diff --git a/backend/app.py b/backend/app.py
index 0a89b85c7..37a848629 100644
--- a/backend/app.py
+++ b/backend/app.py
@@ -1104,7 +1104,7 @@ def handle_mood_search(validated_data):
     # Note: CORS preflight (OPTIONS) is handled globally by Flask-CORS —
     # no manual OPTIONS check needed here.
 
-    from exceptions import (
+    from backend.core.exceptions.exceptions import (
         LLMCircuitBreakerOpenError, AIServiceException,
         ValidationException, InvalidInputError
     )
@@ -1117,19 +1117,26 @@ def handle_mood_search(validated_data):
         # Try to use enhanced mood parsing if available
         try:
             from mood_analysis.mood_query_parser import parse_mood_query, get_recommendation_prompt
+            from mood_analysis.ambient_music import get_ambient_music
             parsed_query = parse_mood_query(mood_query)
             enhanced_prompt = get_recommendation_prompt(mood_query)
-            
+
             logger.info(f"Parsed mood query: {parsed_query.to_dict()}")
-            
+
+            # Map the parsed mood to a curated ambient playlist for the mini-player
+            ambient_music = get_ambient_music(
+                mood_query, primary_moods=parsed_query.primary_moods
+            )
+
             # Use enhanced prompt for recommendations
             recommendations = get_ai_recommendations(enhanced_prompt)
-            
+
             return success_response(
                 data={
                     "recommendations": recommendations,
                     "query": mood_query,
-                    "parsed_mood": parsed_query.to_dict()
+                    "parsed_mood": parsed_query.to_dict(),
+                    "ambient_music": ambient_music
                 }
             )
         except ImportError:
@@ -1139,7 +1146,8 @@ def handle_mood_search(validated_data):
             return success_response(
                 data={
                     "recommendations": recommendations,
-                    "query": mood_query
+                    "query": mood_query,
+                    "ambient_music": {"genre": None, "spotify_embed_url": None}
                 }
             )
         
diff --git a/backend/mood_analysis/ambient_music.py b/backend/mood_analysis/ambient_music.py
new file mode 100644
index 000000000..e0c363509
--- /dev/null
+++ b/backend/mood_analysis/ambient_music.py
@@ -0,0 +1,67 @@
+# Ambient music mapper: maps a parsed mood query to a curated open
+# Spotify playlist. Pure keyword matching on the moods/themes already
+# extracted by MoodQueryParser - no extra LLM call, no external API.
+
+from typing import Dict, Optional
+
+# ponytail: static curated list; swap in Spotify API search if curation matters later.
+MOOD_PLAYLISTS = [
+    # (keywords over moods+themes+raw query, genre label, playlist embed URL)
+    (
+        {"dark", "mysterious", "gothic", "melancholic"},
+        "Dark Academia Jazz",
+        "https://open.spotify.com/embed/playlist/37i9dQZF1DX4sWSpwq3LiO",
+    ),
+    (
+        {"cozy"},
+        "Cozy Reading Cafe",
+        "https://open.spotify.com/embed/playlist/37i9dQZF1DX4WYpdgoIcn6",
+    ),
+    (
+        {"whimsical", "uplifting"},
+        "Whimsical & Light",
+        "https://open.spotify.com/embed/playlist/37i9dQZF1DX7EF8wVxBVhG",
+    ),
+    (
+        {"atmospheric", "thoughtful"},
+        "Classical Reading",
+        "https://open.spotify.com/embed/playlist/37i9dQZF1DX8ymr6UES7vc",
+    ),
+]
+
+DEFAULT_PLAYLIST = (
+    {"genre": "Lo-Fi Reading Chill",
+     "spotify_embed_url": "https://open.spotify.com/embed/playlist/37i9dQZF1DX889Y07vA7vH"}
+)
+
+
+def get_ambient_music(query: str, primary_moods=None) -> Dict:
+    """Return an ambient_music payload for a mood query."""
