README.md

@@ -16,6 +16,9 @@ Based on the [Navicord](https://github.com/logixism/navicord) project.
 ## Features
 
 - Shows currently playing track with title, artist, and album art
+- Clickable track title and artist name link to Spotify (direct track link via [ListenBrainz](https://listenbrainz.org), falls back to Spotify search)
+- Clickable album art links to the Spotify track page
+- Navidrome logo overlay on album art (optional, enabled by default)
 - Customizable activity name: "Navidrome" is default, but can be configured to display track title, artist, or album
 - Displays playback progress with start/end timestamps
 - Automatic presence clearing when track finishes
@@ -120,6 +123,11 @@ Access the plugin configuration in Navidrome: **Settings > Plugins > Discord Ric
 - **What it does**: Automatically uploads album artwork to uguu.se (temporary hosting) so Discord can display it
 - **When to disable**: Your Navidrome is publicly accessible and you've set `ND_BASEURL`
 
+#### Show Navidrome Logo Overlay
+- **Default**: Enabled
+- **What it does**: Displays the Navidrome logo as a small overlay in the corner of the album artwork
+- **When to disable**: If you prefer a clean album art display without the logo badge
+
 #### Users
 Add each Navidrome user who wants Discord Rich Presence. For each user, provide:
 - **Username**: The Navidrome login username (case-sensitive)
@@ -139,14 +147,14 @@ The plugin implements three Navidrome capabilities:
 
 ### Host Services
 
-| Service         | Usage                                                               |
-|-----------------|---------------------------------------------------------------------|
-| **HTTP**        | Discord API calls (gateway discovery, external assets registration) |
-| **WebSocket**   | Persistent connection to Discord gateway                            |
-| **Cache**       | Sequence numbers, processed image URLs                              |
-| **Scheduler**   | Recurring heartbeats, one-time presence clearing                    |
-| **Artwork**     | Track artwork public URL resolution                                 |
-| **SubsonicAPI** | Fetches track artwork data for image hosting upload                 |
+| Service         | Usage                                                                          |
+|-----------------|--------------------------------------------------------------------------------|
+| **HTTP**        | Discord API calls (gateway discovery, external assets registration), ListenBrainz Spotify resolution |
+| **WebSocket**   | Persistent connection to Discord gateway                                       |
+| **Cache**       | Sequence numbers, processed image URLs, resolved Spotify URLs                  |
+| **Scheduler**   | Recurring heartbeats, one-time presence clearing                               |
+| **Artwork**     | Track artwork public URL resolution                                             |
+| **SubsonicAPI** | Fetches track artwork data for image hosting upload                             |
 
 ### Flow
 
@@ -176,15 +184,31 @@ Discord requires images to be registered via their external assets API. The plug
 
 **For non-public Navidrome instances**: If your server isn't publicly accessible (e.g., behind a VPN or firewall), enable the "Upload to uguu.se" option. This uploads artwork to a temporary file host so Discord can display it.
 
+### Spotify Linking
+
+The plugin enriches the Discord presence with clickable Spotify links so others can easily find what you're listening to:
+
+- **Track title** → links to the Spotify track (or a Spotify search as fallback)
+- **Artist name** → links to a Spotify search for the artist
+- **Album art** → links to the Spotify track page
+
+Track URLs are resolved via the [ListenBrainz Labs API](https://labs.api.listenbrainz.org):
+1. If the track has a MusicBrainz Recording ID (MBID), that is used for an exact lookup
+2. Otherwise, artist name, track title, and album are used for a metadata-based lookup
+3. If neither resolves, a Spotify search URL is used as a fallback
+
+Resolved URLs are cached (30 days for direct track links, 4 hours for search fallbacks).
+
 ### Files
 
