source, forKey: .media)
@@ -213,7 +217,8 @@ enum WCallCommand: Equatable, Encodable, Decodable {
            self = .answer(answer: answer, iceCandidates: iceCandidates)
        case "ice":
            let iceCandidates = try container.decode(String.self, forKey: CodingKeys.iceCandidates)
-            self = .ice(iceCandidates: iceCandidates)
+            let session = try container.decodeIfPresent(String.self, forKey: CodingKeys.session)
+            self = .ice(iceCandidates: iceCandidates, session: session)
        case "media":
            let source = try container.decode(CallMediaSource.self, forKey: CodingKeys.source)
            let enable = try container.decode(Bool.self, forKey: CodingKeys.enable)
@@ -231,7 +236,7 @@ enum WCallResponse: Equatable, Decodable {
    case capabilities(capabilities: CallCapabilities)
    case offer(offer: String, iceCandidates: String, capabilities: CallCapabilities)
    case answer(answer: String, iceCandidates: String)
-    case ice(iceCandidates: String)
+    case ice(iceCandidates: String, session: String? = nil)
    case connection(state: ConnectionState)
    case connected(connectionInfo: ConnectionInfo)
    case peerMedia(source: CallMediaSource, enabled: Bool)
@@ -246,6 +251,7 @@ enum WCallResponse: Equatable, Decodable {
        case offer
        case answer
        case iceCandidates
+        case session
        case state
        case connectionInfo
        case message
@@ -290,7 +296,8 @@ enum WCallResponse: Equatable, Decodable {
                self = .answer(answer: answer, iceCandidates: iceCandidates)
            case "ice":
                let iceCandidates = try container.decode(String.self, forKey: CodingKeys.iceCandidates)
-                self = .ice(iceCandidates: iceCandidates)
+                let session = try container.decodeIfPresent(String.self, forKey: CodingKeys.session)
+                self = .ice(iceCandidates: iceCandidates, session: session)
            case "connection":
                let state = try container.decode(ConnectionState.self, forKey: CodingKeys.state)
                self = .connection(state: state)
@@ -333,9 +340,10 @@ extension WCallResponse: Encodable {
            try container.encode("answer", forKey: .type)
            try container.encode(answer, forKey: .answer)
            try container.encode(iceCandidates, forKey: .iceCandidates)
-        case let .ice(iceCandidates):
+        case let .ice(iceCandidates, session):
            try container.encode("ice", forKey: .type)
            try container.encode(iceCandidates, forKey: .iceCandidates)
+            try container.encodeIfPresent(session, forKey: .session)
        case let .connection(state):
            try container.encode("connection", forKey: .type)
            try container.encode(state, forKey: .state)
@@ -20,6 +20,8 @@ final class WebRTCClient: NSObject, RTCVideoViewDelegate, RTCFrameEncryptorDeleg
    }()
    private static let ivTagBytes: Int = 28
    private static let enableEncryption: Bool = true
+    private static let reconnectTimeout: UInt64 = 30_000_000_000
+    private static let iceRestartInterval: UInt64 = 10_000_000_000
    private var chat_ctrl = getChatCtrl()

    struct Call {
@@ -37,6 +39,9 @@ final class WebRTCClient: NSObject, RTCVideoViewDelegate, RTCFrameEncryptorDeleg
        var frameEncryptor: RTCFrameEncryptor?
        var frameDecryptor: RTCFrameDecryptor?
        var peerHasOldVersion: Bool
+        var wasConnected = false
+        var reconnection: Task<Void, Never>? = nil
+        var iceRestarts: Task<Void, Never>? = nil
    }

    struct NotConnectedCall {
@@ -257,11 +262,15 @@ final class WebRTCClient: NSObject, RTCVideoViewDelegate, RTCFrameEncryptorDeleg
                    resp = .error(message: "answer: remote description is not set")
                }
            }
-        case let .ice(iceCandidates):
+        case let .ice(iceCandidates, session):
            if let pc = pc,
               let remoteIceCandidates: [RTCIceCandidate] = decodeJSON(decompressFromBase64(input: iceCandidates)) {
-                addIceCandidates(pc, remoteIceCandidates)
-                resp = .ok
+                if let session {
+                    resp = await receiveRestartSession(pc, session, remoteIceCandidates)
+                } else {
+                    addIceCandidates(pc, remoteIceCandidates)
+                    resp = .ok
+                }
            } else {
                resp = .error(message: "ice: call not started")
            }
@@ -301,6 +310,101 @@ final class WebRTCClient: NSObject, RTCVideoViewDelegate, RTCFrameEncryptorDeleg
        }
    }

