Add QA evidence map overlay

CHANGELOG.md

@@ -7,6 +7,14 @@
 
 # Changelog
 
+## Sprint 112 QA evidence map overlay (2026-06-25)
+
+- Added a read-only QA/QC evidence GeoJSON endpoint for persisted quality checks.
+- The endpoint resolves `match_evidence`, `false_positive_evidence` and `false_negative_evidence` ids back to persisted vector, detection or segmentation geometries where available.
+- Added QA/QC actions to render evidence overlays in the existing MapLibre workspace with distinct match, false-positive and false-negative styling.
+- Added frontend loading/error/clear states for the QA evidence overlay and a compact map legend.
+- No migration, new table, provider fetching, AI behavior or new product domain was introduced.
+
 ## Sprint 111 QA feature evidence persistence (2026-06-25)
 
 - Added feature-level QA evidence to dataset, detection and segmentation QA matching.

backend/app/api/routes/quality_checks.py

@@ -7,6 +7,7 @@ from sqlalchemy.orm import Session
 
 from app.db.session import get_db
 from app.schemas.qa import QualityCheckList
+from app.services.quality_evidence_service import QualityEvidenceService
 from app.services.quality_check_service import QualityCheckService
 from app.utils.response import envelope
 
@@ -27,3 +28,12 @@ def list_quality_checks(
         offset=offset,
     )
     return envelope(QualityCheckList(items=items, total=total, limit=limit, offset=offset).model_dump())
+
+
+@router.get("/quality-checks/{quality_check_id}/evidence/geojson", response_model=dict)
+def get_quality_check_evidence_geojson(
+    project_id: UUID,
+    quality_check_id: UUID,
+    db: Session = Depends(get_db),
+) -> dict:
+    return envelope(QualityEvidenceService.evidence_geojson(db, project_id=project_id, quality_check_id=quality_check_id))

