diff --git a/src-tauri/Cargo.lock b/src-tauri/Cargo.lock
index 64f15df..03a0cc1 100644
--- a/src-tauri/Cargo.lock
+++ b/src-tauri/Cargo.lock
@@ -1723,6 +1723,12 @@ dependencies = [
  "pin-project-lite",
 ]
 
+[[package]]
+name = "http-range"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "21dec9db110f5f872ed9699c3ecf50cf16f423502706ba5c72462e28d3157573"
+
 [[package]]
 name = "httparse"
 version = "1.10.1"
@@ -4007,6 +4013,7 @@ dependencies = [
  "gtk",
  "heck 0.5.0",
  "http",
+ "http-range",
  "jni 0.21.1",
  "libc",
  "log",
diff --git a/src-tauri/Cargo.toml b/src-tauri/Cargo.toml
index 885adf2..7c3b61d 100644
--- a/src-tauri/Cargo.toml
+++ b/src-tauri/Cargo.toml
@@ -18,7 +18,7 @@ crate-type = ["staticlib", "cdylib", "rlib"]
 tauri-build = { version = "2", features = [] }
 
 [dependencies]
-tauri = { version = "2", features = [] }
+tauri = { version = "2", features = ["protocol-asset"] }
 tauri-plugin-opener = "2"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
diff --git a/src-tauri/capabilities/default.json b/src-tauri/capabilities/default.json
index 4cdbf49..4d4367a 100644
--- a/src-tauri/capabilities/default.json
+++ b/src-tauri/capabilities/default.json
@@ -2,9 +2,12 @@
   "$schema": "../gen/schemas/desktop-schema.json",
   "identifier": "default",
   "description": "Capability for the main window",
-  "windows": ["main"],
+  "windows": [
+    "main"
+  ],
   "permissions": [
     "core:default",
-    "opener:default"
+    "opener:default",
+    "dialog:default"
   ]
 }
diff --git a/src-tauri/gen/schemas/capabilities.json b/src-tauri/gen/schemas/capabilities.json
index cb9043a..af42e3e 100644
--- a/src-tauri/gen/schemas/capabilities.json
+++ b/src-tauri/gen/schemas/capabilities.json
@@ -1 +1 @@
-{"default":{"identifier":"default","description":"Capability for the main window","local":true,"windows":["main"],"permissions":["core:default","opener:default"]}}
\ No newline at end of file
+{"default":{"identifier":"default","description":"Capability for the main window","local":true,"windows":["main"],"permissions":["core:default","opener:default","dialog:default"]}}
\ No newline at end of file
diff --git a/src-tauri/src/commands.rs b/src-tauri/src/commands.rs
new file mode 100644
index 0000000..a581ed4
--- /dev/null
+++ b/src-tauri/src/commands.rs
@@ -0,0 +1,527 @@
+//! Tauri command surface. Delegates to the modules; holds no parsing logic.
+
+use crate::db::Db;
+use crate::downloader::{self, Progress};
+use crate::feed;
+use crate::models::{ChannelWithCount, DownloadState, FeedFilter, FeedItem, Prereqs};
+use crate::net;
+use crate::takeout;
+use crate::thumbs;
+
+use futures::stream::StreamExt;
+use serde::Serialize;
+use std::collections::HashMap;
+use std::path::PathBuf;
+use std::sync::Arc;
+use tauri::{AppHandle, Emitter, Manager, State};
+use tokio::io::{AsyncBufReadExt, BufReader};
+use tokio::sync::{Mutex, Semaphore};
+
+/// How many channel feeds we fetch at once. YouTube serves these fine in
+/// parallel; 8 keeps a 300-channel refresh brisk without hammering them.
+const FEED_CONCURRENCY: usize = 8;
+/// Video downloads are bandwidth-bound, so more than a couple at once just
+/// makes every one of them slower.
+const DOWNLOAD_CONCURRENCY: usize = 2;
+/// Cap thumbnail work per refresh so a first-run import doesn't stall for ages.
