feat(network): support custom relay servers

Add strict custom Iroh relay profiles with safe restart and rollback across the Rust core, Compose apps, and Apple apps. Preserve multi-relay invitations and fail closed on configuration or recovery mismatches.

apple/VniDrop/Core/AppPreferences.swift

@@ -19,6 +19,95 @@ enum FolderAccessStatus {
 	case unavailable
 }
 
+enum RelayPreferenceMode: String, Codable, CaseIterable, Sendable {
+	case automatic
+	case custom
+}
+
+struct RelayConfiguration: Equatable, Codable, Sendable {
+	var mode: RelayPreferenceMode
+	var relayURLs: [String]
+
+	static let automatic = RelayConfiguration(mode: .automatic, relayURLs: [])
+}
+
+enum RelayConfigurationValidationError: Error, Equatable, Sendable {
+	case missingURL
+	case tooManyURLs
+	case httpsRequired(index: Int)
+	case invalidURL(index: Int)
+	case duplicateURL(index: Int)
+
+	var urlIndex: Int? {
+		switch self {
+		case .httpsRequired(let index), .invalidURL(let index), .duplicateURL(let index): return index
+		case .missingURL, .tooManyURLs: return nil
+		}
+	}
+}
+
+enum RelayConfigurationValidator {
+	static let maximumRelayCount = 8
+	static let maximumRelayURLBytes = 2_048
+
+	static func validate(
+		mode: RelayPreferenceMode,
+		relayURLs: [String],
+		retainedRelayURLs: [String] = []
+	) throws -> RelayConfiguration {
+		guard mode == .custom else {
+			return RelayConfiguration(mode: .automatic, relayURLs: retainedRelayURLs)
+		}
+
+		let relayEntries = relayURLs.enumerated().compactMap { index, value -> (Int, String)? in
+			let trimmed = value.trimmingCharacters(in: .whitespacesAndNewlines)
+			return trimmed.isEmpty ? nil : (index, trimmed)
+		}
+		guard !relayEntries.isEmpty else {
+			throw RelayConfigurationValidationError.missingURL
+		}
+		guard relayEntries.count <= maximumRelayCount else {
+			throw RelayConfigurationValidationError.tooManyURLs
+		}
+
+		var seen = Set<String>()
+		var normalizedURLs: [String] = []
+		for (index, relayURL) in relayEntries {
+			guard relayURL.lengthOfBytes(using: .utf8) <= maximumRelayURLBytes,
+				relayURL.rangeOfCharacter(from: .whitespacesAndNewlines.union(.controlCharacters)) == nil,
+				var components = URLComponents(string: relayURL) else {
+				throw RelayConfigurationValidationError.invalidURL(index: index)
+			}
+			guard components.scheme?.lowercased() == "https" else {
+				throw RelayConfigurationValidationError.httpsRequired(index: index)
+			}
+			guard
+				let host = components.host,
+				!host.isEmpty,
+				components.port.map({ (1...65_535).contains($0) }) ?? true,
+				components.user == nil,
+				components.password == nil,
+				components.query == nil,
+				components.fragment == nil,
+				components.path.isEmpty || components.path == "/"
+			else {
+				throw RelayConfigurationValidationError.invalidURL(index: index)
+			}
+
+			components.scheme = "https"
+			components.host = host.lowercased()
+			if components.port == 443 { components.port = nil }
+			if components.path == "/" { components.path = "" }
+			guard let canonicalURL = components.string, seen.insert(canonicalURL).inserted else {
+				throw RelayConfigurationValidationError.duplicateURL(index: index)
+			}
+			normalizedURLs.append(canonicalURL)
+		}
+
+		return RelayConfiguration(mode: .custom, relayURLs: normalizedURLs)
+	}
+}
+
 /// Persisted app preferences, ported from `preferences/AppPreferencesRepository.kt`.
 /// Backed by `UserDefaults` instead of DataStore; keys and semantics match.
 struct AppPreferences: Equatable {
@@ -28,6 +117,7 @@ struct AppPreferences: Equatable {
 	var notificationsEnabled: Bool
 	var diagnosticsEnabled: Bool
 	var diagnosticsInstallId: String
+	var relayConfiguration: RelayConfiguration
 }
 