-| File                           | Description                                                            |
-|--------------------------------|------------------------------------------------------------------------|
-| [main.go](main.go)             | Plugin entry point, scrobbler and scheduler implementations            |
-| [rpc.go](rpc.go)               | Discord gateway communication, WebSocket handling, activity management |
-| [coverart.go](coverart.go)     | Artwork URL handling and optional uguu.se image hosting                |
-| [manifest.json](manifest.json) | Plugin metadata and permission declarations                            |
-| [Makefile](Makefile)           | Build automation                                                       |
+| File                               | Description                                                                    |
+|------------------------------------|--------------------------------------------------------------------------------|
+| [main.go](main.go)                 | Plugin entry point, scrobbler and scheduler implementations, Spotify URL resolution |
+| [rpc.go](rpc.go)                   | Discord gateway communication, WebSocket handling, activity management         |
+| [coverart.go](coverart.go)         | Artwork URL handling and optional uguu.se image hosting                        |
+| [manifest.json](manifest.json)     | Plugin metadata and permission declarations                                    |
+| [navidrome.webp](navidrome.webp)   | Navidrome logo used as the album art overlay badge                             |
+| [Makefile](Makefile)               | Build automation                                                               |
 
 ## Building
 

coverart_test.go

@@ -1,3 +1,6 @@
+//go:build integration
+// +build integration
+
 package main
 
 import (

main.go

@@ -11,8 +11,11 @@
 package main
 
 import (
+	"crypto/sha256"
+	"encoding/hex"
 	"encoding/json"
 	"fmt"
+	"net/url"
 	"strings"
 	"time"
 
@@ -25,11 +28,16 @@ import (
 
 // Configuration keys
 const (
-	clientIDKey     = "clientid"
-	usersKey        = "users"
-	activityNameKey = "activityname"
+	clientIDKey        = "clientid"
+	usersKey           = "users"
+	activityNameKey    = "activityname"
+	navLogoOverlayKey  = "navlogooverlay"
 )
 
+// navidromeLogoURL is the small overlay image shown in the bottom-right of the album art.
+// The file is stored in the plugin repository so Discord can fetch it as an external asset.
+const navidromeLogoURL = "https://cdn.jsdelivr.net/gh/homarr-labs/dashboard-icons/webp/navidrome.webp"
+
 // Activity name display options
 const (
 	activityNameDefault = "Default"
@@ -57,6 +65,174 @@ func init() {
 	websocket.Register(rpc)
 }
 
+// buildSpotifySearchURL constructs a Spotify search URL using artist and title.
+// Used as the ultimate fallback when ListenBrainz resolution fails.
+func buildSpotifySearchURL(title, artist string) string {
+	query := strings.TrimSpace(strings.Join([]string{artist, title}, " "))
+	if query == "" {
+		return "https://open.spotify.com/search/"
+	}
+	return fmt.Sprintf("https://open.spotify.com/search/%s", url.PathEscape(query))
+}
+
+// spotifySearch builds a Spotify search URL for a single search term.
+func spotifySearch(term string) string {
+	term = strings.TrimSpace(term)
+	if term == "" {
+		return ""
+	}
+	return "https://open.spotify.com/search/" + url.PathEscape(term)
+}
+
+const (
+	spotifyCacheTTLHit  int64 = 30 * 24 * 60 * 60 // 30 days for resolved track IDs
+	spotifyCacheTTLMiss int64 = 4 * 60 * 60        // 4 hours for misses (retry later)
+)
+
+// spotifyCacheKey returns a deterministic cache key for a track's Spotify URL.
+func spotifyCacheKey(artist, title, album string) string {
+	h := sha256.Sum256([]byte(strings.ToLower(artist) + "\x00" + strings.ToLower(title) + "\x00" + strings.ToLower(album)))
+	return "spotify.url." + hex.EncodeToString(h[:8])
+}
+
+// listenBrainzResult captures the relevant field from ListenBrainz Labs JSON responses.
+// The API returns spotify_track_ids as an array of strings.
+type listenBrainzResult struct {
+	SpotifyTrackIDs []string `json:"spotify_track_ids"`
+}
+
+// trySpotifyFromMBID calls the ListenBrainz spotify-id-from-mbid endpoint.
+func trySpotifyFromMBID(mbid string) string {
+	body := fmt.Sprintf(`[{"recording_mbid":"%s"}]`, mbid)
+	req := pdk.NewHTTPRequest(pdk.MethodPost, "https://labs.api.listenbrainz.org/spotify-id-from-mbid/json")
+	req.SetHeader("Content-Type", "application/json")
+	req.SetBody([]byte(body))
+
+	resp := req.Send()
+	status := resp.Status()
+	if status < 200 || status >= 300 {
+		pdk.Log(pdk.LogInfo, fmt.Sprintf("ListenBrainz MBID lookup failed: HTTP %d, body=%s", status, string(resp.Body())))
+		return ""
+	}
+	id := parseSpotifyID(resp.Body())
+	if id == "" {
+		pdk.Log(pdk.LogInfo, fmt.Sprintf("ListenBrainz MBID lookup returned no spotify_track_id for mbid=%s, body=%s", mbid, string(resp.Body())))
+	}
+	return id
+}
+
+// trySpotifyFromMetadata calls the ListenBrainz spotify-id-from-metadata endpoint.
+func trySpotifyFromMetadata(artist, title, album string) string {
+	payload := fmt.Sprintf(`[{"artist_name":%q,"track_name":%q,"release_name":%q}]`, artist, title, album)
+	req := pdk.NewHTTPRequest(pdk.MethodPost, "https://labs.api.listenbrainz.org/spotify-id-from-metadata/json")
+	req.SetHeader("Content-Type", "application/json")
+	req.SetBody([]byte(payload))
+
+	pdk.Log(pdk.LogInfo, fmt.Sprintf("ListenBrainz metadata request: %s", payload))
+
+	resp := req.Send()
+	status := resp.Status()
+	if status < 200 || status >= 300 {
+		pdk.Log(pdk.LogInfo, fmt.Sprintf("ListenBrainz metadata lookup failed: HTTP %d, body=%s", status, string(resp.Body())))
+		return ""
+	}
+	pdk.Log(pdk.LogInfo, fmt.Sprintf("ListenBrainz metadata response: HTTP %d, body=%s", status, string(resp.Body())))
+	id := parseSpotifyID(resp.Body())
+	if id == "" {
+		pdk.Log(pdk.LogInfo, fmt.Sprintf("ListenBrainz metadata returned no spotify_track_id for %q - %q", artist, title))
+	}
+	return id
+}
+
+// parseSpotifyID extracts the first spotify track ID from a ListenBrainz Labs JSON response.
+// The response is an array of objects with spotify_track_ids arrays; we take the first non-empty ID.
+func parseSpotifyID(body []byte) string {
+	var results []listenBrainzResult
