internal/api/admin_duplicates.go

@@ -22,6 +22,7 @@ import (
 type duplicateMemberView struct {
 	TrackID     string `json:"track_id"`
 	Title       string `json:"title"`
+	ArtistID    string `json:"artist_id"`
 	ArtistName  string `json:"artist_name"`
 	AlbumID     string `json:"album_id"`
 	AlbumTitle  string `json:"album_title"`
@@ -34,6 +35,9 @@ type duplicateMemberView struct {
 	PlayCount   int64  `json:"play_count"`
 	DiscNumber  *int32 `json:"disc_number"`
 	TrackNumber *int32 `json:"track_number"`
+	// StreamURL lets the review play each copy, to hear whether they are the
+	// same song (#6168).
+	StreamURL string `json:"stream_url"`
 }
 
 // duplicateGroupView is one proposal. SurvivorTrackID and SurvivorReason are
@@ -277,6 +281,7 @@ func foldDuplicateGroups(rows []dbq.ListPendingDuplicateGroupMembersRow) []dupli
 		groups[n].Members = append(groups[n].Members, duplicateMemberView{
 			TrackID:     trackID,
 			Title:       row.Title,
+			ArtistID:    uuidToString(row.ArtistID),
 			ArtistName:  row.ArtistName,
 			AlbumID:     uuidToString(row.AlbumID),
 			AlbumTitle:  row.AlbumTitle,
@@ -289,6 +294,7 @@ func foldDuplicateGroups(rows []dbq.ListPendingDuplicateGroupMembersRow) []dupli
 			PlayCount:   row.PlayCount,
 			DiscNumber:  row.DiscNumber,
 			TrackNumber: row.TrackNumber,
+			StreamURL:   streamURL(row.TrackID),
 		})
 		candidates[n] = append(candidates[n], library.SurvivorCandidate{
 			TrackID: trackID, FileFormat: row.FileFormat, FileSize: row.FileSize, AddedAt: row.AddedAt.Time,

internal/db/dbq/duplicates.sql.go

@@ -464,6 +464,7 @@ SELECT p.id                  AS group_id,
                   AND o.track_number = t.track_number)::boolean AS position_clash,
        t.id                  AS track_id,
        t.title,
+       artists.id            AS artist_id,
        artists.name          AS artist_name,
        albums.id             AS album_id,
        albums.title          AS album_title,
@@ -501,6 +502,7 @@ type ListPendingDuplicateGroupMembersRow struct {
 	PositionClash     bool
 	TrackID           pgtype.UUID
 	Title             string
+	ArtistID          pgtype.UUID
 	ArtistName        string
 	AlbumID           pgtype.UUID
 	AlbumTitle        string
@@ -540,6 +542,7 @@ func (q *Queries) ListPendingDuplicateGroupMembers(ctx context.Context, arg List
 			&i.PositionClash,
 			&i.TrackID,
 			&i.Title,
+			&i.ArtistID,
 			&i.ArtistName,
 			&i.AlbumID,
 			&i.AlbumTitle,

internal/db/queries/duplicates.sql

@@ -160,6 +160,7 @@ SELECT p.id                  AS group_id,
                   AND o.track_number = t.track_number)::boolean AS position_clash,
        t.id                  AS track_id,
        t.title,
+       artists.id            AS artist_id,
        artists.name          AS artist_name,
        albums.id             AS album_id,
        albums.title          AS album_title,

web/src/lib/api/types.ts

@@ -433,6 +433,7 @@ export type AdminSuspectResponse = {
 export type AdminDuplicateMember = {
   track_id: string;
   title: string;
+  artist_id: string;
   artist_name: string;
   album_id: string;
   album_title: string;
@@ -445,6 +446,8 @@ export type AdminDuplicateMember = {
   play_count: number;
   disc_number: number | null;
   track_number: number | null;
+  // To play each copy from the review (#6168).
+  stream_url: string;
 };
 
 // The resolver's verdict on a group (M498). null until its first pass.