+const THUMB_BATCH: i64 = 600;
+
+pub struct AppState {
+    pub db: Arc<Mutex<Db>>,
+    pub http: reqwest::Client,
+    pub library: Arc<Mutex<PathBuf>>,
+    pub app_data: PathBuf,
+    pub children: Arc<Mutex<HashMap<String, tokio::process::Child>>>,
+    pub download_slots: Arc<Semaphore>,
+}
+
+#[derive(Clone, Serialize)]
+struct RefreshProgress {
+    done: usize,
+    total: usize,
+    channel: String,
+}
+
+#[derive(Clone, Serialize)]
+struct DownloadProgressEvent {
+    video_id: String,
+    pct: Option<f64>,
+    bytes_done: u64,
+    bytes_total: Option<u64>,
+    speed: Option<f64>,
+    eta: Option<u64>,
+}
+
+#[derive(Clone, Serialize)]
+struct DownloadStateEvent {
+    video_id: String,
+    state: DownloadState,
+    error: Option<String>,
+    path: Option<String>,
+}
+
+#[derive(Serialize)]
+pub struct RefreshSummary {
+    pub channels: usize,
+    pub new_videos: usize,
+    pub failures: Vec<String>,
+}
+
+fn bin(name: &str) -> String {
+    // GUI apps launched from Finder don't inherit a login shell PATH, so
+    // Homebrew's bin dir is invisible to them. Prefer an absolute path when we
+    // can find one, and fall back to the bare name for PATH resolution.
+    for prefix in ["/opt/homebrew/bin", "/usr/local/bin", "/usr/bin"] {
+        let candidate = format!("{prefix}/{name}");
+        if std::path::Path::new(&candidate).exists() {
+            return candidate;
+        }
+    }
+    name.to_string()
+}
+
+fn version_of(name: &str) -> Option<String> {
+    std::process::Command::new(bin(name))
+        .arg("--version")
+        .output()
+        .ok()
+        .filter(|o| o.status.success())
+        .map(|o| {
+            String::from_utf8_lossy(&o.stdout)
+                .lines()
+                .next()
+                .unwrap_or("")
+                .trim()
+                .to_string()
+        })
+        .filter(|s| !s.is_empty())
+}
+
+#[tauri::command]
+pub async fn check_prereqs(state: State<'_, AppState>) -> Result<Prereqs, String> {
+    let library = state.library.lock().await.clone();
+    Ok(Prereqs {
+        yt_dlp: version_of("yt-dlp"),
+        ffmpeg: version_of("ffmpeg").map(|v| {
+            // ffmpeg's first line is long; keep the useful head of it.
+            v.split_whitespace().take(3).collect::<Vec<_>>().join(" ")
+        }),
+        library_path: library.to_string_lossy().to_string(),
+    })
+}
+
+#[tauri::command]
+pub async fn import_takeout_csv(
+    path: String,
+    state: State<'_, AppState>,
+) -> Result<usize, String> {
+    let raw = tokio::fs::read(&path)
+        .await
+        .map_err(|e| format!("Cannot read {path}: {e}"))?;
+    // Takeout exports are UTF-8, sometimes with a BOM.
+    let text = String::from_utf8_lossy(&raw);
+    let text = text.strip_prefix('\u{feff}').unwrap_or(&text);
+
+    let channels = takeout::parse_csv(text)?;
+    if channels.is_empty() {
+        return Err("No channels found in that file.".into());
+    }
+    let mut db = state.db.lock().await;
+    db.upsert_channels(&channels)
+}
+
+#[tauri::command]
+pub async fn list_channels(state: State<'_, AppState>) -> Result<Vec<ChannelWithCount>, String> {
+    state.db.lock().await.list_channels()
+}
+
+#[tauri::command]
+pub async fn list_feed(
+    filter: FeedFilter,
+    state: State<'_, AppState>,
+) -> Result<Vec<FeedItem>, String> {
+    state.db.lock().await.list_feed(&filter)
+}
+
+#[tauri::command]
+pub async fn get_connectivity(state: State<'_, AppState>) -> Result<bool, String> {
+    Ok(net::is_online(&state.http).await)
+}
+
+#[tauri::command]
+pub async fn refresh_feeds(
+    app: AppHandle,
+    state: State<'_, AppState>,
+) -> Result<RefreshSummary, String> {
+    let channel_ids = state.db.lock().await.channel_ids()?;
+    if channel_ids.is_empty() {
+        return Err("No subscriptions imported yet. Import your Takeout CSV first.".into());
+    }
+
+    let total = channel_ids.len();
+    let http = state.http.clone();
+
+    // Fetch with bounded concurrency. One channel failing must not abort the run.
