serve a promoted model at the post-processing it was gated on

scripts/evaluate_belgium_building_candidate.py freezes its post-processing
before the protected test — NMS IoU and a containment threshold selected during
calibration, defaulting to 1.0. The runtime applied a hardcoded 0.85, so a
promoted candidate was served under suppression its evaluation never measured
and dropped detections the gate had counted. Neither report showed the
difference. That constant was mine, added without noticing the evaluation
pipeline already had a tuned value for the same concept.

Containment is now configuration, recorded on every run beside the duplicate
IoU threshold, so an operator can serve a candidate at the value it was gated
at and afterwards see which value produced a given score.

Two runs that post-processed differently produced different candidate sets from
the same model output, so the comparison endpoint refuses to rank them. Runs
recorded before those values were persisted carry none, and absence is not
treated as a difference.

The remaining gap is deliberate and documented rather than closed: the gate
scores the model on its protected test set, the workbench scores the whole
pipeline including coverage clipping and the tile-edge filter. A promoted
candidate will not reproduce its gate F1 exactly, and pretending otherwise
would be the worse answer.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backend/tests/test_postprocessing_parity_with_training_gate.py

@@ -0,0 +1,144 @@
+"""What is promoted must be what the workbench then runs.
+
+The candidate evaluation freezes its post-processing before the protected test
+— NMS IoU and a containment threshold selected during calibration. The runtime
+applied its own hardcoded containment value, so a model gated at one setting
+was served at another and suppressed detections the gate had counted. The
+difference is invisible in both reports.
+
+Containment is therefore configuration, recorded with every run, and two runs
+that post-processed differently are not comparable however good their numbers
+look.
+"""
+
+from __future__ import annotations
+
+import pytest
+from shapely.geometry import box
+
+from app.core.config import Settings
+from app.services.detection_comparison_service import DetectionComparisonService
+from app.services.detection_service import DetectionService
+
+
+def _candidate(name: str, geometry, confidence: float):
+    return {
+        "class_name": "building",
+        "confidence": confidence,
+        "geometry": geometry,
+        "bbox": [0.0, 0.0, 1.0, 1.0],
+        "source_tile_path": f"/tiles/{name}.tif",
+        "properties": {"name": name},
+    }
+
+
+class TestConfigurableContainment:
+    def test_the_runtime_threshold_comes_from_settings(self) -> None:
+        assert Settings(_env_file=None).yolo_containment_nms_threshold == pytest.approx(0.85)
+        assert Settings(
+            _env_file=None, yolo_containment_nms_threshold=1.0
+        ).yolo_containment_nms_threshold == pytest.approx(1.0)
+
+    def test_a_strict_threshold_suppresses_only_a_fully_nested_box(self) -> None:
+        outer = _candidate("outer", box(0, 0, 10, 10), 0.9)
+        # 90% of the smaller box lies inside the larger one, but their IoU is
+        # only 0.09 — so only the containment rule can act on this pair.
+        mostly_nested = _candidate("mostly", box(8.2, 1, 10.2, 6), 0.5)
+
+        kept = DetectionService._suppress_duplicate_candidates(
+            [outer, mostly_nested], iou_threshold=0.5, containment_threshold=1.0
+        )
+
+        assert [item["properties"]["name"] for item in kept] == ["outer", "mostly"]
+
+    def test_a_looser_threshold_suppresses_it(self) -> None:
+        outer = _candidate("outer", box(0, 0, 10, 10), 0.9)
+        mostly_nested = _candidate("mostly", box(8.2, 1, 10.2, 6), 0.5)
+
+        kept = DetectionService._suppress_duplicate_candidates(
+            [outer, mostly_nested], iou_threshold=0.5, containment_threshold=0.7
+        )
+
+        assert [item["properties"]["name"] for item in kept] == ["outer"]
+
+    def test_the_default_matches_the_documented_runtime_value(self) -> None:
+        outer = _candidate("outer", box(0, 0, 10, 10), 0.9)
+        nested = _candidate("nested", box(1, 1, 9, 9), 0.5)
+
+        kept = DetectionService._suppress_duplicate_candidates([outer, nested], iou_threshold=0.5)
+
+        assert [item["properties"]["name"] for item in kept] == ["outer"]
+
+
+class TestComparabilityOfPostProcessing:
+    def _entry(self, *, dataset_id, reference_id, containment: float, duplicate_iou: float = 0.5):
+        from uuid import uuid4
+
+        return {
+            "analysis_run_id": uuid4(),
+            "dataset_id": dataset_id,
+            "model_id": "yolo-configured",
+            "model_asset_id": "asset",
+            "reference_dataset_id": reference_id,
+            "coverage_mode": "persisted_tile_manifest_union",
+            "reference_evaluated_count": 100,
+            "containment_suppression_threshold": containment,
+            "duplicate_iou_threshold": duplicate_iou,
+        }
+
+    def test_runs_with_the_same_post_processing_stay_comparable(self) -> None:
+        from uuid import uuid4
+
+        dataset_id, reference_id = uuid4(), uuid4()
+        report = DetectionComparisonService.assess_comparability(
+            [
+                self._entry(dataset_id=dataset_id, reference_id=reference_id, containment=0.85),
+                self._entry(dataset_id=dataset_id, reference_id=reference_id, containment=0.85),
+            ]
+        )
+
+        assert report["comparable"] is True
+
+    def test_a_different_containment_threshold_blocks_the_comparison(self) -> None:
+        from uuid import uuid4
+
+        dataset_id, reference_id = uuid4(), uuid4()
+        report = DetectionComparisonService.assess_comparability(
+            [
+                self._entry(dataset_id=dataset_id, reference_id=reference_id, containment=0.85),
+                self._entry(dataset_id=dataset_id, reference_id=reference_id, containment=1.0),
+            ]
+        )
+
+        assert report["comparable"] is False
+        assert "different_post_processing" in report["blocking_reasons"]
+
+    def test_a_different_duplicate_iou_blocks_the_comparison(self) -> None:
+        from uuid import uuid4
+
+        dataset_id, reference_id = uuid4(), uuid4()
+        report = DetectionComparisonService.assess_comparability(
+            [
+                self._entry(dataset_id=dataset_id, reference_id=reference_id, containment=0.85, duplicate_iou=0.5),
+                self._entry(dataset_id=dataset_id, reference_id=reference_id, containment=0.85, duplicate_iou=0.7),
+            ]
+        )
+
+        assert report["comparable"] is False
+        assert "different_post_processing" in report["blocking_reasons"]
+
+    def test_runs_from_before_the_setting_existed_do_not_block(self) -> None:
+        """Older runs recorded no threshold; absence is not a difference."""
+
+        from uuid import uuid4
+
+        dataset_id, reference_id = uuid4(), uuid4()
+        entries = [
+            self._entry(dataset_id=dataset_id, reference_id=reference_id, containment=0.85),
+            self._entry(dataset_id=dataset_id, reference_id=reference_id, containment=0.85),
+        ]
+        for entry in entries:
+            entry.pop("containment_suppression_threshold")
+            entry.pop("duplicate_iou_threshold")
+
+        assert DetectionComparisonService.assess_comparability(entries)["comparable"] is True