 struct AppPreferencesDefaults {
@@ -54,6 +144,7 @@ final class AppPreferencesRepository: ObservableObject {
 		static let notificationsEnabled = "notifications_enabled"
 		static let diagnosticsEnabled = "diagnostics_enabled"
 		static let diagnosticsInstallId = "diagnostics_install_id"
+		static let relayConfiguration = "relay_configuration"
 	}
 
 	init(defaults: UserDefaults = .standard, fallback: AppPreferencesDefaults) {
@@ -75,10 +166,25 @@ final class AppPreferencesRepository: ObservableObject {
 			themeMode: themeMode,
 			notificationsEnabled: notifications,
 			diagnosticsEnabled: diagnostics,
-			diagnosticsInstallId: installId
+			diagnosticsInstallId: installId,
+			relayConfiguration: resolveRelayConfiguration(defaults)
 		)
 	}
 
+	private static func resolveRelayConfiguration(_ defaults: UserDefaults) -> RelayConfiguration {
+		guard defaults.object(forKey: Key.relayConfiguration) != nil else { return .automatic }
+		guard
+			let data = defaults.data(forKey: Key.relayConfiguration),
+			let configuration = try? JSONDecoder().decode(RelayConfiguration.self, from: data)
+		else {
+			// A stored profile must never silently fall back to public relays. Keeping
+			// Custom selected with no URLs makes startup fail closed and lets Settings
+			// offer an explicit repair or reset to Automatic.
+			return RelayConfiguration(mode: .custom, relayURLs: [])
+		}
+		return configuration
+	}
+
 	private static func resolveReceiveFolder(_ defaults: UserDefaults, fallback: ReceiveFolder) -> ReceiveFolder {
 		let kind = defaults.string(forKey: Key.receiveFolderKind)
 			.flatMap(ReceiveFolderKind.init(rawValue:)) ?? fallback.kind
@@ -123,6 +229,12 @@ final class AppPreferencesRepository: ObservableObject {
 		reload()
 	}
 
+	func setRelayConfiguration(_ configuration: RelayConfiguration) {
+		guard let encoded = try? JSONEncoder().encode(configuration) else { return }
+		defaults.set(encoded, forKey: Key.relayConfiguration)
+		reload()
+	}
+
 	@discardableResult
 	func ensureDiagnosticsInstallId() -> String {
 		let existing = preferences.diagnosticsInstallId

apple/VniDrop/Core/CoreGateway.swift

@@ -24,7 +24,7 @@ protocol CoreGateway: AnyObject {
 	/// Coalesced change hints emitted by the event sink.
 	var signals: AnyPublisher<CoreSignal, Never> { get }
 
-	func initialize(appDataDir: String) async -> Result<Void, Error>
+	func initialize(appDataDir: String, networkConfiguration: RelayConfiguration) async -> Result<Void, Error>
 	func shutdown()
 	func shareSources(
 		_ sources: [ShareSource],

apple/VniDrop/Core/CoreRepository.swift

@@ -2,6 +2,58 @@ import Foundation
 import Combine
 @preconcurrency import VnidropCore
 
+enum CoreNetworkLifecycleError: Error, Equatable, LocalizedError, Sendable {
+	case transitionInProgress
+	case activeNetworkWork
+
+	var errorDescription: String? {
+		switch self {
+		case .transitionInProgress: return "A network restart is already in progress."
+		case .activeNetworkWork: return "Stop active transfers and shares before restarting the network."
+		}
+	}
+}
+
+enum CoreNetworkLifecycle {
+	nonisolated static func requireIdle(activeTransfers: UInt64, activeShares: UInt64) throws {
+		guard activeTransfers == 0, activeShares == 0 else {
+			throw CoreNetworkLifecycleError.activeNetworkWork
+		}
+	}
+}
+
+protocol CoreBindingFactory: Sendable {
+	func initialize(
+		appDataDir: String,
+		eventSink: CoreEventSink,
+		networkConfiguration: RelayConfiguration
+	) throws -> VnidropCore
+}
+
+struct NativeCoreBindingFactory: CoreBindingFactory {
+	func initialize(
+		appDataDir: String,
+		eventSink: CoreEventSink,
+		networkConfiguration: RelayConfiguration
+	) throws -> VnidropCore {
+		let nativeConfiguration: CoreNetworkConfig
+		switch networkConfiguration.mode {
+		case .automatic:
+			nativeConfiguration = defaultCoreNetworkConfig()
+		case .custom:
+			nativeConfiguration = CoreNetworkConfig(
+				mode: .custom,
+				relayUrls: networkConfiguration.relayURLs
+			)
+		}
+		return try VnidropCore.initializeWithNetworkConfig(
+			appDataDir: appDataDir,
+			eventSink: eventSink,
+			networkConfig: nativeConfiguration
+		)
+	}
+}
+
 /// Swift port of `core/CoreRepository.kt`. Owns the `VnidropCore` handle, maps the
 /// generated UniFFI records into app domain models, publishes an observable
 /// `CoreState`, and emits coalesced `CoreSignal`s from the event sink.
@@ -17,28 +69,63 @@ final class CoreRepository: ObservableObject, CoreGateway {
 	/// Coalesced change hints; subscribe to react to approval/history/transfer changes.
 	var signals: AnyPublisher<CoreSignal, Never> { signalsSubject.eraseToAnyPublisher() }
 