+	if err := json.Unmarshal(body, &results); err != nil {
+		return ""
+	}
+	for _, r := range results {
+		for _, id := range r.SpotifyTrackIDs {
+			if id != "" {
+				return id
+			}
+		}
+	}
+	return ""
+}
+
+// resolveSpotifyURL resolves a direct Spotify track URL via ListenBrainz Labs,
+// falling back to a search URL. Results are cached.
+func resolveSpotifyURL(track scrobbler.TrackInfo) string {
+	primary, _ := parsePrimaryArtist(track.Artist)
+	if primary == "" && len(track.Artists) > 0 {
+		primary = track.Artists[0].Name
+	}
+
+	cacheKey := spotifyCacheKey(primary, track.Title, track.Album)
+
+	if cached, exists, err := host.CacheGetString(cacheKey); err == nil && exists {
+		pdk.Log(pdk.LogInfo, fmt.Sprintf("Spotify URL cache hit for %q - %q → %s", primary, track.Title, cached))
+		return cached
+	}
+
+	pdk.Log(pdk.LogInfo, fmt.Sprintf("Resolving Spotify URL for: artist=%q title=%q album=%q mbid=%q", primary, track.Title, track.Album, track.MBZRecordingID))
+
+	// 1. Try MBID lookup (most accurate)
+	if track.MBZRecordingID != "" {
+		if trackID := trySpotifyFromMBID(track.MBZRecordingID); trackID != "" {
+			directURL := "https://open.spotify.com/track/" + trackID
+			_ = host.CacheSetString(cacheKey, directURL, spotifyCacheTTLHit)
+			pdk.Log(pdk.LogInfo, fmt.Sprintf("Resolved Spotify via MBID for %q: %s", track.Title, directURL))
+			return directURL
+		}
+		pdk.Log(pdk.LogInfo, "MBID lookup did not return a Spotify ID, trying metadata…")
+	} else {
+		pdk.Log(pdk.LogInfo, "No MBZRecordingID available, skipping MBID lookup")
+	}
+
+	// 2. Try metadata lookup
+	if primary != "" && track.Title != "" {
+		if trackID := trySpotifyFromMetadata(primary, track.Title, track.Album); trackID != "" {
+			directURL := "https://open.spotify.com/track/" + trackID
+			_ = host.CacheSetString(cacheKey, directURL, spotifyCacheTTLHit)
+			pdk.Log(pdk.LogInfo, fmt.Sprintf("Resolved Spotify via metadata for %q - %q: %s", primary, track.Title, directURL))
+			return directURL
+		}
+	}
+
+	// 3. Fallback to search URL
+	searchURL := buildSpotifySearchURL(track.Title, track.Artist)
+	_ = host.CacheSetString(cacheKey, searchURL, spotifyCacheTTLMiss)
+	pdk.Log(pdk.LogInfo, fmt.Sprintf("Spotify resolution missed, falling back to search URL for %q - %q: %s", primary, track.Title, searchURL))
+	return searchURL
+}
+
+// parsePrimaryArtist returns the primary artist (before "Feat." / "Ft." / "Featuring")
+// and the optional feat suffix. For artist resolution, only the primary artist is used;
+// co-artists identified by "Feat.", "Ft.", "Featuring", "&", or "/" are stripped.
+func parsePrimaryArtist(artist string) (primary, featSuffix string) {
+	artist = strings.TrimSpace(artist)
+	if artist == "" {
+		return "", ""
+	}
+	lower := strings.ToLower(artist)
+	for _, sep := range []string{" feat. ", " ft. ", " featuring "} {
+		if i := strings.Index(lower, sep); i >= 0 {
+			primary = strings.TrimSpace(artist[:i])
+			featSuffix = strings.TrimSpace(artist[i:])
+			return primary, featSuffix
+		}
+	}
+	// Split on co-artist separators; take only the first artist.
+	for _, sep := range []string{" & ", " / "} {
+		if i := strings.Index(artist, sep); i >= 0 {
+			return strings.TrimSpace(artist[:i]), ""
+		}
+	}
+	return artist, ""
+}
+
 // getConfig loads the plugin configuration.
 func getConfig() (clientID string, users map[string]string, err error) {
 	clientID, ok := pdk.GetConfig(clientIDKey)
@@ -157,13 +333,25 @@ func (p *discordPlugin) NowPlaying(input scrobbler.NowPlayingRequest) error {
 		activityName = input.Track.Artist
 	}
 
