Fix: a '/' in a song title was treated as a path separator (#835)

YouTube/Tidal/Qobuz results encode the name as ``id||title``. When the title
itself contains a '/' (e.g. the Sawano AoT track "YouSeeBIGGIRL/T:T"), two places
wrongly basename-split it on the slash and kept only the last segment ("T:T"):

- core/downloads/file_finder.py — the completed-download finder truncated its
  search target to "T:T", so the real on-disk file (slash sanitised by the
  writer) never matched → "not found after processing" → the download got
  QUARANTINED. Now an encoded ``id||title`` keeps the whole title as the target
  and contributes no remote-directory components; real Soulseek PATHS still get
  basename + dir extraction unchanged.
- webui/static/downloads.js — the manual-search FILE column showed only "T:T".
  Added a ``||``-aware short-label helper (mirrors the correct handling already
  used elsewhere in the file); real file paths still show their basename.

Tests: the finder locates "YouSeeBIGGIRL∕T: T.mp3" from the encoded title
"…||YouSeeBIGGIRL/T:T" (the screenshot case), doesn't match an unrelated file,
and a genuine Soulseek path still resolves to its last segment. 21 finder tests
+ 64 script-split integrity tests pass.

core/downloads/file_finder.py

@@ -83,15 +83,17 @@ def _normalize_for_finding(text: str) -> str:
 
 
 def _extract_basename(api_filename: str) -> str:
-    """Cross-platform rightmost-separator split, with YouTube /
-    Tidal ``id||title`` encoded filenames pre-normalised — the id
-    half is stripped so the title becomes the basename. Mirrors
-    the strip-then-split order ``web_server`` used."""
+    """Cross-platform rightmost-separator split for a real remote PATH.
+
+    A YouTube/Tidal/Qobuz ``id||title`` encoded filename is handled by
+    returning the title VERBATIM: the title is not a filesystem path, so a '/'
+    in it (e.g. the Sawano track ``YouSeeBIGGIRL/T:T``) is part of the name and
+    must NOT be split on (issue #835)."""
     if not api_filename:
         return ""
     if '||' in api_filename:
         _id, title = api_filename.split('||', 1)
-        api_filename = title
+        return title
     last_slash = max(api_filename.rfind('/'), api_filename.rfind('\\'))
     return api_filename[last_slash + 1:] if last_slash != -1 else api_filename
 
@@ -236,14 +238,23 @@ def find_completed_audio_file(
     ``None`` when the file isn't found anywhere — callers should
     treat that as "not yet" (still mid-write) or "lost".
     """
-    # YouTube / Tidal encoded filenames carry the id ahead of ``||``.
-    # Strip it up front so basename + dir-component extraction both
-    # operate on the title half.
+    # YouTube / Tidal / Qobuz encoded filenames carry the id ahead of ``||``.
+    # The title half is NOT a filesystem path: a '/' in it (e.g. the Sawano
+    # track ``YouSeeBIGGIRL/T:T``) is part of the title, so it must NOT be
+    # basename-split or read as a remote directory component — doing so
+    # truncated the search target to ``T:T`` and the real file was never found,
+    # quarantining valid downloads (issue #835). Real remote paths (Soulseek)
+    # still get basename + dir-component extraction.
+    encoded_title = None
     if api_filename and '||' in api_filename:
-        _id, api_filename = api_filename.split('||', 1)
-    target_basename = _extract_basename(api_filename)
+        _id, encoded_title = api_filename.split('||', 1)
+    if encoded_title is not None:
+        target_basename = encoded_title
+        api_dirs = []
+    else:
+        target_basename = _extract_basename(api_filename)
+        api_dirs = _api_dir_parts(api_filename)
     normalized_target = _normalize_for_finding(target_basename)
-    api_dirs = _api_dir_parts(api_filename)
 
     best_dl_path, dl_sim = _search_in_directory(
         download_dir, 'downloads', target_basename, normalized_target, api_dirs,