-	// Set on the main actor (initialize/shutdown) but read from `queue` inside
-	// `runCore`; the underlying core is internally synchronized, so this crossing
-	// is safe. `nonisolated(unsafe)` documents that contract for Swift 6.
+	// Initialization swaps happen on `queue`; shutdown and snapshot reads may also
+	// access the handle from the main actor. The underlying core is internally
+	// synchronized, and `nonisolated(unsafe)` documents that crossing for Swift 6.
 	private nonisolated(unsafe) var core: VnidropCore?
 	private let queue = DispatchQueue(label: "com.vnidrop.core", qos: .userInitiated)
+	private let coreFactory: any CoreBindingFactory
+	private var isNetworkTransitionInProgress = false
 	private lazy var sink = RepositoryEventSink { [weak self] event in
 		Task { @MainActor in self?.handle(event: event) }
 	}
 
 	private nonisolated static let maxEvents = 200
 
+	init(coreFactory: any CoreBindingFactory = NativeCoreBindingFactory()) {
+		self.coreFactory = coreFactory
+	}
+
 	// MARK: - Lifecycle
 
-	func initialize(appDataDir: String) async -> Result<Void, Error> {
-		await runCore { [sink] in
-			self.core?.shutdown()
-			let created = try VnidropCore.initialize(appDataDir: appDataDir, eventSink: sink)
-			return created
-		}.map { created in
+	func initialize(
+		appDataDir: String,
+		networkConfiguration: RelayConfiguration
+	) async -> Result<Void, Error> {
+		guard !isNetworkTransitionInProgress else {
+			return .failure(CoreNetworkLifecycleError.transitionInProgress)
+		}
+		isNetworkTransitionInProgress = true
+		defer { isNetworkTransitionInProgress = false }
+
+		let result = await runCore { [sink] in
+			if let existing = self.core {
+				let status = existing.status()
+				try CoreNetworkLifecycle.requireIdle(
+					activeTransfers: status.activeTransfers,
+					activeShares: status.activeShares
+				)
+				existing.shutdown()
+				self.core = nil
+			}
+			let created = try self.coreFactory.initialize(
+				appDataDir: appDataDir,
+				eventSink: sink,
+				networkConfiguration: networkConfiguration
+			)
 			self.core = created
+			return created
+		}
+		switch result {
+		case .success:
 			self.refreshSnapshot()
 			self.state.isInitialized = true
+			return .success(())
+		case .failure(let error):
+			if error as? CoreNetworkLifecycleError != .activeNetworkWork {
+				self.state = CoreState()
+			}
+			return .failure(error)
 		}
 	}
 
@@ -56,6 +143,9 @@ final class CoreRepository: ObservableObject, CoreGateway {
 		senderName: String,
 		accessPolicy: ShareAccessPolicy
 	) async -> Result<Share, Error> {
+		guard !isNetworkTransitionInProgress else {
+			return .failure(CoreNetworkLifecycleError.transitionInProgress)
+		}
 		guard !sources.isEmpty else {
 			return .failure(InvitationError.message("Select at least one file to share"))
 		}
@@ -89,7 +179,10 @@ final class CoreRepository: ObservableObject, CoreGateway {
 	}
 
