diff --git a/src-tauri/Cargo.toml b/src-tauri/Cargo.toml
index 29a85ec..d77e655 100644
--- a/src-tauri/Cargo.toml
+++ b/src-tauri/Cargo.toml
@@ -30,3 +30,6 @@ tauri-plugin-global-shortcut = "2"
 # Serialisation
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
+
+# Async runtime (spawn_blocking for inference)
+tokio = { version = "1", features = ["rt", "sync"] }
diff --git a/src-tauri/src/commands/audio.rs b/src-tauri/src/commands/audio.rs
new file mode 100644
index 0000000..51d72d6
--- /dev/null
+++ b/src-tauri/src/commands/audio.rs
@@ -0,0 +1,49 @@
+use std::path::PathBuf;
+
+use tauri::Manager;
+
+use kon_core::types::AudioSamples;
+
+/// Save PCM f32 samples as a WAV file. Returns the file path.
+#[tauri::command]
+pub async fn save_audio(
+    app: tauri::AppHandle,
+    samples: Vec<f32>,
+    output_folder: Option<String>,
+) -> Result<String, String> {
+    let recordings_dir = if let Some(ref folder) = output_folder {
+        if !folder.is_empty() {
+            PathBuf::from(folder)
+        } else {
+            app.path()
+                .app_local_data_dir()
+                .map_err(|e: tauri::Error| e.to_string())?
+                .join("recordings")
+        }
+    } else {
+        app.path()
+            .app_local_data_dir()
+            .map_err(|e: tauri::Error| e.to_string())?
+            .join("recordings")
+    };
+
+    std::fs::create_dir_all(&recordings_dir)
+        .map_err(|e| format!("Failed to create recordings dir: {e}"))?;
+
+    let timestamp = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_secs();
+    let filename = format!("kon-{timestamp}.wav");
+    let path = recordings_dir.join(&filename);
+    let path_clone = path.clone();
+
+    tokio::task::spawn_blocking(move || {
+        let audio = AudioSamples::mono_16khz(samples);
+        kon_audio::write_wav(&path_clone, &audio).map_err(|e| e.to_string())
+    })
+    .await
+    .map_err(|e| e.to_string())??;
+
+    Ok(path.to_string_lossy().to_string())
+}
diff --git a/src-tauri/src/commands/llm.rs b/src-tauri/src/commands/llm.rs
new file mode 100644
index 0000000..b5b1411
--- /dev/null
+++ b/src-tauri/src/commands/llm.rs
@@ -0,0 +1,53 @@
+// LLM stubs — ONNX-based local LLM coming post-revenue.
+
+#[tauri::command]
+pub fn check_llm_engine() -> Result<bool, String> {
+    Ok(false)
+}
+
+#[tauri::command]
+pub fn check_llm_model(_size: String) -> Result<bool, String> {
+    Ok(false)
+}
+
+#[tauri::command]
+pub fn list_llm_models() -> Result<Vec<String>, String> {
+    Ok(vec![])
+}
+
+#[tauri::command]
+pub async fn download_llm_model(
+    _app: tauri::AppHandle,
+    _size: String,
+) -> Result<String, String> {
+    Err("LLM not available yet — coming soon".into())
+}
+
+#[tauri::command]
+pub async fn load_llm_model(
+    _size: String,
+) -> Result<String, String> {
+    Err("LLM not available yet — coming soon".into())
+}
+
+#[tauri::command]
+pub async fn llm_generate(
+    _prompt: String,
+    _max_tokens: Option<u32>,
+) -> Result<String, String> {
+    Err("LLM not available yet — coming soon".into())
+}
+
+#[tauri::command]
+pub async fn llm_extract_tasks(
+    _transcript: String,
+) -> Result<Vec<String>, String> {
+    Err("LLM not available yet — coming soon".into())
+}
+
+#[tauri::command]
+pub async fn llm_format_transcript(
+    _transcript: String,
+) -> Result<String, String> {
+    Err("LLM not available yet — coming soon".into())
+}
diff --git a/src-tauri/src/commands/mod.rs b/src-tauri/src/commands/mod.rs
new file mode 100644
index 0000000..40acba1
--- /dev/null
+++ b/src-tauri/src/commands/mod.rs
@@ -0,0 +1,5 @@
+pub mod audio;
+pub mod llm;
+pub mod models;
+pub mod transcription;
+pub mod windows;
diff --git a/src-tauri/src/commands/models.rs b/src-tauri/src/commands/models.rs
new file mode 100644
index 0000000..c5714d3
--- /dev/null
+++ b/src-tauri/src/commands/models.rs
@@ -0,0 +1,172 @@
+use tauri::Emitter;
+
+use crate::AppState;
+use kon_core::types::ModelId;
+use kon_transcription::model_manager;
+
+/// Map legacy size strings to ModelId.
