diff --git a/pomodoro_app/assets/sounds/long_break_done.wav b/pomodoro_app/assets/sounds/long_break_done.wav
new file mode 100644
index 0000000..0ff28b4
Binary files /dev/null and b/pomodoro_app/assets/sounds/long_break_done.wav differ
diff --git a/pomodoro_app/assets/sounds/long_break_start.wav b/pomodoro_app/assets/sounds/long_break_start.wav
new file mode 100644
index 0000000..9b5fba1
Binary files /dev/null and b/pomodoro_app/assets/sounds/long_break_start.wav differ
diff --git a/pomodoro_app/assets/sounds/short_break_done.wav b/pomodoro_app/assets/sounds/short_break_done.wav
new file mode 100644
index 0000000..cce2f11
Binary files /dev/null and b/pomodoro_app/assets/sounds/short_break_done.wav differ
diff --git a/pomodoro_app/assets/sounds/work_done.wav b/pomodoro_app/assets/sounds/work_done.wav
new file mode 100644
index 0000000..972c71b
Binary files /dev/null and b/pomodoro_app/assets/sounds/work_done.wav differ
diff --git a/pomodoro_app/linux/flutter/generated_plugin_registrant.cc b/pomodoro_app/linux/flutter/generated_plugin_registrant.cc
index e71a16d..1830e5c 100644
--- a/pomodoro_app/linux/flutter/generated_plugin_registrant.cc
+++ b/pomodoro_app/linux/flutter/generated_plugin_registrant.cc
@@ -6,6 +6,10 @@
 
 #include "generated_plugin_registrant.h"
 
+#include <audioplayers_linux/audioplayers_linux_plugin.h>
 
 void fl_register_plugins(FlPluginRegistry* registry) {
+  g_autoptr(FlPluginRegistrar) audioplayers_linux_registrar =
+      fl_plugin_registry_get_registrar_for_plugin(registry, "AudioplayersLinuxPlugin");
+  audioplayers_linux_plugin_register_with_registrar(audioplayers_linux_registrar);
 }
diff --git a/pomodoro_app/linux/flutter/generated_plugins.cmake b/pomodoro_app/linux/flutter/generated_plugins.cmake
index 2e1de87..e9abb91 100644
--- a/pomodoro_app/linux/flutter/generated_plugins.cmake
+++ b/pomodoro_app/linux/flutter/generated_plugins.cmake
@@ -3,6 +3,7 @@
 #
 
 list(APPEND FLUTTER_PLUGIN_LIST
+  audioplayers_linux
 )
 
 list(APPEND FLUTTER_FFI_PLUGIN_LIST
diff --git a/pomodoro_app/pubspec.lock b/pomodoro_app/pubspec.lock
index 764bc87..51e620c 100644
--- a/pomodoro_app/pubspec.lock
+++ b/pomodoro_app/pubspec.lock
@@ -9,6 +9,62 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.13.0"
+  audioplayers:
+    dependency: "direct main"
+    description:
+      name: audioplayers
+      sha256: "5441fa0ceb8807a5ad701199806510e56afde2b4913d9d17c2f19f2902cf0ae4"
+      url: "https://pub.dev"
+    source: hosted
+    version: "6.5.1"
+  audioplayers_android:
+    dependency: transitive
+    description:
+      name: audioplayers_android
+      sha256: "60a6728277228413a85755bd3ffd6fab98f6555608923813ce383b190a360605"
+      url: "https://pub.dev"
+    source: hosted
+    version: "5.2.1"
+  audioplayers_darwin:
+    dependency: transitive
+    description:
+      name: audioplayers_darwin
+      sha256: "0811d6924904ca13f9ef90d19081e4a87f7297ddc19fc3d31f60af1aaafee333"
+      url: "https://pub.dev"
+    source: hosted
+    version: "6.3.0"
+  audioplayers_linux:
+    dependency: transitive
+    description:
+      name: audioplayers_linux
+      sha256: f75bce1ce864170ef5e6a2c6a61cd3339e1a17ce11e99a25bae4474ea491d001
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.2.1"
+  audioplayers_platform_interface:
+    dependency: transitive
+    description:
+      name: audioplayers_platform_interface
+      sha256: "0e2f6a919ab56d0fec272e801abc07b26ae7f31980f912f24af4748763e5a656"
+      url: "https://pub.dev"
+    source: hosted
+    version: "7.1.1"
+  audioplayers_web:
+    dependency: transitive
+    description:
+      name: audioplayers_web
+      sha256: "1c0f17cec68455556775f1e50ca85c40c05c714a99c5eb1d2d57cc17ba5522d7"
+      url: "https://pub.dev"
+    source: hosted
+    version: "5.1.1"
+  audioplayers_windows:
+    dependency: transitive
+    description:
+      name: audioplayers_windows
+      sha256: "4048797865105b26d47628e6abb49231ea5de84884160229251f37dfcbe52fd7"
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.2.1"