 	func receive(ticket: String, outputDir: String, receiverName: String) async -> Result<Void, Error> {
-		await runCore {
+		guard !isNetworkTransitionInProgress else {
+			return .failure(CoreNetworkLifecycleError.transitionInProgress)
+		}
+		return await runCore {
 			try self.requireCore().receive(
 				ticket: ticket,
 				outputDir: outputDir,
@@ -105,7 +198,10 @@ final class CoreRepository: ObservableObject, CoreGateway {
 		outputDirectoryUrl: String,
 		receiverName: String
 	) async -> Result<Void, Error> {
-		await runCore {
+		guard !isNetworkTransitionInProgress else {
+			return .failure(CoreNetworkLifecycleError.transitionInProgress)
+		}
+		return await runCore {
 			try withSecurityScopedAccess(pathOrUrl: outputDirectoryUrl) {
 				try self.requireCore().receive(
 					ticket: ticket,

apple/VniDrop/Features/App/AppModel.swift

@@ -26,7 +26,10 @@ final class AppModel: ObservableObject {
 		AppLogger.info("lifecycle", "app started", ["platform": environment.name])
 
 		Task {
-			let result = await repository.initialize(appDataDir: environment.defaultCoreDataDir)
+			let result = await repository.initialize(
+				appDataDir: environment.defaultCoreDataDir,
+				networkConfiguration: preferences.preferences.relayConfiguration
+			)
 			if case .failure(let error) = result { messages.error(error) }
 		}
 

apple/VniDrop/Features/Send/TransferDetailsView.swift

@@ -43,12 +43,14 @@ struct TransferDetailsView: View {
 					count: pendingReceivers + completedReceivers,
 					onTap: model.openReceivers
 				)
-				DetailDestination(
-					title: String(localized: "transfer_share_title"),
-					description: String(localized: "transfer_share_description"),
-					count: 0,
-					onTap: model.openShare
-				)
+				if transfer.invitationPresentation != .unavailable {
+					DetailDestination(
+						title: String(localized: "transfer_share_title"),
+						description: String(localized: "transfer_share_description"),
+						count: 0,
+						onTap: model.openShare
+					)
+				}
 			}
 
 			if isActiveShare {
@@ -276,24 +278,41 @@ struct TransferSharePanel: View {
 
 	var body: some View {
 		PanelContainer(title: String(localized: "transfer_share_title")) {
-			if let ticket = transfer.ticket {
-				qrCard(ticket: ticket)
-				Text(LocalizedStringKey("transfer_scan_qr"))
-					.font(VniType.bodySmall).foregroundStyle(colors.foregroundLighter)
-					.frame(maxWidth: .infinity)
+			switch transfer.invitationPresentation {
+			case .ready(let ticket):
+				let qrImage = QRCode.generate(from: ticket)
+				qrCard(image: qrImage)
+				if qrImage != nil {
+					Text(LocalizedStringKey("transfer_scan_qr"))
+						.font(VniType.bodySmall).foregroundStyle(colors.foregroundLighter)
+						.frame(maxWidth: .infinity)
+				}
 				ShareActionsView(model: model, transfer: transfer, ticket: ticket)
-			} else {
+			case .preparing:
 				Text(LocalizedStringKey("transfer_event_preparing")).foregroundStyle(colors.foregroundLighter)
+			case .unavailable:
+				Text(LocalizedStringKey(
+					transfer.status == .failed ? "transfer_event_failed" : "transfer_event_stopped"
+				))
+				.foregroundStyle(colors.foregroundLighter)
 			}
 		}
 	}
 
-	private func qrCard(ticket: String) -> some View {
+	private func qrCard(image: Image?) -> some View {
 		ZStack {
-			if let qr = QRCode.generate(from: ticket) {
-				qr.interpolation(.none).resizable().scaledToFit().padding(14)
+			if let image {
+				image.interpolation(.none).resizable().scaledToFit().padding(14)
 			} else {
-				ProgressView()
+				VStack(spacing: 10) {
+					Image(systemName: "qrcode")
+						.font(.system(size: 36, weight: .medium))
+					Text(LocalizedStringKey("transfer_qr_unavailable"))
+						.font(VniType.bodySmall)
+						.multilineTextAlignment(.center)
+				}
+				.foregroundStyle(.black.opacity(0.72))
+				.padding(22)
 			}
 		}
 		.frame(width: 268, height: 268)
@@ -302,6 +321,26 @@ struct TransferSharePanel: View {
 	}
 }
 