+    private func startReconnecting(_ connection: RTCPeerConnection) async {
+        activeCall?.reconnection = Task {
+            _ = try? await Task.sleep(nanoseconds: WebRTCClient.reconnectTimeout)
+            if Task.isCancelled { return }
+            await sendConnectionState(connection, "disconnected")
+            endCall()
+        }
+        // Only the party that sent the initial offer restarts ICE, so that restart offers never collide
+        if connection.localDescription?.type == .offer {
+            activeCall?.iceRestarts = Task {
+                while !Task.isCancelled {
+                    await restartIce(connection)
+                    _ = try? await Task.sleep(nanoseconds: WebRTCClient.iceRestartInterval)
+                }
+            }
+        }
+        await sendConnectionState(connection, "reconnecting")
+    }
+
+    private func stopReconnecting() {
+        activeCall?.reconnection?.cancel()
+        activeCall?.reconnection = nil
+        activeCall?.iceRestarts?.cancel()
+        activeCall?.iceRestarts = nil
+    }
+
+    private func restartIce(_ connection: RTCPeerConnection) async {
+        // the previous restart offer is not answered yet
+        if connection.signalingState != .stable { return }
+        let (offer, error) = await connection.offer(iceRestart: true)
+        if let offer {
+            await sendRestartSession(offer)
+        } else {
+            logger.error("WebRTCClient: ICE restart error: \(error?.localizedDescription ?? "unknown error")")
+        }
+    }
+
+    private func receiveRestartSession(_ pc: RTCPeerConnection, _ session: String, _ remoteIceCandidates: [RTCIceCandidate]) async -> WCallResponse {
+        guard let desc: CustomRTCSessionDescription = decodeJSON(decompressFromBase64(input: session)),
+              let type = desc.type, let sdp = desc.sdp else {
+            return .error(message: "ice: invalid session")
+        }
+        let remoteDesc = RTCSessionDescription(type: type.toWebRTCSdpType(), sdp: sdp)
+        if type == .offer && pc.localDescription?.type != .offer {
+            if (try? await pc.setRemoteDescription(remoteDesc)) == nil {
+                return .error(message: "ice: remote offer is not set")
+            }
+            let (answer, error) = await pc.answer()
+            guard let answer else {
+                return .error(message: "ice: answer error: \(error?.localizedDescription ?? "unknown error")")
+            }
+            addIceCandidates(pc, remoteIceCandidates)
+            await sendRestartSession(answer)
+        } else if type == .answer && pc.signalingState == .haveLocalOffer {
+            if (try? await pc.setRemoteDescription(remoteDesc)) == nil {
+                return .error(message: "ice: remote answer is not set")
+            }
+            addIceCandidates(pc, remoteIceCandidates)
+        } else {
+            return .error(message: "ice: unexpected ICE restart \(type.rawValue)")
+        }
+        return .ok
+    }
+
+    private func sendRestartSession(_ desc: RTCSessionDescription) async {
+        await sendCallResponse(.init(
+            corrId: nil,
+            resp: .ice(
+                iceCandidates: compressToBase64(input: encodeJSON(await getInitialIceCandidates())),
+                session: compressToBase64(input: encodeJSON(CustomRTCSessionDescription(type: desc.type.toSdpType(), sdp: desc.sdp)))
+            ),
+            command: nil)
+        )
+        waitForMoreIceCandidates()
+    }
+
+    private func sendConnectionState(_ connection: RTCPeerConnection, _ connectionState: String) async {
+        guard let iceConnectionState = connection.iceConnectionState.toString(),
+              let iceGatheringState = connection.iceGatheringState.toString(),
+              let signalingState = connection.signalingState.toString()
+        else {
+            return
+        }
+        await sendCallResponse(.init(
+            corrId: nil,
+            resp: .connection(state: ConnectionState(
+                connectionState: connectionState,
+                iceConnectionState: iceConnectionState,
+                iceGatheringState: iceGatheringState,
+                signalingState: signalingState)
+            ),
+            command: nil)
+        )
+    }
+
    // Spec: spec/services/calls.md#sendIceCandidates
    func sendIceCandidates(_ candidates: [RTCIceCandidate]) async {
        await self.sendCallResponse(.init(
@@ -657,6 +761,8 @@ final class WebRTCClient: NSObject, RTCVideoViewDelegate, RTCFrameEncryptorDeleg
        (notConnectedCall?.localCameraAndTrack?.0 as? RTCCameraVideoCapturer)?.stopCapture()
        guard let call = activeCall else { return }
        logger.debug("WebRTCClient: ending the call")
+        call.reconnection?.cancel()
+        call.iceRestarts?.cancel()
        call.connection.close()
        call.connection.delegate = nil
        call.frameEncryptor?.delegate = nil
@@ -678,16 +784,18 @@ final class WebRTCClient: NSObject, RTCVideoViewDelegate, RTCFrameEncryptorDeleg


 extension WebRTC.RTCPeerConnection {
-    func mediaConstraints() -> RTCMediaConstraints {
-        RTCMediaConstraints(
-            mandatoryConstraints: [kRTCMediaConstraintsOfferToReceiveAudio: kRTCMediaConstraintsValueTrue,
-                                   kRTCMediaConstraintsOfferToReceiveVideo: kRTCMediaConstraintsValueTrue],
-            optionalConstraints: nil)
+    func mediaConstraints(iceRestart: Bool = false) -> RTCMediaConstraints {
+        var constraints = [kRTCMediaConstraintsOfferToReceiveAudio: kRTCMediaConstraintsValueTrue,
+                           kRTCMediaConstraintsOfferToReceiveVideo: kRTCMediaConstraintsValueTrue]
+        if iceRestart {
+            constraints[kRTCMediaConstraintsIceRestart] = kRTCMediaConstraintsValueTrue
+        }
+        return RTCMediaConstraints(mandatoryConstraints: constraints, optionalConstraints: nil)
    }

-    func offer() async -> (RTCSessionDescription?, Error?) {
+    func offer(iceRestart: Bool = false) async -> (RTCSessionDescription?, Error?) {
        await withCheckedContinuation { cont in
-            offer(for: mediaConstraints()) { (sdp, error) in
+            offer(for: mediaConstraints(iceRestart: iceRestart)) { (sdp, error) in
                self.processSDP(cont, sdp, error)
            }
        }
@@ -766,24 +874,20 @@ extension WebRTCClient: RTCPeerConnectionDelegate {
    func peerConnection(_ connection: RTCPeerConnection, didChange newState: RTCIceConnectionState) {
        debugPrint("Connection new connection state: \(newState.toString() ?? "" + newState.rawValue.description) \(connection.receivers)")

-        guard let connectionStateString = newState.toString(),
-              let iceConnectionStateString = connection.iceConnectionState.toString(),
-              let iceGatheringStateString = connection.iceGatheringState.toString(),
-              let signalingStateString = connection.signalingState.toString()
-        else {
-            return
-        }
+        guard let connectionStateString = newState.toString() else { return }
        Task {
-            await sendCallResponse(.init(
-                corrId: nil,
-                resp: .connection(state: ConnectionState(
-                    connectionState: connectionStateString,
-                    iceConnectionState: iceConnectionStateString,
-                    iceGatheringState: iceGatheringStateString,
-                    signalingState: signalingStateString)
-                ),
-                command: nil)
-            )
+            if activeCall?.wasConnected == true {
+                switch newState {
+                case .disconnected, .failed:
+                    if activeCall?.reconnection == nil {
+                        await startReconnecting(connection)
+                    }
+                    return
+                case .new, .checking: return
+                default: ()
+                }
+            }
+            await sendConnectionState(connection, connectionStateString)

            switch newState {
            case .checking:
@@ -792,7 +896,10 @@ extension WebRTCClient: RTCPeerConnectionDelegate {
                }
                let enableSpeaker: Bool = ChatModel.shared.activeCall?.localMediaSources.hasVideo == true
                setSpeakerEnabledAndConfigureSession(enableSpeaker)
-            case .connected: sendConnectedEvent(connection)
+            case .connected:
+                stopReconnecting()
+                activeCall?.wasConnected = true
+                sendConnectedEvent(connection)
            case .disconnected, .failed: endCall()
            default: ()
            }
@@ -34,10 +34,12 @@ public struct WebRTCSession: Codable {

 // Spec: spec/services/calls.md#WebRTCExtraInfo
 public struct WebRTCExtraInfo: Codable {
-    public init(rtcIceCandidates: String) {
+    public init(rtcSession: String?, rtcIceCandidates: String) {
+        self.rtcSession = rtcSession
        self.rtcIceCandidates = rtcIceCandidates
    }

+    public var rtcSession: String?
    public var rtcIceCandidates: String
 }

@@ -103,6 +103,14 @@ All signaling messages are exchanged via E2E encrypted SMP messages (no central
 5. `CallViewRenderers` manages WebRTC video rendering surfaces.
 6. Call status updates are sent via `apiCallStatus(contact:status:)`.