+fn whisper_model_id(size: &str) -> ModelId {
+    match size.to_lowercase().as_str() {
+        "tiny" => ModelId::new("whisper-tiny-en"),
+        "base" => ModelId::new("whisper-base-en"),
+        "small" => ModelId::new("whisper-small-en"),
+        "medium" => ModelId::new("whisper-medium-en"),
+        other => ModelId::new(other),
+    }
+}
+
+fn parakeet_model_id(name: &str) -> ModelId {
+    match name {
+        "ctc-int8" => ModelId::new("parakeet-ctc-0.6b-int8"),
+        other => ModelId::new(other),
+    }
+}
+
+// --- Whisper model commands ---
+
+#[tauri::command]
+pub async fn download_model(
+    app: tauri::AppHandle,
+    size: String,
+) -> Result<String, String> {
+    let id = whisper_model_id(&size);
+    let app_clone = app.clone();
+    model_manager::download(&id, move |progress| {
+        let _ = app_clone.emit("model-download-progress", &progress);
+    })
+    .await
+    .map_err(|e| e.to_string())?;
+    Ok(format!("Model {} downloaded", size))
+}
+
+#[tauri::command]
+pub fn check_model(size: String) -> Result<bool, String> {
+    let id = whisper_model_id(&size);
+    Ok(model_manager::is_downloaded(&id))
+}
+
+#[tauri::command]
+pub fn list_models() -> Result<Vec<String>, String> {
+    let ids = model_manager::list_downloaded();
+    Ok(ids
+        .into_iter()
+        .filter(|id| id.as_str().starts_with("whisper-"))
+        .map(|id| {
+            match id.as_str() {
+                "whisper-tiny-en" => "Tiny".to_string(),
+                "whisper-base-en" => "Base".to_string(),
+                "whisper-small-en" => "Small".to_string(),
+                "whisper-medium-en" => "Medium".to_string(),
+                other => other.to_string(),
+            }
+        })
+        .collect())
+}
+
+#[tauri::command]
+pub async fn load_model(
+    state: tauri::State<'_, AppState>,
+    size: String,
+) -> Result<String, String> {
+    let id = whisper_model_id(&size);
+    let dir = model_manager::model_dir(&id);
+    let model_file = dir.join(
+        kon_core::model_registry::find_model(&id)
+            .ok_or_else(|| format!("Unknown model: {size}"))?
+            .files
+            .first()
+            .ok_or_else(|| format!("No files for model: {size}"))?
+            .filename,
+    );
+
+    if !model_file.exists() {
+        return Err(format!("Model not downloaded: {size}"));
+    }
+
+    let engine = state.whisper_engine.clone();
+    tokio::task::spawn_blocking(move || {
+        let model = kon_transcription::load_whisper(&model_file)
+            .map_err(|e| e.to_string())?;
+        engine.load(model);
+        Ok::<_, String>(())
+    })
+    .await
+    .map_err(|e| e.to_string())??;
+
+    Ok(format!("Model {} loaded", size))
+}
+
+#[tauri::command]
+pub fn check_engine(state: tauri::State<AppState>) -> Result<bool, String> {
+    Ok(state.whisper_engine.is_loaded())
+}
+
+// --- Parakeet model commands ---
+
+#[tauri::command]
+pub async fn download_parakeet_model(
+    app: tauri::AppHandle,
+    name: String,
+) -> Result<String, String> {
+    let id = parakeet_model_id(&name);
+    let app_clone = app.clone();
+    model_manager::download(&id, move |progress| {
+        let _ = app_clone.emit("parakeet-download-progress", &progress);
+    })
+    .await
+    .map_err(|e| e.to_string())?;
+    Ok(format!("Parakeet model {} downloaded", name))
+}
+
+#[tauri::command]
+pub fn check_parakeet_model(name: String) -> Result<bool, String> {
+    let id = parakeet_model_id(&name);
+    Ok(model_manager::is_downloaded(&id))
+}
+
+#[tauri::command]
+pub fn list_parakeet_models() -> Result<Vec<String>, String> {
+    let ids = model_manager::list_downloaded();
+    Ok(ids
+        .into_iter()
+        .filter(|id| id.as_str().starts_with("parakeet-"))
+        .map(|id| {
+            match id.as_str() {
+                "parakeet-ctc-0.6b-int8" => "ctc-int8".to_string(),
+                other => other.to_string(),
+            }
+        })
+        .collect())
+}
+
+#[tauri::command]
+pub async fn load_parakeet_model(
+    state: tauri::State<'_, AppState>,
+    name: String,
+) -> Result<String, String> {
+    let id = parakeet_model_id(&name);
+    let dir = model_manager::model_dir(&id);
+
+    if !dir.exists() {
+        return Err(format!("Parakeet model not downloaded: {name}"));
+    }
+
+    let engine = state.parakeet_engine.clone();