+enum TransferInvitationPresentation: Equatable {
+	case preparing
+	case ready(String)
+	case unavailable
+}
+
+extension Transfer {
+	var invitationPresentation: TransferInvitationPresentation {
+		switch status {
+		case .importing:
+			return .preparing
+		case .sharing:
+			guard let ticket, !ticket.isEmpty else { return .preparing }
+			return .ready(ticket)
+		case .receiving, .done, .failed, .cancelled, .stopped:
+			return .unavailable
+		}
+	}
+}
+
 // MARK: - QR generation (CoreImage)
 
 enum QRCode {

apple/VniDrop/Features/Settings/SettingsModel.swift

@@ -7,6 +7,7 @@ enum SettingsSection: Hashable {
 	case preferences
 	case appearance
 	case notifications
+	case network
 	case storage
 	case about
 	case bugReport
@@ -17,6 +18,7 @@ enum SettingsSection: Hashable {
 		case .preferences: return "preferences_title"
 		case .appearance: return "appearance_title"
 		case .notifications: return "notifications_title"
+		case .network: return "settings_network_title"
 		case .storage: return "storage_title"
 		case .about: return "about_title"
 		case .bugReport: return "about_bug_report"
@@ -44,6 +46,14 @@ struct SettingsState: Equatable {
 	var notificationsEnabled = false
 	var notificationPermission: NotificationPermission = .notDetermined
 	var diagnosticsEnabled = false
+	var relayMode: RelayPreferenceMode = .automatic
+	var relayURLs: [String] = []
+	var relayValidationError: RelayConfigurationValidationError?
+	var relayConfigurationIsDirty = false
+	var isApplyingRelayConfiguration = false
+	var hasActiveNetworkWork = false
+	var endpointId: String?
+	var relayApplyErrorKey: String?
 	var deviceInfo: DeviceInfo?
 	var appVersion = ""
 	var isLoadingDeviceInfo = false
@@ -66,6 +76,13 @@ struct SettingsState: Equatable {
 			&& lhs.themeMode == rhs.themeMode && lhs.notificationsEnabled == rhs.notificationsEnabled
 			&& lhs.notificationPermission == rhs.notificationPermission
 			&& lhs.diagnosticsEnabled == rhs.diagnosticsEnabled && lhs.appVersion == rhs.appVersion
+			&& lhs.relayMode == rhs.relayMode && lhs.relayURLs == rhs.relayURLs
+			&& lhs.relayValidationError == rhs.relayValidationError
+			&& lhs.relayConfigurationIsDirty == rhs.relayConfigurationIsDirty
+			&& lhs.isApplyingRelayConfiguration == rhs.isApplyingRelayConfiguration
+			&& lhs.hasActiveNetworkWork == rhs.hasActiveNetworkWork
+			&& lhs.endpointId == rhs.endpointId
+			&& lhs.relayApplyErrorKey == rhs.relayApplyErrorKey
 			&& lhs.isLoadingDeviceInfo == rhs.isLoadingDeviceInfo
 			&& lhs.bugWhatHappened == rhs.bugWhatHappened && lhs.bugExpected == rhs.bugExpected
 			&& lhs.bugSteps == rhs.bugSteps && lhs.bugContact == rhs.bugContact
@@ -96,6 +113,7 @@ final class SettingsModel: ObservableObject {
 	private var enableNotificationsAfterSettings = false
 	private var usernamePersistTask: Task<Void, Never>?
 	private var hasLocalUsernameDraft = false
+	private var hasRelayConfigurationDraft = false
 	private var cancellables = Set<AnyCancellable>()
 
 	init(
@@ -133,10 +151,29 @@ final class SettingsModel: ObservableObject {
 				self.state.themeMode = prefs.themeMode
 				self.state.notificationsEnabled = prefs.notificationsEnabled
 				self.state.diagnosticsEnabled = prefs.diagnosticsEnabled
+				if !self.hasRelayConfigurationDraft {
+					self.state.relayMode = prefs.relayConfiguration.mode
+					self.state.relayURLs = prefs.relayConfiguration.relayURLs
+					self.state.relayConfigurationIsDirty = false
+				}
 				if folder != previousFolder { Task { await self.validateFolder(folder) } }
 			}
 			.store(in: &cancellables)
 
