feat(grafana-metric-gateway): slice 1 — backend gateway transport

Route all prometheus widget queries through Grafana /api/ds/query instead of
direct Prom HTTP. PrometheusConfig: drop base_url, add grafana_url +
datasource_uid; secret grafana_api_key (required). PrometheusWidgetSource →
MetricSource with _gateway_query POST method. normalize_grafana_frames
recovered from 65bae95 + shared _dedup_label helper. Gateway-path status
check. Startup old-config validation. CHANGELOG migration note. All adapter
tests rewritten for POST /api/ds/query + Grafana frames mock. Backend: 331
pytest pass, ruff clean. Frontend: build green (unchanged in S1).

backend/src/media_library_viewer_api/integrations/prometheus.py

@@ -13,9 +13,10 @@ from media_library_viewer_api.integrations.base import (
 
 
 class PrometheusConfig(ServiceConfigBase):
-    """Non-secret Prometheus connection config."""
+    """Non-secret Prometheus-via-Grafana gateway config."""
 
-    base_url: ServiceBaseUrl
+    grafana_url: ServiceBaseUrl
+    datasource_uid: str = "prometheus"
     timeout_seconds: int = 10
 
 
@@ -57,7 +58,12 @@ DEFINITION = ServiceDefinition(
     description="Metrics storage and PromQL queries.",
     config_model=PrometheusConfig,
     secret_fields=[
-        SecretField(key="api_key", label="API key", helper="Optional bearer token"),
+        SecretField(
+            key="grafana_api_key",
+            label="Grafana API key",
+            required=True,
+            helper="Service account token or API key for the Grafana gateway",
+        ),
     ],
     widget_kinds=[
         widget_kind(

backend/src/media_library_viewer_api/main.py

@@ -37,6 +37,23 @@ from .version import get_backend_version, get_version_info
 logger = logging.getLogger(__name__)
 
 
+def _validate_prometheus_gateway_config() -> None:
+    """Warn (not crash) about old-shape prometheus services needing migration (GM-113)."""
+    try:
+        store = get_settings_store()
+        for service in store.list_services("prometheus"):
+            config = service.get("config") or {}
+            if "base_url" in config and "grafana_url" not in config:
+                logger.warning(
+                    "Prometheus service '%s' (id=%s) uses the old 'base_url' config shape. "
+                    "Reconfigure with grafana_url + grafana_api_key (see CHANGELOG).",
+                    service.get("name"),
+                    service.get("id"),
+                )
+    except Exception:  # pragma: no cover - startup best-effort
+        logger.exception("Failed to validate prometheus gateway config during startup")
+
+
 @asynccontextmanager
 async def lifespan(app: FastAPI):
     """Application lifespan — startup/shutdown."""
@@ -58,6 +75,7 @@ async def lifespan(app: FastAPI):
         get_service_data_harness()
     except Exception:
         logger.exception("Failed to initialize service data harness during startup")
+    _validate_prometheus_gateway_config()
     mail_queue = get_mail_queue()
     backup_poller = get_backup_poller()
     mail_queue.start()