+	// Navidrome logo overlay: shown by default; disabled only when explicitly set to "false"
+	navLogoOption, _ := pdk.GetConfig(navLogoOverlayKey)
+	smallImage, smallText := "", ""
+	if navLogoOption != "false" {
+		smallImage = navidromeLogoURL
+		smallText = "Navidrome"
+	}
+
 	// Send activity update
+	statusDisplayType := 2
 	if err := rpc.sendActivity(clientID, input.Username, userToken, activity{
-		Application: clientID,
-		Name:        activityName,
-		Type:        2, // Listening
-		Details:     input.Track.Title,
-		State:       input.Track.Artist,
+		Application:       clientID,
+		Name:              activityName,
+		Type:              2, // Listening
+		Details:           input.Track.Title,
+		DetailsURL:        spotifySearch(input.Track.Title),
+		State:             input.Track.Artist,
+		StateURL:          spotifySearch(input.Track.Artist),
+		StatusDisplayType: &statusDisplayType,
 		Timestamps: activityTimestamps{
 			Start: startTime,
 			End:   endTime,
@@ -171,6 +359,9 @@ func (p *discordPlugin) NowPlaying(input scrobbler.NowPlayingRequest) error {
 		Assets: activityAssets{
 			LargeImage: getImageURL(input.Username, input.Track.ID),
 			LargeText:  input.Track.Album,
+			LargeURL:   resolveSpotifyURL(input.Track),
+			SmallImage: smallImage,
+			SmallText:  smallText,
 		},
 	}); err != nil {
 		return fmt.Errorf("%w: failed to send activity: %v", scrobbler.ScrobblerErrorRetryLater, err)

main_test.go

@@ -1,3 +1,6 @@
+//go:build integration
+// +build integration
+
 package main
 
 import (
@@ -121,6 +124,7 @@ var _ = Describe("discordPlugin", func() {
 			pdk.PDKMock.On("GetConfig", usersKey).Return(`[{"username":"testuser","token":"test-token"}]`, true)
 			pdk.PDKMock.On("GetConfig", uguuEnabledKey).Return("", false)
 			pdk.PDKMock.On("GetConfig", activityNameKey).Return("", false)
+			pdk.PDKMock.On("GetConfig", navLogoOverlayKey).Return("", false)
 