+    haystack = set((primary_moods or []))
+    tokens = {t.strip(".,!?") for t in query.lower().split()}
+    haystack |= tokens
+
+    best: Optional[tuple] = None
+    best_score = 0
+    for keywords, genre, url in MOOD_PLAYLISTS:
+        score = len(keywords & haystack)
+        if score > best_score:
+            best_score = score
+            best = (genre, url)
+
+    if best:
+        return {"genre": best[0], "spotify_embed_url": best[1]}
+    return dict(DEFAULT_PLAYLIST)
+
+
+def self_check():
+    assert get_ambient_music("cozy autumn night with warm tea")["genre"] == "Cozy Reading Cafe"
+    assert get_ambient_music("dark academia gothic mystery")["genre"] == "Dark Academia Jazz"
+    assert get_ambient_music("something random")["genre"] == DEFAULT_PLAYLIST["genre"]
+    r = get_ambient_music("cozy", ["cozy"])
+    assert r["spotify_embed_url"].startswith("https://open.spotify.com/embed/")
+    print("ambient_music self-check passed")
+
+
+if __name__ == "__main__":
+    self_check()
diff --git a/frontend/css/style.css b/frontend/css/style.css
index 47630fbda..2952caf55 100644
--- a/frontend/css/style.css
+++ b/frontend/css/style.css
@@ -6096,6 +6096,42 @@ textarea:focus {
     gap: 10px;
 }
 
+/* Mood-based Ambient Music mini-player (#1404) */
+.music-player {
+    bottom: 6.1rem !important; /* stacked above the sanctuary leaf button */
+}
+
+#musicToggle {
+    width: 2.8rem !important;
+    height: 2.8rem !important;
+    border-radius: 50% !important;
+    background: var(--header-bg) !important;
+    color: var(--text-main) !important;
+    border: 1px solid var(--glass-border) !important;
+    display: flex !important;
+    align-items: center !important;
+    justify-content: center !important;
+    cursor: pointer !important;
+    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.2) !important;
+    transition: all 0.3s ease !important;
+}
+
+#musicToggle:hover {
+    background: var(--accent-gold) !important;
+    color: white !important;
+    transform: scale(1.05);
+}
+
+.music-panel {
+    width: 280px;
+}
+
+.music-panel .music-empty {
+    color: var(--text-muted);
+    font-size: 0.85rem;
+    margin: 0;
+}
+
 .ambient-option span {
     display: flex;
     align-items: center;
diff --git a/frontend/js/ambient-music.js b/frontend/js/ambient-music.js
new file mode 100644
index 000000000..defec8a7c
--- /dev/null
+++ b/frontend/js/ambient-music.js
@@ -0,0 +1,57 @@
+/**
+ * Mood-based Ambient Music mini-player for BiblioDrift.
+ * Listens for mood-search responses (window event) and swaps the Spotify
+ * embed inside a glassmorphic floating panel, styled after Ambient Sanctuary.
+ * Hidden until the first search provides an ambient_music payload.
+ */
+
+class AmbientMusicPlayer {
+    constructor() {
+        this.root = document.getElementById('musicPlayer');
+        this.toggleBtn = document.getElementById('musicToggle');
+        this.panel = document.getElementById('musicPanel');
+        this.embed = document.getElementById('musicEmbed');
+        this.genreLabel = document.getElementById('musicGenre');
+        this.emptyMsg = document.getElementById('musicEmpty');
+
+        if (!this.root || !this.toggleBtn || !this.panel || !this.embed) return;
+
+        this.toggleBtn.setAttribute('aria-controls', 'musicPanel');
+        this.currentUrl = null;
+
+        this.toggleBtn.addEventListener('click', (e) => {
+            e.stopPropagation();
+            const isActive = this.panel.classList.toggle('active');
+            this.toggleBtn.classList.toggle('active', isActive);
+            this.toggleBtn.setAttribute('aria-expanded', isActive ? 'true' : 'false');
+        });
+
+        document.addEventListener('click', (e) => {
+            if (!this.panel.contains(e.target) && e.target !== this.toggleBtn && !this.toggleBtn.contains(e.target)) {
+                this.panel.classList.remove('active');
+                this.toggleBtn.classList.remove('active');
+                this.toggleBtn.setAttribute('aria-expanded', 'false');
+            }
+        });
+
+        // app.js dispatches this after every mood-search API response
+        window.addEventListener('bibliodrift:ambient-music', (e) => this.update(e.detail));
+    }
+
+    update(ambientMusic) {
+        if (!ambientMusic || !ambientMusic.spotify_embed_url) return;
+        if (ambientMusic.spotify_embed_url === this.currentUrl) return;
+        this.currentUrl = ambientMusic.spotify_embed_url;
+        this.embed.src = `${ambientMusic.spotify_embed_url}?utm_source=generator&theme=0`;
+        this.embed.style.display = 'block';
+        if (this.emptyMsg) this.emptyMsg.style.display = 'none';
+        if (this.genreLabel && ambientMusic.genre) {
+            this.genreLabel.textContent = `Now vibing: ${ambientMusic.genre}`;
+        }
+        this.root.hidden = false;
+    }
+}
+
+document.addEventListener('DOMContentLoaded', () => {
+    window.ambientMusicPlayer = new AmbientMusicPlayer();
+});
diff --git a/frontend/js/app.js b/frontend/js/app.js
index 36a0fdefa..522e83e96 100644
--- a/frontend/js/app.js
+++ b/frontend/js/app.js
@@ -3279,6 +3279,17 @@ document.addEventListener('DOMContentLoaded', async () => {
         });
 
         renderer.renderCuratedSection(query, 'search-results-grid', 20);
+
+        // Fire-and-forget: fetch a matching ambient playlist for this mood query
+        fetch(`${MOOD_API_BASE}/mood-search`, {
+            method: 'POST',
+            headers: { 'Content-Type': 'application/json' },
+            body: JSON.stringify({ query })
+        }).then(res => res.ok ? res.json() : null).then(data => {
+            window.dispatchEvent(new CustomEvent('bibliodrift:ambient-music', {
+                detail: data?.data?.ambient_music || null
+            }));
+        }).catch(() => { /* playlist is optional; search results still render */ });
     } else if (document.getElementById('dynamic-shelves-container')) {
         console.log('📚 Initializing Curated Discovery Sections...');
         const container = document.getElementById('dynamic-shelves-container');
diff --git a/frontend/js/chat.js b/frontend/js/chat.js
index 8aefd0bce..a09f80c5a 100644
--- a/frontend/js/chat.js
+++ b/frontend/js/chat.js
@@ -332,6 +332,10 @@ Tell me: what is stirring in you today?`,
             if (moodResponse.ok) {
                 const moodData = await moodResponse.json();
                 if (moodData.success) {
+                    // Surface the ambient music payload for the mini-player
+                    window.dispatchEvent(new CustomEvent('bibliodrift:ambient-music', {
+                        detail: moodData.data?.ambient_music || null
+                    }));
                     const books = await this.searchGoogleBooks(userMessage);
                     return {
                         message: this.generateContextualResponse(userMessage, books),
diff --git a/frontend/pages/app.html b/frontend/pages/app.html
index 816797e97..d0caace03 100644
--- a/frontend/pages/app.html
+++ b/frontend/pages/app.html
@@ -424,6 +424,20 @@ <h3>Your Reading Mood Tags</h3>
   </button>
 
   <!-- Ambient Sanctuary UI -->
+  <div class="ambient-sanctuary music-player" id="musicPlayer" hidden>
+    <button id="musicToggle" title="Ambient Music" aria-expanded="false" aria-controls="musicPanel">
+      <i class="fa-solid fa-music"></i>
+    </button>
+
+    <div id="musicPanel" class="ambient-panel music-panel">
+      <h3 style="color: var(--text-main) !important;" id="musicGenre">Ambient Music</h3>
+      <iframe id="musicEmbed" src="" width="100%" height="80" frameborder="0"
+        allowtransparency="true" allow="encrypted-media" title="Ambient playlist player"
+        style="border-radius: 12px; display: none;"></iframe>
+      <p id="musicEmpty" class="music-empty">Search for a mood to get a matching playlist.</p>
+    </div>
+  </div>
+
   <div class="ambient-sanctuary">
     <button id="ambientToggle" title="Ambient Sanctuary" aria-expanded="false" aria-controls="ambientPanel">
       <i class="fa-solid fa-leaf"></i>
@@ -515,9 +529,9 @@ <h3 style="color: var(--text-main) !important;">Ambient Sanctuary</h3>
   </div>
 
   <script src="../js/ambient.js"></script>
+  <script src="../js/ambient-music.js"></script>
   <script src="../js/security.js"></script>
   <script src="../js/pwa.js"></script>
-  <!-- AI Chatbot Widget -->
   <div id="ai-chatbot-widget" class="chatbot-widget">
     <button id="chatbot-toggle-btn" class="chatbot-toggle-btn" title="Chat with Elara">
       <i class="fa-solid fa-robot"></i>
diff --git a/tests/test_ambient_music.py b/tests/test_ambient_music.py
new file mode 100644
index 000000000..ed6179d06
--- /dev/null
+++ b/tests/test_ambient_music.py
@@ -0,0 +1,59 @@
+"""Tests for ambient music mapping (#1404): unit tests for the mapper and
+an endpoint check that /api/v1/mood-search includes an ambient_music payload."""
+
+# Load the mapper module directly: importing the mood_analysis package pulls in
+# heavy NLP deps that conftest deliberately stubs out for the test environment.
+import importlib.util
+import os
+
+_SPEC = importlib.util.spec_from_file_location(
+    "ambient_music",
+    os.path.join(
+        os.path.dirname(__file__), "..", "backend", "mood_analysis", "ambient_music.py"
+    ),
+)
+_ambient_music = importlib.util.module_from_spec(_SPEC)
+_SPEC.loader.exec_module(_ambient_music)
+
+get_ambient_music = _ambient_music.get_ambient_music
+DEFAULT_PLAYLIST = _ambient_music.DEFAULT_PLAYLIST
+self_check = _ambient_music.self_check
+
+
+def test_cozy_query_maps_to_cozy_playlist():
+    result = get_ambient_music("cozy autumn night with warm tea")
+    assert result["genre"] == "Cozy Reading Cafe"
+    assert result["spotify_embed_url"].startswith("https://open.spotify.com/embed/")
+
+
+def test_dark_query_maps_to_dark_academia():
+    result = get_ambient_music("dark academia gothic mystery", primary_moods=["dark"])
+    assert result["genre"] == "Dark Academia Jazz"
+
+
+def test_unknown_query_falls_back_to_default():
+    result = get_ambient_music("zzz qqq xyz")
+    assert result == DEFAULT_PLAYLIST
+
+
+def test_self_check():
+    self_check()
+
+
+def test_mood_search_includes_ambient_music(client):
+    """Endpoint returns ambient_music in data (AI recommendations are mocked
+    away by patching; we only assert on the new field's presence/shape)."""
+    from unittest.mock import patch
+    from flask import url_for
+
+    client.application.config["WTF_CSRF_ENABLED"] = False
+    with patch("backend.app.get_ai_recommendations", return_value=["book1"]):
+        resp = client.post(
+            "/api/v1/mood-search",
+            json={"query": "cozy mystery"},
+        )
+    assert resp.status_code == 200
+    body = resp.get_json()
+    # success_response flattens the data dict into the top-level JSON body
+    assert "ambient_music" in body
+    assert set(body["ambient_music"].keys()) == {"genre", "spotify_embed_url"}