+### 6.1 Reconnection
+
+1. A connected call loses its connection, e.g. when the device switches between Wi-Fi and mobile network.
+2. The call shows "reconnecting…" and plays the connecting sound. Call duration continues, as this state is not reported to the core.
+3. The callee (the party that sent the initial offer) restarts ICE every 10 seconds, sending the new offer via `apiSendCallExtraInfo` with `rtcSession`; the caller answers the same way.
+4. When the connection is restored, the call returns to connected state.
+5. If the connection is not restored in 30 seconds, the call ends. Clients without ICE restart support ignore the restart offer, so the call ends in this case.
+
 ### 7. Audio Routing

 1. `CallAudioDeviceManager` handles audio device selection.
@@ -141,7 +149,7 @@ All signaling messages are exchanged via E2E encrypted SMP messages (no central
 | `RcvCallInvitation` | `SimpleXChat/CallTypes.swift` | Incoming call: user, contact, callType, sharedKey, callUUID, callTs |
 | `WebRTCCallOffer` | `SimpleXChat/CallTypes.swift` | SDP offer with call type and WebRTC session data |
 | `WebRTCSession` | `SimpleXChat/CallTypes.swift` | `rtcSession` (SDP) and `rtcIceCandidates` (serialized) |
-| `WebRTCExtraInfo` | `SimpleXChat/CallTypes.swift` | Additional ICE candidates sent after initial offer/answer |
+| `WebRTCExtraInfo` | `SimpleXChat/CallTypes.swift` | Additional ICE candidates sent after initial offer/answer, and ICE restart offer/answer |
 | `WebRTCCallStatus` | `SimpleXChat/CallTypes.swift` | Call lifecycle states for status reporting |
 | `CallMediaSource` | `SimpleXChat/CallTypes.swift` | `.mic`, `.camera`, `.screenAudio`, `.screenVideo`, `.unknown` |
 | `VideoCamera` | `SimpleXChat/CallTypes.swift` | `.user` (front) or `.environment` (rear) camera |
@@ -152,7 +160,7 @@ All signaling messages are exchanged via E2E encrypted SMP messages (no central
 |-------|-------|----------|
 | Chat not ready on CallKit answer | App suspended, slow startup | `waitUntilChatStarted` with 30s timeout; `action.fail()` on timeout |
 | Call invitation not found | Race condition between notification and event processing | `justRefreshCallInvitations()` retry |
-| WebRTC peer connection failure | NAT traversal, network issues | Call ends with error status |
+| WebRTC peer connection failure | NAT traversal, network issues | Before connection: call ends with error status; after connection: reconnection with ICE restart, call ends if not reconnected in 30 seconds |
 | CallKit action fail | Internal state mismatch | `action.fail()` called, call cleaned up |
 | No camera/mic permission | User denied permissions | Permission request dialog shown |

@@ -179,7 +179,7 @@ The `ChatCommand` enum ([`AppAPITypes.swift` L15](../Shared/Model/AppAPITypes.sw
 | `apiRejectCall` | `contact` | Reject incoming call | [L158](../Shared/Model/AppAPITypes.swift#L158) |
 | `apiSendCallOffer` | `contact, callOffer: WebRTCCallOffer` | Send SDP offer | [L159](../Shared/Model/AppAPITypes.swift#L159) |
 | `apiSendCallAnswer` | `contact, answer: WebRTCSession` | Send SDP answer | [L160](../Shared/Model/AppAPITypes.swift#L160) |
-| `apiSendCallExtraInfo` | `contact, extraInfo: WebRTCExtraInfo` | Send ICE candidates | [L161](../Shared/Model/AppAPITypes.swift#L161) |
+| `apiSendCallExtraInfo` | `contact, extraInfo: WebRTCExtraInfo` | Send ICE candidates or ICE restart offer/answer | [L171](../Shared/Model/AppAPITypes.swift#L171) |
 | `apiEndCall` | `contact` | End active call | [L162](../Shared/Model/AppAPITypes.swift#L162) |
 | `apiGetCallInvitations` | -- | Get pending call invitations | [L163](../Shared/Model/AppAPITypes.swift#L163) |
 | `apiCallStatus` | `contact, callStatus` | Report call status change | [L164](../Shared/Model/AppAPITypes.swift#L164) |
@@ -116,7 +116,10 @@ Manages the WebRTC peer connection, media streams, and data channels.
 | [`sendCallCommand`](../../Shared/Views/Call/WebRTCClient.swift#L176) | Dispatches WCallCommand (offer/answer/ICE) | L176 |
 | [`addIceCandidates`](../../Shared/Views/Call/WebRTCClient.swift#L165) | `peerConnection.add(RTCIceCandidate)` | L165 |
 | [`getInitialIceCandidates`](../../Shared/Views/Call/WebRTCClient.swift#L285) | Collects initial ICE candidates | L285 |
-| [`sendIceCandidates`](../../Shared/Views/Call/WebRTCClient.swift#L305) | Sends gathered ICE candidates | L305 |
+| [`sendIceCandidates`](../../Shared/Views/Call/WebRTCClient.swift#L409) | Sends gathered ICE candidates | L409 |
+| [`startReconnecting`](../../Shared/Views/Call/WebRTCClient.swift#L313) | Reports "reconnecting", starts reconnection timeout and, for the party that sent the initial offer, periodic ICE restarts | L313 |
+| [`restartIce`](../../Shared/Views/Call/WebRTCClient.swift#L339) | Creates ICE restart offer and sends it with candidates in `.ice(iceCandidates:session:)` | L339 |
+| [`receiveRestartSession`](../../Shared/Views/Call/WebRTCClient.swift#L350) | Applies ICE restart offer (and sends the answer) or answer received in `.ice` command | L350 |
 | [`enableMedia`](../../Shared/Views/Call/WebRTCClient.swift#L365) | Enable/disable audio or video track | L365 |
 | [`setupLocalTracks`](../../Shared/Views/Call/WebRTCClient.swift#L423) | Creates audio/video tracks and adds to connection | L423 |
 | [`startCaptureLocalVideo`](../../Shared/Views/Call/WebRTCClient.swift#L581) | Front/back camera toggle and capture start | L581 |
@@ -179,6 +182,10 @@ All call signaling travels through the same encrypted SMP message channels used
 5. P2P connection established
 ```

+### Reconnection
+
+When a connected call loses ICE connection (`.disconnected` or `.failed`), `WebRTCClient` reports `"reconnecting"` connection state instead of ending the call. `ActiveCallView` sets `.reconnecting` call state and plays the connecting sound; this state is not sent to the core via `apiCallStatus`, and `connectedAt` is kept. The party that sent the initial offer (callee) restarts ICE every 10 seconds: the restart offer and answer are sent via `apiSendCallExtraInfo` with `rtcSession` (`x.call.extra`). When ICE connects again, the call returns to `.connected`. If it does not reconnect in 30 seconds, `WebRTCClient` reports `"disconnected"` and ends the call.
+
 ### API Commands

 | Command | Direction | Purpose |
@@ -187,7 +194,7 @@ All call signaling travels through the same encrypted SMP message channels used
 | `apiRejectCall(contact:)` | Callee -> Caller | Reject call |
 | `apiSendCallOffer(contact:, callOffer:)` | Callee -> Caller | Send SDP offer |
 | `apiSendCallAnswer(contact:, answer:)` | Caller -> Callee | Send SDP answer |
-| `apiSendCallExtraInfo(contact:, extraInfo:)` | Both | Send ICE candidates |
+| `apiSendCallExtraInfo(contact:, extraInfo:)` | Both | Send ICE candidates, or ICE restart offer/answer in `rtcSession` |
 | `apiEndCall(contact:)` | Either | End call |
 | `apiGetCallInvitations` | -- | Get pending invitations |
 | `apiCallStatus(contact:, callStatus:)` | -- | Report status change |
@@ -317,10 +324,11 @@ struct WebRTCSession {
 }
 ```

