Startup and shutdown

Entry point

Program.Main ([STAThread]) first decides whether the process is the application or a worker process:

flowchart LR
    A(["Program.Main"]) --> B{"Is args[1] --worker<br/>with 5 or more arguments?"}
    B -->|yes| W["WorkerHost.Run<br/>and Environment.Exit with its code"]
    B -->|no| C["new App()<br/>InitializeComponent · Run"]
    class W io
    class C ok

A worker process never creates App or any window.

App.xaml is declared as a Page and not as an ApplicationDefinition (the .csproj does this) so that this is the Main used, not the one WPF generates. That way a worker process starts without loading anything from the UI. See Worker processes.

App.OnStartup

In this order:

1. CrashHandler.Install subscribes to DispatcherUnhandledException, AppDomain.UnhandledException and TaskScheduler.UnobservedTaskException. It comes first so it also covers startup itself.
2. SingleInstance.TryAcquire takes the Local\LoopbackTranscriber-B6E1F6C4-… mutex. If another instance already holds it, it signals that instance's …-Activate event (with AllowSetForegroundWindow so it can come to the front) and this one exits. A mutex abandoned by an instance that crashed is taken over anyway.
3. Settings: creates UserNotices and SettingsService. EnsureDefaultUserName() suggests the Windows name the first time, and the language is set with Strings.Instance.SetLanguage(...).
4. Theme: WPF-UI dark, with the #6A2BD9 accent.
5. Container: AppServices.Build(settings, notices) registers every service and ViewModel and validates the graph when building it (ValidateOnBuild = true).
6. Resolves MainWindow, registers it with CrashHandler.Attach together with RecordingViewModel so the recording can be rescued, starts listening for activations from other instances and shows the window.

The MainWindow constructor calls MainViewModel.Start(), which:

• starts the process watcher (TargetsViewModel.Start);
• loads the history;
• starts, in the background, the recovery of orphan recordings and the verification of the installed models.

The container (AppServices)

Everything is a singleton except the ViewModels of the secondary pages, which are transient and created on demand through IPageFactory:

Registration	Implementation
ISettingsStore	SettingsService (created before the container)
UserNotices	shared instance of user notices
ITargetWatcher	TargetProcessWatcher
ICustomAppsService	CustomAppsService
ISummarizer	SummarizationService
IModelVerifier	ModelVerifier
IWhisperTranscriber	WhisperTranscriptionService, which is also registered as its own type
IAudioPreparer	NaudioAudioPreparer
TranscriptHistoryService, TranscriptsFolderWatcher	—
RecordingProcessor, TranscriptSaver, TranscriptRetranscriber	—
FailedRecordingStore	folder %LocalAppData%\LoopbackTranscriber\failed
CaptureCoordinator	with ProcessLoopbackRecorder, DeviceLoopbackRecorder, MicrophoneRecorder and the FailedRecordingStore
RecordingWorkflow	—
IDialogService	WpfDialogService
IUiDispatcher	WpfUiDispatcher.Instance
IMessenger	WeakReferenceMessenger.Default
Shell ViewModels	HistoryViewModel, ViewerViewModel, TargetsViewModel, RecordingViewModel, MainViewModel
IRecordingHost	RecordingHost
ILiveTranslationFactory	LiveTranslationFactory
Others	TrayMenuViewModel, AppExitWorkflow, UserNoticePresenter, MainWindow
Transient	FirstRunViewModel, ConfigViewModel, ApplicationsViewModel, LiveTranslationSettingsViewModel
IPageFactory	ServiceProviderPageFactory, which resolves them from the container

First run or application

The MainViewModel constructor checks whether both models exist, models\whisper\ggml-turbo.bin and models\llm\Qwen3-4B-Q4_K_M.gguf:

• If they do, it sets FirstRunSetupCompleted, selects the first application and shows AppView.
• If not, it creates FirstRunViewModel and shows FirstRun. When that completes, it opens Config.

If the startup verification deletes a damaged model, the app goes back to FirstRun, unless a recording is in progress or being processed.

Shutdown

There are four ways for the application to end. None of them deletes unprocessed audio.

Situation	What happens
Window X	Closing is cancelled and the window is hidden to the tray (HideToTray).
Exit from the tray	AppExitWorkflow.ConfirmExitAsync decides (see below). If a summary is being generated, you are asked to confirm because it would be lost.
Windows sign-out or shutdown	SessionEnding lets the app close and calls RecordingViewModel.PreserveInterruptedRecording(3 s): it stops the capture and keeps the audio unprocessed.
Unhandled error	CrashHandler preserves the recording (3 s), shows the message with the log path and exits with code 1.

AppExitWorkflow

1. Waits, for 10 s at most, for a half-started recording to finish starting.
2. With a recording in progress, asks Yes / No / Cancel:
   • Yes: shows the window, stops and processes (IRecordingHost.StopRecordingAsync) and exits.
   • No: keeps the audio unprocessed (PreserveInterruptedRecordingAsync, 10 s at most) and exits.
   • Cancel: does not exit.
3. With a recording being processed, asks whether to wait. If accepted, it shows the window and waits until IsBusy becomes false.
4. While an exit is pending, further exit requests are ignored.

App.OnExit

Disposes the container, which disposes recorders, watchers and timers. Then it writes any settings that could not be saved (FlushPendingWrite) and releases the single-instance mutex.

CrashHandler

Event	Handling
DispatcherUnhandledException (UI thread)	Marks it handled, logs it, rescues the recording, shows CrashBody, CrashBodyPreserved or CrashBodyLost and closes the application.
AppDomain.UnhandledException (other thread)	Logs it, rescues the recording on the UI thread (giving it 2 s to respond) and shows the same message. The process ends anyway.
UnobservedTaskException	Only logs it and marks it observed.

A second error while the first one is being handled is only logged.