+    let results = futures::stream::iter(channel_ids.into_iter().map(|cid| {
+        let http = http.clone();
+        async move {
+            let res = feed::fetch_channel(&http, &cid).await;
+            (cid, res)
+        }
+    }))
+    .buffer_unordered(FEED_CONCURRENCY)
+    .collect::<Vec<_>>()
+    .await;
+
+    let mut new_videos = 0usize;
+    let mut failures = Vec::new();
+    let mut done = 0usize;
+
+    for (cid, res) in results {
+        done += 1;
+        match res {
+            Ok(videos) => {
+                if !videos.is_empty() {
+                    let mut db = state.db.lock().await;
+                    new_videos += db.upsert_videos(&videos)?;
+                }
+            }
+            Err(e) => failures.push(format!("{cid}: {e}")),
+        }
+        let _ = app.emit(
+            "refresh:progress",
+            RefreshProgress {
+                done,
+                total,
+                channel: cid,
+            },
+        );
+    }
+
+    cache_thumbnails(&state).await;
+
+    Ok(RefreshSummary {
+        channels: total,
+        new_videos,
+        failures,
+    })
+}
+
+/// Mirrors thumbnails to disk so the feed still renders with no network.
+async fn cache_thumbnails(state: &State<'_, AppState>) {
+    let pending = match state.db.lock().await.videos_missing_thumbs(THUMB_BATCH) {
+        Ok(p) => p,
+        Err(_) => return,
+    };
+    if pending.is_empty() {
+        return;
+    }
+
+    let dir = thumbs::cache_dir(&state.app_data);
+    let http = state.http.clone();
+
+    let cached = futures::stream::iter(pending.into_iter().map(|(id, url)| {
+        let http = http.clone();
+        let dir = dir.clone();
+        async move {
+            let res = thumbs::cache_one(&http, &id, &url, &dir).await;
+            (id, res)
+        }
+    }))
+    .buffer_unordered(FEED_CONCURRENCY)
+    .collect::<Vec<_>>()
+    .await;
+
+    let db = state.db.lock().await;
+    for (id, res) in cached {
+        if let Ok(path) = res {
+            let _ = db.set_thumb_path(&id, &path.to_string_lossy());
+        }
+    }
+}
+
+#[tauri::command]
+pub async fn download_video(
+    video_id: String,
+    app: AppHandle,
+    state: State<'_, AppState>,
+) -> Result<(), String> {
+    let library = state.library.lock().await.clone();
+    tokio::fs::create_dir_all(&library)
+        .await
+        .map_err(|e| format!("Cannot create library dir: {e}"))?;
+
+    {
+        let db = state.db.lock().await;
+        db.set_download_state(&video_id, DownloadState::Queued, None)?;
+    }
+    let _ = app.emit(
+        "download:state",
+        DownloadStateEvent {
+            video_id: video_id.clone(),
+            state: DownloadState::Queued,
+            error: None,
+            path: None,
+        },
+    );
+
+    let permit = state
+        .download_slots
+        .clone()
+        .acquire_owned()
+        .await
+        .map_err(|e| format!("Download queue closed: {e}"))?;
+
+    let out_template = library.join("%(id)s.%(ext)s").to_string_lossy().to_string();
+    let args = downloader::build_args(&video_id, &out_template);
+
+    let mut child = tokio::process::Command::new(bin("yt-dlp"))
+        .args(&args)
+        .stdout(std::process::Stdio::piped())
+        .stderr(std::process::Stdio::piped())
+        .spawn()
+        .map_err(|e| {
+            format!("Could not start yt-dlp: {e}. Install it with: brew install yt-dlp ffmpeg")
+        })?;
+
+    let stdout = child.stdout.take().ok_or("yt-dlp produced no stdout")?;
+    let stderr = child.stderr.take().ok_or("yt-dlp produced no stderr")?;
+
+    state
+        .children
+        .lock()
+        .await
+        .insert(video_id.clone(), child);
+
+    {
+        let db = state.db.lock().await;
+        db.set_download_state(&video_id, DownloadState::Running, None)?;
+    }
+    let _ = app.emit(
+        "download:state",
+        DownloadStateEvent {
+            video_id: video_id.clone(),
+            state: DownloadState::Running,
+            error: None,
+            path: None,
+        },
+    );
+
+    // Collect stderr concurrently so a failure has a real message, and so a
+    // full stderr pipe can't deadlock the child.