-### [WebRTCExtraInfo](../../SimpleXChat/CallTypes.swift#L36-L42)
+### [WebRTCExtraInfo](../../SimpleXChat/CallTypes.swift#L36-L45)

 ```swift
 struct WebRTCExtraInfo {
+    var rtcSession: String?       // ICE restart offer or answer
    var rtcIceCandidates: String  // Additional ICE candidates
 }
 ```
@@ -330,7 +338,7 @@ struct WebRTCExtraInfo {
 Stored in `ChatModel.activeCall`:
 - Contact reference
 - Call UUID
- Call state (enum: `.waitCapabilities`, `.invitationAccepted`, `.offerSent`, `.answerReceived`, `.connected`, etc.)
+- Call state (enum: `.waitCapabilities`, `.invitationAccepted`, `.offerSent`, `.answerReceived`, `.connected`, `.reconnecting`, etc.)
 - Media type
 - WebRTCClient reference

@@ -52,8 +52,7 @@ import dev.icerock.moko.resources.StringResource
 import dev.icerock.moko.resources.compose.painterResource
 import dev.icerock.moko.resources.compose.stringResource
 import kotlinx.coroutines.*
-import kotlinx.coroutines.flow.distinctUntilChanged
-import kotlinx.coroutines.flow.filterNotNull
+import kotlinx.coroutines.flow.first
 import kotlinx.datetime.Clock
 import kotlinx.serialization.encodeToString
 import java.io.Closeable
@@ -168,13 +167,24 @@ actual fun ActiveCallView() {
            CallSoundsPlayer.stop()
          }
          is WCallResponse.Ice -> withBGApi {
-            chatModel.controller.apiSendCallExtraInfo(callRh, call.contact, r.iceCandidates)
+            chatModel.controller.apiSendCallExtraInfo(callRh, call.contact, r.session, r.iceCandidates)
          }
          is WCallResponse.Connection ->
-            try {
+            // the call is restored and NOT sent to the core
+            // Makes sure the core DOES NOT record the duration wrong if a reconnect happens
+            if (r.state.connectionState == "reconnecting") {
+              if (call.callState != CallState.Reconnecting) {
+                CallSoundsPlayer.startConnectingCallSound(scope)
+              }
+              updateActiveCall(call) { it.copy(callState = CallState.Reconnecting) }
+            } else try {
              val callStatus = json.decodeFromString<WebRTCCallStatus>("\"${r.state.connectionState}\"")
              if (callStatus == WebRTCCallStatus.Connected) {
-                updateActiveCall(call) { it.copy(callState = CallState.Connected, connectedAt = Clock.System.now()) }
+                if (call.callState == CallState.Reconnecting) {
+                  CallSoundsPlayer.stop()
+                }
+                // connectedAt is only set ONCE, this way call duration is NOT reset when the call is restored from reconnecting
+                updateActiveCall(call) { it.copy(callState = CallState.Connected, connectedAt = it.connectedAt ?: Clock.System.now()) }
              }
              withBGApi { chatModel.controller.apiCallStatus(callRh, call.contact, callStatus) }
            } catch (e: Throwable) {
@@ -705,18 +715,17 @@ fun WebRTCView(callCommand: SnapshotStateList<WCallCommand>, onResponse: (WVAPIM
  val wv = webView.value
  if (wv != null) {
    LaunchedEffect(Unit) {
-      snapshotFlow { callCommand.firstOrNull() }
-        .distinctUntilChanged()
-        .filterNotNull()
-        .collect {
-          while (callCommand.isNotEmpty()) {
-            val cmd = callCommand.removeFirstOrNull()
-            Log.d(TAG, "WebRTCView LaunchedEffect executing ${cmd?.javaClass?.simpleName}")
-            if (cmd != null) {
-              processCommand(wv, cmd)
-            }
+      while (isActive) {
+        // waiting for the first command would miss a command equal to the previous one
+        snapshotFlow { callCommand.isNotEmpty() }.first { it }
+        while (callCommand.isNotEmpty()) {
+          val cmd = callCommand.removeFirstOrNull()
+          Log.d(TAG, "WebRTCView LaunchedEffect executing ${cmd?.javaClass?.simpleName}")
+          if (cmd != null) {
+            processCommand(wv, cmd)
          }
        }
+      }
    }
  }
  val assetLoader = WebViewAssetLoader.Builder()
@@ -2185,8 +2185,8 @@ object ChatController {
    return r.result is CR.CmdOk
  }

-  suspend fun apiSendCallExtraInfo(rh: Long?, contact: Contact, rtcIceCandidates: String): Boolean {
-    val extraInfo = WebRTCExtraInfo(rtcIceCandidates)
+  suspend fun apiSendCallExtraInfo(rh: Long?, contact: Contact, rtcSession: String?, rtcIceCandidates: String): Boolean {
+    val extraInfo = WebRTCExtraInfo(rtcSession, rtcIceCandidates)
    val r = sendCmd(rh, CC.ApiSendCallExtraInfo(contact, extraInfo))
    return r.result is CR.CmdOk
  }
@@ -3436,7 +3436,7 @@ object ChatController {
      }
      is CR.CallExtraInfo -> {
        withCall(r, r.contact) { _ ->
-          chatModel.callCommand.add(WCallCommand.Ice(iceCandidates = r.extraInfo.rtcIceCandidates))
+          chatModel.callCommand.add(WCallCommand.Ice(iceCandidates = r.extraInfo.rtcIceCandidates, session = r.extraInfo.rtcSession))
        }
      }
      is CR.CallEnded -> {
@@ -56,6 +56,7 @@ enum class CallState {
  AnswerReceived,
  Negotiated,
  Connected,
+  Reconnecting,
  Ended;