web/src/routes/collection/duplicates/+page.svelte

@@ -2,7 +2,8 @@
   import { plural } from '#lib/utils/plural.js';
   import { page } from '$app/state';
   import { pageTitle } from '#lib/branding.js';
-  import { Copy, Info, TriangleAlert } from 'lucide-svelte';
+  import { Copy, Info, Play, TriangleAlert } from 'lucide-svelte';
+  import { playQueue } from '#lib/player/store.svelte.js';
   import {
     createDuplicatesQuery,
     createResolvedDuplicatesQuery,
@@ -19,6 +20,7 @@
     AdminDuplicateGroup,
     AdminDuplicateMember,
     DuplicatesView,
+    TrackRef,
     ResolvedDuplicateActivity
   } from '#lib/api/types.js';
   import ListContinuation from '#lib/components/ListContinuation.svelte';
@@ -127,19 +129,35 @@
   // "Identical audio" and "same recording" are different claims, and an
   // operator deciding whether to merge needs to know which one they are
   // looking at before anything else.
-  function tierLabel(g: AdminDuplicateGroup): string {
-    if (g.tier === 'exact') return 'Identical audio';
-    const match = Math.round((1 - (g.worst_bit_error_rate ?? 0)) * 100);
-    return `Same recording · ${match}% match`;
+  function matchPercent(g: AdminDuplicateGroup): number {
+    return Math.round((1 - (g.worst_bit_error_rate ?? 0)) * 100);
   }
 
-  // Identical audio under different titles means at least one file's tags are
+  function tierLabel(g: AdminDuplicateGroup): string {
+    if (g.tier === 'exact') return 'Identical audio';
+    return `Same music · ${matchPercent(g)}% match`;
+  }
+
+  // What the match rests on, said outright: the copies' sizes and lengths sit
+  // beside them, and an operator reading only those took the match for a guess
+  // made from them (2026-10-20, #6168).
+  function evidence(g: AdminDuplicateGroup): string {
+    if (g.tier === 'exact') {
+      return 'Matched on the audio itself: these files hold the same audio data, byte for byte, once their tags are set aside.';
+    }
+    return `Matched by listening, not by size or length: ${matchPercent(g)}% of their audio fingerprints agree, so these files play the same music.`;
+  }
+
+  // The same audio under different titles means at least one file's tags are
   // wrong, and the recording the other title names may not be in the library at
   // all. #3885: "WWW" was a second copy of the instrumental, and the vocal was
-  // missing with nothing to say so. Exact tier only: an acoustic match spans
-  // encodings, where a "Remastered" suffix is routine rather than a lie.
+  // missing with nothing to say so. Savant's Mortals held one recording as 16
+  // of its tracks, each cut to its own song's length (#6169). An acoustic match
+  // spans encodings, where a "Remastered" suffix is routine rather than a lie,
+  // so there it is raised only when the resolver found different songs on one
+  // album (class mismatch).
   function differingTitles(g: AdminDuplicateGroup): string[] {
-    if (g.tier !== 'exact') return [];
+    if (g.tier !== 'exact' && g.class !== 'mismatch') return [];
     const byKey = new Map<string, string>();
     for (const m of g.members) {
       const title = m.title.trim().replace(/\s+/g, ' ');
@@ -170,6 +188,21 @@
   function basename(path: string): string {
     return path.slice(path.lastIndexOf('/') + 1);
   }
+
+  // Hearing the copies settles what the fingerprints claim (#6168).
+  function play(m: AdminDuplicateMember) {
+    const track: TrackRef = {
+      id: m.track_id,
+      title: m.title,
+      album_id: m.album_id,
+      album_title: m.album_title,
+      artist_id: m.artist_id,
+      artist_name: m.artist_name,
+      duration_sec: m.duration_sec,
+      stream_url: m.stream_url
+    };
+    playQueue([track], 0);
+  }
 </script>
 
 <svelte:head><title>{pageTitle('Collection · Duplicates')}</title></svelte:head>
@@ -378,6 +411,10 @@
             </p>
           {/if}
 
+          <p class="border-b border-border px-4 py-3 text-xs text-text-secondary" data-testid="match-evidence">
+            {evidence(group)}
+          </p>
+
           {#if titles.length > 0}
             <p
               class="flex items-start gap-2 border-b border-border bg-surface-hover px-4 py-3 text-xs text-text-secondary"
@@ -385,9 +422,10 @@
             >
               <TriangleAlert size={14} class="mt-0.5 shrink-0 text-warning-fg" aria-hidden="true" />
               <span>
-                The audio is identical, but the copies are titled {quotedList(titles)}. If those
-                name different recordings, one file is mislabelled and the other recording isn't in
-                your library. Keep the copy whose title matches what you hear.
+                {group.tier === 'exact' ? 'The audio is identical' : 'The music is the same'}, but the
+                copies are titled {quotedList(titles)}. If those name different recordings, one file is
+                mislabelled and the other recording isn't in your library. Play each and keep the copy
+                whose title matches what you hear.
               </span>
             </p>
           {/if}
@@ -445,6 +483,15 @@
                     {m.file_path}
                   </div>
                 </div>
+                <button
+                  type="button"
+                  onclick={() => play(m)}
+                  class="mt-0.5 shrink-0 rounded-md p-1.5 text-text-secondary hover:bg-surface-hover hover:text-text-primary"
+                  aria-label="Play {m.title}"
+                  data-testid="member-play"
+                >
+                  <Play size={16} aria-hidden="true" />
+                </button>
                 <div class="shrink-0 space-y-0.5 text-right text-xs text-text-muted">
                   <div data-testid="member-file">{m.file_format.toUpperCase()} · {formatBytes(m.file_size)} · {formatDuration(m.duration_sec)}</div>
                   <div data-testid="member-history">{historyLabel(m)}</div>