+		repository.statePublisher
+			.sink { [weak self] coreState in
+				guard let self else { return }
+				let hasActiveWork = (coreState.status?.activeTransfers ?? 0) > 0
+					|| (coreState.status?.activeShares ?? 0) > 0
+					|| coreState.transfers.contains(where: { $0.status.isActiveTransfer })
+				self.state.hasActiveNetworkWork = hasActiveWork
+				self.state.endpointId = coreState.status?.endpointId
+				if !hasActiveWork && self.state.relayApplyErrorKey == "relay_apply_active_transfers" {
+					self.state.relayApplyErrorKey = nil
+				}
+			}
+			.store(in: &cancellables)
+
 		refreshNotificationPermission()
 		loadDeviceInfo()
 	}
@@ -206,6 +243,119 @@ final class SettingsModel: ObservableObject {
 		}
 	}
 
+	// MARK: - Network
+
+	func setRelayMode(_ mode: RelayPreferenceMode) {
+		hasRelayConfigurationDraft = true
+		state.relayMode = mode
+		if mode == .custom && state.relayURLs.isEmpty { state.relayURLs = [""] }
+		updateRelayConfigurationDraft()
+	}
+
+	func setRelayURL(_ value: String, at index: Int) {
+		guard state.relayURLs.indices.contains(index) else { return }
+		hasRelayConfigurationDraft = true
+		state.relayURLs[index] = value
+		updateRelayConfigurationDraft()
+	}
+
+	func addRelayURL() {
+		guard state.relayURLs.count < RelayConfigurationValidator.maximumRelayCount else { return }
+		hasRelayConfigurationDraft = true
+		state.relayURLs.append("")
+		updateRelayConfigurationDraft()
+	}
+
+	func removeRelayURL(at index: Int) {
+		guard state.relayURLs.indices.contains(index) else { return }
+		hasRelayConfigurationDraft = true
+		state.relayURLs.remove(at: index)
+		if state.relayURLs.isEmpty { state.relayURLs = [""] }
+		updateRelayConfigurationDraft()
+	}
+
+	func applyRelayConfiguration() {
+		guard !state.isApplyingRelayConfiguration, state.relayConfigurationIsDirty else { return }
+
+		let configuration: RelayConfiguration
+		do {
+			configuration = try RelayConfigurationValidator.validate(
+				mode: state.relayMode,
+				relayURLs: state.relayURLs,
+				retainedRelayURLs: preferences.preferences.relayConfiguration.relayURLs
+			)
+		} catch let error as RelayConfigurationValidationError {
+			state.relayValidationError = error
+			state.relayApplyErrorKey = nil
+			return
+		} catch {
+			return
+		}
+
+		let coreState = repository.state
+		let hasActiveWork = (coreState.status?.activeTransfers ?? 0) > 0
+			|| (coreState.status?.activeShares ?? 0) > 0
+			|| coreState.transfers.contains(where: { $0.status.isActiveTransfer })
+		guard !hasActiveWork else {
+			state.hasActiveNetworkWork = true
+			state.relayApplyErrorKey = "relay_apply_active_transfers"
+			messages.show(UiMessage(text: .resource("relay_apply_active_transfers"), tone: .warning))
+			return
+		}
+
+		let previousConfiguration = preferences.preferences.relayConfiguration
+		state.relayValidationError = nil
+		state.relayApplyErrorKey = nil
+		state.isApplyingRelayConfiguration = true
+		Task {
+			let applyResult = await repository.initialize(
+				appDataDir: environment.defaultCoreDataDir,
+				networkConfiguration: configuration
+			)
+			switch applyResult {
+			case .success:
+				hasRelayConfigurationDraft = false
+				preferences.setRelayConfiguration(configuration)
+				state.isApplyingRelayConfiguration = false
+				state.relayConfigurationIsDirty = false
+				messages.show(UiMessage(text: .resource("relay_settings_applied"), tone: .success))
+			case .failure(let error):
+				if let lifecycleError = error as? CoreNetworkLifecycleError {
+					state.isApplyingRelayConfiguration = false
+					switch lifecycleError {
+					case .activeNetworkWork:
+						state.hasActiveNetworkWork = true
+						state.relayApplyErrorKey = "relay_apply_active_transfers"
+					case .transitionInProgress:
+						state.relayApplyErrorKey = "relay_apply_failed"
+					}
+					return
+				}
+				let rollbackResult = await repository.initialize(
+					appDataDir: environment.defaultCoreDataDir,
+					networkConfiguration: previousConfiguration
+				)
+				state.isApplyingRelayConfiguration = false
+				if case .success = rollbackResult {
+					state.relayApplyErrorKey = "relay_apply_failed"
+					messages.show(UiMessage(text: .resource("relay_apply_failed"), tone: .error))
+				} else {
+					state.relayApplyErrorKey = "relay_restore_failed"
+					messages.show(UiMessage(text: .resource("relay_restore_failed"), tone: .error))
+				}
+			}
+		}
+	}
+
+	private func updateRelayConfigurationDraft() {
+		state.relayValidationError = nil
+		state.relayApplyErrorKey = nil
+		let saved = preferences.preferences.relayConfiguration
+		let draftURLs = state.relayMode == .automatic ? saved.relayURLs : state.relayURLs
+		state.relayConfigurationIsDirty = saved != RelayConfiguration(mode: state.relayMode, relayURLs: draftURLs)
+		hasRelayConfigurationDraft = state.relayConfigurationIsDirty
+	}
+
 	func setBugWhatHappened(_ value: String) { state.bugWhatHappened = value }
 	func setBugExpected(_ value: String) { state.bugExpected = value }
 	func setBugSteps(_ value: String) { state.bugSteps = value }