  val text: String get() = when(this) {
@@ -67,6 +68,7 @@ enum class CallState {
    AnswerReceived -> generalGetString(MR.strings.callstate_received_confirmation)
    Negotiated -> generalGetString(MR.strings.callstate_connecting)
    Connected -> generalGetString(MR.strings.callstate_connected)
+    Reconnecting -> generalGetString(MR.strings.callstate_reconnecting)
    Ended -> generalGetString(MR.strings.callstate_ended)
  }
 }
@@ -91,7 +93,7 @@ sealed class WCallCommand {
  @Serializable @SerialName("start") data class Start(val media: CallMediaType, val aesKey: String? = null, val iceServers: List<RTCIceServer>? = null, val relay: Boolean? = null): WCallCommand()
  @Serializable @SerialName("offer") data class Offer(val offer: String, val iceCandidates: String, val media: CallMediaType, val aesKey: String? = null, val iceServers: List<RTCIceServer>? = null, val relay: Boolean? = null): WCallCommand()
  @Serializable @SerialName("answer") data class Answer (val answer: String, val iceCandidates: String): WCallCommand()
-  @Serializable @SerialName("ice") data class Ice(val iceCandidates: String): WCallCommand()
+  @Serializable @SerialName("ice") data class Ice(val iceCandidates: String, val session: String? = null): WCallCommand()
  @Serializable @SerialName("media") data class Media(val source: CallMediaSource, val enable: Boolean): WCallCommand()
  @Serializable @SerialName("camera") data class Camera(val camera: VideoCamera): WCallCommand()
  @Serializable @SerialName("description") data class Description(val state: String, val description: String): WCallCommand()
@@ -104,7 +106,7 @@ sealed class WCallResponse {
  @Serializable @SerialName("capabilities") data class Capabilities(val capabilities: CallCapabilities): WCallResponse()
  @Serializable @SerialName("offer") data class Offer(val offer: String, val iceCandidates: String, val capabilities: CallCapabilities): WCallResponse()
  @Serializable @SerialName("answer") data class Answer(val answer: String, val iceCandidates: String): WCallResponse()
-  @Serializable @SerialName("ice") data class Ice(val iceCandidates: String): WCallResponse()
+  @Serializable @SerialName("ice") data class Ice(val iceCandidates: String, val session: String? = null): WCallResponse()
  @Serializable @SerialName("connection") data class Connection(val state: ConnectionState): WCallResponse()
  @Serializable @SerialName("connected") data class Connected(val connectionInfo: ConnectionInfo): WCallResponse()
  @Serializable @SerialName("peerMedia") data class PeerMedia(val source: CallMediaSource, val enabled: Boolean): WCallResponse()
@@ -116,7 +118,7 @@ sealed class WCallResponse {

@Serializable data class WebRTCCallOffer(val callType: CallType, val rtcSession: WebRTCSession)
@Serializable data class WebRTCSession(val rtcSession: String, val rtcIceCandidates: String)
-@Serializable data class WebRTCExtraInfo(val rtcIceCandidates: String)
+@Serializable data class WebRTCExtraInfo(val rtcSession: String? = null, val rtcIceCandidates: String)
@Serializable data class CallType(val media: CallMediaType, val capabilities: CallCapabilities)
@Serializable data class RcvCallInvitation(
  val remoteHostId: Long?,
@@ -1301,6 +1301,7 @@
  <string name="callstate_received_answer">received answer…</string>
  <string name="callstate_received_confirmation">received confirmation…</string>
  <string name="callstate_connecting">connecting…</string>
+  <string name="callstate_reconnecting">reconnecting…</string>
  <string name="callstate_connected">connected</string>
  <string name="callstate_ended">ended</string>