backend/src/media_library_viewer_api/routers/monitoring.py

@@ -177,23 +177,52 @@ def get_prometheus_status(
     service_id: str | None = None,
     store: SettingsStore = Depends(get_settings_store),
 ) -> dict[str, Any]:
-    """Probe a Prometheus service instance's health and build info."""
+    """Probe a Prometheus service's health via the Grafana gateway path (GM-110).
+
+    Issues a trivial ``up`` query through Grafana ``/api/ds/query``. Success
+    validates the full path: Grafana is reachable, the API key works, and the
+    Prometheus datasource responds.
+    """
     service = resolve_service_record(store, "prometheus", service_id)
     if service is None:
         return _status_response(None, error="no_service_configured")
-    base = _base_url(service)
-    timeout = _timeout(service, 10)
-    headers = _auth_headers(service)
+    grafana_url = str(service.config.get("grafana_url") or "").rstrip("/")
+    api_key = str(service.secrets.get("grafana_api_key") or "")
+    datasource_uid = str(service.config.get("datasource_uid") or "prometheus")
+    timeout = int(service.config.get("timeout_seconds") or 10)
+    if not grafana_url or not api_key:
+        return _status_response(service, error="gateway_not_configured")
+    body = {
+        "queries": [
+            {
+                "datasource": {"uid": datasource_uid, "type": "prometheus"},
+                "expr": "up",
+                "format": "time_series",
+                "intervalMs": 15_000,
+                "maxDataPoints": 1,
+                "refId": "A",
+            }
+        ],
+        "from": "now-1m",
+        "to": "now",
+    }
     try:
-        health = requests.get(f"{base}/-/healthy", headers=headers, timeout=timeout)
-        health.raise_for_status()
-        build_info = requests.get(f"{base}/api/v1/status/buildinfo", headers=headers, timeout=timeout)
-        build_info.raise_for_status()
-        version = build_info.json().get("data", {}).get("version", "")
-    except Exception:
-        logger.exception("Failed to fetch Prometheus status")
+        resp = requests.post(
+            f"{grafana_url}/api/ds/query",
+            json=body,
+            headers={"Authorization": f"Bearer {api_key}", "Content-Type": "application/json"},
+            timeout=timeout,
+        )
+        resp.raise_for_status()
+    except requests.HTTPError as exc:
+        status_code = exc.response.status_code if exc.response else 0
+        if status_code in (401, 403):
+            return _status_response(service, error="auth_failed")
+        return _status_response(service, error="gateway_error")
+    except requests.RequestException:
+        logger.exception("Failed to fetch Prometheus status via gateway")
         return _status_response(service, error="prometheus_unreachable")
-    return _status_response(service, version=version)
+    return _status_response(service, version="ok")
 
 
 @router.post("/alertmanager-webhook")

backend/src/media_library_viewer_api/widgets/prometheus_range.py

@@ -43,6 +43,15 @@ def step_for_window(window_seconds: int, target_points: int = 200) -> int:
     return max(15, round(window_seconds / target_points))
 
 
+def _dedup_label(label: str, seen: dict[str, int]) -> str:
+    """Apply `` (n)`` suffix on collision. Mutates and reads from ``seen`` dict."""
+    if label in seen:
+        seen[label] += 1
+        return f"{label} ({seen[label]})"
+    seen[label] = 0
+    return label
+
+
 def normalize_prometheus_matrix(result: list[dict[str, Any]]) -> list[dict[str, Any]]:
     """Turn a Prometheus ``/api/v1/query_range`` ``data.result`` matrix into the
     ``{label, points:[{t:int, v:float|None}]}`` series shape the frontend chart
@@ -62,12 +71,7 @@ def normalize_prometheus_matrix(result: list[dict[str, Any]]) -> list[dict[str,
         metric = entry.get("metric") or {}
         values = entry.get("values") or []
         parts = [f"{k}={v}" for k, v in sorted(metric.items()) if not str(k).startswith("__")]
-        label = " ".join(parts) if parts else "value"
-        if label in seen:
-            seen[label] += 1
-            label = f"{label} ({seen[label]})"
-        else:
-            seen[label] = 0
+        label = _dedup_label(" ".join(parts) if parts else "value", seen)
         points: list[dict[str, Any]] = []
         for ts, raw in values:
             t = _safe_int(ts)
@@ -79,6 +83,52 @@ def normalize_prometheus_matrix(result: list[dict[str, Any]]) -> list[dict[str,
     return series
 