backend/app/services/quality_evidence_service.py

@@ -0,0 +1,203 @@
+from __future__ import annotations
+
+from typing import Any
+from uuid import UUID
+
+from geoalchemy2.shape import to_shape
+from shapely.geometry import mapping
+from sqlalchemy.orm import Session
+
+from app.core.errors import AppError
+from app.models import Detection, QualityCheck, Segmentation, VectorFeature
+
+
+class QualityEvidenceService:
+    @staticmethod
+    def evidence_geojson(db: Session, *, project_id: UUID, quality_check_id: UUID) -> dict[str, Any]:
+        quality_check = db.get(QualityCheck, quality_check_id)
+        if not quality_check or quality_check.project_id != project_id:
+            raise AppError(code="QUALITY_CHECK_NOT_FOUND", message="Quality check not found", status_code=404)
+
+        findings = quality_check.findings_json or {}
+        features: list[dict[str, Any]] = []
+        warnings: list[str] = []
+        candidate_index = QualityEvidenceService._candidate_feature_index(db, quality_check)
+        reference_index = QualityEvidenceService._reference_feature_index(db, quality_check)
+
+        for evidence in QualityEvidenceService._evidence_items(findings.get("match_evidence")):
+            candidate_id = QualityEvidenceService._string_value(evidence.get("candidate_feature_id"))
+            reference_id = QualityEvidenceService._string_value(evidence.get("reference_feature_id"))
+            iou = evidence.get("iou")
+            if candidate_id:
+                row = candidate_index.get(candidate_id)
+                if row is not None:
+                    features.append(
+                        QualityEvidenceService._row_to_feature(
+                            row,
+                            role="match_candidate",
+                            quality_check=quality_check,
+                            evidence=evidence,
+                        )
+                    )
+                else:
+                    warnings.append(f"Candidate evidence feature not found: {candidate_id}")
+            if reference_id:
+                row = reference_index.get(reference_id)
+                if row is not None:
+                    features.append(
+                        QualityEvidenceService._row_to_feature(
+                            row,
+                            role="match_reference",
+                            quality_check=quality_check,
+                            evidence={"candidate_feature_id": candidate_id, "reference_feature_id": reference_id, "iou": iou},
+                        )
+                    )
+                else:
+                    warnings.append(f"Reference evidence feature not found: {reference_id}")
+
+        for evidence in QualityEvidenceService._evidence_items(findings.get("false_positive_evidence")):
+            candidate_id = QualityEvidenceService._string_value(evidence.get("candidate_feature_id"))
+            if not candidate_id:
+                continue
+            row = candidate_index.get(candidate_id)
+            if row is not None:
+                features.append(
+                    QualityEvidenceService._row_to_feature(
+                        row,
+                        role="false_positive",
+                        quality_check=quality_check,
+                        evidence=evidence,
+                    )
+                )
+            else:
+                warnings.append(f"False-positive evidence feature not found: {candidate_id}")
+
+        for evidence in QualityEvidenceService._evidence_items(findings.get("false_negative_evidence")):
+            reference_id = QualityEvidenceService._string_value(evidence.get("reference_feature_id"))
+            if not reference_id:
+                continue
+            row = reference_index.get(reference_id)
+            if row is not None:
+                features.append(
+                    QualityEvidenceService._row_to_feature(
+                        row,
+                        role="false_negative",
+                        quality_check=quality_check,
+                        evidence=evidence,
+                    )
+                )
+            else:
+                warnings.append(f"False-negative evidence feature not found: {reference_id}")
+
+        return {
+            "quality_check_id": str(quality_check.id),
+            "project_id": str(quality_check.project_id),
+            "candidate_dataset_id": str(quality_check.candidate_dataset_id) if quality_check.candidate_dataset_id else None,
+            "reference_dataset_id": str(quality_check.reference_dataset_id),
+            "analysis_run_id": str(quality_check.analysis_run_id) if quality_check.analysis_run_id else None,
+            "feature_count": len(features),
+            "warnings": warnings,
+            "geojson": {
+                "type": "FeatureCollection",
+                "features": features,
+            },
+        }
+
+    @staticmethod
+    def _evidence_items(value: Any) -> list[dict[str, Any]]:
+        if not isinstance(value, list):
+            return []
+        return [item for item in value if isinstance(item, dict)]
+
+    @staticmethod
+    def _string_value(value: Any) -> str | None:
+        if value is None:
+            return None
+        text = str(value).strip()
+        return text or None
+
+    @staticmethod
+    def _candidate_feature_index(db: Session, quality_check: QualityCheck) -> dict[str, Any]:
+        index: dict[str, Any] = {}
+        if quality_check.candidate_dataset_id:
+            for row in db.query(VectorFeature).filter(VectorFeature.dataset_id == quality_check.candidate_dataset_id).all():
+                QualityEvidenceService._add_index_keys(index, row)
+            for row in db.query(Detection).filter(Detection.dataset_id == quality_check.candidate_dataset_id).all():
+                QualityEvidenceService._add_index_keys(index, row)
+            for row in db.query(Segmentation).filter(Segmentation.dataset_id == quality_check.candidate_dataset_id).all():
+                QualityEvidenceService._add_index_keys(index, row)
+            if quality_check.analysis_run_id:
+                for row in db.query(Detection).filter(Detection.analysis_run_id == quality_check.analysis_run_id).all():
+                    QualityEvidenceService._add_index_keys(index, row)
+                for row in db.query(Segmentation).filter(Segmentation.analysis_run_id == quality_check.analysis_run_id).all():
+                    QualityEvidenceService._add_index_keys(index, row)
+        elif quality_check.analysis_run_id:
+            for row in db.query(Detection).filter(Detection.analysis_run_id == quality_check.analysis_run_id).all():
+                QualityEvidenceService._add_index_keys(index, row)
+            for row in db.query(Segmentation).filter(Segmentation.analysis_run_id == quality_check.analysis_run_id).all():
+                QualityEvidenceService._add_index_keys(index, row)
+        return index
+
+    @staticmethod
+    def _reference_feature_index(db: Session, quality_check: QualityCheck) -> dict[str, Any]:
+        index: dict[str, Any] = {}
+        for row in db.query(VectorFeature).filter(VectorFeature.dataset_id == quality_check.reference_dataset_id).all():
+            QualityEvidenceService._add_index_keys(index, row)
+        return index
+
+    @staticmethod
+    def _add_index_keys(index: dict[str, Any], row: Any) -> None:
+        for key in QualityEvidenceService._row_identifiers(row):
+            index.setdefault(key, row)
+
+    @staticmethod
+    def _row_identifiers(row: Any) -> set[str]:
+        identifiers = {str(row.id)}
+        source_feature_id = getattr(row, "source_feature_id", None)
+        if source_feature_id:
+            identifiers.add(str(source_feature_id))
+        properties = getattr(row, "properties_json", None) or {}
+        if isinstance(properties, dict):
+            for property_key in ("vector_feature_id", "source_feature_id", "detection_id", "segmentation_id", "id", "name"):
+                value = properties.get(property_key)
+                if value is not None:
+                    identifiers.add(str(value))
+        return identifiers
+
+    @staticmethod
+    def _row_to_feature(row: Any, *, role: str, quality_check: QualityCheck, evidence: dict[str, Any]) -> dict[str, Any]:
+        try:
+            geometry = to_shape(row.geometry)
+        except Exception as exc:
+            raise AppError(
+                code="INVALID_QA_EVIDENCE_GEOMETRY",
+                message="Persisted QA evidence geometry could not be converted to GeoJSON",
+                details={"feature_id": str(getattr(row, "id", ""))},
+                status_code=500,
+            ) from exc
+
+        properties = dict(getattr(row, "properties_json", None) or {})
+        properties.update(
+            {
+                "qa_evidence_role": role,
+                "quality_check_id": str(quality_check.id),
+                "project_id": str(quality_check.project_id),
+                "candidate_dataset_id": str(quality_check.candidate_dataset_id) if quality_check.candidate_dataset_id else None,
+                "reference_dataset_id": str(quality_check.reference_dataset_id),
+                "analysis_run_id": str(quality_check.analysis_run_id) if quality_check.analysis_run_id else None,
+                "feature_id": str(row.id),
+                "dataset_id": str(getattr(row, "dataset_id", "")) if getattr(row, "dataset_id", None) else None,
+                "source_feature_id": getattr(row, "source_feature_id", None),
+                "feature_class": getattr(row, "feature_class", None) or getattr(row, "class_name", None),
+                "candidate_feature_id": QualityEvidenceService._string_value(evidence.get("candidate_feature_id")),
+                "reference_feature_id": QualityEvidenceService._string_value(evidence.get("reference_feature_id")),
+                "iou": evidence.get("iou"),
+            }
+        )
+
+        return {
+            "type": "Feature",
+            "id": f"{role}:{row.id}",
+            "geometry": mapping(geometry),
+            "properties": properties,
+        }

