diff --git a/CHANGELOG.md b/CHANGELOG.md
index da846552..e54113b3 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -122,6 +122,16 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 
 
+### Development — parallel `tauri dev` alongside release
+
+**By [@cucadmuh](https://github.com/cucadmuh), PR [#866](https://github.com/Psychotoxical/psysonic/pull/866)**
+
+* Debug builds skip `tauri-plugin-single-instance` so `./dev.sh` can run next to an installed release while sharing the same app data directory.
+* Debug-only chrome: window title `Psysonic (Dev)`, red sidebar brand, monochrome custom titlebar buttons, mobile `DEV` badge, horizontally flipped tray icon.
+* Debug builds do not register OS global shortcuts, MPRIS/media keys, or Windows taskbar media controls — release keeps system-wide input when both are open.
+
+
+
 ### Interface Scale — covers the whole window
 
 **By [@Psychotoxical](https://github.com/Psychotoxical), PR [#781](https://github.com/Psychotoxical/psysonic/pull/781)**
diff --git a/src-tauri/src/lib.rs b/src-tauri/src/lib.rs
index 399b0e2b..62768a16 100644
--- a/src-tauri/src/lib.rs
+++ b/src-tauri/src/lib.rs
@@ -38,6 +38,28 @@ const MAX_DL_CONCURRENCY: usize = 4;
 /// `None` if souvlaki failed to initialize (e.g. no D-Bus session on Linux).
 type MprisControls = Mutex<Option<souvlaki::MediaControls>>;
 
+/// Release builds only: focus or CLI-hand off when a second instance is launched.
+#[cfg(not(debug_assertions))]
+fn on_second_instance<R: tauri::Runtime>(
+    app: &tauri::AppHandle<R>,
+    argv: Vec<String>,
+    _cwd: String,
+) {
+    if !crate::cli::handle_cli_on_primary_instance(app, &argv) {
+        let window = app.get_webview_window("main").expect("no main window");
+        // The window may have been hidden via the close-to-tray path,
+        // which injects PAUSE_RENDERING_JS (sets `__psyHidden=true`,
+        // pauses CSS animations). Tray-icon restore mirrors this with
+        // RESUME_RENDERING_JS — second-launch restore must do the same,
+        // otherwise the webview comes back with rendering still paused
+        // and navigation looks blank (issue #497).
+        let _ = window.eval(RESUME_RENDERING_JS);
+        let _ = window.show();
+        let _ = window.unminimize();
+        let _ = window.set_focus();
+    }
+}
+
 pub fn run() {
     // Linux: second `psysonic --player …` forwards over D-Bus before heavy startup.
     #[cfg(target_os = "linux")]
@@ -57,7 +79,7 @@ pub fn run() {
 
     let (audio_engine, _audio_thread) = audio::create_engine();
 
-    tauri::Builder::default()
+    let builder = tauri::Builder::default()
         .manage(audio_engine)
         .manage(ShortcutMap::default())
         .manage(discord::DiscordState::new())
@@ -78,24 +100,18 @@ pub fn run() {
         .plugin(tauri_plugin_global_shortcut::Builder::new().build())
         .plugin(tauri_plugin_store::Builder::default().build())
         .plugin(tauri_plugin_dialog::init())
-        .plugin(tauri_plugin_fs::init())
-        .plugin(tauri_plugin_single_instance::init(|app, argv, _cwd| {
-            if !crate::cli::handle_cli_on_primary_instance(app, &argv) {
-                let window = app.get_webview_window("main").expect("no main window");
-                // The window may have been hidden via the close-to-tray path,
-                // which injects PAUSE_RENDERING_JS (sets `__psyHidden=true`,
-                // pauses CSS animations). Tray-icon restore mirrors this with
-                // RESUME_RENDERING_JS — second-launch restore must do the same,
-                // otherwise the webview comes back with rendering still paused
-                // and navigation looks blank (issue #497).
-                let _ = window.eval(RESUME_RENDERING_JS);
-                let _ = window.show();
-                let _ = window.unminimize();
-                let _ = window.set_focus();
-            }
-        }))
+        .plugin(tauri_plugin_fs::init());
 
+    #[cfg(not(debug_assertions))]
+    let builder = builder.plugin(tauri_plugin_single_instance::init(on_second_instance));
+
+    builder
         .setup(|app| {
+            #[cfg(debug_assertions)]
+            if let Some(window) = app.get_webview_window("main") {
+                let _ = window.set_title("Psysonic (Dev)");
+            }
+
             // ── Analysis cache (SQLite) ───────────────────────────────────
             {
                 let cache = analysis_cache::AnalysisCache::init(app.handle())
@@ -386,6 +402,8 @@ pub fn run() {
             }
 
             // ── MPRIS2 / OS media controls via souvlaki ──────────────────
+            // Release only: debug builds share the D-Bus name / SMTC slot with prod.
+            #[cfg(not(debug_assertions))]
             {
                 use souvlaki::{MediaControlEvent, MediaControls, PlatformConfig};
 
@@ -474,9 +492,13 @@ pub fn run() {
 
                 app.manage(MprisControls::new(maybe_controls));
             }
+            #[cfg(debug_assertions)]
+            {
+                app.manage(MprisControls::new(None));
+            }
 
             // ── Windows Taskbar Thumbnail Toolbar ────────────────────────
-            #[cfg(target_os = "windows")]
+            #[cfg(all(target_os = "windows", not(debug_assertions)))]
             {
                 use tauri::Manager;
                 if let Some(w) = app.get_webview_window("main") {
diff --git a/src-tauri/src/lib_commands/app_api/integration.rs b/src-tauri/src/lib_commands/app_api/integration.rs
index 204265e8..3009ff05 100644
--- a/src-tauri/src/lib_commands/app_api/integration.rs
+++ b/src-tauri/src/lib_commands/app_api/integration.rs
@@ -1,3 +1,4 @@
+#[cfg(not(debug_assertions))]
 use tauri::Emitter;
 
 use crate::{MprisControls, ShortcutMap};
@@ -9,32 +10,42 @@ pub(crate) fn register_global_shortcut(
     shortcut: String,
     action: String,
 ) -> Result<(), String> {
-    use tauri_plugin_global_shortcut::{GlobalShortcutExt, Shortcut, ShortcutState};
-
-    let mut map = shortcut_map.lock().unwrap();
-
-    // Idempotent: if this exact shortcut+action is already registered, skip.
-    // This prevents on_shortcut() from accumulating duplicate handlers when
-    // registerAll() is called again after a JS HMR reload or StrictMode double-effect.
-    if map.get(&shortcut).map(|a| a == &action).unwrap_or(false) {
-        return Ok(());
+    // Debug builds run alongside release with shared settings — do not grab OS shortcuts.
+    #[cfg(debug_assertions)]
+    {
+        let _ = (app, shortcut_map, shortcut, action);
+        Ok(())
     }
 
-    // Unregister any existing OS grab for this shortcut before re-registering.
-    if let Ok(s) = shortcut.parse::<Shortcut>() {
-        let _ = app.global_shortcut().unregister(s);
-    }
-    map.insert(shortcut.clone(), action.clone());
-    drop(map); // release lock before the blocking OS call
+    #[cfg(not(debug_assertions))]
+    {
+        use tauri_plugin_global_shortcut::{GlobalShortcutExt, Shortcut, ShortcutState};
 
-    let parsed: Shortcut = shortcut.parse().map_err(|_| format!("Invalid shortcut: {shortcut}"))?;
-    app.global_shortcut()
-        .on_shortcut(parsed, move |app, _shortcut, event| {
-            if event.state == ShortcutState::Pressed {
-                let _ = app.emit("shortcut:global-action", action.clone());
-            }
-        })
-        .map_err(|e| e.to_string())
+        let mut map = shortcut_map.lock().unwrap();
+
+        // Idempotent: if this exact shortcut+action is already registered, skip.
+        // This prevents on_shortcut() from accumulating duplicate handlers when
+        // registerAll() is called again after a JS HMR reload or StrictMode double-effect.
+        if map.get(&shortcut).map(|a| a == &action).unwrap_or(false) {
+            return Ok(());
+        }
+
+        // Unregister any existing OS grab for this shortcut before re-registering.
+        if let Ok(s) = shortcut.parse::<Shortcut>() {
+            let _ = app.global_shortcut().unregister(s);
+        }
+        map.insert(shortcut.clone(), action.clone());
+        drop(map); // release lock before the blocking OS call
+
+        let parsed: Shortcut = shortcut.parse().map_err(|_| format!("Invalid shortcut: {shortcut}"))?;
+        app.global_shortcut()
+            .on_shortcut(parsed, move |app, _shortcut, event| {
+                if event.state == ShortcutState::Pressed {
+                    let _ = app.emit("shortcut:global-action", action.clone());
+                }
+            })
+            .map_err(|e| e.to_string())
+    }
 }
 