 
+def normalize_grafana_frames(raw: dict[str, Any]) -> list[dict[str, Any]]:
+    """Turn a Grafana ``/api/ds/query`` response into the ``{label, points}`` series shape.
+
+    Parses ``results.<refId>.frames[]`` where each frame has:
+      - ``data.values``: ``[[timestamps...], [values...]]``
+      - ``schema.fields``: ``[{name, labels?, config?: {displayName?}}, ...]``
+
+    Label rule (same as ``normalize_prometheus_matrix``, shared via ``_dedup_label``):
+    1. Prefer ``config.displayName`` (explicitly set in Grafana).
+    2. Else use Prometheus metric labels (sorted ``k=v``, excluding ``__``-prefixed).
+    3. Else fall back to the field name, or ``"value"``.
+    4. Dedup collisions with `` (n)`` suffix.
+    """
+    series: list[dict[str, Any]] = []
+    seen: dict[str, int] = {}
+    results = raw.get("results", {})
+    for _ref_id, ref_data in results.items():
+        for frame in ref_data.get("frames", []):
+            values = frame.get("data", {}).get("values", [])
+            if len(values) < 2:
+                continue
+            timestamps = values[0]
+            vals = values[1]
+            # Derive a meaningful series label from the frame metadata.
+            fields = frame.get("schema", {}).get("fields", [])
+            value_field = fields[-1] if fields else {}
+            display_name = value_field.get("config", {}).get("displayName") or value_field.get("displayName")
+            frame_labels = value_field.get("labels") or {}
+            if display_name:
+                label = str(display_name)
+            elif frame_labels:
+                parts = [f"{k}={v}" for k, v in sorted(frame_labels.items()) if not str(k).startswith("__")]
+                label = " ".join(parts) if parts else "value"
+            else:
+                label = str(value_field.get("name", "value"))
+            label = _dedup_label(label, seen)
+            points = []
+            for t, v in zip(timestamps, vals):
+                safe_t = _safe_int(t)
+                if safe_t is None:
+                    continue
+                points.append({"t": safe_t, "v": _safe_float(v)})
+            series.append({"label": label, "points": points})
+    return series
+
+
 def _safe_float(raw: Any) -> float | None:
     """Best-effort float conversion; Prometheus sentinels and junk → ``None``."""
     if raw in _NON_NUMERIC:

backend/src/media_library_viewer_api/widgets/sources.py

@@ -30,7 +30,8 @@ from media_library_viewer_api.services.settings_store import SettingsStore, get_
 from media_library_viewer_api.services.task_runner import run_saved_task
 from media_library_viewer_api.widgets.prometheus_range import (
     WINDOW_PRESETS,
-    normalize_prometheus_matrix,
+    normalize_grafana_frames,
+    normalize_prometheus_matrix,  # noqa: F401 — kept for future direct_url path (design decision 5)
     step_for_window,
 )
 
@@ -104,113 +105,118 @@ class StaticWidgetSource:
 # ---------------------------------------------------------------------------
 
 
-class PrometheusWidgetSource:
-    """Run PromQL queries against a Prometheus service (instant + range)."""
+class MetricSource:
+    """Run PromQL queries through a Grafana gateway (``/api/ds/query``)."""
 
     async def fetch(self, service: ServiceRecord | None, widget_kind: str, config: dict[str, Any]) -> dict[str, Any]:
         try:
             if service is None:
                 return {"error": "Prometheus widget is missing its service"}
-            base_url = str(service.config.get("base_url") or "").rstrip("/")
+            grafana_url = str(service.config.get("grafana_url") or "").rstrip("/")
+            api_key = str(service.secrets.get("grafana_api_key") or "")
+            datasource_uid = str(service.config.get("datasource_uid") or "prometheus")
             timeout = int(service.config.get("timeout_seconds") or 10)
             if widget_kind == "chart":
-                return await self._fetch_chart(base_url, timeout, config)
+                return await self._fetch_chart(grafana_url, api_key, datasource_uid, timeout, config)
             if widget_kind == "gauge":
-                return await self._fetch_gauge(base_url, timeout, config)
+                return await self._fetch_gauge(grafana_url, api_key, datasource_uid, timeout, config)
             if widget_kind == "mean":
-                return await self._fetch_mean(base_url, timeout, config)
-            # Default: instant-query metric path (unchanged).
-            raw = await self._instant_query(base_url, timeout, config.get("promql", ""))
-            return raw
+                return await self._fetch_mean(grafana_url, api_key, datasource_uid, timeout, config)
+            # Default: instant-query metric path.
+            return await self._fetch_metric(grafana_url, api_key, datasource_uid, timeout, config)
         except Exception as exc:
             logger.exception("prometheus adapter failed")
             return {"error": f"Prometheus query failed: {exc}"}
 
