fix: resolve multiple critical bugs identified in code review

- fix(engine): resolve aria2 port TOCTOU race and secure conf file

- fix(server): eliminate main queue deadlock risk in local extension server

- fix(controller): ensure synchronous state save on app termination

- fix(ui): fix table skipping new items by diffing identity instead of count

- fix(scheduler): use 2-letter abbreviations to resolve day name collisions

- fix(settings): purge keychain orphans when primer access is denied

- fix(metadata): prevent synchronous DNS resolution from blocking async pool

- refactor: clean up dead code and unused variables

Sources/Firelink/AddDownloadsView.swift

@@ -322,7 +322,7 @@ struct AddDownloadsView: View {
                         ProgressView().controlSize(.small)
                         Text("Fetching media options...")
                             .foregroundStyle(.secondary)
-                    } else if case .failed(let error) = firstMedia.state {
+                    } else if case .failed(_) = firstMedia.state {
                         Image(systemName: "exclamationmark.triangle.fill").foregroundStyle(.red)
                         Text("Failed to load options.")
                             .foregroundStyle(.secondary)

Sources/Firelink/AppSettings.swift

@@ -445,7 +445,7 @@ final class AppSettings: ObservableObject {
                 extensionPairingToken = Self.generateSecureToken()
             }
         } else {
-            isKeychainAccessGranted = false
+            revokeKeychainAccess()
         }
     }
 

Sources/Firelink/Aria2DownloadEngine.swift

@@ -2,7 +2,7 @@ import Foundation
 import CFNetwork
 import Network
 
-final class Aria2DownloadEngine {
+final class Aria2DownloadEngine: Sendable {
     struct Handle {
         let processIdentifier: Int32
         let rpcPort: Int
@@ -107,7 +107,7 @@ final class Aria2DownloadEngine {
         speedLimitKiBPerSecond: Int?,
         progress: @escaping @Sendable (DownloadProgress) -> Void,
         completion: @escaping @Sendable (Result<Void, Error>) -> Void
-    ) throws -> Handle {
+    ) async throws -> Handle {
         guard let executableURL else {
             throw EngineError.executableNotFound
         }
@@ -117,30 +117,48 @@ final class Aria2DownloadEngine {
             withIntermediateDirectories: true
         )
 
-        let rpcPort = Self.findFreePort()
-        let rpcSecret = UUID().uuidString
-        let confURL = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent("firelink-aria2-\(UUID().uuidString).conf")
-        do {
-            let confContent = "rpc-secret=\(rpcSecret)\n"
-            try confContent.write(to: confURL, atomically: true, encoding: .utf8)
-            try FileManager.default.setAttributes([.posixPermissions: 0o600], ofItemAtPath: confURL.path)
-        } catch {
-            throw EngineError.launchFailed("Could not write secure configuration file: \(error.localizedDescription)")
-        }
+        var lastError: Error?
 
-        let process = Process()
-        process.executableURL = executableURL
-        process.arguments = try arguments(
-            for: item,
-            proxyConfiguration: proxyConfiguration,
-            speedLimitKiBPerSecond: speedLimitKiBPerSecond,
-            rpcPort: rpcPort,
-            confURL: confURL
-        )
+        for _ in 1...5 {
+            let rpcPort = Self.findFreePort()
+            let rpcSecret = UUID().uuidString
+            let tempDir = URL(fileURLWithPath: NSTemporaryDirectory()).appendingPathComponent("firelink-aria2-\(UUID().uuidString)")
+            
+            do {
+                try FileManager.default.createDirectory(at: tempDir, withIntermediateDirectories: true, attributes: [.posixPermissions: 0o700])
+            } catch {
+                lastError = EngineError.launchFailed("Could not create secure temporary directory: \(error.localizedDescription)")
+                continue
+            }
+            
+            let confURL = tempDir.appendingPathComponent("aria2.conf")
+            do {
+                let confContent = "rpc-secret=\(rpcSecret)\n"
+                try confContent.write(to: confURL, atomically: true, encoding: .utf8)
+            } catch {
+                lastError = EngineError.launchFailed("Could not write secure configuration file: \(error.localizedDescription)")
+                continue
+            }
 