apple/VniDrop/Features/Settings/SettingsScreen.swift

@@ -38,6 +38,17 @@ struct SettingsScreen: View {
 					NavigationLink(value: SettingsSection.storage) {
 						SettingsRow(icon: "internaldrive", title: String(localized: "storage_title"), value: nil)
 					}
+				}
+				Section(String(localized: "settings_advanced_title")) {
+					NavigationLink(value: SettingsSection.network) {
+						SettingsRow(
+							icon: "network",
+							title: String(localized: "settings_network_title"),
+							value: relayModeLabel(model.state.relayMode)
+						)
+					}
+				}
+				Section {
 					NavigationLink(value: SettingsSection.about) {
 						SettingsRow(icon: "info.circle", title: String(localized: "about_title"), value: nil)
 					}
@@ -99,6 +110,8 @@ private struct SettingsSectionContent: View {
 			AppearanceSettings(model: model)
 		case .notifications:
 			NotificationSettings(model: model)
+		case .network:
+			NetworkSettings(model: model)
 		case .storage:
 			StorageSettings(model: model)
 		case .about:
@@ -109,6 +122,13 @@ private struct SettingsSectionContent: View {
 	}
 }
 
+func relayModeLabel(_ mode: RelayPreferenceMode) -> String {
+	switch mode {
+	case .automatic: return String(localized: "relay_mode_automatic")
+	case .custom: return String(localized: "relay_mode_custom")
+	}
+}
+
 struct SettingsRow: View {
 	let icon: String
 	let title: String