@@ -54,6 +54,8 @@ let inactiveCallMediaSources = {
 let activeCall;
 let notConnectedCall;
 let answerTimeout = 30000;
+let reconnectTimeout = 30000;
+let iceRestartInterval = 10000;
 var useWorker = false;
 var isDesktop = false;
 var localizedState = "";
@@ -75,7 +77,8 @@ const processCommand = (function () {
        return {
            peerConnectionConfig: {
                iceServers: iceServers !== null && iceServers !== void 0 ? iceServers : defaultIceServers,
-                iceCandidatePoolSize: 10,
+                // Chrome gathers no candidates on ICE restart when candidates pool is used
+                iceCandidatePoolSize: 0,
                encodedInsertableStreams,
                iceTransportPolicy: relay ? "relay" : "all",
                // needed for Android WebView >= 69 && <= 72 where default was "plan-b" which is incompatible with transceivers
@@ -202,10 +205,14 @@ const processCommand = (function () {
            layout: (_c = notConnectedCall === null || notConnectedCall === void 0 ? void 0 : notConnectedCall.layout) !== null && _c !== void 0 ? _c : LayoutType.Default,
            cameraTrackWasSetBefore: localStream.getVideoTracks().length > 0,
            peerHasOldVersion: false,
+            receiveRestartSession,
        };
        localOrPeerMediaSourcesChanged(call);
        await setupMediaStreams(call);
        let connectionTimeout = setTimeout(connectionHandler, answerTimeout);
+        let reconnectingTimeout;
+        let iceRestartTimeout;
+        let wasConnected = false;
        if (pc.connectionState) {
            pc.addEventListener("connectionstatechange", connectionStateChange);
        }
@@ -216,30 +223,49 @@ const processCommand = (function () {
        async function connectionStateChange() {
            // "failed" means the second party did not answer in time (15 sec timeout in Chrome WebView)
            // See https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/p2p/base/p2p_constants.cc;l=70)
-            if (pc.connectionState !== "failed")
+            if (pc.connectionState !== "failed" || wasConnected)
                connectionHandler();
        }
-        async function connectionHandler() {
+        async function connectionHandler(reconnectTimedOut = false) {
            var _a;
+            let state = (_a = pc.connectionState) !== null && _a !== void 0 ? _a : (pc.iceConnectionState != "completed" && pc.iceConnectionState != "checking"
+                ? pc.iceConnectionState
+                : pc.iceConnectionState == "completed"
+                    ? "connected"
+                    : "connecting"); /* webView 69-70 doesn't have connectionState yet */
+            if (wasConnected) {
+                if (reconnectTimedOut) {
+                    reconnectingTimeout = undefined;
+                    if (activeCall !== call || state == "connected")
+                        return;
+                    state = "disconnected";
+                }
+                else if (state == "disconnected" || state == "failed") {
+                    if (reconnectingTimeout !== undefined)
+                        return;
+                    reconnectingTimeout = setTimeout(() => connectionHandler(true), reconnectTimeout);
+                    if (isIceRestarter())
+                        restartIce();
+                    state = "reconnecting";
+                }
+                else if (state == "connecting" || state == "new") {
+                    return;
+                }
+            }
            sendMessageToNative({
                resp: {
                    type: "connection",
                    state: {
-                        connectionState: (_a = pc.connectionState) !== null && _a !== void 0 ? _a : (pc.iceConnectionState != "completed" && pc.iceConnectionState != "checking"
-                            ? pc.iceConnectionState
-                            : pc.iceConnectionState == "completed"
-                                ? "connected"
-                                : "connecting") /* webView 69-70 doesn't have connectionState yet */,
+                        connectionState: state,
                        iceConnectionState: pc.iceConnectionState,
                        iceGatheringState: pc.iceGatheringState,
                        signalingState: pc.signalingState,
                    },
                },
            });
-            if (pc.connectionState == "disconnected" ||
-                pc.connectionState == "failed" ||
-                (!pc.connectionState && (pc.iceConnectionState == "disconnected" || pc.iceConnectionState == "failed"))) {
+            if (state == "disconnected" || state == "failed") {
                clearConnectionTimeout();
+                clearReconnecting();
                if (pc.connectionState) {
                    pc.removeEventListener("connectionstatechange", connectionStateChange);
                }
@@ -251,8 +277,10 @@ const processCommand = (function () {
                }
                endCall();
            }
-            else if (pc.connectionState == "connected" || (!pc.connectionState && pc.iceConnectionState == "connected")) {
+            else if (state == "connected") {
                clearConnectionTimeout();
+                clearReconnecting();
+                wasConnected = true;
                const stats = (await pc.getStats());
                for (const stat of stats.values()) {
                    const { type, state } = stat;
@@ -278,6 +306,53 @@ const processCommand = (function () {
                connectionTimeout = undefined;
            }
        }
+        function clearReconnecting() {
+            clearTimeout(reconnectingTimeout);
+            reconnectingTimeout = undefined;
+            clearTimeout(iceRestartTimeout);
+            iceRestartTimeout = undefined;
+        }
+        // Only the party that sent the initial offer restarts ICE, so that restart offers never collide
+        function isIceRestarter() {
+            var _a;
+            return ((_a = pc.localDescription) === null || _a === void 0 ? void 0 : _a.type) == "offer";
+        }
+        async function restartIce() {
+            if (activeCall !== call || reconnectingTimeout === undefined)
+                return;
+            iceRestartTimeout = setTimeout(restartIce, iceRestartInterval);
+            // the previous restart offer is not answered yet
+            if (pc.signalingState != "stable")
+                return;
+            try {
+                const iceCandidates = getIceCandidates(pc, config);
+                const offer = await pc.createOffer({ iceRestart: true });
+                await pc.setLocalDescription(offer);
+                sendMessageToNative({ resp: { type: "ice", session: serialize(offer), iceCandidates: await iceCandidates } });
+            }
+            catch (e) {
+                console.log("ICE restart error", e);
+            }
+        }
+        async function receiveRestartSession(session, iceCandidates) {
+            const desc = parse(session);
+            const remoteDesc = new RTCSessionDescription(!webView69Or70() ? desc : adaptSdpToOldWebView(desc));
+            if (desc.type == "offer" && !isIceRestarter()) {
+                await pc.setRemoteDescription(remoteDesc);
+                const localIceCandidates = getIceCandidates(pc, config);
+                const answer = await pc.createAnswer();
+                await pc.setLocalDescription(answer);
+                addIceCandidates(pc, iceCandidates);
+                sendMessageToNative({ resp: { type: "ice", session: serialize(answer), iceCandidates: await localIceCandidates } });
+            }
+            else if (desc.type == "answer" && pc.signalingState == "have-local-offer") {
+                await pc.setRemoteDescription(remoteDesc);
+                addIceCandidates(pc, iceCandidates);
+            }
+            else {
+                throw new Error(`unexpected ICE restart ${desc.type} in ${pc.signalingState} state`);
+            }
+        }
    }
    function serialize(x) {
        return LZString.compressToBase64(JSON.stringify(x));
@@ -296,6 +371,8 @@ const processCommand = (function () {
                    console.log("starting outgoing call - capabilities");
                    if (activeCall)
                        endCall();
+                    // Stop a preview stream from an earlier pre-connect outgoing call being replaced (activeCall may be null here)
+                    stopNotConnectedCall();
                    let localStream = null;
                    try {
                        localStream = await getLocalMediaStream(true, command.media == CallMediaType.Video && (await browserHasCamera()), VideoCamera.User);
@@ -332,7 +409,8 @@ const processCommand = (function () {
                    if (activeCall)
                        endCall();
                    // It can be already defined on Android when switching calls (if the previous call was outgoing)
-                    notConnectedCall = undefined;
+                    // Stop its preview tracks before clearing, otherwise camera/mic stay live
+                    stopNotConnectedCall();
                    inactiveCallMediaSources.mic = true;
                    inactiveCallMediaSources.camera = command.media == CallMediaType.Video;
                    inactiveCallMediaSourcesChanged(inactiveCallMediaSources);
@@ -436,7 +514,11 @@ const processCommand = (function () {
                    break;
                case "ice":
                    const remoteIceCandidates = parse(command.iceCandidates);
-                    if (pc) {
+                    if (activeCall && command.session) {
+                        await activeCall.receiveRestartSession(command.session, remoteIceCandidates);
+                        resp = { type: "ok" };
+                    }
+                    else if (pc) {
                        addIceCandidates(pc, remoteIceCandidates);
                        resp = { type: "ok" };
                    }
@@ -1131,6 +1213,13 @@ const processCommand = (function () {
            activeCall.localScreenStream.getTracks().forEach((track) => track.stop());
        }
    }
+    // Call on any path that abandons notConnectedCall, otherwise its preview camera/mic tracks stay live.
+    function stopNotConnectedCall() {
+        if (notConnectedCall) {
+            notConnectedCall.localStream.getTracks().forEach((track) => track.stop());
+            notConnectedCall = undefined;
+        }
+    }
    function resetVideoElements() {
        const videos = getVideoElements();
        if (!videos)
@@ -2,7 +2,7 @@
 // Override defaults to enable worker on Chrome and Safari
 useWorker = typeof window.Worker !== "undefined";
 isDesktop = true;
-// Create WebSocket connection.
+// Create WebSocket connection. location.search carries the per-call ?token=... capability required by the server.
 const socket = new WebSocket(`ws://${location.host}${location.search}`);
 socket.addEventListener("open", (_event) => {
    console.log("Opened socket");
@@ -192,4 +192,4 @@ function updateCallInfoView(state, description) {
    document.getElementById("state").innerText = state;
    document.getElementById("description").innerText = description;
 }
-//# sourceMappingURL=ui.js.map
+//# sourceMappingURL=ui.js.map
@@ -313,7 +313,9 @@ actual object CallSoundsPlayer: CallSoundsPlayerInterface {
  override fun startConnectingCallSound(scope: CoroutineScope) {
    // Taken from https://github.com/TelegramOrg/Telegram-Android
    // https://github.com/TelegramOrg/Telegram-Android/blob/master/LICENSE
-    start("/media/connecting_call.mp3", 3000, scope)
+    // the delay is the length of the track exactly, so it repeats with no delay, which already happens on ios and android
+    // Android (isLooping) and iOS (which sleeps for the track duration)
+    start("/media/connecting_call.mp3", 3536, scope)
  }