-        let inputPipe = Pipe()
-        let outputPipe = Pipe()
-        let errorPipe = Pipe()
+            let process = Process()
+            process.executableURL = executableURL
+            
+            do {
+                process.arguments = try arguments(
+                    for: item,
+                    proxyConfiguration: proxyConfiguration,
+                    speedLimitKiBPerSecond: speedLimitKiBPerSecond,
+                    rpcPort: rpcPort,
+                    confURL: confURL
+                )
+            } catch {
+                lastError = error
+                break
+            }
+
+            let inputPipe = Pipe()
+            let outputPipe = Pipe()
+            let errorPipe = Pipe()
         process.standardInput = inputPipe
         process.standardOutput = outputPipe
         process.standardError = errorPipe
@@ -169,7 +187,7 @@ final class Aria2DownloadEngine {
         }
 
         process.terminationHandler = { finishedProcess in
-            try? FileManager.default.removeItem(at: confURL)
+            try? FileManager.default.removeItem(at: tempDir)
             completionMonitor.cancel()
             outputPipe.fileHandleForReading.readabilityHandler = nil
             errorPipe.fileHandleForReading.readabilityHandler = nil
@@ -190,33 +208,54 @@ final class Aria2DownloadEngine {
             completionGate.complete(.failure(EngineError.launchFailed(message.isEmpty ? "exit code \(finishedProcess.terminationStatus)" : message)))
         }
 
-        do {
-            try process.run()
-            if let input = inputFileContent(for: item).data(using: .utf8) {
-                inputPipe.fileHandleForWriting.write(input)
+            var didThrow = false
+            do {
+                try process.run()
+                if let input = inputFileContent(for: item).data(using: .utf8) {
+                    inputPipe.fileHandleForWriting.write(input)
+                }
+                inputPipe.fileHandleForWriting.closeFile()
+            } catch {
+                didThrow = true
+                lastError = EngineError.launchFailed(error.localizedDescription)
+            }
+            
+            if didThrow {
+                try? FileManager.default.removeItem(at: tempDir)
+                continue
+            }
+            
+            try? await Task.sleep(nanoseconds: 100_000_000)
+            
+            if !process.isRunning {
+                let stderr = String(data: errorBuffer.data, encoding: .utf8) ?? ""
+                if stderr.contains("Address already in use") || stderr.contains("Failed to bind") || stderr.contains("bind: Address") {
+                    try? FileManager.default.removeItem(at: tempDir)
+                    continue
+                }
+                // If it exited for another reason, we might still want to fail or let the terminationHandler process it.
+                // But the terminationHandler will hit completionGate, so we just return the handle.
             }
-            inputPipe.fileHandleForWriting.closeFile()
-        } catch {
-            try? FileManager.default.removeItem(at: confURL)
-            throw EngineError.launchFailed(error.localizedDescription)
-        }
 
-        completionMonitor.set(
-            Self.monitorCompletion(
-                rpcPort: rpcPort,
-                rpcSecret: rpcSecret,
-                process: process,
-                completionGate: completionGate
+            completionMonitor.set(
+                Self.monitorCompletion(
+                    rpcPort: rpcPort,
+                    rpcSecret: rpcSecret,
+                    process: process,
+                    completionGate: completionGate
+                )
             )
-        )
 
-        return Handle(processIdentifier: process.processIdentifier, rpcPort: rpcPort, rpcSecret: rpcSecret) {
-            completionMonitor.cancel()
-            if process.isRunning {
-                process.terminate()
+            return Handle(processIdentifier: process.processIdentifier, rpcPort: rpcPort, rpcSecret: rpcSecret) {
+                completionMonitor.cancel()
+                if process.isRunning {
+                    process.terminate()
+                }
+                try? FileManager.default.removeItem(at: tempDir)
             }
-            try? FileManager.default.removeItem(at: confURL)
         }
+        
+        throw lastError ?? EngineError.launchFailed("Failed to start aria2c after 5 attempts.")
     }
 
     private static func monitorCompletion(

Sources/Firelink/DownloadController.swift

@@ -74,7 +74,7 @@ final class DownloadController: ObservableObject {
 
         NotificationCenter.default.publisher(for: NSApplication.willTerminateNotification)
             .sink { [weak self] _ in
-                self?.saveDownloads()
+                self?.saveDownloadsSync()
             }
             .store(in: &cancellables)
 