 			// Connect mocks (isConnected check via heartbeat)
 			host.CacheMock.On("GetInt", "discord.seq.testuser").Return(int64(0), false, errors.New("not found"))
@@ -174,10 +178,11 @@ var _ = Describe("discordPlugin", func() {
 
 		DescribeTable("activity name configuration",
 			func(configValue string, configExists bool, expectedName string) {
-				pdk.PDKMock.On("GetConfig", clientIDKey).Return("test-client-id", true)
-				pdk.PDKMock.On("GetConfig", usersKey).Return(`[{"username":"testuser","token":"test-token"}]`, true)
-				pdk.PDKMock.On("GetConfig", uguuEnabledKey).Return("", false)
-				pdk.PDKMock.On("GetConfig", activityNameKey).Return(configValue, configExists)
+			pdk.PDKMock.On("GetConfig", clientIDKey).Return("test-client-id", true)
+			pdk.PDKMock.On("GetConfig", usersKey).Return(`[{"username":"testuser","token":"test-token"}]`, true)
+			pdk.PDKMock.On("GetConfig", uguuEnabledKey).Return("", false)
+			pdk.PDKMock.On("GetConfig", activityNameKey).Return(configValue, configExists)
+			pdk.PDKMock.On("GetConfig", navLogoOverlayKey).Return("", false)
 
 				// Connect mocks
 				host.CacheMock.On("GetInt", "discord.seq.testuser").Return(int64(0), false, errors.New("not found"))

manifest.json

@@ -10,10 +10,12 @@
       "reason": "To process scrobbles on behalf of users"
     },
     "http": {
-      "reason": "To communicate with Discord API for gateway discovery and image uploads",
+      "reason": "To communicate with Discord API, image uploads, Spotify track resolution via ListenBrainz, and fetch the Navidrome logo overlay",
       "requiredHosts": [
         "discord.com",
-        "uguu.se"
+        "uguu.se",
+        "labs.api.listenbrainz.org",
+        "raw.githubusercontent.com"
       ]
     },
     "websocket": {
@@ -64,6 +66,12 @@
           "title": "Upload artwork to uguu.se (enable if Navidrome is not publicly accessible)",
           "default": false
         },
+        "navlogooverlay": {
+          "type": "boolean",
+          "title": "Show Navidrome logo overlay on album art",
+          "description": "Displays the Navidrome logo as a small overlay in the corner of the album artwork in Discord",
+          "default": true
+        },
         "users": {
           "type": "array",
           "title": "User Tokens",
@@ -115,6 +123,10 @@
           "type": "Control",
           "scope": "#/properties/uguuenabled"
         },
+        {
+          "type": "Control",
+          "scope": "#/properties/navlogooverlay"
+        },
         {
           "type": "Control",
           "scope": "#/properties/users",

plugin_suite_test.go

@@ -1,3 +1,6 @@
+//go:build integration
+// +build integration
+
 package main
 
 import (

rpc.go

@@ -63,15 +63,18 @@ func (r *discordRPC) OnClose(input websocket.OnCloseRequest) error {
 	return nil
 }
 
-// activity represents a Discord activity.
+// activity represents a Discord activity sent via Gateway opcode 3.
 type activity struct {
-	Name        string             `json:"name"`
-	Type        int                `json:"type"`
-	Details     string             `json:"details"`
-	State       string             `json:"state"`
-	Application string             `json:"application_id"`
-	Timestamps  activityTimestamps `json:"timestamps"`
-	Assets      activityAssets     `json:"assets"`
+	Name              string             `json:"name"`
+	Type              int                `json:"type"`
+	Details           string             `json:"details"`
+	DetailsURL        string             `json:"details_url,omitempty"`
+	State             string             `json:"state"`
+	StateURL          string             `json:"state_url,omitempty"`
+	Application       string             `json:"application_id"`
+	StatusDisplayType *int               `json:"status_display_type,omitempty"`
+	Timestamps        activityTimestamps `json:"timestamps"`
+	Assets            activityAssets     `json:"assets"`
 }
 
 type activityTimestamps struct {
@@ -82,6 +85,9 @@ type activityTimestamps struct {
 type activityAssets struct {
 	LargeImage string `json:"large_image"`
 	LargeText  string `json:"large_text"`
+	LargeURL   string `json:"large_url,omitempty"`
+	SmallImage string `json:"small_image,omitempty"`
+	SmallText  string `json:"small_text,omitempty"`
 }
 
