feat(discover): explain the taste match on both clients — #2377 (clients)

"Matches your taste in shoegaze and dream pop." replaces the seed
attribution when the candidate's own tags overlap the taste profile.

The preference order is the point of slice 6: the tag reason describes the
MUSIC ("sounds like what you like"), while seed attribution describes the
graph ("adjacent to something you played"). When we can say the former, it
is strictly the better explanation. When we can't — the common case, since
tag coverage for out-of-library artists is partial by nature (#2376) — the
card falls back to attribution rather than going blank.

Both clients share the wording, Oxford comma included, and both have tests
asserting the exact strings. That's deliberate: identical copy across two
codebases silently diverges unless something fails when it does.

Android caps at 3 tags client-side even though the server already does.
The server contract could widen; a run-on subtitle shouldn't be how we
find out.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/fabledsword/minstrel/discover/data/DiscoverRepository.kt

@@ -179,6 +179,7 @@ private fun ArtistSuggestionWire.toDomain(): ArtistSuggestionRef = ArtistSuggest
     name = name,
     imageUrl = imageUrl,
     attribution = attribution.map { it.toDomain() },
+    matchedTags = matchedTags,
 )
 
 private fun SeedContributionWire.toDomain(): SeedContributionRef = SeedContributionRef(

android/app/src/main/java/com/fabledsword/minstrel/discover/ui/DiscoverTiles.kt

@@ -61,7 +61,7 @@ internal fun SuggestionTile(
             // Once parked, the "because you liked X" line is no longer the
             // useful thing to say — confirming what just happened is.
             val secondary =
-                if (snoozed) "Not right now — hidden for a while" else s.attributionText
+                if (snoozed) "Not right now — hidden for a while" else s.reasonText
             if (secondary.isNotEmpty()) {
                 Text(
                     text = secondary,

android/app/src/main/java/com/fabledsword/minstrel/models/Discover.kt

@@ -52,6 +52,8 @@ data class ArtistSuggestionRef(
     val name: String,
     val imageUrl: String = "",
     val attribution: List<SeedContributionRef> = emptyList(),
+    /** Taste-profile tags this candidate matches, strongest first (#2377). */
+    val matchedTags: List<String> = emptyList(),
 ) {
     val attributionText: String
         get() {
@@ -66,6 +68,30 @@ data class ArtistSuggestionRef(
             }
         }
 
+    /**
+     * The subtitle line for the card.
+     *
+     * Prefers the taste-tag reason over seed attribution when we have one,
+     * because it describes the MUSIC ("sounds like what you like") rather than
+     * the graph ("adjacent to something you played") — the whole point of
+     * milestone #268 slice 6. Falls back to attribution, which is the common
+     * case: tag coverage for out-of-library artists is partial by nature
+     * (#2376), so most candidates have no matched tags.
+     *
+     * Kept in lockstep with the web client's reasonText() in
+     * SuggestionFeed.svelte — same wording, same Oxford comma.
+     */
+    val reasonText: String
+        get() {
+            val tags = matchedTags.take(MAX_ATTRIBUTION_PHRASES)
+            return when (tags.size) {
+                0 -> attributionText
+                1 -> "Matches your taste in ${tags[0]}."
+                2 -> "Matches your taste in ${tags[0]} and ${tags[1]}."
+                else -> "Matches your taste in ${tags[0]}, ${tags[1]}, and ${tags[2]}."
+            }
+        }
+
     companion object {
         private const val MAX_ATTRIBUTION_PHRASES = 3
     }

android/app/src/main/java/com/fabledsword/minstrel/models/wire/DiscoverWire.kt

@@ -35,6 +35,13 @@ data class ArtistSuggestionWire(
     val name: String = "",
     @SerialName("image_url") val imageUrl: String = "",
     val attribution: List<SeedContributionWire> = emptyList(),
+    /**
+     * Tags this candidate shares with the user's taste profile, strongest
+     * first (max 3, #2377). Absent for most candidates — tag coverage for
+     * out-of-library artists is partial by nature (#2376) — so the default
+     * empty list is the common case, not an error.
+     */
+    @SerialName("matched_tags") val matchedTags: List<String> = emptyList(),
 )
 
 /**

android/app/src/test/java/com/fabledsword/minstrel/models/ArtistSuggestionReasonTest.kt

@@ -0,0 +1,85 @@
+package com.fabledsword.minstrel.models
+
+import org.junit.jupiter.api.Test
+import kotlin.test.assertEquals
+
+/**
+ * The card's subtitle line (#2377). Wording is kept in lockstep with the web
+ * client's reasonText() in SuggestionFeed.svelte — these assertions are the
+ * record of what that wording IS, so a change on one client without the other
+ * shows up as a failure rather than as silent divergence between the two
+ * surfaces.
+ */
+class ArtistSuggestionReasonTest {
+
+    private val seeds = listOf(
+        SeedContributionRef(name = "Seed", isLiked = true),
+    )
+
+    private fun suggestion(
+        matched: List<String> = emptyList(),
+        attribution: List<SeedContributionRef> = seeds,
+    ) = ArtistSuggestionRef(
+        mbid = "mb",
+        name = "Candidate",
+        attribution = attribution,
+        matchedTags = matched,
+    )
+
+    @Test
+    fun `one matched tag reads in the singular`() {
+        assertEquals(
+            "Matches your taste in shoegaze.",
+            suggestion(matched = listOf("shoegaze")).reasonText,
+        )
+    }
+
+    @Test
+    fun `two matched tags join with and`() {
+        assertEquals(
+            "Matches your taste in shoegaze and dream pop.",
+            suggestion(matched = listOf("shoegaze", "dream pop")).reasonText,
+        )
+    }
+
+    @Test
+    fun `three matched tags use an Oxford comma`() {
+        assertEquals(
+            "Matches your taste in a, b, and c.",
+            suggestion(matched = listOf("a", "b", "c")).reasonText,
+        )
+    }
+
+    // The server caps at 3, but the client must not render a run-on line if a
+    // future server sends more.
+    @Test
+    fun `more than three matched tags are capped at three`() {
+        assertEquals(
+            "Matches your taste in a, b, and c.",
+            suggestion(matched = listOf("a", "b", "c", "d", "e")).reasonText,
+        )
+    }
+
+    // The COMMON case: most candidates have no cached tags (#2376), so the card
+    // must fall back to seed attribution rather than going blank.
+    @Test
+    fun `no matched tags falls back to seed attribution`() {
+        assertEquals("Because you liked Seed.", suggestion().reasonText)
+    }
+
+    // Nothing to say at all — a candidate with neither tags nor attribution
+    // yields an empty line, which the tile suppresses rather than rendering as
+    // a blank row.
+    @Test
+    fun `neither tags nor attribution yields an empty line`() {
+        assertEquals("", suggestion(attribution = emptyList()).reasonText)
+    }
+
+    // The taste reason WINS over attribution when both exist: describing the
+    // music beats describing the similarity graph.
+    @Test
+    fun `a taste match supersedes seed attribution`() {
+        val got = suggestion(matched = listOf("shoegaze")).reasonText
+        assertEquals("Matches your taste in shoegaze.", got)
+    }
+}