   boolean_selector:
     dependency: transitive
     description:
@@ -33,6 +89,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.1.2"
+  code_assets:
+    dependency: transitive
+    description:
+      name: code_assets
+      sha256: "83ccdaa064c980b5596c35dd64a8d3ecc68620174ab9b90b6343b753aa721687"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.0.0"
   collection:
     dependency: transitive
     description:
@@ -41,6 +105,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.19.1"
+  crypto:
+    dependency: transitive
+    description:
+      name: crypto
+      sha256: c8ea0233063ba03258fbcf2ca4d6dadfefe14f02fab57702265467a19f27fadf
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.0.7"
   cupertino_icons:
     dependency: "direct main"
     description:
@@ -57,6 +129,30 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.3.3"
+  ffi:
+    dependency: transitive
+    description:
+      name: ffi
+      sha256: "6d7fd89431262d8f3125e81b50d3847a091d846eafcd4fdb88dd06f36d705a45"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.2.0"
+  file:
+    dependency: transitive
+    description:
+      name: file
+      sha256: a3b4f84adafef897088c160faf7dfffb7696046cb13ae90b508c2cbc95d3b8d4
+      url: "https://pub.dev"
+    source: hosted
+    version: "7.0.1"
+  fixnum:
+    dependency: transitive
+    description:
+      name: fixnum
+      sha256: b6dc7065e46c974bc7c5f143080a6764ec7a4be6da1285ececdc37be96de53be
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.1.1"
   flutter:
     dependency: "direct main"
     description: flutter
@@ -75,6 +171,43 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
+  flutter_web_plugins:
+    dependency: transitive
+    description: flutter
+    source: sdk
+    version: "0.0.0"
+  glob:
+    dependency: transitive
+    description:
+      name: glob
+      sha256: c3f1ee72c96f8f78935e18aa8cecced9ab132419e8625dc187e1c2408efc20de
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.1.3"
+  hooks:
+    dependency: transitive
+    description:
+      name: hooks
+      sha256: "7a08a0d684cb3b8fb604b78455d5d352f502b68079f7b80b831c62220ab0a4f6"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.0.1"
+  http:
+    dependency: transitive
+    description:
+      name: http
+      sha256: "87721a4a50b19c7f1d49001e51409bddc46303966ce89a65af4f4e6004896412"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.6.0"
+  http_parser:
+    dependency: transitive
+    description:
+      name: http_parser
+      sha256: "178d74305e7866013777bab2c3d8726205dc5a4dd935297175b19a23a2e66571"
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.1.2"
   leak_tracker:
     dependency: transitive
     description:
@@ -107,6 +240,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "6.1.0"
+  logging:
+    dependency: transitive
+    description:
+      name: logging
+      sha256: c8245ada5f1717ed44271ed1c26b8ce85ca3228fd2ffdb75468ab01979309d61
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.3.0"
   matcher:
     dependency: transitive
     description:
@@ -131,6 +272,22 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.17.0"
+  native_toolchain_c:
+    dependency: transitive
+    description:
+      name: native_toolchain_c
+      sha256: "89e83885ba09da5fdf2cdacc8002a712ca238c28b7f717910b34bcd27b0d03ac"
+      url: "https://pub.dev"
+    source: hosted
+    version: "0.17.4"
+  objective_c:
+    dependency: transitive
+    description:
+      name: objective_c
+      sha256: "100a1c87616ab6ed41ec263b083c0ef3261ee6cd1dc3b0f35f8ddfa4f996fe52"
+      url: "https://pub.dev"
+    source: hosted
+    version: "9.3.0"
   path:
     dependency: transitive
     description:
@@ -139,6 +296,78 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.9.1"
+  path_provider:
+    dependency: transitive
+    description:
+      name: path_provider
+      sha256: "50c5dd5b6e1aaf6fb3a78b33f6aa3afca52bf903a8a5298f53101fdaee55bbcd"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.1.5"
+  path_provider_android:
+    dependency: transitive
+    description:
+      name: path_provider_android
+      sha256: f2c65e21139ce2c3dad46922be8272bb5963516045659e71bb16e151c93b580e
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.2.22"
+  path_provider_foundation:
+    dependency: transitive
+    description:
+      name: path_provider_foundation
+      sha256: "2a376b7d6392d80cd3705782d2caa734ca4727776db0b6ec36ef3f1855197699"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.6.0"
+  path_provider_linux:
+    dependency: transitive
+    description:
+      name: path_provider_linux
+      sha256: f7a1fe3a634fe7734c8d3f2766ad746ae2a2884abe22e241a8b301bf5cac3279
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.2.1"
+  path_provider_platform_interface:
+    dependency: transitive
+    description:
+      name: path_provider_platform_interface
+      sha256: "88f5779f72ba699763fa3a3b06aa4bf6de76c8e5de842cf6f29e2e06476c2334"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.1.2"
+  path_provider_windows:
+    dependency: transitive
+    description:
+      name: path_provider_windows
+      sha256: bd6f00dbd873bfb70d0761682da2b3a2c2fccc2b9e84c495821639601d81afe7
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.3.0"
+  platform:
+    dependency: transitive
+    description:
+      name: platform
+      sha256: "5d6b1b0036a5f331ebc77c850ebc8506cbc1e9416c27e59b439f917a902a4984"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.1.6"
+  plugin_platform_interface:
+    dependency: transitive
+    description:
+      name: plugin_platform_interface
+      sha256: "4820fbfdb9478b1ebae27888254d445073732dae3d6ea81f0b7e06d5dedc3f02"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.1.8"
+  pub_semver:
+    dependency: transitive
+    description:
+      name: pub_semver
+      sha256: "5bfcf68ca79ef689f8990d1160781b4bad40a3bd5e5218ad4076ddb7f4081585"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.2.0"
   sky_engine:
     dependency: transitive
     description: flutter
@@ -176,6 +405,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.4.1"
+  synchronized:
+    dependency: transitive
+    description:
+      name: synchronized
+      sha256: c254ade258ec8282947a0acbbc90b9575b4f19673533ee46f2f6e9b3aeefd7c0
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.4.0"
   term_glyph:
     dependency: transitive
     description:
@@ -192,6 +429,22 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "0.7.9"
+  typed_data:
+    dependency: transitive
+    description:
+      name: typed_data
+      sha256: f9049c039ebfeb4cf7a7104a675823cd72dba8297f264b6637062516699fa006
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.4.0"
+  uuid:
+    dependency: transitive
+    description:
+      name: uuid
+      sha256: a11b666489b1954e01d992f3d601b1804a33937b5a8fe677bd26b8a9f96f96e8
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.5.2"
   vector_math:
     dependency: transitive
     description:
@@ -208,6 +461,30 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "15.0.2"
+  web:
+    dependency: transitive
+    description:
+      name: web
+      sha256: "868d88a33d8a87b18ffc05f9f030ba328ffefba92d6c127917a2ba740f9cfe4a"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.1.1"
+  xdg_directories:
+    dependency: transitive
+    description:
+      name: xdg_directories
+      sha256: "7a3f37b05d989967cdddcbb571f1ea834867ae2faa29725fd085180e0883aa15"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.1.0"
+  yaml:
+    dependency: transitive
+    description:
+      name: yaml
+      sha256: b9da305ac7c39faa3f030eccd175340f968459dae4af175130b3fc47e40d76ce
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.1.3"
 sdks:
   dart: ">=3.11.0 <4.0.0"
-  flutter: ">=3.18.0-18.0.pre.54"
+  flutter: ">=3.38.4"
diff --git a/pomodoro_app/pubspec.yaml b/pomodoro_app/pubspec.yaml
index e1389cc..7610d6c 100644
--- a/pomodoro_app/pubspec.yaml
+++ b/pomodoro_app/pubspec.yaml
@@ -34,6 +34,7 @@ dependencies:
   # The following adds the Cupertino Icons font to your application.
   # Use with the CupertinoIcons class for iOS style icons.
   cupertino_icons: ^1.0.8
+  audioplayers: ^6.1.0
 
 dev_dependencies:
   flutter_test:
@@ -56,10 +57,8 @@ flutter:
   # the material Icons class.
   uses-material-design: true
 
-  # To add assets to your application, add an assets section, like this:
-  # assets:
-  #   - images/a_dot_burr.jpeg
-  #   - images/a_dot_ham.jpeg
+  assets:
+    - assets/sounds/
 
   # An image asset can refer to one or more resolution-specific "variants", see
   # https://flutter.dev/to/resolution-aware-images
diff --git a/pomodoro_app/test/services/sound_service_test.dart b/pomodoro_app/test/services/sound_service_test.dart
new file mode 100644
index 0000000..840fb7e
--- /dev/null
+++ b/pomodoro_app/test/services/sound_service_test.dart
@@ -0,0 +1,63 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:pomodoro_app/models/pomodoro_state.dart';
+import 'package:pomodoro_app/services/sound_service.dart';
+
+void main() {
+  group('SoundService', () {
+    late List<String> playedAssets;
+    late SoundService service;
+
+    setUp(() {
+      playedAssets = [];
+      service = SoundService(
+        playCallback: (assetPath) async => playedAssets.add(assetPath),
+      );
+    });
+
+    tearDown(() {
+      service.dispose();
+    });
+
+    test('plays work_done when work ends with short break next', () async {
+      await service.playTransitionSound(
+        completedMode: PomodoroMode.work,
+        nextMode: PomodoroMode.shortBreak,
+      );
+      expect(playedAssets, ['work_done.wav']);
+    });
+
+    test('plays long_break_start when work ends with long break next',
+        () async {
+      await service.playTransitionSound(
+        completedMode: PomodoroMode.work,
+        nextMode: PomodoroMode.longBreak,
+      );
+      expect(playedAssets, ['long_break_start.wav']);
+    });
+
+    test('plays short_break_done when short break ends', () async {
+      await service.playTransitionSound(
+        completedMode: PomodoroMode.shortBreak,
+        nextMode: PomodoroMode.work,
+      );
+      expect(playedAssets, ['short_break_done.wav']);
+    });
+
+    test('plays long_break_done when long break ends', () async {
+      await service.playTransitionSound(
+        completedMode: PomodoroMode.longBreak,
+        nextMode: PomodoroMode.work,
+      );
+      expect(playedAssets, ['long_break_done.wav']);
+    });
+
+    test('does nothing after dispose', () async {
+      service.dispose();
+      await service.playTransitionSound(
+        completedMode: PomodoroMode.work,
+        nextMode: PomodoroMode.shortBreak,
+      );
+      expect(playedAssets, isEmpty);
+    });
+  });
+}
diff --git a/pomodoro_app/tools/__init__.py b/pomodoro_app/tools/__init__.py
new file mode 100644
index 0000000..9fae973
--- /dev/null
+++ b/pomodoro_app/tools/__init__.py
@@ -0,0 +1 @@
+"""Pomodoro app development tools."""
diff --git a/pomodoro_app/tools/generate_sounds.py b/pomodoro_app/tools/generate_sounds.py
new file mode 100644
index 0000000..35796e2
--- /dev/null
+++ b/pomodoro_app/tools/generate_sounds.py
@@ -0,0 +1,101 @@
+"""Generate distinct notification sounds for the Pomodoro app."""