@@ -371,12 +371,7 @@ final class DownloadController: ObservableObject {
         pumpQueue()
     }
 
-    func remove(at offsets: IndexSet, deleteFiles: Bool = false) {
-        for index in offsets {
-            let item = downloads[index]
-            delete(item, deleteFiles: deleteFiles)
-        }
-    }
+
 
     func delete(_ item: DownloadItem, deleteFiles: Bool = false) {
         activeHandles[item.id]?.cancel()
@@ -598,49 +593,61 @@ final class DownloadController: ObservableObject {
                 }
             }
         } else {
-            do {
-                let handle = try engine.start(
-                    item: injectedEngineItem(from: item),
-                    proxyConfiguration: settings.downloadProxyConfiguration,
-                    speedLimitKiBPerSecond: effectiveSpeedLimitKiBPerSecond(for: item),
-                    progress: { [weak self] progress in
-                        Task { @MainActor in
-                            let now = Date()
-                            if let last = self?.lastProgressUpdateTimes[item.id], now.timeIntervalSince(last) < 0.25 {
-                                return
+            Task {
+                do {
+                    let liveItem = injectedEngineItem(from: item)
+                    let handle = try await engine.start(
+                        item: liveItem,
+                        proxyConfiguration: settings.downloadProxyConfiguration,
+                        speedLimitKiBPerSecond: effectiveSpeedLimitKiBPerSecond(for: liveItem),
+                        progress: { [weak self] progress in
+                            Task { @MainActor in
+                                let now = Date()
+                                if let last = self?.lastProgressUpdateTimes[item.id], now.timeIntervalSince(last) < 0.25 {
+                                    return
+                                }
+                                self?.lastProgressUpdateTimes[item.id] = now
+                                self?.update(item.id) {
+                                    guard $0.status == .downloading else { return }
+                                    $0.progress = progress.fraction
+                                    $0.bytesText = progress.bytesText
+                                    $0.speedText = progress.speedText
+                                    $0.etaText = progress.etaText
+                                    $0.connectionCount = progress.connectionCount
+                                    $0.message = "Downloading"
+                                }
                             }
-                            self?.lastProgressUpdateTimes[item.id] = now
-                            self?.update(item.id) {
-                                guard $0.status == .downloading else { return }
-                                $0.progress = progress.fraction
-                                $0.bytesText = progress.bytesText
-                                $0.speedText = progress.speedText
-                                $0.etaText = progress.etaText
-                                $0.connectionCount = progress.connectionCount
-                                $0.message = "Downloading"
+                        },
+                        completion: { [weak self] result in
+                            Task { @MainActor in
+                                self?.handleCompletion(item: item, result: result)
                             }
                         }
-                    },
-                    completion: { [weak self] result in
-                        Task { @MainActor in
-                            self?.handleCompletion(item: item, result: result)
+                    )
+                    
+                    await MainActor.run {
+                        guard activeDownloadItem(id: item.id) != nil else {
+                            handle.cancel()
+                            return
                         }
+                        activeHandles[item.id] = handle
+                        update(item.id) {
+                            $0.rpcPort = handle.rpcPort
+                            $0.rpcSecret = handle.rpcSecret
+                            $0.message = "Starting..."
+                        }
+                        saveDownloads()
+                        applySpeedLimitsToActiveDownloads()
+                        updateSleepActivity()
+                    }
+                } catch {
+                    await MainActor.run {
+                        handleDownloadFailure(itemID: item.id, error: error)
+                        applySpeedLimitsToActiveDownloads()
+                        updateSleepActivity()
+                        pumpQueue()
                     }
-                )
-                activeHandles[item.id] = handle
-                update(item.id) {
-                    $0.rpcPort = handle.rpcPort
-                    $0.rpcSecret = handle.rpcSecret
-                    $0.message = "Starting..."
                 }
-                saveDownloads()
-                applySpeedLimitsToActiveDownloads()
-                updateSleepActivity()
-            } catch {
-                handleDownloadFailure(itemID: item.id, error: error)
-                applySpeedLimitsToActiveDownloads()
-                updateSleepActivity()
-                pumpQueue()
             }
         }
     }
@@ -996,6 +1003,22 @@ final class DownloadController: ObservableObject {
         }
     }
 