+    let stderr_task = tokio::spawn(async move {
+        let mut lines = BufReader::new(stderr).lines();
+        let mut buf = Vec::new();
+        while let Ok(Some(l)) = lines.next_line().await {
+            buf.push(l);
+        }
+        buf
+    });
+
+    let mut final_path: Option<String> = None;
+    let mut reader = BufReader::new(stdout).lines();
+    while let Ok(Some(line)) = reader.next_line().await {
+        if let Some(p) = downloader::parse_final_path(&line) {
+            final_path = Some(p);
+            continue;
+        }
+        if let Some(Progress {
+            downloaded,
+            total,
+            speed,
+            eta,
+        }) = downloader::parse_progress_line(&line)
+        {
+            let pct = Progress {
+                downloaded,
+                total,
+                speed,
+                eta,
+            }
+            .pct();
+            {
+                let db = state.db.lock().await;
+                let _ = db.set_download_progress(&video_id, downloaded, total, pct);
+            }
+            let _ = app.emit(
+                "download:progress",
+                DownloadProgressEvent {
+                    video_id: video_id.clone(),
+                    pct,
+                    bytes_done: downloaded,
+                    bytes_total: total,
+                    speed,
+                    eta,
+                },
+            );
+        }
+    }
+
+    let mut child = state
+        .children
+        .lock()
+        .await
+        .remove(&video_id)
+        .ok_or_else(|| "Download was cancelled.".to_string())?;
+
+    let status = child
+        .wait()
+        .await
+        .map_err(|e| format!("yt-dlp did not exit cleanly: {e}"))?;
+    let stderr_lines = stderr_task.await.unwrap_or_default();
+    drop(permit);
+
+    if status.success() {
+        let path = final_path.unwrap_or_else(|| {
+            library
+                .join(format!("{video_id}.mp4"))
+                .to_string_lossy()
+                .to_string()
+        });
+        let db = state.db.lock().await;
+        db.set_download_state(&video_id, DownloadState::Done, None)?;
+        db.set_download_path(&video_id, &path)?;
+        drop(db);
+        let _ = app.emit(
+            "download:state",
+            DownloadStateEvent {
+                video_id,
+                state: DownloadState::Done,
+                error: None,
+                path: Some(path),
+            },
+        );
+        Ok(())
+    } else {
+        let msg = stderr_lines
+            .iter()
+            .rev()
+            .find(|l| l.contains("ERROR"))
+            .cloned()
+            .unwrap_or_else(|| format!("yt-dlp exited with {status}"));
+        let db = state.db.lock().await;
+        db.set_download_state(&video_id, DownloadState::Failed, Some(&msg))?;
+        drop(db);
+        let _ = app.emit(
+            "download:state",
+            DownloadStateEvent {
+                video_id,
+                state: DownloadState::Failed,
+                error: Some(msg.clone()),
+                path: None,
+            },
+        );
+        Err(msg)
+    }
+}
+
+#[tauri::command]
+pub async fn cancel_download(
+    video_id: String,
+    app: AppHandle,
+    state: State<'_, AppState>,
+) -> Result<(), String> {
+    if let Some(mut child) = state.children.lock().await.remove(&video_id) {
+        let _ = child.kill().await;
+    }
+    {
+        let db = state.db.lock().await;
+        db.set_download_state(&video_id, DownloadState::Cancelled, None)?;
+    }
+    cleanup_partials(state.library.lock().await.clone(), &video_id).await;
+    let _ = app.emit(
+        "download:state",
+        DownloadStateEvent {
+            video_id,
+            state: DownloadState::Cancelled,
+            error: None,
+            path: None,
+        },
+    );
+    Ok(())
+}
+
+/// yt-dlp leaves `.part`, `.ytdl` and format-specific fragments behind when
+/// killed; without this the library slowly fills with dead bytes.