backend/tests/test_sprint112_qa_evidence_overlay.py

@@ -0,0 +1,161 @@
+from __future__ import annotations
+
+from uuid import uuid4
+
+import pytest
+from fastapi.testclient import TestClient
+from geoalchemy2.shape import from_shape
+from shapely.geometry import box
+
+from app.core.errors import AppError
+from app.db.session import get_db
+from app.main import app
+from app.models import QualityCheck, VectorFeature
+from app.services.quality_evidence_service import QualityEvidenceService
+
+
+class FakeQuery:
+    def __init__(self, rows):
+        self.rows = list(rows)
+
+    def filter(self, *criteria):
+        for criterion in criteria:
+            left = getattr(criterion, "left", None)
+            right = getattr(criterion, "right", None)
+            operator = getattr(criterion, "operator", None)
+            name = getattr(left, "name", None)
+            value = getattr(right, "value", right)
+            if name and operator and operator.__name__ == "eq":
+                self.rows = [row for row in self.rows if getattr(row, name) == value]
+        return self
+
+    def all(self):
+        return list(self.rows)
+
+
+class FakeSession:
+    def __init__(self, objects=None, query_rows=None) -> None:
+        self.objects = objects or {}
+        self.query_rows = query_rows or {}
+
+    def get(self, model, item_id):
+        return self.objects.get((model, item_id))
+
+    def query(self, model):
+        return FakeQuery(self.query_rows.get(model, []))
+
+
+def _vector_feature(dataset_id, *, feature_id=None, source_feature_id: str, geom=None) -> VectorFeature:
+    return VectorFeature(
+        id=feature_id or uuid4(),
+        dataset_id=dataset_id,
+        source_feature_id=source_feature_id,
+        feature_class="building",
+        properties_json={"name": source_feature_id},
+        geometry=from_shape(geom or box(4.0, 51.0, 4.1, 51.1), srid=4326),
+    )
+
+
+def test_quality_check_evidence_geojson_resolves_persisted_vector_features() -> None:
+    project_id = uuid4()
+    quality_check_id = uuid4()
+    candidate_dataset_id = uuid4()
+    reference_dataset_id = uuid4()
+    candidate_match = _vector_feature(candidate_dataset_id, source_feature_id="candidate-match")
+    candidate_extra = _vector_feature(candidate_dataset_id, source_feature_id="candidate-extra", geom=box(4.4, 51.4, 4.5, 51.5))
+    reference_match = _vector_feature(reference_dataset_id, source_feature_id="reference-match")
+    reference_missing = _vector_feature(reference_dataset_id, source_feature_id="reference-missing", geom=box(4.7, 51.7, 4.8, 51.8))
+    quality_check = QualityCheck(
+        id=quality_check_id,
+        project_id=project_id,
+        candidate_dataset_id=candidate_dataset_id,
+        reference_dataset_id=reference_dataset_id,
+        check_type="candidate_vs_reference",
+        status="ok",
+        findings_json={
+            "match_evidence": [
+                {
+                    "candidate_feature_id": "candidate-match",
+                    "reference_feature_id": "reference-match",
+                    "iou": 1.0,
+                }
+            ],
+            "false_positive_evidence": [{"candidate_feature_id": "candidate-extra"}],
+            "false_negative_evidence": [{"reference_feature_id": "reference-missing"}],
+        },
+    )
+    db = FakeSession(
+        objects={(QualityCheck, quality_check_id): quality_check},
+        query_rows={VectorFeature: [candidate_match, candidate_extra, reference_match, reference_missing]},
+    )
+
+    result = QualityEvidenceService.evidence_geojson(db, project_id=project_id, quality_check_id=quality_check_id)
+
+    assert result["quality_check_id"] == str(quality_check_id)
+    assert result["feature_count"] == 4
+    assert result["geojson"]["type"] == "FeatureCollection"
+    roles = [feature["properties"]["qa_evidence_role"] for feature in result["geojson"]["features"]]
+    assert roles == ["match_candidate", "match_reference", "false_positive", "false_negative"]
+    match_candidate = result["geojson"]["features"][0]
+    assert match_candidate["properties"]["quality_check_id"] == str(quality_check_id)
+    assert match_candidate["properties"]["candidate_feature_id"] == "candidate-match"
+    assert match_candidate["properties"]["reference_feature_id"] == "reference-match"
+    assert match_candidate["properties"]["iou"] == 1.0
+    assert match_candidate["properties"]["source_feature_id"] == "candidate-match"
+
+
+def test_quality_check_evidence_geojson_rejects_cross_project_access() -> None:
+    quality_check_id = uuid4()
+    quality_check = QualityCheck(
+        id=quality_check_id,
+        project_id=uuid4(),
+        reference_dataset_id=uuid4(),
+        check_type="candidate_vs_reference",
+        status="ok",
+        findings_json={},
+    )
+    db = FakeSession(objects={(QualityCheck, quality_check_id): quality_check})
+
+    with pytest.raises(AppError) as exc:
+        QualityEvidenceService.evidence_geojson(db, project_id=uuid4(), quality_check_id=quality_check_id)
+
+    assert exc.value.code == "QUALITY_CHECK_NOT_FOUND"
+
+
+def test_quality_check_evidence_geojson_api_uses_canonical_envelope(monkeypatch) -> None:
+    project_id = uuid4()
+    quality_check_id = uuid4()
+    payload = {
+        "quality_check_id": str(quality_check_id),
+        "project_id": str(project_id),
+        "feature_count": 0,
+        "geojson": {"type": "FeatureCollection", "features": []},
+    }
+
+    monkeypatch.setattr(
+        "app.api.routes.quality_checks.QualityEvidenceService.evidence_geojson",
+        lambda *_args, **_kwargs: payload,
+    )
+    app.dependency_overrides[get_db] = lambda: FakeSession()
+    try:
+        response = TestClient(app).get(f"/api/v1/projects/{project_id}/quality-checks/{quality_check_id}/evidence/geojson")
+    finally:
+        app.dependency_overrides.pop(get_db, None)
+
+    assert response.status_code == 200
+    assert response.json() == {"data": payload}
+
+
+def test_frontend_quality_evidence_overlay_contract_is_wired() -> None:
+    from pathlib import Path
+
+    root = Path(__file__).resolve().parents[2]
+    geo_map = (root / "frontend" / "src" / "components" / "GeoMap.tsx").read_text(encoding="utf-8")
+    map_workspace = (root / "frontend" / "src" / "components" / "map" / "MapWorkspace.tsx").read_text(encoding="utf-8")
+    qa_api = (root / "frontend" / "src" / "services" / "api" / "qa.ts").read_text(encoding="utf-8")
+
+    assert "qaEvidenceData" in geo_map
+    assert "qa-evidence-fill" in geo_map
+    assert "qa_evidence_role" in geo_map
+    assert "qualityEvidenceGeoJson" in map_workspace
+    assert "getQualityEvidenceGeoJson" in qa_api