 #[tauri::command]
@@ -43,10 +54,19 @@ pub(crate) fn unregister_global_shortcut(
     shortcut_map: tauri::State<ShortcutMap>,
     shortcut: String,
 ) -> Result<(), String> {
-    use tauri_plugin_global_shortcut::{GlobalShortcutExt, Shortcut};
-    shortcut_map.lock().unwrap().remove(&shortcut);
-    let parsed: Shortcut = shortcut.parse().map_err(|_| format!("Invalid shortcut: {shortcut}"))?;
-    app.global_shortcut().unregister(parsed).map_err(|e| e.to_string())
+    #[cfg(debug_assertions)]
+    {
+        let _ = (app, shortcut_map, shortcut);
+        Ok(())
+    }
+
+    #[cfg(not(debug_assertions))]
+    {
+        use tauri_plugin_global_shortcut::{GlobalShortcutExt, Shortcut};
+        shortcut_map.lock().unwrap().remove(&shortcut);
+        let parsed: Shortcut = shortcut.parse().map_err(|_| format!("Invalid shortcut: {shortcut}"))?;
+        app.global_shortcut().unregister(parsed).map_err(|e| e.to_string())
+    }
 }
 
 #[tauri::command]
diff --git a/src-tauri/src/lib_commands/sync/tray.rs b/src-tauri/src/lib_commands/sync/tray.rs
index 33fd3d57..e97a124a 100644
--- a/src-tauri/src/lib_commands/sync/tray.rs
+++ b/src-tauri/src/lib_commands/sync/tray.rs
@@ -10,6 +10,59 @@ use crate::tray_runtime::{
 };
 
 use super::super::ui::{PAUSE_RENDERING_JS, RESUME_RENDERING_JS};
+use tauri::image::Image;
+
+/// Debug builds: mirror the default app icon horizontally so the tray differs from release.
+fn app_tray_icon(app: &tauri::AppHandle) -> Image<'static> {
+    let icon = app.default_window_icon().expect("default window icon");
+    #[cfg(debug_assertions)]
+    {
+        flip_image_horizontal(icon)
+    }
+    #[cfg(not(debug_assertions))]
+    {
+        icon.clone().to_owned()
+    }
+}
+
+#[cfg(debug_assertions)]
+fn flip_image_horizontal(icon: &Image<'_>) -> Image<'static> {
+    let width = icon.width();
+    let height = icon.height();
+    let mut rgba = icon.rgba().to_vec();
+    flip_rgba_horizontal(&mut rgba, width, height);
+    Image::new_owned(rgba, width, height)
+}
+
+#[cfg(debug_assertions)]
+fn flip_rgba_horizontal(rgba: &mut [u8], width: u32, height: u32) {
+    let w = width as usize;
+    let h = height as usize;
+    if w == 0 || h == 0 || rgba.len() < w * h * 4 {
+        return;
+    }
+    for y in 0..h {
+        let row = y * w * 4;
+        for x in 0..w / 2 {
+            let l = row + x * 4;
+            let r = row + (w - 1 - x) * 4;
+            let left = [
+                rgba[l],
+                rgba[l + 1],
+                rgba[l + 2],
+                rgba[l + 3],
+            ];
+            let right = [
+                rgba[r],
+                rgba[r + 1],
+                rgba[r + 2],
+                rgba[r + 3],
+            ];
+            rgba[l..l + 4].copy_from_slice(&right);
+            rgba[r..r + 4].copy_from_slice(&left);
+        }
+    }
+}
 
 pub(crate) fn build_tray_icon(app: &tauri::AppHandle) -> tauri::Result<TrayIcon> {
     let labels = app
@@ -92,7 +145,7 @@ pub(crate) fn build_tray_icon(app: &tauri::AppHandle) -> tauri::Result<TrayIcon>
 
     #[cfg(target_os = "windows")]
     let tray_builder = TrayIconBuilder::new()
-        .icon(app.default_window_icon().unwrap().clone())
+        .icon(app_tray_icon(app))
         .menu(&menu)
         .tooltip(&tooltip_with_icon)
         // tray-icon defaults to opening the context menu on every WM_LBUTTONUP when this is true.
@@ -102,7 +155,7 @@ pub(crate) fn build_tray_icon(app: &tauri::AppHandle) -> tauri::Result<TrayIcon>
         .show_menu_on_left_click(false);
     #[cfg(not(target_os = "windows"))]
     let tray_builder = TrayIconBuilder::new()
-        .icon(app.default_window_icon().unwrap().clone())
+        .icon(app_tray_icon(app))
         .menu(&menu)
         .tooltip(&cached_tooltip);
 