-    async def _range_query(self, base_url: str, timeout: int, promql: str, window: int) -> dict[str, Any]:
-        """Run a Prometheus ``/api/v1/query_range`` over a window (seconds).
+    async def _gateway_query(
+        self,
+        grafana_url: str,
+        api_key: str,
+        datasource_uid: str,
+        timeout: int,
+        promql: str,
+        window_seconds: int | None = None,
+        max_data_points: int = 200,
+    ) -> dict[str, Any]:
+        """POST ``{grafana_url}/api/ds/query``; return raw Grafana JSON or ``{error}``.
 
-        Shared by the ``chart`` (SC-101) and ``mean`` widget kinds. Returns
-        ``{"matrix": result}`` on success or ``{"error": str}`` (never raises,
-        per SC-103).
+        - ``window_seconds=None`` → instant mapping (``from=now-1m, maxDataPoints=1``).
+        - ``window_seconds=<N>`` → range query (``from=now-Ns``, step derived).
         """
-        step = step_for_window(window)
-        end = int(time.time())
-        start = end - window
-        try:
-            response = await asyncio.wait_for(
-                asyncio.to_thread(
-                    requests.get,
-                    f"{base_url}/api/v1/query_range",
-                    params={"query": promql, "start": start, "end": end, "step": step},
-                    timeout=timeout,
-                ),
+        if not grafana_url:
+            return {"error": "grafana_url is required"}
+        if not api_key:
+            return {"error": "grafana_api_key is required"}
+        step = step_for_window(window_seconds) if window_seconds else 15
+        interval_ms = step * 1000
+        body = {
+            "queries": [
+                {
+                    "datasource": {"uid": datasource_uid, "type": "prometheus"},
+                    "expr": promql,
+                    "format": "time_series",
+                    "intervalMs": interval_ms,
+                    "maxDataPoints": 1 if window_seconds is None else max_data_points,
+                    "refId": "A",
+                }
+            ],
+            "from": f"now-{window_seconds or 60}s" if window_seconds else "now-1m",
+            "to": "now",
+        }
+
+        def _do_post() -> dict[str, Any]:
+            resp = requests.post(
+                f"{grafana_url}/api/ds/query",
+                json=body,
+                headers={"Authorization": f"Bearer {api_key}", "Content-Type": "application/json"},
                 timeout=timeout,
             )
-            response.raise_for_status()
-            payload = response.json()
-        except asyncio.TimeoutError:
-            return {"error": "Prometheus query timed out"}
-        except requests.RequestException as exc:
-            logger.exception("prometheus range query failed")
-            return {"error": f"Prometheus query failed: {exc}"}
-        result = payload.get("data", {}).get("result", [])
-        return {"matrix": result}
+            resp.raise_for_status()
+            return resp.json()
 