+    private func saveDownloadsSync() {
+        let queuesCopy = queues
+        let downloadsCopy = downloads.map(\.redactedForPersistence)
+        let storageURL = self.storageURL
+
+        do {
+            let directory = storageURL.deletingLastPathComponent()
+            try FileManager.default.createDirectory(at: directory, withIntermediateDirectories: true, attributes: nil)
+            let state = StoredDownloadState(queues: queuesCopy, downloads: downloadsCopy)
+            let data = try JSONEncoder().encode(state)
+            try data.write(to: storageURL, options: .atomic)
+        } catch {
+            print("Failed to synchronously save downloads: \(error)")
+        }
+    }
+
     private func saveDownloads() {
         let queuesCopy = queues
         let downloadsCopy = downloads.map(\.redactedForPersistence)

Sources/Firelink/DownloadMetadataFetcher.swift

@@ -54,9 +54,14 @@ enum DownloadMetadataFetcher {
             return pending
         }
 
-        if isAutoFetch, let host = url.host, isPrivateHost(host) {
-            pending.state = .loaded
-            return pending
+        if isAutoFetch, let host = url.host {
+            let isPrivate = await Task.detached {
+                isPrivateHost(host)
+            }.value
+            if isPrivate {
+                pending.state = .loaded
+                return pending
+            }
         }
 
         var request = URLRequest(url: url)

Sources/Firelink/DownloadTable.swift

@@ -126,7 +126,9 @@ struct DownloadTable: View {
         }
         .onAppear { sortedItems = items.sorted(using: sortOrder) }
         .onChange(of: items) { _, newItems in
-            if newItems.count != sortedItems.count {
+            let existingIDs = Set(sortedItems.map(\.id))
+            let newIDs = Set(newItems.map(\.id))
+            if existingIDs != newIDs {
                 sortedItems = newItems.sorted(using: sortOrder)
             } else {
                 let itemsDict = Dictionary(uniqueKeysWithValues: newItems.map { ($0.id, $0) })

Sources/Firelink/LocalExtensionServer.swift

@@ -1,6 +1,7 @@
 import Foundation
 import Network
 import AppKit
+import Combine
 
 final class LocalExtensionServer: @unchecked Sendable {
     private enum Constants {
@@ -16,7 +17,12 @@ final class LocalExtensionServer: @unchecked Sendable {
     private let settings: AppSettings
     private let queue = DispatchQueue(label: "local.firelink.server")
     let port: UInt16
+    
+    private let tokenLock = NSLock()
+    private var _pairingToken: String = ""
+    private var cancellables = Set<AnyCancellable>()
 
+    @MainActor
     init?(downloadController: DownloadController, settings: AppSettings) {
         self.downloadController = downloadController
         self.settings = settings
@@ -42,6 +48,16 @@ final class LocalExtensionServer: @unchecked Sendable {
 
         self.listener = createdListener
         self.port = selectedPort ?? 6412
+
+        settings.$extensionPairingToken
+            .sink { [weak self] token in
+                self?.tokenLock.withLock { self?._pairingToken = token }
+            }
+            .store(in: &cancellables)
+    }
+
+    private var currentPairingToken: String {
+        tokenLock.withLock { _pairingToken }
     }
 
     func start() {
@@ -139,7 +155,7 @@ final class LocalExtensionServer: @unchecked Sendable {
             return isAllowedExtensionOrigin(request.header(named: "origin") ?? "") ? .noContent : .forbidden
         }
 
-        let expectedToken = DispatchQueue.main.sync { settings.extensionPairingToken }
+        let expectedToken = currentPairingToken
         guard let token = request.header(named: Constants.extensionRequestHeader),
               token == expectedToken else {
             return .forbidden

Sources/Firelink/SchedulerController.swift

@@ -18,13 +18,13 @@ enum SchedulerDay: Int, Codable, CaseIterable, Identifiable {
 
     var shortName: String {
         switch self {
-        case .sunday: "S"
-        case .monday: "M"
-        case .tuesday: "T"
-        case .wednesday: "W"
-        case .thursday: "T"
-        case .friday: "F"
-        case .saturday: "S"
+        case .sunday: "Su"
+        case .monday: "Mo"
+        case .tuesday: "Tu"
+        case .wednesday: "We"
+        case .thursday: "Th"
+        case .friday: "Fr"
+        case .saturday: "Sa"
         }
     }
 }