+    tokio::task::spawn_blocking(move || {
+        let model = kon_transcription::load_parakeet(&dir)
+            .map_err(|e| e.to_string())?;
+        engine.load(model);
+        Ok::<_, String>(())
+    })
+    .await
+    .map_err(|e| e.to_string())??;
+
+    Ok(format!("Parakeet model {} loaded", name))
+}
+
+#[tauri::command]
+pub fn check_parakeet_engine(
+    state: tauri::State<AppState>,
+) -> Result<bool, String> {
+    Ok(state.parakeet_engine.is_loaded())
+}
diff --git a/src-tauri/src/commands/transcription.rs b/src-tauri/src/commands/transcription.rs
new file mode 100644
index 0000000..dbc8ccc
--- /dev/null
+++ b/src-tauri/src/commands/transcription.rs
@@ -0,0 +1,165 @@
+// Tauri command handlers must match the frontend's invoke() parameter lists,
+// so the argument counts are dictated by the Svelte code.
+#![allow(clippy::too_many_arguments)]
+
+use std::path::Path;
+
+use tauri::Emitter;
+
+use crate::AppState;
+use kon_ai_formatting::{post_process_segments, FormatMode, PostProcessOptions};
+use kon_core::types::{Segment, TranscriptionOptions};
+
+/// Transcribe raw PCM f32 samples (Whisper). Emits "transcription-result" event.
+#[tauri::command]
+pub async fn transcribe_pcm(
+    state: tauri::State<'_, AppState>,
+    app: tauri::AppHandle,
+    samples: Vec<f32>,
+    chunk_id: u32,
+    language: String,
+    initial_prompt: String,
+    remove_fillers: bool,
+    british_english: bool,
+    anti_hallucination: bool,
+    format_mode: String,
+) -> Result<(), String> {
+    let engine = state.whisper_engine.clone();
+    let audio = kon_core::AudioSamples::mono_16khz(samples);
+    let options = TranscriptionOptions {
+        language: Some(language),
+        initial_prompt: Some(initial_prompt),
+    };
+
+    let result = tokio::task::spawn_blocking(move || {
+        let transcript = engine.transcribe_sync(&audio, &options)
+            .map_err(|e| e.to_string())?;
+        Ok::<_, String>(transcript)
+    })
+    .await
+    .map_err(|e| e.to_string())??;
+
+    let mut segments: Vec<Segment> = result.segments().to_vec();
+    post_process_segments(
+        &mut segments,
+        &PostProcessOptions {
+            remove_fillers,
+            british_english,
+            anti_hallucination,
+            format_mode: FormatMode::parse(&format_mode),
+        },
+    );
+
+    app.emit(
+        "transcription-result",
+        serde_json::json!({
+            "status": "transcription",
+            "segments": segments,
+            "language": result.language(),
+            "duration": result.duration(),
+            "chunk_id": chunk_id,
+        }),
+    )
+    .map_err(|e| format!("Failed to emit result: {e}"))?;
+
+    Ok(())
+}
+
+/// Transcribe an audio file by path. Decodes, resamples to 16kHz, runs Whisper.
+#[tauri::command]
+pub async fn transcribe_file(
+    state: tauri::State<'_, AppState>,
+    path: String,
+    language: String,
+    initial_prompt: String,
+    remove_fillers: bool,
+    british_english: bool,
+    anti_hallucination: bool,
+    format_mode: String,
+) -> Result<serde_json::Value, String> {
+    let engine = state.whisper_engine.clone();
+    let options = TranscriptionOptions {
+        language: Some(language),
+        initial_prompt: Some(initial_prompt),
+    };
+
+    let result = tokio::task::spawn_blocking(move || {
+        let audio = kon_audio::decode_audio_file(Path::new(&path))
+            .map_err(|e| e.to_string())?;
+        let resampled = kon_audio::resample_to_16khz(&audio)
+            .map_err(|e| e.to_string())?;
+        let transcript = engine
+            .transcribe_sync(&resampled, &options)
+            .map_err(|e| e.to_string())?;
+        Ok::<_, String>(transcript)
+    })
+    .await
+    .map_err(|e| e.to_string())??;
+
+    let mut segments: Vec<Segment> = result.segments().to_vec();
+    post_process_segments(
+        &mut segments,
+        &PostProcessOptions {
+            remove_fillers,
+            british_english,
+            anti_hallucination,
+            format_mode: FormatMode::parse(&format_mode),
+        },
+    );
+
+    Ok(serde_json::json!({
+        "segments": segments,
+        "language": result.language(),
+        "duration": result.duration(),
+    }))
+}
+
+/// Transcribe raw PCM f32 samples (Parakeet). Emits "transcription-result" event.