-    async def _instant_query(self, base_url: str, timeout: int, promql: str) -> dict[str, Any]:
-        """Run a Prometheus ``/api/v1/query`` instant query.
-
-        Shared by the ``metric`` and ``gauge`` widget kinds. Returns
-        ``{"result": data}`` on success or ``{"error": str}`` (never raises,
-        per SC-103).
-        """
-        if not promql:
-            return {"error": "promql is required"}
         try:
-            response = await asyncio.wait_for(
-                asyncio.to_thread(
-                    requests.get,
-                    f"{base_url}/api/v1/query",
-                    params={"query": promql},
-                    timeout=timeout,
-                ),
-                timeout=timeout,
-            )
-            response.raise_for_status()
-            payload = response.json()
+            return await asyncio.wait_for(asyncio.to_thread(_do_post), timeout=timeout)
         except asyncio.TimeoutError:
-            return {"error": "Prometheus query timed out"}
+            return {"error": "Grafana query timed out"}
         except requests.RequestException as exc:
-            logger.exception("prometheus instant query failed")
-            return {"error": f"Prometheus query failed: {exc}"}
-        return {"result": payload.get("data", {})}
+            logger.exception("grafana gateway query failed")
+            return {"error": f"Grafana query failed: {exc}"}
 
-    async def _fetch_chart(self, base_url: str, timeout: int, config: dict[str, Any]) -> dict[str, Any]:
-        """Range query → ``{series}`` for the chart widget (SC-101..SC-104)."""
+    async def _fetch_chart(
+        self, grafana_url: str, api_key: str, datasource_uid: str, timeout: int, config: dict[str, Any]
+    ) -> dict[str, Any]:
+        """Range query → ``{series}`` for the chart widget (GM-106)."""
         promql = config.get("promql")
         if not promql:
             return {"error": "promql is required"}
         window = WINDOW_PRESETS.get(config.get("window", "1h"), WINDOW_PRESETS["1h"])
-        raw = await self._range_query(base_url, timeout, promql, window)
+        raw = await self._gateway_query(grafana_url, api_key, datasource_uid, timeout, promql, window_seconds=window)
         if "error" in raw:
             return raw
-        return {"series": normalize_prometheus_matrix(raw["matrix"])}
+        return {"series": normalize_grafana_frames(raw)}
 
-    async def _fetch_gauge(self, base_url: str, timeout: int, config: dict[str, Any]) -> dict[str, Any]:
-        """Instant query → scalar for the gauge widget (SC-109, SC-110, SC-111).
+    async def _fetch_gauge(
+        self, grafana_url: str, api_key: str, datasource_uid: str, timeout: int, config: dict[str, Any]
+    ) -> dict[str, Any]:
+        """Instant query → scalar for the gauge widget (GM-107).
 
-        Scalar-only: a multi-series query returns an error (SC-111). Threshold
-        config (``warn_at``/``crit_at``/``min``/``max``/``unit``) is passed
-        through for the frontend renderer.
+        Scalar-only: a multi-series query returns an error. Threshold config is
+        passed through for the frontend renderer.
         """
-        raw = await self._instant_query(base_url, timeout, config.get("promql") or "")
+        promql = config.get("promql") or ""
+        if not promql:
+            return {"error": "promql is required"}
+        raw = await self._gateway_query(grafana_url, api_key, datasource_uid, timeout, promql, window_seconds=None)
         if "error" in raw:
             return raw
-        result = raw["result"].get("result", [])
-        if len(result) != 1:
+        series = normalize_grafana_frames(raw)
+        if len(series) != 1:
             return {"error": "Gauge requires a single-series query; refine your PromQL"}
-        try:
-            value = float(result[0]["value"][1])
-        except (KeyError, IndexError, ValueError, TypeError):
+        points = series[0]["points"]
+        if not points:
+            return {"error": "Gauge query returned no scalar value"}
+        value = points[-1]["v"]
+        if value is None:
             return {"error": "Gauge query returned no scalar value"}
         return {
             "value": value,
@@ -221,36 +227,46 @@ class PrometheusWidgetSource:
             "unit": config.get("unit"),
         }
 
-    async def _fetch_mean(self, base_url: str, timeout: int, config: dict[str, Any]) -> dict[str, Any]:
-        """Range query → client-side mean for the mean widget (SC-112..SC-114).
+    async def _fetch_mean(
+        self, grafana_url: str, api_key: str, datasource_uid: str, timeout: int, config: dict[str, Any]
+    ) -> dict[str, Any]:
+        """Range query → client-side mean for the mean widget (GM-108).
 