+
+from __future__ import annotations
+
+import logging
+import math
+from pathlib import Path
+import struct
+import wave
+
+logger = logging.getLogger(__name__)
+
+SAMPLE_RATE = 44100
+
+
+def _write_wav(path: Path, samples: list[int]) -> None:
+    with wave.open(str(path), "w") as w:
+        w.setnchannels(1)
+        w.setsampwidth(2)
+        w.setframerate(SAMPLE_RATE)
+        w.writeframes(struct.pack(f"<{len(samples)}h", *samples))
+
+
+def _tone(freq: float, duration: float, volume: float = 0.7) -> list[int]:
+    n = int(SAMPLE_RATE * duration)
+    return [
+        int(volume * 32767 * math.sin(2 * math.pi * freq * i / SAMPLE_RATE))
+        for i in range(n)
+    ]
+
+
+def _fade(samples: list[int], fade_ms: int = 20) -> list[int]:
+    n = int(SAMPLE_RATE * fade_ms / 1000)
+    out = list(samples)
+    for i in range(min(n, len(out))):
+        out[i] = int(out[i] * i / n)
+    for i in range(min(n, len(out))):
+        out[-(i + 1)] = int(out[-(i + 1)] * i / n)
+    return out
+
+
+def _silence(duration: float) -> list[int]:
+    return [0] * int(SAMPLE_RATE * duration)
+
+
+def work_done(out: Path) -> None:
+    """End of pomodoro: upward three-note chime (C5-E5-G5)."""
+    samples = (
+        _fade(_tone(523.25, 0.2))
+        + _silence(0.05)
+        + _fade(_tone(659.25, 0.2))
+        + _silence(0.05)
+        + _fade(_tone(783.99, 0.4))
+    )
+    _write_wav(out, samples)
+
+
+def short_break_done(out: Path) -> None:
+    """End of short break: two gentle pings (G5-C6)."""
+    samples = _fade(_tone(783.99, 0.15)) + _silence(0.08) + _fade(_tone(1046.50, 0.3))
+    _write_wav(out, samples)
+
+
+def long_break_start(out: Path) -> None:
+    """Start of long break: descending celebration (G5-E5-C5-C4 long)."""
+    samples = (
+        _fade(_tone(783.99, 0.15))
+        + _silence(0.04)
+        + _fade(_tone(659.25, 0.15))
+        + _silence(0.04)
+        + _fade(_tone(523.25, 0.15))
+        + _silence(0.04)
+        + _fade(_tone(261.63, 0.6, volume=0.5))
+    )
+    _write_wav(out, samples)
+
+
+def long_break_done(out: Path) -> None:
+    """End of long break: wake-up alarm — rapid repeated beeps."""
+    beep = _fade(_tone(880.0, 0.1))
+    gap = _silence(0.08)
+    samples = (beep + gap) * 4 + _fade(_tone(1046.50, 0.3))
+    _write_wav(out, samples)
+
+
+def main() -> None:
+    """Generate all notification sounds and log file sizes."""
+    out_dir = Path(__file__).resolve().parent.parent / "assets" / "sounds"
+    out_dir.mkdir(parents=True, exist_ok=True)
+
+    work_done(out_dir / "work_done.wav")
+    short_break_done(out_dir / "short_break_done.wav")
+    long_break_start(out_dir / "long_break_start.wav")
+    long_break_done(out_dir / "long_break_done.wav")
+
+    for f in sorted(out_dir.glob("*.wav")):
+        logger.info("  %s (%d bytes)", f.name, f.stat().st_size)
+
+
+if __name__ == "__main__":
+    main()