web/src/routes/collection/duplicates/duplicates.test.ts

@@ -17,8 +17,10 @@ vi.mock('#lib/api/admin.js', () => ({
     removed_paths: ['/music/Moe Shop/WWW (2020)/www-02.mp3']
   })
 }));
+vi.mock('#lib/player/store.svelte.js', () => ({ playQueue: vi.fn() }));
 
 import AdminDuplicatesPage from './+page.svelte';
+import { playQueue } from '#lib/player/store.svelte.js';
 import {
   createDuplicatesQuery,
   createResolvedDuplicatesQuery,
@@ -45,6 +47,7 @@ function member(id: string, extra: Partial<AdminDuplicatesResponse['groups'][num
   return {
     track_id: id,
     title: 'WWW',
+    artist_id: 'ar-1',
     artist_name: 'Moe Shop',
     album_id: 'al-1',
     album_title: 'WWW',
@@ -57,6 +60,7 @@ function member(id: string, extra: Partial<AdminDuplicatesResponse['groups'][num
     play_count: 0,
     disc_number: null,
     track_number: null,
+    stream_url: `/api/tracks/${id}/stream`,
     ...extra
   };
 }
@@ -164,7 +168,30 @@ describe('admin duplicates', () => {
     const r = response();
     r.groups[0] = { ...r.groups[0], tier: 'acoustic', worst_bit_error_rate: 0.04 };
     renderWith(r);
-    expect(text(screen.getByTestId('duplicate-tier'))).toBe('Same recording · 96% match');
+    expect(text(screen.getByTestId('duplicate-tier'))).toBe('Same music · 96% match');
+  });
+
+  // The operator took the match for a guess from size and length (#6168).
+  test('each group says what the match rests on', () => {
+    const r = response();
+    r.groups.push({ ...r.groups[0], id: 'g-2', tier: 'acoustic', worst_bit_error_rate: 0.04 });
+    renderWith(r);
+    const lines = screen.getAllByTestId('match-evidence').map(text);
+    expect(lines[0]).toContain('the same audio data, byte for byte');
+    expect(lines[1]).toBe(
+      'Matched by listening, not by size or length: 96% of their audio fingerprints agree, so these files play the same music.'
+    );
+  });
+
+  test('each copy can be played', async () => {
+    renderWith(response());
+    const plays = screen.getAllByTestId('member-play');
+    expect(plays).toHaveLength(2);
+    await fireEvent.click(plays[1]);
+    expect(playQueue).toHaveBeenLastCalledWith(
+      [expect.objectContaining({ id: 'www-02', artist_id: 'ar-1', stream_url: '/api/tracks/www-02/stream' })],
+      0
+    );
   });
 
   // #3885: identical audio titled "WWW" and "WWW (instrumental)". One file
@@ -220,6 +247,17 @@ describe('admin duplicates', () => {
       renderWith(r);
       expect(screen.queryByTestId('title-mismatch')).toBeNull();
     });
+
+    // Unless the resolver found different songs on one album: Savant's Mortals
+    // held one recording as 16 tracks, each cut to its own song's length (#6169).
+    test('an acoustic group the resolver found to be different songs says so', () => {
+      const r = www();
+      r.groups[0] = { ...r.groups[0], tier: 'acoustic', worst_bit_error_rate: 0, class: 'mismatch' };
+      renderWith(r);
+      const notice = text(screen.getByTestId('title-mismatch'));
+      expect(notice).toContain('The music is the same, but the copies are titled “WWW” and “WWW (instrumental)”');
+      expect(notice).toContain('Play each');
+    });
   });
 
   // Three states all show zero groups. Each must say which it is.