-        Runs ``query_range`` over the configured window preset, averages all
-        non-null numeric samples of the single series, and returns a scalar.
-        Scalar-only: a multi-series query returns an error (SC-114).
+        Runs a gateway range query over the configured window preset, averages
+        all non-null numeric samples of the single series, and returns a scalar.
+        Scalar-only: a multi-series query returns an error.
         """
         promql = config.get("promql")
         if not promql:
             return {"error": "promql is required"}
         window = WINDOW_PRESETS.get(config.get("window", "1h"), WINDOW_PRESETS["1h"])
-        raw = await self._range_query(base_url, timeout, promql, window)
+        raw = await self._gateway_query(grafana_url, api_key, datasource_uid, timeout, promql, window_seconds=window)
         if "error" in raw:
             return raw
-        result = raw["matrix"]
-        if len(result) != 1:
+        series = normalize_grafana_frames(raw)
+        if len(series) != 1:
             return {"error": "Mean requires a single-series query; refine your PromQL"}
-        points = result[0].get("values") or []
-        nums: list[float] = []
-        for _, v in points:
-            if v in (None, "NaN", "+Inf", "-Inf"):
-                continue
-            try:
-                nums.append(float(v))
-            except (TypeError, ValueError):
-                continue
+        nums = [p["v"] for p in series[0]["points"] if p["v"] is not None]
         if not nums:
             return {"error": "Mean query returned no numeric samples in the window"}
-        mean = sum(nums) / len(nums)
-        return {"value": mean, "unit": config.get("unit")}
+        return {"value": sum(nums) / len(nums), "unit": config.get("unit")}
+
+    async def _fetch_metric(
+        self, grafana_url: str, api_key: str, datasource_uid: str, timeout: int, config: dict[str, Any]
+    ) -> dict[str, Any]:
+        """Instant query → ``{result}`` for the metric widget (GM-109).
+
+        Returns ``{result: [{label, points}]}`` — the normalized series shape.
+        The frontend ``PrometheusMetricWidget`` renders the last point of each
+        series.
+        """
+        promql = config.get("promql") or ""
+        if not promql:
+            return {"error": "promql is required"}
+        raw = await self._gateway_query(grafana_url, api_key, datasource_uid, timeout, promql, window_seconds=None)
+        if "error" in raw:
+            return raw
+        return {"result": normalize_grafana_frames(raw)}
 
 
 class AlertmanagerWidgetSource:
@@ -437,7 +453,7 @@ class QbittorrentWidgetSource:
 # ---------------------------------------------------------------------------
 
 SERVICE_ADAPTERS: dict[str, WidgetSource] = {
-    "prometheus": PrometheusWidgetSource(),
+    "prometheus": MetricSource(),
     "qbittorrent": QbittorrentWidgetSource(),
     "alertmanager": AlertmanagerWidgetSource(),
     "jellyfin": JellyfinWidgetSource(),

backend/tests/test_api.py

@@ -751,11 +751,15 @@ class TestPrometheusStatus:
 
     def test_prometheus_status_when_unreachable(self, test_client):
         service = ServiceRecord(
-            id="p1", service_type="prometheus", name="Prometheus", config={"base_url": "http://prometheus:9090"}
+            id="p1",
+            service_type="prometheus",
+            name="Prometheus",
+            config={"grafana_url": "http://grafana:3000", "datasource_uid": "prometheus"},
+            secrets={"grafana_api_key": "key"},
         )
         with (
             patch(f"{_MON}.resolve_service_record", return_value=service),
-            patch(f"{_MON}.requests.get", side_effect=Exception("refused")),
+            patch(f"{_MON}.requests.post", side_effect=__import__("requests").ConnectionError("refused")),
         ):
             response = test_client.get("/api/monitoring/prometheus-status")
         assert response.status_code == 200
@@ -763,22 +767,23 @@ class TestPrometheusStatus:
         assert data["up"] is False
         assert data["error"] == "prometheus_unreachable"
 