apple/VniDrop/Features/Settings/SettingsSections.swift

@@ -57,6 +57,178 @@ struct NotificationSettings: View {
 	}
 }
 
+struct NetworkSettings: View {
+	@ObservedObject var model: SettingsModel
+
+	var body: some View {
+		Section {
+			Picker(
+				String(localized: "settings_network_title"),
+				selection: Binding(get: { model.state.relayMode }, set: { model.setRelayMode($0) })
+			) {
+				ForEach(RelayPreferenceMode.allCases, id: \.self) { mode in
+					Text(relayModeLabel(mode)).tag(mode)
+				}
+			}
+			.pickerStyle(.segmented)
+			.labelsHidden()
+			.disabled(model.state.isApplyingRelayConfiguration)
+		} footer: {
+			Text(LocalizedStringKey(
+				model.state.relayMode == .automatic
+					? "relay_mode_automatic_description"
+					: "relay_mode_custom_description"
+			))
+		}
+
+		Section {
+			Label {
+				Text(LocalizedStringKey("relay_privacy_description"))
+					.fixedSize(horizontal: false, vertical: true)
+			} icon: {
+				Image(systemName: "lock.shield")
+			}
+			.foregroundStyle(.secondary)
+		}
+
+		if let endpointId = model.state.endpointId, !endpointId.isEmpty {
+			Section {
+				Text(String(format: String(localized: "approval_endpoint_id"), endpointId))
+					.font(.footnote.monospaced())
+					.textSelection(.enabled)
+			}
+		}
+
+		if model.state.relayMode == .custom {
+			Section {
+				Label {
+					Text(LocalizedStringKey("relay_strict_warning"))
+						.fixedSize(horizontal: false, vertical: true)
+				} icon: {
+					Image(systemName: "exclamationmark.shield.fill")
+				}
+				.foregroundStyle(.orange)
+
+				ForEach(Array(model.state.relayURLs.indices), id: \.self) { index in
+					VStack(alignment: .leading, spacing: 6) {
+						HStack {
+							TextField(
+								"https://relay.example.com",
+								text: Binding(
+									get: {
+										model.state.relayURLs.indices.contains(index)
+											? model.state.relayURLs[index]
+											: ""
+									},
+									set: { model.setRelayURL($0, at: index) }
+								)
+							)
+							#if os(iOS)
+							.keyboardType(.URL)
+							.textInputAutocapitalization(.never)
+							#endif
+							.autocorrectionDisabled()
+							.disabled(model.state.isApplyingRelayConfiguration)
+
+							Button(role: .destructive) {
+								model.removeRelayURL(at: index)
+							} label: {
+								Image(systemName: "minus.circle.fill")
+							}
+							.buttonStyle(.borderless)
+							.accessibilityLabel(Text(LocalizedStringKey("relay_remove_url")))
+							.disabled(model.state.isApplyingRelayConfiguration)
+						}
+
+						if let error = model.state.relayValidationError, error.urlIndex == index {
+							Text(relayValidationMessage(error))
+								.font(.caption)
+								.foregroundStyle(.red)
+						}
+					}
+				}
+
+				Button(action: model.addRelayURL) {
+					Label(String(localized: "relay_add_url"), systemImage: "plus.circle")
+				}
+				.disabled(
+					model.state.relayURLs.count >= RelayConfigurationValidator.maximumRelayCount
+						|| model.state.isApplyingRelayConfiguration
+				)
+			} header: {
+				Text(LocalizedStringKey("relay_custom_urls_label"))
+			} footer: {
+				Text(LocalizedStringKey("relay_custom_urls_help"))
+			}
+		}
+
+		if let error = model.state.relayValidationError, error.urlIndex == nil {
+			Section {
+				Label {
+					Text(relayValidationMessage(error))
+				} icon: {
+					Image(systemName: "exclamationmark.triangle.fill")
+				}
+				.foregroundStyle(.red)
+			}
+		}
+
+		if model.state.hasActiveNetworkWork || model.state.relayApplyErrorKey != nil {
+			Section {
+				Label {
+					Text(LocalizedStringKey(
+						model.state.hasActiveNetworkWork
+							? "relay_apply_active_transfers"
+							: model.state.relayApplyErrorKey ?? "relay_apply_failed"
+					))
+				} icon: {
+					Image(systemName: "exclamationmark.triangle.fill")
+				}
+				.foregroundStyle(.red)
+			}
+		}
+
+		Section {
+			Button(action: model.applyRelayConfiguration) {
+				HStack {
+					Text(LocalizedStringKey(
+						model.state.isApplyingRelayConfiguration ? "relay_applying" : "relay_apply"
+					))
+					if model.state.isApplyingRelayConfiguration {
+						Spacer()
+						ProgressView()
+					}
+				}
+			}
+			.disabled(
+				!model.state.relayConfigurationIsDirty
+					|| model.state.isApplyingRelayConfiguration
+					|| model.state.hasActiveNetworkWork
+			)
+		} footer: {
+			Text(LocalizedStringKey("relay_apply_restart_description"))
+		}
+	}
+}
+
+private func relayValidationMessage(_ error: RelayConfigurationValidationError) -> String {
+	switch error {
+	case .missingURL:
+		return String(localized: "relay_validation_missing_url")
+	case .tooManyURLs:
+		return String(
+			format: String(localized: "relay_validation_too_many_urls"),
+			RelayConfigurationValidator.maximumRelayCount
+		)
+	case .httpsRequired(let index):
+		return String(format: String(localized: "relay_validation_https_required"), index + 1)
+	case .invalidURL(let index):
+		return String(format: String(localized: "relay_validation_invalid_url"), index + 1)
+	case .duplicateURL(let index):
+		return String(format: String(localized: "relay_validation_duplicate_url"), index + 1)
+	}
+}
+
 struct StorageSettings: View {
 	@ObservedObject var model: SettingsModel
 	@State private var showDeleteConfirmation = false