fix: address four validation correctness issues from review

- Invalid audio rows (bad path or sample-rate mismatch) no longer
  increment valid_samples; has_error is now set on any audio failure
- _check_audio_file now enforces the expected sample rate when soundfile
  is available, making --sample-rate actually useful
- ref_audio missing-file warning is emitted for every invalid entry
  independently, not only before the first valid one is seen
- New tests cover each of the four corrected behaviours: invalid audio
  count, sample-rate mismatch, mixed ref_audio, and CLI exit code

src/voxcpm/training/validate.py

@@ -31,7 +31,10 @@ class ValidationResult:
 
 
 def _check_audio_file(audio_path: str, sample_rate: int) -> Optional[str]:
-    """Check if an audio file exists and is readable. Returns error message or None."""
+    """Check if an audio file exists, is readable, and matches expected sample rate.
+
+    Returns an error message, or None if the file is valid.
+    """
     if not os.path.isfile(audio_path):
         return f"Audio file not found: {audio_path}"
     try:
@@ -40,6 +43,11 @@ def _check_audio_file(audio_path: str, sample_rate: int) -> Optional[str]:
         info = sf.info(audio_path)
         if info.frames == 0:
             return f"Audio file is empty: {audio_path}"
+        if info.samplerate != sample_rate:
+            return (
+                f"Sample rate mismatch in {audio_path}: "
+                f"expected {sample_rate} Hz, got {info.samplerate} Hz"
+            )
         return None
     except ImportError:
         # soundfile not available; just check existence
@@ -173,6 +181,7 @@ def validate_manifest(
                 missing_audio_count += 1
                 if missing_audio_count <= 5:
                     result.errors.append(f"Line {i + 1}: {audio_error}")
+                has_error = True
             else:
                 duration = _get_audio_duration(audio_path)
                 if duration is not None:
@@ -187,6 +196,7 @@ def validate_manifest(
                         )
         else:
             result.errors.append(f"Line {i + 1}: Invalid audio path")
+            has_error = True
 
         # Validate optional ref_audio
         if "ref_audio" in entry:
@@ -198,7 +208,7 @@ def validate_manifest(
                     ref_path = str(manifest_dir / ref_path)
                 if os.path.isfile(ref_path):
                     result.has_ref_audio += 1
-                elif result.has_ref_audio == 0:
+                else:
                     result.warnings.append(
                         f"Line {i + 1}: ref_audio file not found: {ref_path}"
                     )

tests/test_validate.py

@@ -183,3 +183,68 @@ class TestValidateManifest:
 
         r3 = ValidationResult(total_samples=0, valid_samples=0)
         assert not r3.is_valid
+
+    def test_invalid_audio_not_counted_as_valid(self, tmp_dir):
+        """A row with a bad audio path must not increment valid_samples."""
+        manifest = tmp_dir / "bad_audio.jsonl"
+        _write_manifest(
+            manifest,
+            [{"text": "hello", "audio": "/nonexistent/audio.wav"}],
+        )
+        result = validate_manifest(str(manifest))
+        assert result.total_samples == 1
+        assert result.valid_samples == 0
+        assert not result.is_valid
+        assert any("not found" in e for e in result.errors)
+
+    def test_sample_rate_mismatch(self, tmp_dir):
+        """A file with a different sample rate should be reported as an error."""
+        try:
+            import soundfile as sf
+            import numpy as np
+        except ImportError:
+            pytest.skip("soundfile not available")
+
+        audio = tmp_dir / "audio_8k.wav"
+        import numpy as np
+        samples = np.zeros(8000, dtype=np.float32)
+        sf.write(str(audio), samples, 8000)
+
+        manifest = tmp_dir / "sr_mismatch.jsonl"
+        _write_manifest(manifest, [{"text": "hello", "audio": str(audio)}])
+
+        result = validate_manifest(str(manifest), sample_rate=16000)
+        assert result.valid_samples == 0
+        assert not result.is_valid
+        assert any("Sample rate mismatch" in e or "sample rate" in e.lower() for e in result.errors)
+
+    def test_mixed_ref_audio_warns_for_each_missing(self, tmp_dir):
+        """Missing ref_audio entries should each generate a warning independently."""
+        audio = tmp_dir / "audio.wav"
+        ref_good = tmp_dir / "ref_good.wav"
+        _create_wav(audio)
+        _create_wav(ref_good)
+
+        manifest = tmp_dir / "mixed_ref.jsonl"
+        _write_manifest(
+            manifest,
+            [
+                {"text": "row1", "audio": str(audio), "ref_audio": str(ref_good)},
+                {"text": "row2", "audio": str(audio), "ref_audio": "/nonexistent/ref.wav"},
+            ],
+        )
+        result = validate_manifest(str(manifest))
+        assert result.has_ref_audio == 1
+        assert any("ref_audio file not found" in w for w in result.warnings)
+
+    def test_cli_validate_exit_code(self, tmp_dir):
+        """validate subcommand must exit non-zero on error."""
+        import subprocess
+        manifest = tmp_dir / "bad.jsonl"
+        _write_manifest(manifest, [{"text": "hi", "audio": "/nonexistent/x.wav"}])
+
+        proc = subprocess.run(
+            [sys.executable, "-m", "voxcpm.cli", "validate", str(manifest)],
+            capture_output=True,
+        )
+        assert proc.returncode != 0