HiFi preview: abort the source, don't cascade to a lower-tier preview — #895

The log from a fresh run showed detection working but a second bug: rejecting the
lossless preview ('decoded 30s of 180s — rejecting') just dropped to the SAME track's
'high' (lossy m4a) tier — the same 30s clip — which the bitrate check can't see (m4a,
not FLAC), so it was accepted. A preview at any tier means the SOURCE only has a
preview of the track; lower tiers are the same clip. So on preview detection (manifest
OR post-download) we now return None to FAIL HiFi entirely, letting the orchestrator's
hybrid fallback try the next SOURCE (soulseek/youtube) instead of landing a lower-tier
preview. (A genuinely-missing tier still falls through to the next tier as before.)

Integration test drives the post-download abort end-to-end and pins 'no tier cascade'.

core/hifi_client.py

@@ -984,14 +984,16 @@ class HiFiClient(DownloadSourcePlugin):
                 continue
 
             # Preview guard #1 (pre-download): a preview manifest serves only ~30s of
-            # segments for a full-length track. Catch it from the EXTINF sum before
-            # wasting the download, so the orchestrator falls through to the next source.
+            # segments for a full-length track. A preview means THIS SOURCE only has a
+            # preview of the track — lower quality tiers are the SAME preview — so abort
+            # HiFi entirely and let the orchestrator fall through to the next SOURCE
+            # (soulseek/youtube/…), rather than landing a lower-tier preview.
             manifest_s = float(manifest_info.get('manifest_duration') or 0)
             if is_short_audio(manifest_s, expected_s):
                 logger.warning(
-                    "HiFi served a PREVIEW manifest at %s for '%s' (%.0fs of %.0fs) — skipping",
-                    q_key, display_name, manifest_s, expected_s)
-                continue
+                    "HiFi has only a PREVIEW of '%s' (manifest %.0fs of %.0fs at %s) — "
+                    "failing HiFi so the next source is tried", display_name, manifest_s, expected_s, q_key)
+                return None
 
             extension = manifest_info['extension']
             safe_name = re.sub(r'[<>:"/\\|?*]', '_', display_name)
@@ -1087,11 +1089,15 @@ class HiFiClient(DownloadSourcePlugin):
                     bits_per_sample=(props[1] if props else 0),
                     channels=(props[2] if props else 0))
                 if fake:
+                    # A preview at this tier means the SOURCE only has a preview — every
+                    # lower tier is the same 30s clip (and the lossy ones dodge the
+                    # bitrate check). Abort HiFi so the orchestrator tries the next
+                    # SOURCE, instead of cascading down into an accepted lower-tier preview.
                     logger.warning(
-                        "HiFi served a PREVIEW/truncated file at %s for '%s' (%s) — rejecting",
-                        q_key, display_name, why)
+                        "HiFi has only a PREVIEW of '%s' (%s at %s) — failing HiFi so the "
+                        "next source is tried", display_name, why, q_key)
                     out_path.unlink(missing_ok=True)
-                    continue
+                    return None
 
                 logger.info(f"HiFi download complete ({q_key}): {out_path} "
                             f"({final_size / (1024*1024):.1f} MB)")

tests/test_hifi_preview_guard.py

@@ -96,7 +96,9 @@ def test_download_sync_skips_preview_manifests_and_never_downloads(tmp_path, mon
 
     result = c._download_sync('dl1', 12345, 'The Weeknd - Save Your Tears')
     assert result is None                                       # → orchestrator falls back
-    assert tiers                                                # it did consult the manifest(s)
+    # A preview means the SOURCE only has a preview — every lower tier is the same clip,
+    # so it must ABORT on the first preview, not cascade down into a lower-tier preview.
+    assert tiers == ['lossless']
 
 
 def test_download_sync_proceeds_past_the_gate_for_a_full_manifest(tmp_path, monkeypatch):
@@ -117,6 +119,27 @@ def test_download_sync_proceeds_past_the_gate_for_a_full_manifest(tmp_path, monk
     assert seg_calls                                           # it got PAST the preview gate to download
 
 
+def test_download_sync_aborts_on_a_faked_full_length_file_no_tier_cascade(tmp_path, monkeypatch):
+    # The real #895 case: manifest + container claim FULL length, but the finished file
+    # decodes to 30s. It must abort HiFi (return None) on the first tier — NOT drop to the
+    # lossy 'high' tier (the same 30s preview, which dodges the bitrate check).
+    monkeypatch.setattr(hc, 'config_manager', _Cfg())
+    c = _bare_client(tmp_path)
+    c.get_track_info = lambda tid: {'duration_s': 215}
+    tiers = []
+    c._get_hls_manifest = lambda tid, quality='lossless': (
+        tiers.append(quality) or
+        {'segment_uris': ['seg'], 'init_uri': None, 'extension': 'flac', 'manifest_duration': 215.0})
+    c._download_segment_with_retry = lambda url: b'\x00' * 200_000      # > MIN_AUDIO_SIZE
+    c._demux_flac = lambda i, o: o.write_bytes(b'\x00' * 200_000)        # produce the 'flac'
+    c._probe_real_seconds = lambda p: 30.0                              # decodes to 30s
+    c._probe_audio_seconds = lambda p: 215.0                           # faked container claim
+    c._flac_props = lambda p: (44100, 16, 2)
+
+    result = c._download_sync('dl1', 12345, 'The Weeknd - Save Your Tears')
+    assert result is None and tiers == ['lossless']                    # aborted, did NOT try 'high'
+
+
 def test_download_sync_does_not_reject_when_track_length_unknown(tmp_path, monkeypatch):
     monkeypatch.setattr(hc, 'config_manager', _Cfg())
     c = _bare_client(tmp_path)