tests/downloads/test_file_finder.py

@@ -343,3 +343,56 @@ def test_fuzzy_rejects_low_similarity(tmp_path):
 
 if __name__ == '__main__':
     pytest.main([__file__, '-v'])
+
+
+# ---------------------------------------------------------------------------
+# Issue #835 — a '/' in a YouTube/Tidal title is part of the NAME, not a path
+# separator. The encoded ``id||title`` finder previously basename-split the
+# title ("YouSeeBIGGIRL/T:T" -> "T:T"), so the real on-disk file (with the
+# slash sanitised) never matched and valid downloads got quarantined.
+# ---------------------------------------------------------------------------
+
+from core.downloads.file_finder import _extract_basename
+
+
+def test_encoded_title_with_slash_is_not_basename_split():
+    # The Sawano AoT track. The id||title encoding must keep the whole title.
+    assert _extract_basename('vy63u2hKoPE||YouSeeBIGGIRL/T:T') == 'YouSeeBIGGIRL/T:T'
+
+
+def test_finds_youtube_file_whose_title_contains_a_slash(tmp_path):
+    downloads = tmp_path / 'downloads'
+    # On disk the slash is sanitised to a look-alike and the colon spaced out,
+    # exactly as in the issue screenshot.
+    target = downloads / 'YouSeeBIGGIRL∕T: T.mp3'
+    _touch(target)
+
+    found, location = find_completed_audio_file(
+        str(downloads), 'vy63u2hKoPE||YouSeeBIGGIRL/T:T',
+    )
+
+    assert found == str(target), 'pre-#835 this truncated the target to "T:T" and missed the file'
+    assert location == 'downloads'
+
+
+def test_slash_title_does_not_match_an_unrelated_file(tmp_path):
+    # Guard against the fix being too loose: a different track must NOT match.
+    downloads = tmp_path / 'downloads'
+    _touch(downloads / 'Some Totally Different Song.mp3')
+
+    found, _ = find_completed_audio_file(
+        str(downloads), 'vy63u2hKoPE||YouSeeBIGGIRL/T:T',
+    )
+    assert found is None
+
+
+def test_real_soulseek_path_still_basenamed(tmp_path):
+    # Regression: a genuine remote PATH must still resolve to its last segment.
+    downloads = tmp_path / 'downloads'
+    target = downloads / '01 - Suddenly.flac'
+    _touch(target)
+    assert _extract_basename(r'shared\Billy Ocean\Very Best Of\01 - Suddenly.flac') == '01 - Suddenly.flac'
+    found, _ = find_completed_audio_file(
+        str(downloads), r'shared\Billy Ocean\Very Best Of\01 - Suddenly.flac',
+    )
+    assert found == str(target)

webui/static/downloads.js

@@ -3060,8 +3060,19 @@ function _candidatesFmtDur(ms) {
 // rows (different click binding scope). ``showSourceBadge`` adds a small
 // per-row source pill — used in hybrid "All sources" mode where the user
 // otherwise can't tell which source a row came from.
+// Display label for a candidate's filename. Encoded ``id||title`` sources
+// (youtube/tidal/qobuz/hifi) carry the title after ``||`` — a '/' in that title
+// is part of the name, NOT a path separator, so it must not be basename-split
+// (issue #835: "YouSeeBIGGIRL/T:T" was showing as just "T:T"). Real file paths
+// (Soulseek) keep the rightmost-segment basename.
+function _ssShortFileLabel(filename) {
+    if (!filename) return '-';
+    if (filename.includes('||')) return filename.split('||').slice(1).join('||');
+    return filename.split(/[/\\]/).pop();
+}
+
 function _renderCandidateRow(c, index, rowClass, showSourceBadge) {
-    const shortFile = c.filename ? c.filename.split(/[/\\]/).pop() : '-';
+    const shortFile = _ssShortFileLabel(c.filename);
     const qBadge = c.quality
         ? `<span class="candidates-quality-badge candidates-quality-${c.quality.toLowerCase()}">${c.quality.toUpperCase()}</span>`
         : '';