  override fun startInCallSound(scope: CoroutineScope) {
@@ -8,6 +8,7 @@ import chat.simplex.common.platform.*
 import chat.simplex.common.views.helpers.*
 import chat.simplex.res.*
 import kotlinx.coroutines.delay
+import kotlinx.coroutines.isActive
 import kotlinx.coroutines.flow.*
 import kotlinx.datetime.Clock
 import kotlinx.serialization.encodeToString
@@ -55,13 +56,24 @@ actual fun ActiveCallView() {
          CallSoundsPlayer.stop()
        }
        is WCallResponse.Ice -> withBGApi {
-          chatModel.controller.apiSendCallExtraInfo(callRh, call.contact, r.iceCandidates)
+          chatModel.controller.apiSendCallExtraInfo(callRh, call.contact, r.session, r.iceCandidates)
        }
        is WCallResponse.Connection ->
-          try {
+          // the call is restored and NOT sent to the core
+          // Makes sure the core DOES NOT record the duration wrong if a reconnect happens
+          if (r.state.connectionState == "reconnecting") {
+            if (call.callState != CallState.Reconnecting) {
+              CallSoundsPlayer.startConnectingCallSound(scope)
+            }
+            chatModel.activeCall.value = call.copy(callState = CallState.Reconnecting)
+          } else try {
            val callStatus = json.decodeFromString<WebRTCCallStatus>("\"${r.state.connectionState}\"")
            if (callStatus == WebRTCCallStatus.Connected) {
-              chatModel.activeCall.value = call.copy(callState = CallState.Connected, connectedAt = Clock.System.now())
+              if (call.callState == CallState.Reconnecting) {
+                CallSoundsPlayer.stop()
+              }
+              // connectedAt is only set ONCE, this way call duration is NOT reset when the call is restored from reconnecting
+              chatModel.activeCall.value = call.copy(callState = CallState.Connected, connectedAt = call.connectedAt ?: Clock.System.now())
            }
            withBGApi { chatModel.controller.apiCallStatus(callRh, call.contact, callStatus) }
          } catch (e: Throwable) {
@@ -194,21 +206,20 @@ fun WebRTCController(callCommand: SnapshotStateList<WCallCommand>, onResponse: (
    }
  }
  LaunchedEffect(Unit) {
-    snapshotFlow { callCommand.firstOrNull() }
-      .distinctUntilChanged()
-      .filterNotNull()
-      .collect {
-        while (connections.isEmpty()) {
-          delay(100)
-        }
-        while (callCommand.isNotEmpty()) {
-          val cmd = callCommand.removeFirstOrNull()
-          Log.d(TAG, "WebRTCController LaunchedEffect executing ${cmd?.javaClass?.simpleName}")
-          if (cmd != null) {
-            processCommand(cmd)
-          }
+    while (isActive) {
+      // waiting for the first command would miss a command equal to the previous one
+      snapshotFlow { callCommand.isNotEmpty() }.first { it }
+      while (connections.isEmpty()) {
+        delay(100)
+      }
+      while (callCommand.isNotEmpty()) {
+        val cmd = callCommand.removeFirstOrNull()
+        Log.d(TAG, "WebRTCController LaunchedEffect executing ${cmd?.javaClass?.simpleName}")
+        if (cmd != null) {
+          processCommand(cmd)
        }
      }
+    }
  }
 }

@@ -99,6 +99,7 @@ Both platforms share a common signaling flow through the Haskell core API.
 ```
 Outgoing: WaitCapabilities -> InvitationSent -> OfferSent -> AnswerReceived -> Negotiated -> Connected -> Ended
 Incoming: InvitationAccepted -> OfferReceived -> Negotiated -> Connected -> Ended
+Reconnection: Connected -> Reconnecting -> Connected | Ended
 ```

 | State | Description |
@@ -111,8 +112,17 @@ Incoming: InvitationAccepted -> OfferReceived -> Negotiated -> Connected -> Ende
 | `AnswerReceived` | Caller received SDP answer |
 | `Negotiated` | ICE negotiation complete |
 | `Connected` | Media flowing |
+| `Reconnecting` | Connection lost, waiting for ICE restart |
 | `Ended` | Call terminated |

+### 3.1 Reconnection
+
+1. A connected call loses its WebRTC connection, e.g. when the device switches between Wi-Fi and mobile network.
+2. The WebRTC engine reports `"reconnecting"` connection state; the app shows "reconnecting…" and plays the connecting sound. This state is not reported to the core, and `connectedAt` is kept, so call duration continues.
+3. The callee's WebRTC engine (the party that sent the initial offer) restarts ICE every 10 seconds, sending the new offer in `WCallResponse.Ice` with `session` via `apiSendCallExtraInfo`. The caller answers the same way.
+4. When the connection is restored, the call returns to `Connected` and the sound stops.
+5. If the connection is not restored in 30 seconds, the call ends as disconnected. Clients without ICE restart support ignore the restart offer, so the call ends in this case.
+
 ---

 ## 4. Ending a Call
@@ -184,7 +194,7 @@ Incoming: InvitationAccepted -> OfferReceived -> Negotiated -> Connected -> Ende
 | `apiRejectCall(rh, contact)` | Reject incoming call |
 | `apiSendCallOffer(rh, contact, rtcSession, rtcIceCandidates, media, capabilities)` | Send SDP offer |
 | `apiSendCallAnswer(rh, contact, rtcSession, rtcIceCandidates)` | Send SDP answer |
-| `apiSendCallExtraInfo(rh, contact, rtcIceCandidates)` | Send additional ICE candidates |
+| `apiSendCallExtraInfo(rh, contact, rtcSession, rtcIceCandidates)` | Send additional ICE candidates, or ICE restart offer/answer |
 | `apiEndCall(rh, contact)` | End active call |
 | `apiCallStatus(rh, contact, status)` | Report WebRTC connection status |