+async fn cleanup_partials(library: PathBuf, video_id: &str) {
+    let Ok(mut entries) = tokio::fs::read_dir(&library).await else {
+        return;
+    };
+    while let Ok(Some(entry)) = entries.next_entry().await {
+        let name = entry.file_name().to_string_lossy().to_string();
+        if name.starts_with(video_id) && (name.contains(".part") || name.ends_with(".ytdl")) {
+            let _ = tokio::fs::remove_file(entry.path()).await;
+        }
+    }
+}
+
+#[tauri::command]
+pub async fn delete_download(
+    video_id: String,
+    state: State<'_, AppState>,
+) -> Result<(), String> {
+    let path = state.db.lock().await.get_download_path(&video_id)?;
+    if let Some(p) = path {
+        let _ = tokio::fs::remove_file(&p).await;
+    }
+    cleanup_partials(state.library.lock().await.clone(), &video_id).await;
+    state.db.lock().await.clear_download(&video_id)
+}
+
+#[tauri::command]
+pub async fn set_library_path(
+    path: String,
+    state: State<'_, AppState>,
+) -> Result<String, String> {
+    let p = PathBuf::from(&path);
+    tokio::fs::create_dir_all(&p)
+        .await
+        .map_err(|e| format!("Cannot use that folder: {e}"))?;
+    *state.library.lock().await = p.clone();
+    Ok(p.to_string_lossy().to_string())
+}
+
+#[tauri::command]
+pub async fn open_external(app: AppHandle, url: String) -> Result<(), String> {
+    use tauri_plugin_opener::OpenerExt;
+    app.opener()
+        .open_url(url, None::<&str>)
+        .map_err(|e| format!("Could not open link: {e}"))
+}
+
+pub fn default_library() -> PathBuf {
+    dirs_home()
+        .map(|h| h.join("Movies").join("FlightTube"))
+        .unwrap_or_else(|| PathBuf::from("FlightTube"))
+}
+
+fn dirs_home() -> Option<PathBuf> {
+    std::env::var_os("HOME").map(PathBuf::from)
+}
+
+pub fn build_state(app: &AppHandle) -> Result<AppState, String> {
+    let app_data = app
+        .path()
+        .app_data_dir()
+        .map_err(|e| format!("No app data dir: {e}"))?;
+    std::fs::create_dir_all(&app_data).map_err(|e| format!("Cannot create app data dir: {e}"))?;
+
+    let db = Db::open(&app_data.join("flighttube.db"))?;
+    let library = default_library();
+    let _ = std::fs::create_dir_all(&library);
+
+    let http = reqwest::Client::builder()
+        .user_agent("FlightTube/0.1 (+desktop)")
+        .timeout(std::time::Duration::from_secs(20))
+        .build()
+        .map_err(|e| format!("Cannot build HTTP client: {e}"))?;
+
+    Ok(AppState {
+        db: Arc::new(Mutex::new(db)),
+        http,
+        library: Arc::new(Mutex::new(library)),
+        app_data,
+        children: Arc::new(Mutex::new(HashMap::new())),
+        download_slots: Arc::new(Semaphore::new(DOWNLOAD_CONCURRENCY)),
+    })
+}
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index 00a5394..3e5da5d 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -1,14 +1,37 @@
+pub mod commands;
 pub mod db;
 pub mod downloader;
 pub mod feed;
 pub mod models;
+pub mod net;
 pub mod takeout;
+pub mod thumbs;
+
+use tauri::Manager;
 
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
     tauri::Builder::default()
         .plugin(tauri_plugin_opener::init())
         .plugin(tauri_plugin_dialog::init())
+        .setup(|app| {
+            let state = commands::build_state(&app.handle().clone())?;
+            app.manage(state);
+            Ok(())
+        })
+        .invoke_handler(tauri::generate_handler![
+            commands::check_prereqs,
+            commands::import_takeout_csv,
+            commands::list_channels,
+            commands::list_feed,
+            commands::refresh_feeds,
+            commands::download_video,
+            commands::cancel_download,
+            commands::delete_download,
+            commands::get_connectivity,
+            commands::set_library_path,
+            commands::open_external,
+        ])
         .run(tauri::generate_context!())
         .expect("error while running tauri application");
 }
diff --git a/src-tauri/src/net.rs b/src-tauri/src/net.rs
new file mode 100644
index 0000000..6f18f7a
--- /dev/null
+++ b/src-tauri/src/net.rs
@@ -0,0 +1,17 @@
+//! Connectivity probing.