docs/API_CONTRACTS.md

@@ -1060,6 +1060,58 @@ Response:
 }
 ```
 
+### GET `/api/v1/projects/{project_id}/quality-checks/{quality_check_id}/evidence/geojson`
+
+Returns a canonical envelope containing a read-only QA/QC evidence overlay for a
+persisted quality check. The endpoint reads feature ids from
+`quality_checks.findings_json.match_evidence`,
+`false_positive_evidence` and `false_negative_evidence`, resolves them against
+persisted candidate/reference geometries and returns a GeoJSON FeatureCollection.
+
+Supported resolution paths:
+
+- dataset QA candidate/reference geometries from `vector_features`;
+- detection QA candidate geometries from persisted `detections`;
+- segmentation QA candidate geometries from persisted `segmentations`;
+- reference geometries from persisted `vector_features`.
+
+Response:
+
+```json
+{
+  "data": {
+    "quality_check_id": "uuid",
+    "project_id": "uuid",
+    "candidate_dataset_id": "uuid-or-null",
+    "reference_dataset_id": "uuid",
+    "analysis_run_id": "uuid-or-null",
+    "feature_count": 4,
+    "warnings": [],
+    "geojson": {
+      "type": "FeatureCollection",
+      "features": [
+        {
+          "type": "Feature",
+          "id": "match_candidate:feature-id",
+          "geometry": {},
+          "properties": {
+            "qa_evidence_role": "match_candidate",
+            "quality_check_id": "uuid",
+            "candidate_feature_id": "candidate-feature-id",
+            "reference_feature_id": "reference-feature-id",
+            "iou": 0.83
+          }
+        }
+      ]
+    }
+  }
+}
+```
+
+`qa_evidence_role` is one of `match_candidate`, `match_reference`,
+`false_positive` or `false_negative`. Missing persisted feature ids are reported
+in `warnings`; no fake geometries are produced.
+
 ## Exports
 
 ### POST `/api/v1/exports/geojson`

docs/CODEX_EXECUTION_LOG.md

@@ -1,3 +1,39 @@
+## Sprint 112 QA evidence map overlay (2026-06-25)
+
+Changed:
+- Added `QualityEvidenceService` to resolve persisted QA/QC evidence ids back to stored geometries.
+- Added `GET /api/v1/projects/{project_id}/quality-checks/{quality_check_id}/evidence/geojson`.
+- The endpoint returns a canonical envelope with `quality_check_id`, dataset/run provenance, warnings and a GeoJSON FeatureCollection.
+- Evidence resolution supports candidate dataset `vector_features`, candidate persisted `detections`/`segmentations` for analysis-run QA, and reference `vector_features`.
+- Added QA/QC panel actions to show selected or latest evidence on the Map workspace.
+- Added a MapLibre QA evidence source/layers with distinct match candidate, match reference, false-positive and false-negative styling.
+- Added map overlay loading/error/clear state and a compact legend.
+- Updated `docs/API_CONTRACTS.md`, `frontend/README.md`, `CHANGELOG.md` and `docs/TODO.md`.
+- Added regression coverage in `backend/tests/test_sprint112_qa_evidence_overlay.py`.
+
+Validation:
+- RED: `python -m pytest backend\tests\test_sprint112_qa_evidence_overlay.py -q` failed before implementation because `app.services.quality_evidence_service` did not exist.
+- RED: after backend implementation, the same test failed until frontend `qaEvidenceData`/API wiring existed.
+- `python -m pytest backend\tests\test_sprint112_qa_evidence_overlay.py -q` passed: 4 tests.
+- `cd frontend && npm run typecheck` passed after making the MapLibre expression type explicit.
+- `python -m pytest backend\tests\test_sprint112_qa_evidence_overlay.py backend\tests\test_qa_service.py backend\tests\test_sprint8c_detection_visualization_qa.py backend\tests\test_sprint9_segmentation_foundation.py -q` passed: 25 tests.
+- `python -m compileall backend/app` passed.
+- `cd backend && python -m pytest -q` passed: 356 tests.
+- `cd frontend && npm run typecheck` passed.
+- `cd frontend && npm run build` passed.
+- `cd backend && python -m alembic heads` passed: `202606120900 (head)`.
+- `cd backend && python -m alembic upgrade head --sql` passed.
+- `bash -n scripts/live_migration_smoke.sh` passed.
+- `bash scripts/run_readiness_check.sh` passed: 356 backend tests plus frontend typecheck/build.
+
+Limitations:
+- The overlay is generated read-only from existing persisted evidence and geometries; no new evidence table or migration was introduced.
+- Missing evidence ids are reported as warnings and do not create fake geometries.
+- No provider fetching, AI dependency, real model behavior or new product domain was added.
+
+Next recommended pass:
+- Add live browser validation for the QA evidence overlay against the deployed demo workflow, then consider a small export/handoff action for the evidence overlay GeoJSON.
+
 ## Sprint 111 QA feature evidence persistence (2026-06-25)
 
 Changed:

docs/TODO.md

@@ -378,3 +378,4 @@ This file now starts with the current implementation status. Older preparation/b
 - [x] Add Map workspace QA/QC shortcut for saved derived selection datasets.
 - [x] Add Map workspace QA/QC evidence drilldown handoff for saved selection comparisons.
 - [x] Persist QA/QC feature-level evidence for matches, false positives and false negatives.
+- [x] Render persisted QA/QC feature-level evidence as Map workspace overlays.

frontend/README.md

@@ -288,6 +288,7 @@ AI Lab run controls explicitly explain when no raster dataset is available, inst
 - The QA/QC workspace shows candidate/reference handoff cards and resolves persisted quality-check dataset IDs back to dataset names when the datasets are loaded in the current project context.
 - The QA/QC workspace includes a selected-check evidence drilldown with candidate/reference provenance, false-positive/negative metric evidence, map handoff context and parameters/findings JSON.
 - QA/QC findings now persist feature-level evidence in `findings_json`: matched candidate/reference feature ids with IoU, false-positive candidate feature ids and false-negative reference feature ids. The QA/QC drilldown renders these as compact evidence lists before the raw JSON.
+- Persisted QA/QC checks can be rendered as a Map workspace evidence overlay. The QA/QC panel calls `GET /api/v1/projects/{project_id}/quality-checks/{quality_check_id}/evidence/geojson`, then MapLibre draws matched candidate/reference geometries, false positives and false negatives with distinct styling and a compact legend.
 
 ## Raster dependency visibility
 

frontend/src/App.tsx

@@ -205,7 +205,12 @@ function App(): JSX.Element {
     qaError,
     qualityChecks,
     qualityChecksError,
+    qualityEvidenceGeoJson,
+    qualityEvidenceLoading,
+    qualityEvidenceError,
     loadQualityChecks,
+    loadQualityEvidenceGeoJson,
+    clearQualityEvidenceGeoJson,
     runQaComparison,
     setQaCandidateDatasetId,
     setQaReferenceDatasetId,
@@ -417,6 +422,13 @@ function App(): JSX.Element {
   const openMapSelectionQualityEvidence = () => {
     setActiveWorkspace('analysis')
   }
+  const openQualityEvidenceOnMap = async (qualityCheckId: string) => {
+    const result = await loadQualityEvidenceGeoJson(qualityCheckId)
+    if (result) {
+      setMapLayerVisible(true)
+      setActiveWorkspace('map')
+    }
+  }
   const {
     loadingDemoWorkflow,
     demoWorkflowMessage,
@@ -824,6 +836,11 @@ function App(): JSX.Element {
               selectedMapAreaId={selectedMapAreaId}
               areaFeatureCollection={areaFeatureCollection}
               mapFeatureCollection={mapFeatureCollection}
+              qualityEvidenceGeoJson={qualityEvidenceGeoJson?.geojson ?? null}
+              qualityEvidenceFeatureCount={qualityEvidenceGeoJson?.feature_count ?? 0}
+              qualityEvidenceLoading={qualityEvidenceLoading}
+              qualityEvidenceError={qualityEvidenceError}
+              qualityEvidenceWarnings={qualityEvidenceGeoJson?.warnings ?? []}
               mapLayerLabel={mapLayerLabel}
               mapLayerSourceLabel={mapLayerSourceLabel}
               mapLayerProvenance={mapLayerProvenance}
@@ -867,6 +884,7 @@ function App(): JSX.Element {
               onSelectMapQaReferenceDataset={setSelectedMapQaReferenceDatasetId}
               onRunMapSelectionQa={runMapSelectionQa}
               onOpenMapSelectionQualityEvidence={openMapSelectionQualityEvidence}
+              onClearQualityEvidence={clearQualityEvidenceGeoJson}
             />
           ) : null}
 
@@ -895,6 +913,9 @@ function App(): JSX.Element {
                 candidateDatasets={candidateDatasets}
                 referenceDatasets={referenceDatasets}
                 onRefresh={() => loadQualityChecks()}
+                onOpenEvidenceMap={openQualityEvidenceOnMap}
+                evidenceLoading={qualityEvidenceLoading}
+                evidenceError={qualityEvidenceError}
               />
             </div>
           ) : null}

frontend/src/components/GeoMap.tsx

@@ -7,6 +7,7 @@ interface GeoMapProps {
   areaData?: GeoJSON.FeatureCollection | null
   selectedFeature?: GeoJSON.Feature | null
   selectionData?: GeoJSON.FeatureCollection | null
+  qaEvidenceData?: GeoJSON.FeatureCollection | null
   selectionBbox?: { min_x: number; min_y: number; max_x: number; max_y: number } | null
   bboxSelectionMode?: boolean
   visible?: boolean
@@ -97,6 +98,7 @@ function GeoMap({
   areaData = null,
   selectedFeature = null,
   selectionData = null,
+  qaEvidenceData = null,
   selectionBbox = null,
   bboxSelectionMode = false,
   visible = true,
@@ -148,7 +150,18 @@ function GeoMap({
         onMapCoordinateSelectRef.current?.([event.lngLat.lng, event.lngLat.lat])
         return
       }
-      const layers = ['dataset-fill', 'dataset-line', 'area-fill', 'area-line'].filter((layerId) => map.getLayer(layerId))
+      const layers = [
+        'qa-evidence-fill',
+        'qa-evidence-line',
+        'qa-evidence-circle',
+        'selection-result-fill',
+        'selection-result-line',
+        'selection-result-circle',
+        'dataset-fill',
+        'dataset-line',
+        'area-fill',
+        'area-line',
+      ].filter((layerId) => map.getLayer(layerId))
       if (layers.length === 0) {
         onFeatureSelectRef.current?.(null)
         return
@@ -463,6 +476,74 @@ function GeoMap({
     })
   }, [selectionData, mapStyleReady])
 
+  useEffect(() => {
+    const map = mapRef.current
+    if (!map || !mapStyleReady || !map.isStyleLoaded()) {
+      return
+    }
+
+    const evidenceCollection = qaEvidenceData ?? EMPTY_FEATURE_COLLECTION
+    if (map.getSource('qa-evidence')) {
+      ;(map.getSource('qa-evidence') as maplibregl.GeoJSONSource).setData(evidenceCollection)
+      return
+    }
+
+    map.addSource('qa-evidence', { type: 'geojson', data: evidenceCollection })
+    const evidenceColor = [
+      'match',
+      ['get', 'qa_evidence_role'],
+      'match_candidate',
+      '#2563eb',
+      'match_reference',
+      '#0f766e',
+      'false_positive',
+      '#dc2626',
+      'false_negative',
+      '#d97706',
+      '#475569',
+    ] as maplibregl.ExpressionSpecification
+    map.addLayer({
+      id: 'qa-evidence-fill',
+      type: 'fill',
+      source: 'qa-evidence',
+      filter: ['match', ['geometry-type'], ['Polygon', 'MultiPolygon'], true, false],
+      paint: {
+        'fill-color': evidenceColor,
+        'fill-opacity': 0.28,
+      },
+    })
+    map.addLayer({
+      id: 'qa-evidence-line',
+      type: 'line',
+      source: 'qa-evidence',
+      filter: ['match', ['geometry-type'], ['Polygon', 'MultiPolygon', 'LineString', 'MultiLineString'], true, false],
+      paint: {
+        'line-color': evidenceColor,
+        'line-width': [
+          'match',
+          ['get', 'qa_evidence_role'],
+          'false_positive',
+          4,
+          'false_negative',
+          4,
+          3,
+        ],
+      },
+    })
+    map.addLayer({
+      id: 'qa-evidence-circle',
+      type: 'circle',
+      source: 'qa-evidence',
+      filter: ['match', ['geometry-type'], ['Point', 'MultiPoint'], true, false],
+      paint: {
+        'circle-color': evidenceColor,
+        'circle-radius': 7,
+        'circle-stroke-color': '#ffffff',
+        'circle-stroke-width': 2,
+      },
+    })
+  }, [qaEvidenceData, mapStyleReady])
+
   return <div className="map-container" ref={containerRef} />
 }
 

frontend/src/components/map/MapWorkspace.tsx

@@ -176,6 +176,11 @@ interface MapWorkspaceProps {
   selectedMapAreaId: string
   areaFeatureCollection: GeoJSON.FeatureCollection | null
   mapFeatureCollection: GeoJSON.FeatureCollection | null
+  qualityEvidenceGeoJson?: GeoJSON.FeatureCollection | null
+  qualityEvidenceFeatureCount?: number
+  qualityEvidenceLoading?: boolean
+  qualityEvidenceError?: string | null
+  qualityEvidenceWarnings?: string[]
   mapLayerLabel: string
   mapLayerSourceLabel: string
   mapLayerProvenance: string
@@ -219,6 +224,7 @@ interface MapWorkspaceProps {
   onSelectMapQaReferenceDataset: (datasetId: string) => void
   onRunMapSelectionQa: () => void
   onOpenMapSelectionQualityEvidence: () => void
+  onClearQualityEvidence?: () => void
 }
 
 export function MapWorkspace({
@@ -226,6 +232,11 @@ export function MapWorkspace({
   selectedMapAreaId,
   areaFeatureCollection,
   mapFeatureCollection,
+  qualityEvidenceGeoJson = null,
+  qualityEvidenceFeatureCount = 0,
+  qualityEvidenceLoading = false,
+  qualityEvidenceError = null,
+  qualityEvidenceWarnings = [],
   mapLayerLabel,
   mapLayerSourceLabel,
   mapLayerProvenance,
@@ -269,6 +280,7 @@ export function MapWorkspace({
   onSelectMapQaReferenceDataset,
   onRunMapSelectionQa,
   onOpenMapSelectionQualityEvidence,
+  onClearQualityEvidence,
 }: MapWorkspaceProps): JSX.Element {
   const [bboxSelectionMode, setBboxSelectionMode] = useState(false)
   const [firstSelectionCorner, setFirstSelectionCorner] = useState<[number, number] | null>(null)
@@ -398,6 +410,11 @@ export function MapWorkspace({
           <strong>{mapFeatureCollection ? `${mapFeatureCount} rendered features` : 'No layer rendered'}</strong>
           <small>{mapLayerProvenance}</small>
         </div>
+        <div>
+          <span>QA/QC evidence</span>
+          <strong>{qualityEvidenceGeoJson ? `${qualityEvidenceFeatureCount} evidence features` : 'No evidence overlay'}</strong>
+          <small>{qualityEvidenceLoading ? 'Loading persisted evidence' : 'Matches, false positives and false negatives'}</small>
+        </div>
       </div>
 
       <div className="map-control-surface" aria-label="Map workspace controls">
@@ -483,8 +500,36 @@ export function MapWorkspace({
             <span>Draw state</span>
             <strong>{mapFeatureCollection ? `${mapFeatureCount} rendered features` : 'No active vector or result layer'}</strong>
           </div>
+          <div>
+            <span>QA evidence overlay</span>
+            <strong>{qualityEvidenceGeoJson ? `${qualityEvidenceFeatureCount} rendered` : 'off'}</strong>
           </div>
         </div>
+      </div>
+
+      {qualityEvidenceGeoJson || qualityEvidenceError || qualityEvidenceWarnings.length > 0 ? (
+        <div className="qa-evidence-map-status" aria-label="QA/QC evidence map overlay status">
+          <div>
+            <span>QA/QC evidence overlay</span>
+            <strong>{qualityEvidenceGeoJson ? `${qualityEvidenceFeatureCount} persisted features` : 'Not loaded'}</strong>
+            {qualityEvidenceError ? <p className="error">{qualityEvidenceError}</p> : null}
+            {qualityEvidenceWarnings.length > 0 ? (
+              <p className="muted">{qualityEvidenceWarnings.length} evidence id{qualityEvidenceWarnings.length === 1 ? '' : 's'} could not be resolved.</p>
+            ) : null}
+          </div>
+          <div className="qa-evidence-legend" aria-label="QA/QC evidence overlay legend">
+            <span><i className="qa-evidence-swatch qa-evidence-swatch-match-candidate" /> Match candidate</span>