+#[tauri::command]
+pub async fn transcribe_pcm_parakeet(
+    state: tauri::State<'_, AppState>,
+    app: tauri::AppHandle,
+    samples: Vec<f32>,
+    chunk_id: u32,
+    remove_fillers: bool,
+    british_english: bool,
+    anti_hallucination: bool,
+) -> Result<(), String> {
+    let engine = state.parakeet_engine.clone();
+    let audio = kon_core::AudioSamples::mono_16khz(samples);
+    let options = TranscriptionOptions::default();
+
+    let result = tokio::task::spawn_blocking(move || {
+        let transcript = engine
+            .transcribe_sync(&audio, &options)
+            .map_err(|e| e.to_string())?;
+        Ok::<_, String>(transcript)
+    })
+    .await
+    .map_err(|e| e.to_string())??;
+
+    let mut segments: Vec<Segment> = result.segments().to_vec();
+    post_process_segments(
+        &mut segments,
+        &PostProcessOptions {
+            remove_fillers,
+            british_english,
+            anti_hallucination,
+            format_mode: FormatMode::parse("Clean"),
+        },
+    );
+
+    app.emit(
+        "transcription-result",
+        serde_json::json!({
+            "status": "transcription",
+            "segments": segments,
+            "language": result.language(),
+            "duration": result.duration(),
+            "chunk_id": chunk_id,
+        }),
+    )
+    .map_err(|e| format!("Failed to emit result: {e}"))?;
+
+    Ok(())
+}
diff --git a/src-tauri/src/commands/windows.rs b/src-tauri/src/commands/windows.rs
new file mode 100644
index 0000000..234d380
--- /dev/null
+++ b/src-tauri/src/commands/windows.rs
@@ -0,0 +1,58 @@
+use tauri::{Emitter, Manager, WebviewUrl, WebviewWindowBuilder};
+
+/// Open a floating always-on-top task window.
+#[tauri::command]
+pub async fn open_task_window(
+    app: tauri::AppHandle,
+) -> Result<(), String> {
+    if let Some(window) = app.get_webview_window("tasks-float") {
+        window.show().map_err(|e| e.to_string())?;
+        window.set_focus().map_err(|e| e.to_string())?;
+        app.emit("task-window-focus", ())
+            .map_err(|e| e.to_string())?;
+        return Ok(());
+    }
+
+    WebviewWindowBuilder::new(
+        &app,
+        "tasks-float",
+        WebviewUrl::App("/float".into()),
+    )
+    .title("Kon Tasks")
+    .inner_size(480.0, 520.0)
+    .min_inner_size(400.0, 400.0)
+    .always_on_top(true)
+    .decorations(false)
+    .resizable(true)
+    .build()
+    .map_err(|e| e.to_string())?;
+
+    Ok(())
+}
+
+/// Open the transcript viewer window.
+#[tauri::command]
+pub async fn open_viewer_window(
+    app: tauri::AppHandle,
+) -> Result<(), String> {
+    if let Some(window) = app.get_webview_window("transcript-viewer") {
+        window.show().map_err(|e| e.to_string())?;
+        window.set_focus().map_err(|e| e.to_string())?;
+        return Ok(());
+    }
+
+    WebviewWindowBuilder::new(
+        &app,
+        "transcript-viewer",
+        WebviewUrl::App("/viewer".into()),
+    )
+    .title("Kon - Viewer")
+    .inner_size(600.0, 700.0)
+    .min_inner_size(450.0, 500.0)
+    .decorations(false)
+    .resizable(true)
+    .build()
+    .map_err(|e| e.to_string())?;
+
+    Ok(())
+}
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index 349c213..359bba6 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -1,9 +1,83 @@
+mod commands;
+mod tray;
+
+use std::sync::Arc;
+
+use tauri::Manager;
+
+use kon_core::types::EngineName;
+use kon_transcription::LocalEngine;
+
+/// Shared app state holding the transcription engines.
