feat(startup): pre-warm default Whisper model at launch in background thread

src-tauri/src/commands/models.rs

@@ -72,7 +72,7 @@ fn model_capability(
     }
 }
 
-fn load_model_from_disk(model_id: &ModelId) -> Result<Box<dyn kon_transcription::SpeechModel + Send>, String> {
+pub fn load_model_from_disk(model_id: &ModelId) -> Result<Box<dyn kon_transcription::SpeechModel + Send>, String> {
     let entry = model_registry::find_model(model_id)
         .ok_or_else(|| format!("Unknown model: {model_id}"))?;
 
@@ -155,6 +155,42 @@ pub async fn ensure_model_loaded(
     Ok(())
 }
 
+/// Spawns a background task that loads the default Whisper model into memory
+/// if it is already downloaded. Returns immediately — errors are logged, never panicked.
+///
+/// Call this once from app setup() after AppState is managed.
+pub fn prewarm_default_model(whisper_engine: Arc<LocalEngine>) {
+    let model_id = default_model_id_for_engine("whisper");
+
+    if !model_manager::is_downloaded(&model_id) {
+        return;
+    }
+
+    if whisper_engine
+        .loaded_model_id()
+        .as_ref()
+        .map(|id| id == &model_id)
+        .unwrap_or(false)
+    {
+        return;
+    }
+
+    tokio::spawn(async move {
+        let result = tokio::task::spawn_blocking(move || {
+            load_model_from_disk(&model_id).map(|model| {
+                whisper_engine.load(model, model_id);
+            })
+        })
+        .await;
+
+        match result {
+            Ok(Ok(())) => eprintln!("[startup] Whisper model pre-warmed successfully"),
+            Ok(Err(e)) => eprintln!("[startup] Whisper pre-warm failed: {e}"),
+            Err(e) => eprintln!("[startup] Whisper pre-warm task panicked: {e}"),
+        }
+    });
+}
+
 #[derive(Serialize)]
 #[serde(rename_all = "camelCase")]
 pub struct RuntimeCapabilities {

src-tauri/src/lib.rs

@@ -215,6 +215,11 @@ pub fn run() {
                 db,
             });
 
+            {
+                let whisper = app.state::<AppState>().whisper_engine.clone();
+                crate::commands::models::prewarm_default_model(whisper);
+            }
+
             if let Err(e) = tray::setup(app) {
                 eprintln!("Failed to setup tray: {e}");
             }