@@ -423,3 +476,22 @@ pub(crate) fn is_tiling_wm() -> bool {
 pub(crate) fn is_tiling_wm_cmd() -> bool {
     is_tiling_wm()
 }
+
+#[cfg(all(test, debug_assertions))]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn flip_rgba_horizontal_mirrors_pixels() {
+        // 3×1: A B C → C B A
+        let mut rgba = vec![
+            1, 0, 0, 255, // A
+            2, 0, 0, 255, // B
+            3, 0, 0, 255, // C
+        ];
+        flip_rgba_horizontal(&mut rgba, 3, 1);
+        assert_eq!(rgba[0], 3);
+        assert_eq!(rgba[4], 2);
+        assert_eq!(rgba[8], 1);
+    }
+}
diff --git a/src/app/AppShell.tsx b/src/app/AppShell.tsx
index 09d7c174..85738289 100644
--- a/src/app/AppShell.tsx
+++ b/src/app/AppShell.tsx
@@ -189,6 +189,9 @@ export function AppShell() {
       onContextMenu={e => e.preventDefault()}
     >
       {IS_LINUX && useCustomTitlebar && !isWindowFullscreen && !isTilingWm && <TitleBar />}
+      {import.meta.env.DEV && isMobile && (
+        <span className="dev-build-badge" aria-hidden>DEV</span>
+      )}
       {!isMobile && (
         <Sidebar
           isCollapsed={isSidebarCollapsed}
diff --git a/src/app/bootstrap.ts b/src/app/bootstrap.ts
index 736ce86a..8351f369 100644
--- a/src/app/bootstrap.ts
+++ b/src/app/bootstrap.ts
@@ -35,10 +35,18 @@ export function pushLoggingModeToBackend(): void {
   }
 }
 
+/** Mark the document in Vite dev so CSS can show dev-only chrome. */
+export function markDevBuildDocument(): void {
+  if (import.meta.env.DEV) {
+    document.documentElement.dataset.devBuild = 'true';
+  }
+}
+
 /** Orchestrates everything that must run before React mounts. */
 export function runPreReactBootstrap(): void {
   // Pre-warm the window-kind cache so subsequent reads are sync + safe.
   getWindowKind();
+  markDevBuildDocument();
   pushUserAgentToBackend();
   pushLoggingModeToBackend();
   installQueueUndoHotkey();
diff --git a/src/store/globalShortcutsStore.ts b/src/store/globalShortcutsStore.ts
index b24e133f..9c7711e5 100644
--- a/src/store/globalShortcutsStore.ts
+++ b/src/store/globalShortcutsStore.ts
@@ -4,6 +4,9 @@ import { invoke } from '@tauri-apps/api/core';
 import { MODIFIER_KEY_CODES, formatBinding } from './keybindingsStore';
 import { DEFAULT_GLOBAL_SHORTCUTS, isGlobalShortcutActionId, type GlobalAction } from '../config/shortcutActions';
 
+/** Dev builds run alongside release — OS-level grabs stay on the release instance. */
+const GLOBAL_SHORTCUTS_OS_ENABLED = !import.meta.env.DEV;
+
 /** Build a Tauri-compatible shortcut string from a KeyboardEvent, or null if invalid. */
 export function buildGlobalShortcut(e: KeyboardEvent): string | null {
   if ((MODIFIER_KEY_CODES as readonly string[]).includes(e.code)) return null;
@@ -42,15 +45,19 @@ export const useGlobalShortcutsStore = create<GlobalShortcutsState>()(
 
       setShortcut: async (action, shortcut) => {
         const prev = get().shortcuts[action];
-        if (prev) {
+        if (GLOBAL_SHORTCUTS_OS_ENABLED && prev) {
           try { await invoke('unregister_global_shortcut', { shortcut: prev }); } catch {}
         }
         if (shortcut) {
-          try {
-            await invoke('register_global_shortcut', { shortcut, action });
+          if (GLOBAL_SHORTCUTS_OS_ENABLED) {
+            try {
+              await invoke('register_global_shortcut', { shortcut, action });
+              set(s => ({ shortcuts: { ...s.shortcuts, [action]: shortcut } }));
+            } catch (e) {
+              console.warn('[GlobalShortcuts] Failed to register:', shortcut, e);
+            }
+          } else {
             set(s => ({ shortcuts: { ...s.shortcuts, [action]: shortcut } }));
-          } catch (e) {
-            console.warn('[GlobalShortcuts] Failed to register:', shortcut, e);
           }
         } else {
           set(s => {
@@ -62,6 +69,7 @@ export const useGlobalShortcutsStore = create<GlobalShortcutsState>()(
       },
 
