fix(tune): accept MOT-layout ground truth in Tuner validation

src/trackers/eval/evaluate.py

@@ -338,6 +338,27 @@ def _discover_sequences(
         return sorted(p.parent.parent.name for p in gt_dir.glob("*/gt/gt.txt") if not p.name.startswith("."))
 
 
+def _ground_truth_path(
+    gt_dir: Path,
+    seq_name: str,
+    data_format: Literal["flat", "mot"],
+) -> Path:
+    """Get the ground truth file path for a sequence.
+
+    Args:
+        gt_dir: Ground truth directory (direct parent of sequences).
+        seq_name: Sequence name.
+        data_format: Directory format.
+
+    Returns:
+        Path to the sequence's ground truth file, which is not guaranteed to exist.
+    """
+    if data_format == "flat":
+        return gt_dir / f"{seq_name}.txt"
+    # MOT format: gt_dir/{seq}/gt/gt.txt
+    return gt_dir / seq_name / "gt" / "gt.txt"
+
+
 def _get_paths(
     gt_dir: Path,
     tracker_dir: Path,
@@ -355,16 +376,8 @@ def _get_paths(
     Returns:
         Tuple of (gt_path, tracker_path).
     """
-    if data_format == "flat":
-        gt_path = gt_dir / f"{seq_name}.txt"
-    else:
-        # MOT format: gt_dir/{seq}/gt/gt.txt
-        gt_path = gt_dir / seq_name / "gt" / "gt.txt"
-
     # Tracker files are always flat: tracker_dir/{seq}.txt
-    tracker_path = tracker_dir / f"{seq_name}.txt"
-
-    return gt_path, tracker_path
+    return _ground_truth_path(gt_dir, seq_name, data_format), tracker_dir / f"{seq_name}.txt"
 
 
 def _parse_seqmap(seqmap_path: str | Path) -> list[str]:

src/trackers/tune/tuner.py

@@ -17,7 +17,7 @@
 import supervision as sv
 
 from trackers.core.base import BaseTracker
-from trackers.eval.evaluate import evaluate_mot_sequences
+from trackers.eval.evaluate import _detect_format, _ground_truth_path, evaluate_mot_sequences
 from trackers.eval.results import BenchmarkResult
 from trackers.io.frames import load_mot_frame_image
 from trackers.io.mot import _mot_frame_to_detections, _MOTOutput, load_mot_file
@@ -201,7 +201,8 @@ def _validate_sequence_files(self) -> None:
         """Validate that every selected sequence has required MOT files.
 
         This performs eager filesystem validation so configuration errors are reported during tuner initialization
-        rather than later during trial execution.
+        rather than later during trial execution. Ground truth is accepted in either the flat `{seq}.txt` layout or the
+        MOT `{seq}/gt/gt.txt` layout, matching what `evaluate_mot_sequences` detects.
         """
         missing_detection_files = [
             str(self._detections_dir / f"{seq_name}.txt")
@@ -213,11 +214,14 @@ def _validate_sequence_files(self) -> None:
                 "Missing detection files for selected sequences: " + ", ".join(missing_detection_files)
             )
 
-        missing_gt_files = [
-            str(self._gt_dir / f"{seq_name}.txt")
-            for seq_name in self._sequences
-            if not (self._gt_dir / f"{seq_name}.txt").is_file()
-        ]
+        # Ground truth may use either layout that `evaluate_mot_sequences` accepts, so validation
+        # resolves paths the same way rather than assuming the flat one.
+        gt_format = _detect_format(self._gt_dir)
+        missing_gt_files = []
+        for seq_name in self._sequences:
+            gt_path = _ground_truth_path(self._gt_dir, seq_name, gt_format)
+            if not gt_path.is_file():
+                missing_gt_files.append(str(gt_path))
         if missing_gt_files:
             raise FileNotFoundError("Missing ground-truth files for selected sequences: " + ", ".join(missing_gt_files))
 

tests/tune/test_tuner.py

@@ -257,6 +257,49 @@ def test_objective_normalized_to_uppercase(self, tmp_path: Path) -> None:
         assert tuner._objective_metric == "MOTA"
 
 
+class TestTunerGroundTruthLayout:
+    """Ground-truth validation must accept every layout evaluation accepts.
+
+    `Tuner` hands `gt_dir` straight to `evaluate_mot_sequences`, which auto-detects the flat `{seq}.txt` layout and the
+    MOT `{seq}/gt/gt.txt` layout that downloaded datasets ship in. Eager validation has to agree, or it rejects trees
+    that would evaluate fine.
+    """
+
+    def test_accepts_mot_layout_ground_truth(self, tmp_path: Path) -> None:
+        """A MOT-layout ground-truth tree initializes instead of being reported as missing."""
+        det_dir = tmp_path / "det"
+        det_dir.mkdir()
+        (det_dir / "seq1.txt").write_text(_MOT_LINE)
+        gt_dir = tmp_path / "gt"
+        (gt_dir / "seq1" / "gt").mkdir(parents=True)
+        (gt_dir / "seq1" / "gt" / "gt.txt").write_text(_MOT_LINE)
+
+        tuner = Tuner("bytetrack", gt_dir, det_dir)
+
+        assert tuner._sequences == ["seq1"]
+
+    def test_reports_missing_ground_truth_at_mot_layout_path(self, tmp_path: Path) -> None:
+        """A sequence missing from a MOT-layout tree is reported at its MOT path."""
+        det_dir = tmp_path / "det"
+        det_dir.mkdir()
+        (det_dir / "seq1.txt").write_text(_MOT_LINE)
+        (det_dir / "seq2.txt").write_text(_MOT_LINE)
+        gt_dir = tmp_path / "gt"
+        (gt_dir / "seq1" / "gt").mkdir(parents=True)
+        (gt_dir / "seq1" / "gt" / "gt.txt").write_text(_MOT_LINE)
+
+        with pytest.raises(FileNotFoundError, match=r"seq2.*gt.*gt\.txt"):
+            Tuner("bytetrack", gt_dir, det_dir)
+
+    def test_still_reports_missing_flat_ground_truth(self, tmp_path: Path) -> None:
+        """The flat layout keeps reporting missing files at the flat path."""
+        gt_dir, det_dir = _setup_dirs(tmp_path)
+        (det_dir / "seq2.txt").write_text(_MOT_LINE)
+
+        with pytest.raises(FileNotFoundError, match=r"seq2\.txt"):
+            Tuner("bytetrack", gt_dir, det_dir)
+
+
 class TestTunerSeed:
     def test_create_optuna_study_uses_seeded_sampler(self) -> None:
         with patch.object(optuna, "create_study", wraps=optuna.create_study) as mock_create: