fix(scada): preserve observation fields in chart evidence

tests/unit/test_mcp_query.py

@@ -1116,6 +1116,31 @@ def test_time_series_sql_is_bounded_and_field_names_cannot_inject_sql():
     asyncio.run(check())
 
 
+@pytest.mark.parametrize("field", ["monitored_value", "cleaned_value"])
+def test_scada_detail_preserves_the_requested_field_with_its_value_alias(monkeypatch, field):
+    at = datetime.now(timezone.utc)
+    monkeypatch.setattr(query_service, "permissions_for_context", lambda ctx: PERMISSIONS)
+    monkeypatch.setattr(query_service.reads, "series_rows", AsyncMock(return_value=[{
+        "device_id": "D1", "time": at, "value": 32.0,
+    }]))
+    monkeypatch.setattr(query_service.reads, "scada_devices", AsyncMock(return_value=[{
+        "device_id": "D1", "measurement_unit": "m",
+    }]))
+
+    class Scope:
+        project = object()
+        connection = Connection()
+
+        @asynccontextmanager
+        async def timescale(self):
+            yield self.connection
+
+    args = ScadaInput(context_handle="a" * 43, device_ids=["D1"], field=field,
+                      start=at - timedelta(hours=3), end=at)
+    result = asyncio.run(query_service.execute_query(Scope(), binding(), TOOLS["query_scada_readings"], args))
+    assert result.data[0][field] == result.data[0]["value"] == 32.0
+
+
 def test_analysis_preserves_run_units_and_reports_inference(monkeypatch):
     from app.mcp.models import AnalysisValuesInput
     from unittest.mock import AsyncMock

tests/unit/test_scada_presentation_coverage.py

@@ -1,5 +1,6 @@
 """SCADA display coverage is independent of whether a device supports a conclusion."""
 from datetime import datetime, timedelta, timezone
+from copy import deepcopy
 from uuid import uuid4
 
 import pytest
@@ -16,6 +17,44 @@ END = datetime(2026, 7, 16, tzinfo=timezone.utc)
 START = END - timedelta(hours=3)
 
 
+@pytest.mark.anyio
+async def test_value_only_detail_evidence_cannot_claim_missing_observations():
+    from app.services.scada_presentation_coverage import verify_chart
+    task, repository, _, evidence_id = await investigation()
+    detail = deepcopy(repository.evidence[evidence_id])
+    detail["evidence_id"] = "detail-values"
+    rows = detail["data_snapshot"]["data"]["data"]["readings"]
+    detail["data_snapshot"]["data"]["data"] = [
+        {"device_id": row["device_id"], "time": row["time"], "value": row["monitored_value"]}
+        for row in rows
+    ]
+    value = chart(devices=["524529"])
+    value["series"][0].update(data=[None] * 13, sample_times=[None] * 13)
+    with pytest.raises(DomainError) as failure:
+        verify_chart(task, value, [repository.evidence[evidence_id], detail], ["detail-values"])
+    assert failure.value.code == "SCADA_CHART_EVIDENCE_REQUIRED"
+
+
+@pytest.mark.anyio
+@pytest.mark.parametrize("field", ["monitored_value", "cleaned_value"])
+async def test_detail_fields_do_not_discard_other_observed_fields(field):
+    from app.services.scada_presentation_coverage import verify_chart
+    task, repository, _, evidence_id = await investigation()
+    detail = deepcopy(repository.evidence[evidence_id])
+    detail["evidence_id"] = "detail-cleaned"
+    rows = detail["data_snapshot"]["data"]["data"]["readings"]
+    detail["data_snapshot"]["data"]["data"] = [
+        {"device_id": row["device_id"], "time": row["time"], "value": row["cleaned_value"] + 10,
+         "cleaned_value": row["cleaned_value"] + 10} for row in rows
+    ]
+    value = chart(devices=["524529"])
+    value["scada"]["value_field"] = field
+    if field == "cleaned_value":
+        value["series"][0]["data"] = [point + 10 for point in value["series"][0]["data"]]
+    result = verify_chart(task, value, [repository.evidence[evidence_id], detail], [evidence_id, "detail-cleaned"])
+    assert result["gaps"] == []
+
+
 @pytest.fixture
 def anyio_backend():
     return "asyncio"