       registerAll: async () => {
+        if (!GLOBAL_SHORTCUTS_OS_ENABLED) return;
         if (_registerAllCalled) return;
         _registerAllCalled = true;
         const { shortcuts } = get();
@@ -79,9 +87,11 @@ export const useGlobalShortcutsStore = create<GlobalShortcutsState>()(
 
       resetAll: async () => {
         const { shortcuts } = get();
-        for (const shortcut of Object.values(shortcuts)) {
-          if (shortcut) {
-            try { await invoke('unregister_global_shortcut', { shortcut }); } catch {}
+        if (GLOBAL_SHORTCUTS_OS_ENABLED) {
+          for (const shortcut of Object.values(shortcuts)) {
+            if (shortcut) {
+              try { await invoke('unregister_global_shortcut', { shortcut }); } catch {}
+            }
           }
         }
         set({ shortcuts: { ...DEFAULT_GLOBAL_SHORTCUTS } });
diff --git a/src/styles/layout/dev-build-chrome.css b/src/styles/layout/dev-build-chrome.css
new file mode 100644
index 00000000..09d7f9a1
--- /dev/null
+++ b/src/styles/layout/dev-build-chrome.css
@@ -0,0 +1,63 @@
+/* Dev-only chrome: shared data dir with prod, but visually unmistakable. */
+html[data-dev-build] .sidebar-brand {
+  background: #b91c1c;
+  border-bottom-color: rgba(0, 0, 0, 0.22);
+}
+
+html[data-dev-build] .sidebar-brand svg {
+  --logo-color-start: #fff;
+  --logo-color-end: #fecaca;
+}
+
+html[data-dev-build] .titlebar-btn-close,
+html[data-dev-build] .titlebar-btn-minimize,
+html[data-dev-build] .titlebar-btn-maximize {
+  background: #8b8b8b;
+}
+
+html[data-dev-build] .titlebar-btn-close:hover,
+html[data-dev-build] .titlebar-btn-minimize:hover,
+html[data-dev-build] .titlebar-btn-maximize:hover {
+  background: #a3a3a3;
+  box-shadow: inset 0 0 0 0.5px rgba(0, 0, 0, 0.18);
+}
+
+html[data-dev-build] .titlebar-btn-close:hover,
+html[data-dev-build] .titlebar-btn-minimize:hover,
+html[data-dev-build] .titlebar-btn-maximize:hover {
+  filter: none;
+}
+
+html[data-dev-build] .titlebar-btn:focus-visible {
+  box-shadow: inset 0 0 0 0.5px rgba(0, 0, 0, 0.18), 0 0 0 2px rgba(255, 255, 255, 0.35);
+}
+
+/* Narrow/mobile: sidebar logo is hidden — fixed red DEV square top-left. */
+html[data-dev-build] .dev-build-badge {
+  display: none;
+}
+
+html[data-dev-build] .app-shell[data-mobile] .dev-build-badge {
+  display: flex;
+  position: fixed;
+  top: 0;
+  left: 0;
+  z-index: 10050;
+  width: 32px;
+  height: 32px;
+  align-items: center;
+  justify-content: center;
+  background: #b91c1c;
+  color: #fff;
+  font-family: var(--font-ui, system-ui, sans-serif);
+  font-size: 9px;
+  font-weight: 800;
+  letter-spacing: 0.05em;
+  line-height: 1;
+  pointer-events: none;
+  user-select: none;
+}
+
+html[data-dev-build] .app-shell[data-mobile][data-titlebar] .dev-build-badge {
+  top: var(--titlebar-height);
+}
diff --git a/src/styles/layout/index.css b/src/styles/layout/index.css
index 61303c3a..e3bb1449 100644
--- a/src/styles/layout/index.css
+++ b/src/styles/layout/index.css
@@ -1,4 +1,5 @@
 @import './_intro.css';
+@import './dev-build-chrome.css';
 @import './custom-title-bar-linux-only-decorations-false.css';
 @import './resizer-handles.css';
 @import './sidebar.css';