+            <span><i className="qa-evidence-swatch qa-evidence-swatch-match-reference" /> Match reference</span>
+            <span><i className="qa-evidence-swatch qa-evidence-swatch-false-positive" /> False positive</span>
+            <span><i className="qa-evidence-swatch qa-evidence-swatch-false-negative" /> False negative</span>
+          </div>
+          {onClearQualityEvidence ? (
+            <button className="secondary-action" type="button" onClick={onClearQualityEvidence}>
+              Clear QA evidence
+            </button>
+          ) : null}
+        </div>
+      ) : null}
 
       {!mapFeatureCollection ? (
         <div className="empty-state map-empty-state">
@@ -514,6 +559,7 @@ export function MapWorkspace({
           areaData={areaFeatureCollection}
           selectedFeature={selectedFeature}
           selectionData={mapSelectionResult?.geojson ?? null}
+          qaEvidenceData={qualityEvidenceGeoJson}
           selectionBbox={mapSelectionBbox}
           bboxSelectionMode={bboxSelectionMode}
           visible={mapLayerVisible}

frontend/src/components/quality/QualityResultsPanel.tsx

@@ -17,6 +17,9 @@ interface QualityResultsPanelProps {
   candidateDatasets: DatasetCreateResponse[]
   referenceDatasets: DatasetCreateResponse[]
   onRefresh: () => void
+  onOpenEvidenceMap?: (qualityCheckId: string) => void
+  evidenceLoading?: boolean
+  evidenceError?: string | null
 }
 
 function qualityMetricLabel(metricKey: string): string {
@@ -95,6 +98,9 @@ export function QualityResultsPanel({
   candidateDatasets,
   referenceDatasets,
   onRefresh,
+  onOpenEvidenceMap,
+  evidenceLoading = false,
+  evidenceError = null,
 }: QualityResultsPanelProps): JSX.Element {
   const [showAllQualityChecks, setShowAllQualityChecks] = useState(false)
   const [qualityStatusFilter, setQualityStatusFilter] = useState('all')
@@ -204,7 +210,21 @@ export function QualityResultsPanel({
             >
               Inspect latest check
             </button>
+            <button
+              type="button"
+              className="secondary-action"
+              onClick={() => latestCheck?.id && onOpenEvidenceMap?.(latestCheck.id)}
+              disabled={!latestCheck || evidenceLoading || !onOpenEvidenceMap}
+            >
+              {evidenceLoading ? 'Loading map evidence...' : 'Show latest on map'}
+            </button>
           </div>
+          {evidenceError ? (
+            <div className="result-state result-state-error">
+              <strong>QA/QC evidence overlay could not be loaded.</strong>
+              <p>{evidenceError}</p>
+            </div>
+          ) : null}
           {selectedQualityCheck ? (
             <>
               <div className="quality-drilldown-grid">
@@ -254,6 +274,14 @@ export function QualityResultsPanel({
                   <span>Map evidence handoff</span>
                   <strong>{selectedCandidateName} / {selectedReferenceName}</strong>
                   <p>Use the candidate and reference datasets as map layers for spatial review.</p>
+                  <button
+                    type="button"
+                    className="secondary-action"
+                    onClick={() => onOpenEvidenceMap?.(selectedQualityCheck.id)}
+                    disabled={evidenceLoading || !onOpenEvidenceMap}
+                  >
+                    {evidenceLoading ? 'Loading overlay...' : 'Show evidence overlay'}
+                  </button>
                 </div>
               </div>
               <div className="quality-feature-evidence-grid" aria-label="Feature-level QA/QC evidence">
@@ -440,6 +468,14 @@ export function QualityResultsPanel({
                   <button type="button" className="secondary-action" onClick={() => setSelectedQualityCheckId(check.id)}>
                     Inspect check
                   </button>
+                  <button
+                    type="button"
+                    className="secondary-action"
+                    onClick={() => onOpenEvidenceMap?.(check.id)}
+                    disabled={evidenceLoading || !onOpenEvidenceMap}
+                  >
+                    Show evidence on map
+                  </button>
                 </div>
                 <div className="quality-score-row">
                   <div>

frontend/src/hooks/useQualityWorkflow.ts

@@ -1,6 +1,6 @@
 import { useState } from 'react'
 import { qaApi } from '../services/api'
-import type { JobRead, QaComparisonRequest, QaComparisonResult, QualityCheckRead } from '../types'
+import type { JobRead, QaComparisonRequest, QaComparisonResult, QualityCheckRead, QualityEvidenceGeoJsonResponse } from '../types'
 import { formatError } from '../lib/formatError'
 
 interface QualityWorkflowOptions {
@@ -18,6 +18,9 @@ export function useQualityWorkflow({ selectedProjectId, loadProjectData }: Quali
   const [qaError, setQaError] = useState<string | null>(null)
   const [qualityChecks, setQualityChecks] = useState<QualityCheckRead[]>([])
   const [qualityChecksError, setQualityChecksError] = useState<string | null>(null)
+  const [qualityEvidenceGeoJson, setQualityEvidenceGeoJson] = useState<QualityEvidenceGeoJsonResponse | null>(null)
+  const [qualityEvidenceLoading, setQualityEvidenceLoading] = useState(false)