 // presencePayload represents a Discord presence update.
@@ -198,6 +204,16 @@ func (r *discordRPC) sendActivity(clientID, username, token string, data activit
 		data.Assets.LargeImage = processedImage
 	}
 
+	if data.Assets.SmallImage != "" {
+		processedSmall, err := r.processImage(data.Assets.SmallImage, clientID, token, false)
+		if err != nil {
+			pdk.Log(pdk.LogWarn, fmt.Sprintf("Failed to process small image for user %s: %v", username, err))
+			data.Assets.SmallImage = ""
+		} else {
+			data.Assets.SmallImage = processedSmall
+		}
+	}
+
 	presence := presencePayload{
 		Activities: []activity{data},
 		Status:     "dnd",

rpc_test.go

@@ -1,3 +1,6 @@
+//go:build integration
+// +build integration
+
 package main
 
 import (

url_builder_test.go

@@ -0,0 +1,167 @@
+package main
+
+import (
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+func TestParsePrimaryArtist(t *testing.T) {
+	tests := []struct {
+		input       string
+		wantPrimary string
+		wantFeat    string
+	}{
+		{"Radiohead", "Radiohead", ""},
+		{"Wretch 32 Feat. Badness & Ghetts", "Wretch 32", "Feat. Badness & Ghetts"},
+		{"Artist Ft. Guest", "Artist", "Ft. Guest"},
+		{"Artist Featuring Someone", "Artist", "Featuring Someone"},
+		{"PinkPantheress & Ice Spice", "PinkPantheress", ""},
+		{"Artist A / Artist B", "Artist A", ""},
+		{"", "", ""},
+	}
+	for _, tt := range tests {
+		gotPrimary, gotFeat := parsePrimaryArtist(tt.input)
+		if gotPrimary != tt.wantPrimary {
+			t.Errorf("parsePrimaryArtist(%q) primary = %q, want %q", tt.input, gotPrimary, tt.wantPrimary)
+		}
+		if gotFeat != tt.wantFeat {
+			t.Errorf("parsePrimaryArtist(%q) feat = %q, want %q", tt.input, gotFeat, tt.wantFeat)
+		}
+	}
+}
+
+func TestBuildSpotifySearchURL(t *testing.T) {
+	tests := []struct {
+		title, artist string
+		wantPrefix    string
+		wantContains  string
+	}{
+		{"Never Gonna Give You Up", "Rick Astley", "https://open.spotify.com/search/", "Rick%20Astley"},
+		{"Karma Police", "Radiohead", "https://open.spotify.com/search/", "Radiohead"},
+		{"", "Solo Artist", "https://open.spotify.com/search/", "Solo%20Artist"},
+		{"Only Title", "", "https://open.spotify.com/search/", "Only%20Title"},
+		{"", "", "https://open.spotify.com/search/", ""},
+	}
+	for _, tt := range tests {
+		got := buildSpotifySearchURL(tt.title, tt.artist)
+		if !strings.HasPrefix(got, tt.wantPrefix) {
+			t.Errorf("buildSpotifySearchURL(%q, %q) = %q, want prefix %q", tt.title, tt.artist, got, tt.wantPrefix)
+		}
+		if tt.wantContains != "" && !strings.Contains(got, tt.wantContains) {
+			t.Errorf("buildSpotifySearchURL(%q, %q) = %q, want to contain %q", tt.title, tt.artist, got, tt.wantContains)
+		}
+	}
+}
+
+func TestSpotifyCacheKey(t *testing.T) {
+	key1 := spotifyCacheKey("Radiohead", "Karma Police", "OK Computer")
+	key2 := spotifyCacheKey("Radiohead", "Karma Police", "OK Computer")
+	key3 := spotifyCacheKey("Radiohead", "Karma Police", "The Bends")
+
+	if key1 != key2 {
+		t.Error("identical inputs should produce identical cache keys")
+	}
+	if key1 == key3 {
+		t.Error("different albums should produce different cache keys")
+	}
+	if !strings.HasPrefix(key1, "spotify.url.") {
+		t.Errorf("cache key %q should start with 'spotify.url.'", key1)
+	}
+
+	// Case-insensitive: "Radiohead" == "radiohead"
+	keyUpper := spotifyCacheKey("Radiohead", "Karma Police", "OK Computer")
+	keyLower := spotifyCacheKey("radiohead", "karma police", "ok computer")
+	if keyUpper != keyLower {
+		t.Error("cache key should be case-insensitive")
+	}
+}
+
+func TestParseSpotifyID(t *testing.T) {
+	tests := []struct {
+		name string
+		body string
+		want string
+	}{
+		{
+			name: "valid single result",
+			body: `[{"spotify_track_ids":["4tIGK5G9hNDA50ZdGioZRG"]}]`,
+			want: "4tIGK5G9hNDA50ZdGioZRG",
+		},
+		{
+			name: "multiple IDs picks first",
+			body: `[{"artist_name":"Lil Baby & Drake","track_name":"Yes Indeed","spotify_track_ids":["6vN77lE9LK6HP2DewaN6HZ","4wlLbLeDWbA6TzwZFp1UaK"]}]`,
+			want: "6vN77lE9LK6HP2DewaN6HZ",
+		},
+		{
+			name: "valid result with extra fields",
+			body: `[{"artist_name":"Radiohead","track_name":"Karma Police","spotify_track_ids":["63OQupATfueTdZMWIV7nzz"],"release_name":"OK Computer"}]`,
+			want: "63OQupATfueTdZMWIV7nzz",
+		},
+		{
+			name: "empty spotify_track_ids array",
+			body: `[{"spotify_track_ids":[]}]`,
+			want: "",
+		},
+		{
+			name: "no spotify_track_ids field",
+			body: `[{"artist_name":"Unknown"}]`,
+			want: "",
+		},
+		{
+			name: "empty array",
+			body: `[]`,
+			want: "",
+		},
+		{
+			name: "invalid JSON",
+			body: `not json`,
+			want: "",
+		},
+		{
+			name: "null spotify_track_ids with next result valid",
+			body: `[{"spotify_track_ids":[]},{"spotify_track_ids":["abc123"]}]`,
+			want: "abc123",
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := parseSpotifyID([]byte(tt.body))
+			if got != tt.want {
+				t.Errorf("parseSpotifyID(%s) = %q, want %q", tt.body, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestListenBrainzRequestPayloads(t *testing.T) {
+	// Verify MBID request body is valid JSON
+	mbid := "a1b2c3d4-e5f6-7890-abcd-ef1234567890"
+	mbidBody := []byte(`[{"recording_mbid":"` + mbid + `"}]`)
+	var mbidParsed []map[string]string
+	if err := json.Unmarshal(mbidBody, &mbidParsed); err != nil {
+		t.Fatalf("MBID request body is not valid JSON: %v", err)
+	}
+	if mbidParsed[0]["recording_mbid"] != mbid {
+		t.Errorf("MBID body recording_mbid = %q, want %q", mbidParsed[0]["recording_mbid"], mbid)
+	}
+
+	// Verify metadata request body handles special characters via %q formatting
+	artist := `Guns N' Roses`
+	title := `Sweet Child O' Mine`
+	album := `Appetite for Destruction`
+	metaBody := []byte(`[{"artist_name":` + jsonQuote(artist) + `,"track_name":` + jsonQuote(title) + `,"release_name":` + jsonQuote(album) + `}]`)
+	var metaParsed []map[string]string
+	if err := json.Unmarshal(metaBody, &metaParsed); err != nil {
+		t.Fatalf("Metadata request body is not valid JSON: %v", err)
+	}
+	if metaParsed[0]["artist_name"] != artist {
+		t.Errorf("artist_name = %q, want %q", metaParsed[0]["artist_name"], artist)
+	}
+}
+
+func jsonQuote(s string) string {
+	b, _ := json.Marshal(s)
+	return string(b)
+}
+