@@ -71,8 +71,8 @@ Sound: `SoundPlayer.start()` plays ringtone while banner is visible (unless call
 | 1. Capabilities | `WCallResponse.Capabilities` | Local capabilities reported; `apiSendCallInvitation()` called |
 | 2. Offer | `WCallResponse.Offer` | SDP offer + ICE candidates sent via `apiSendCallOffer()` |
 | 3. Answer | `WCallResponse.Answer` | SDP answer + ICE candidates sent via `apiSendCallAnswer()` |
-| 4. ICE | `WCallResponse.Ice` | Additional ICE candidates exchanged via `apiSendCallExtraInfo()` |
-| 5. Connection | `WCallResponse.Connection` | WebRTC connection state changes; `CallState.Connected` set on success |
+| 4. ICE | `WCallResponse.Ice` | Additional ICE candidates, and ICE restart offer/answer in `session`, exchanged via `apiSendCallExtraInfo()` |
+| 5. Connection | `WCallResponse.Connection` | WebRTC connection state changes; `CallState.Connected` set on success, `CallState.Reconnecting` when a connected call loses connection |
 | 6. Connected | `WCallResponse.Connected` | Connection info (relay/direct) stored in `call.connectionInfo` |
 | 7. PeerMedia | `WCallResponse.PeerMedia` | Remote party media source changes (mic, camera, screen) |
 | 8. Media control | `WCallCommand.Media` | Toggle local media sources (mic, camera, screen audio/video) |
@@ -90,14 +90,15 @@ Sound: `SoundPlayer.start()` plays ringtone while banner is visible (unless call
 | `OfferReceived` | Callee received SDP offer |
 | `AnswerReceived` | Caller received SDP answer |
 | `Negotiated` | ICE negotiation complete |
-| `Connected` | WebRTC media flowing; `connectedAt` timestamp set |
+| `Connected` | WebRTC media flowing; `connectedAt` timestamp set on the first connection |
+| `Reconnecting` | Connection lost; "reconnecting…" shown while ICE restarts, call ends after 30 seconds without connection |
 | `Ended` | Call terminated |

 ### Call Sounds

 | Sound | Trigger |
 |---|---|
-| Connecting sound | `CallSoundsPlayer.startConnectingCallSound()` after invitation sent |
+| Connecting sound | `CallSoundsPlayer.startConnectingCallSound()` after invitation sent, and while reconnecting |
 | In-call sound | `CallSoundsPlayer.startInCallSound()` when delivery receipt received |
 | Ringtone | `SoundPlayer.start()` for incoming calls |
 | End vibration | `CallSoundsPlayer.vibrate()` on call end (if was connected) |
@@ -225,7 +225,7 @@ All functions below are `suspend fun` members of `ChatController` ([SimpleXAPI.k
 | `apiRejectCall` | `rh: Long?, contact: Contact` | Reject an incoming call | [L1854](../common/src/commonMain/kotlin/chat/simplex/common/model/SimpleXAPI.kt#L1854) |
 | `apiSendCallOffer` | `rh, contact, rtcSession, rtcIceCandidates, media, capabilities` | Send a WebRTC call offer | [L1859](../common/src/commonMain/kotlin/chat/simplex/common/model/SimpleXAPI.kt#L1859) |
 | `apiSendCallAnswer` | `rh: Long?, contact: Contact, rtcSession: String, rtcIceCandidates: String` | Send a WebRTC call answer | [L1866](../common/src/commonMain/kotlin/chat/simplex/common/model/SimpleXAPI.kt#L1866) |
-| `apiSendCallExtraInfo` | `rh: Long?, contact: Contact, rtcIceCandidates: String` | Send additional ICE candidates during a call | [L1872](../common/src/commonMain/kotlin/chat/simplex/common/model/SimpleXAPI.kt#L1872) |
+| `apiSendCallExtraInfo` | `rh: Long?, contact: Contact, rtcSession: String?, rtcIceCandidates: String` | Send additional ICE candidates or ICE restart offer/answer during a call | [L2156](../common/src/commonMain/kotlin/chat/simplex/common/model/SimpleXAPI.kt#L2156) |
 | `apiEndCall` | `rh: Long?, contact: Contact` | End an active call | [L1878](../common/src/commonMain/kotlin/chat/simplex/common/model/SimpleXAPI.kt#L1878) |
 | `apiCallStatus` | `rh: Long?, contact: Contact, status: WebRTCCallStatus` | Report call status updates to the core | [L1883](../common/src/commonMain/kotlin/chat/simplex/common/model/SimpleXAPI.kt#L1883) |

@@ -43,6 +43,7 @@ enum class CallState {
  AnswerReceived,      // SDP answer received from peer
  Negotiated,          // ICE negotiation in progress
  Connected,           // Media flowing
+  Reconnecting,        // Connection lost, waiting for ICE to recover
  Ended;               // Call terminated
 }
 ```
@@ -53,6 +54,8 @@ enum class CallState {

 State transitions are driven by `WCallResponse` messages from the WebRTC layer. Each transition typically triggers a corresponding API command (e.g., `apiSendCallInvitation`, `apiSendCallOffer`).

+**Reconnection**: `Connected` -> `Reconnecting` -> `Connected` or `Ended`. When a connected call loses its WebRTC connection, `call.js` reports `"reconnecting"` connection state instead of ending the call. The app sets `CallState.Reconnecting` and plays the connecting sound; this state is not sent to the core with `apiCallStatus`, so the call item duration is not affected, and `connectedAt` is kept. The party that sent the initial offer (callee) restarts ICE every 10 seconds until reconnected: the restart offer and the answer are sent as `WCallResponse.Ice` / `WCallCommand.Ice` with `session`, via `apiSendCallExtraInfo` (`x.call.extra` with `rtcSession`). If the connection is not restored in 30 seconds, `call.js` reports `"disconnected"` and ends the call.
+
 ---

 <a id="ActiveCallView"></a>
@@ -140,7 +143,7 @@ Defined in [`SimpleXAPI.kt`](../../common/src/commonMain/kotlin/chat/simplex/com
 | `apiRejectCall` | [L1854](../../common/src/commonMain/kotlin/chat/simplex/common/model/SimpleXAPI.kt#L1854) | Reject an incoming call |
 | `apiSendCallOffer` | [L1859](../../common/src/commonMain/kotlin/chat/simplex/common/model/SimpleXAPI.kt#L1859) | Send SDP offer with ICE candidates and capabilities |
 | `apiSendCallAnswer` | [L1866](../../common/src/commonMain/kotlin/chat/simplex/common/model/SimpleXAPI.kt#L1866) | Send SDP answer with ICE candidates |
-| `apiSendCallExtraInfo` | [L1872](../../common/src/commonMain/kotlin/chat/simplex/common/model/SimpleXAPI.kt#L1872) | Send additional ICE candidates discovered after initial exchange |
+| `apiSendCallExtraInfo` | [L2156](../../common/src/commonMain/kotlin/chat/simplex/common/model/SimpleXAPI.kt#L2156) | Send additional ICE candidates discovered after initial exchange, or ICE restart offer/answer in `rtcSession` |
 | `apiEndCall` | [L1878](../../common/src/commonMain/kotlin/chat/simplex/common/model/SimpleXAPI.kt#L1878) | Terminate a call |
 | `apiCallStatus` | [L1883](../../common/src/commonMain/kotlin/chat/simplex/common/model/SimpleXAPI.kt#L1883) | Report WebRTC connection status to the backend |