+  const [qualityEvidenceError, setQualityEvidenceError] = useState<string | null>(null)
 
   const loadQualityChecks = async (projectId = selectedProjectId): Promise<QualityCheckRead[] | void> => {
     if (!projectId) {
@@ -34,6 +37,30 @@ export function useQualityWorkflow({ selectedProjectId, loadProjectData }: Quali
     }
   }
 
+  const loadQualityEvidenceGeoJson = async (qualityCheckId: string, projectId = selectedProjectId): Promise<QualityEvidenceGeoJsonResponse | null> => {
+    if (!projectId) {
+      setQualityEvidenceError('Select a project first')
+      return null
+    }
+    setQualityEvidenceLoading(true)
+    setQualityEvidenceError(null)
+    try {
+      const response = await qaApi.getQualityEvidenceGeoJson(projectId, qualityCheckId)
+      setQualityEvidenceGeoJson(response)
+      return response
+    } catch (error) {
+      setQualityEvidenceError(formatError(error, 'Failed to load QA/QC evidence overlay'))
+      return null
+    } finally {
+      setQualityEvidenceLoading(false)
+    }
+  }
+
+  const clearQualityEvidenceGeoJson = () => {
+    setQualityEvidenceGeoJson(null)
+    setQualityEvidenceError(null)
+  }
+
   const runQaComparison = async () => {
     if (!selectedProjectId) {
       setQaError('Select a project first')
@@ -102,7 +129,12 @@ export function useQualityWorkflow({ selectedProjectId, loadProjectData }: Quali
     qaError,
     qualityChecks,
     qualityChecksError,
+    qualityEvidenceGeoJson,
+    qualityEvidenceLoading,
+    qualityEvidenceError,
     loadQualityChecks,
+    loadQualityEvidenceGeoJson,
+    clearQualityEvidenceGeoJson,
     runQaComparison,
     setQaCandidateDatasetId,
     setQaReferenceDatasetId,

frontend/src/services/api/qa.ts

@@ -1,9 +1,11 @@
 import { apiGet, apiPost } from './client'
-import type { QaComparisonRequest, JobRead, QualityCheckListResponse } from '../../types'
+import type { QaComparisonRequest, JobRead, QualityCheckListResponse, QualityEvidenceGeoJsonResponse } from '../../types'
 
 export const qaApi = {
   runQa: (payload: QaComparisonRequest): Promise<JobRead> =>
     apiPost<JobRead>('/api/v1/qa/detections-vs-reference', payload),
   listQualityChecks: (projectId: string): Promise<QualityCheckListResponse> =>
     apiGet<QualityCheckListResponse>(`/api/v1/projects/${projectId}/quality-checks`),
+  getQualityEvidenceGeoJson: (projectId: string, qualityCheckId: string): Promise<QualityEvidenceGeoJsonResponse> =>
+    apiGet<QualityEvidenceGeoJsonResponse>(`/api/v1/projects/${projectId}/quality-checks/${qualityCheckId}/evidence/geojson`),
 }

frontend/src/styles/app.css

@@ -2564,11 +2564,81 @@ button.entity-card {
 
 .layer-provenance-rail {
   display: grid;
-  grid-template-columns: 0.85fr minmax(0, 1.5fr) 0.85fr;
+  grid-template-columns: repeat(auto-fit, minmax(10rem, 1fr));
   gap: 0.65rem;
   margin-bottom: 0;
 }
 
+.qa-evidence-map-status {
+  display: grid;
+  grid-template-columns: minmax(0, 1.2fr) minmax(0, 1.6fr) auto;
+  gap: 0.65rem;
+  align-items: center;
+  border: 1px solid #bfdbfe;
+  border-left: 4px solid #2563eb;
+  border-radius: 8px;
+  padding: 0.72rem;
+  background: #eff6ff;
+}
+
+.qa-evidence-map-status span,
+.qa-evidence-map-status strong {
+  display: block;
+}
+
+.qa-evidence-map-status > div:first-child span {
+  color: #1d4ed8;
+  font-size: 0.68rem;
+  font-weight: 850;
+  letter-spacing: 0.05em;
+  text-transform: uppercase;
+}
+
+.qa-evidence-map-status > div:first-child strong {
+  margin-top: 0.18rem;
+  color: #172554;
+}
+
+.qa-evidence-legend {
+  display: grid;
+  grid-template-columns: repeat(auto-fit, minmax(8.5rem, 1fr));
+  gap: 0.38rem;
+}
+
+.qa-evidence-legend span {
+  display: inline-flex;
+  align-items: center;
+  gap: 0.38rem;
+  color: #1e3a8a;
+  font-size: 0.78rem;
+  font-weight: 750;
+}
+
+.qa-evidence-swatch {
+  display: inline-block;
+  width: 0.72rem;
+  height: 0.72rem;
+  border-radius: 999px;
+  border: 2px solid #ffffff;
+  box-shadow: 0 0 0 1px rgba(15, 23, 42, 0.18);
+}
+
+.qa-evidence-swatch-match-candidate {
+  background: #2563eb;
+}
+
+.qa-evidence-swatch-match-reference {
+  background: #0f766e;
+}
+
+.qa-evidence-swatch-false-positive {
+  background: #dc2626;
+}
+
+.qa-evidence-swatch-false-negative {
+  background: #d97706;
+}
+
 .layer-provenance-rail > div,
 .feature-property-chip {
   min-width: 0;

frontend/src/types.ts

@@ -600,6 +600,9 @@ export interface QaComparisonResult {
   iou_threshold: number
   unsupported_geometry: boolean
   unsupported_geometries: string[]
+  match_evidence?: Record<string, unknown>[]
+  false_positive_evidence?: Record<string, unknown>[]
+  false_negative_evidence?: Record<string, unknown>[]
   generated_at: string
   quality_check_id?: string
 }
@@ -640,6 +643,17 @@ export interface QualityCheckListResponse {
   offset: number
 }
 
+export interface QualityEvidenceGeoJsonResponse {
+  quality_check_id: string
+  project_id: string
+  candidate_dataset_id?: string | null
+  reference_dataset_id: string
+  analysis_run_id?: string | null
+  feature_count: number
+  warnings: string[]
+  geojson: GeoJSON.FeatureCollection
+}
+
 export type ExportKind = 'dataset' | 'detection_run' | 'segmentation_run' | 'vector_selection'
 
 export interface ExportRead {