+pub struct AppState {
+    pub whisper_engine: Arc<LocalEngine>,
+    pub parakeet_engine: Arc<LocalEngine>,
+}
+
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
     tauri::Builder::default()
         .plugin(tauri_plugin_opener::init())
         .plugin(tauri_plugin_dialog::init())
         .plugin(tauri_plugin_global_shortcut::Builder::new().build())
+        .manage(AppState {
+            whisper_engine: Arc::new(LocalEngine::new(
+                EngineName::new("whisper"),
+            )),
+            parakeet_engine: Arc::new(LocalEngine::new(
+                EngineName::new("parakeet"),
+            )),
+        })
+        .setup(|app| {
+            if let Err(e) = tray::setup(app) {
+                eprintln!("Failed to setup tray: {e}");
+            }
+
+            // Close-to-tray: hide window instead of exiting
+            let main_window = app.get_webview_window("main").unwrap();
+            let win = main_window.clone();
+            main_window.on_window_event(move |event| {
+                if let tauri::WindowEvent::CloseRequested { api, .. } = event
+                {
+                    api.prevent_close();
+                    let _ = win.hide();
+                }
+            });
+
+            Ok(())
+        })
+        .invoke_handler(tauri::generate_handler![
+            // Whisper model management
+            commands::models::download_model,
+            commands::models::check_model,
+            commands::models::list_models,
+            commands::models::load_model,
+            commands::models::check_engine,
+            // Parakeet model management
+            commands::models::download_parakeet_model,
+            commands::models::check_parakeet_model,
+            commands::models::list_parakeet_models,
+            commands::models::load_parakeet_model,
+            commands::models::check_parakeet_engine,
+            // Transcription
+            commands::transcription::transcribe_pcm,
+            commands::transcription::transcribe_file,
+            commands::transcription::transcribe_pcm_parakeet,
+            // Audio
+            commands::audio::save_audio,
+            // Windows
+            commands::windows::open_task_window,
+            commands::windows::open_viewer_window,
+            // LLM stubs
+            commands::llm::download_llm_model,
+            commands::llm::check_llm_model,
+            commands::llm::list_llm_models,
+            commands::llm::load_llm_model,
+            commands::llm::check_llm_engine,
+            commands::llm::llm_generate,
+            commands::llm::llm_extract_tasks,
+            commands::llm::llm_format_transcript,
+        ])
         .run(tauri::generate_context!())
         .expect("error while running Kon");
 }
diff --git a/src-tauri/src/tray.rs b/src-tauri/src/tray.rs
new file mode 100644
index 0000000..f635ea4
--- /dev/null
+++ b/src-tauri/src/tray.rs
@@ -0,0 +1,59 @@
+use tauri::image::Image;
+use tauri::menu::{MenuBuilder, MenuItemBuilder};
+use tauri::tray::TrayIconBuilder;
+use tauri::Manager;
+
+pub fn setup(app: &tauri::App) -> Result<(), Box<dyn std::error::Error>> {
+    let show = MenuItemBuilder::with_id("show", "Show Kon").build(app)?;
+    let status = MenuItemBuilder::with_id("status", "Ready")
+        .enabled(false)
+        .build(app)?;
+    let quit = MenuItemBuilder::with_id("quit", "Quit").build(app)?;
+
+    let menu = MenuBuilder::new(app)
+        .item(&show)
+        .separator()
+        .item(&status)
+        .separator()
+        .item(&quit)
+        .build()?;
+
+    let icon = app
+        .default_window_icon()
+        .cloned()
+        .unwrap_or_else(|| Image::new(&[0u8; 4], 1, 1));
+
+    let _tray = TrayIconBuilder::new()
+        .icon(icon)
+        .tooltip("Kon — Ready")
+        .menu(&menu)
+        .on_menu_event(move |app, event| match event.id().as_ref() {
+            "show" => {
+                if let Some(window) = app.get_webview_window("main") {
+                    let _ = window.show();
+                    let _ = window.set_focus();
+                }
+            }
+            "quit" => {
+                app.exit(0);
+            }
+            _ => {}
+        })
+        .on_tray_icon_event(|tray, event| {
+            if let tauri::tray::TrayIconEvent::Click {
+                button: tauri::tray::MouseButton::Left,
+                ..
+            } = event
+            {
+                if let Some(window) =
+                    tray.app_handle().get_webview_window("main")
+                {
+                    let _ = window.show();
+                    let _ = window.set_focus();
+                }
+            }
+        })
+        .build(app)?;
+
+    Ok(())
+}