+//!
+//! The webview's `navigator.onLine` reports link state, not reachability — it
+//! is true on a captive-portal wifi with no real internet, which is exactly the
+//! situation this app exists for. So we actually talk to YouTube.
+
+use std::time::Duration;
+
+pub async fn is_online(client: &reqwest::Client) -> bool {
+    client
+        .head("https://www.youtube.com/")
+        .timeout(Duration::from_secs(5))
+        .send()
+        .await
+        .map(|r| r.status().is_success() || r.status().is_redirection())
+        .unwrap_or(false)
+}
diff --git a/src-tauri/src/thumbs.rs b/src-tauri/src/thumbs.rs
new file mode 100644
index 0000000..6c1a18d
--- /dev/null
+++ b/src-tauri/src/thumbs.rs
@@ -0,0 +1,55 @@
+//! Local thumbnail cache.
+//!
+//! Feed thumbnails are remote `ytimg.com` URLs. Offline — the whole point of
+//! this app — those fail to load and the feed becomes a wall of broken images.
+//! So every thumbnail we learn about gets mirrored to disk.
+
+use std::path::{Path, PathBuf};
+
+pub fn cache_dir(app_data: &Path) -> PathBuf {
+    app_data.join("thumbs")
+}
+
+/// Downloads one thumbnail if it isn't already cached. Returns its path.
+pub async fn cache_one(
+    client: &reqwest::Client,
+    video_id: &str,
+    url: &str,
+    dir: &Path,
+) -> Result<PathBuf, String> {
+    let dest = dir.join(format!("{video_id}.jpg"));
+    if dest.exists() {
+        return Ok(dest);
+    }
+
+    tokio::fs::create_dir_all(dir)
+        .await
+        .map_err(|e| format!("Cannot create thumbnail cache dir: {e}"))?;
+
+    let resp = client
+        .get(url)
+        .send()
+        .await
+        .map_err(|e| format!("Thumbnail request failed: {e}"))?;
+
+    if !resp.status().is_success() {
+        return Err(format!("Thumbnail returned HTTP {}", resp.status()));
+    }
+
+    let bytes = resp
+        .bytes()
+        .await
+        .map_err(|e| format!("Cannot read thumbnail body: {e}"))?;
+
+    // Write to a temp name then rename, so an interrupted download never leaves
+    // a half-written JPEG that later looks cached.
+    let tmp = dir.join(format!("{video_id}.jpg.part"));
+    tokio::fs::write(&tmp, &bytes)
+        .await
+        .map_err(|e| format!("Cannot write thumbnail: {e}"))?;
+    tokio::fs::rename(&tmp, &dest)
+        .await
+        .map_err(|e| format!("Cannot finalize thumbnail: {e}"))?;
+
+    Ok(dest)
+}
diff --git a/src-tauri/tauri.conf.json b/src-tauri/tauri.conf.json
index 9811f1f..8490ca9 100644
--- a/src-tauri/tauri.conf.json
+++ b/src-tauri/tauri.conf.json
@@ -1,6 +1,6 @@
 {
   "$schema": "https://schema.tauri.app/config/2",
-  "productName": "flighttube",
+  "productName": "FlightTube",
   "version": "0.1.0",
   "identifier": "com.vincent.flighttube",
   "build": {
@@ -12,13 +12,23 @@
   "app": {
     "windows": [
       {
-        "title": "flighttube",
-        "width": 800,
-        "height": 600
+        "title": "FlightTube",
+        "width": 1280,
+        "height": 840,
+        "minWidth": 940,
+        "minHeight": 600
       }
     ],
     "security": {
-      "csp": null
+      "csp": null,
+      "assetProtocol": {
+        "enable": true,
+        "scope": [
+          "$HOME/Movies/FlightTube/**",
+          "$APPDATA/**",
+          "$APPLOCALDATA/**"
+        ]
+      }
     }
   },
   "bundle": {