-    def test_prometheus_status_returns_version(self, test_client):
+    def test_prometheus_status_returns_ok(self, test_client):
         service = ServiceRecord(
-            id="p1", service_type="prometheus", name="Prometheus", config={"base_url": "http://prometheus:9090"}
+            id="p1",
+            service_type="prometheus",
+            name="Prometheus",
+            config={"grafana_url": "http://grafana:3000", "datasource_uid": "prometheus"},
+            secrets={"grafana_api_key": "key"},
         )
-        health = MagicMock()
-        health.raise_for_status = MagicMock()
-        build_info = MagicMock()
-        build_info.raise_for_status = MagicMock()
-        build_info.json.return_value = {"status": "success", "data": {"version": "2.55.1"}}
+        gateway_resp = MagicMock()
+        gateway_resp.raise_for_status = MagicMock()
         with (
             patch(f"{_MON}.resolve_service_record", return_value=service),
-            patch(f"{_MON}.requests.get", side_effect=[health, build_info]),
+            patch(f"{_MON}.requests.post", return_value=gateway_resp),
         ):
             response = test_client.get("/api/monitoring/prometheus-status")
         assert response.status_code == 200
         data = response.json()
         assert data["up"] is True
-        assert data["version"] == "2.55.1"
+        assert data["version"] == "ok"
         assert data["service_id"] == "p1"

backend/tests/test_prometheus_range.py

@@ -6,6 +6,8 @@ import pytest
 
 from media_library_viewer_api.widgets.prometheus_range import (
     WINDOW_PRESETS,
+    _dedup_label,
+    normalize_grafana_frames,
     normalize_prometheus_matrix,
     step_for_window,
 )
@@ -104,3 +106,152 @@ class TestNormalizePrometheusMatrix:
             {"t": 1, "v": 3.5},
             {"t": 3, "v": None},
         ]
+
+
+class TestDedupLabel:
+    """The shared label-dedup helper used by both normalizers (GM-104)."""
+
+    def test_first_use_returns_label_unchanged(self) -> None:
+        seen: dict[str, int] = {}
+        assert _dedup_label("value", seen) == "value"
+        assert seen == {"value": 0}
+
+    def test_collision_appends_suffix(self) -> None:
+        seen: dict[str, int] = {}
+        assert _dedup_label("job=x", seen) == "job=x"
+        assert _dedup_label("job=x", seen) == "job=x (1)"
+        assert _dedup_label("job=x", seen) == "job=x (2)"
+
+    def test_different_labels_dont_collide(self) -> None:
+        seen: dict[str, int] = {}
+        assert _dedup_label("a", seen) == "a"
+        assert _dedup_label("b", seen) == "b"
+
+
+class TestNormalizeGrafanaFrames:
+    """GM-104: frames normalizer recovered from 65bae95 + shared dedup."""
+
+    def test_empty_response(self) -> None:
+        assert normalize_grafana_frames({"results": {}}) == []
+        assert normalize_grafana_frames({}) == []
+
+    def test_single_frame_with_values(self) -> None:
+        raw = {
+            "results": {
+                "A": {
+                    "frames": [
+                        {
+                            "data": {"values": [[1000, 2000], [1.5, 2.5]]},
+                            "schema": {"fields": [{"name": "Time"}, {"name": "Value"}]},
+                        }
+                    ]
+                }
+            }
+        }
+        out = normalize_grafana_frames(raw)
+        assert len(out) == 1
+        assert out[0]["label"] == "Value"
+        assert out[0]["points"] == [
+            {"t": 1000, "v": 1.5},
+            {"t": 2000, "v": 2.5},
+        ]
+
+    def test_display_name_takes_priority(self) -> None:
+        raw = {
+            "results": {
+                "A": {
+                    "frames": [
+                        {
+                            "data": {"values": [[100, 200], [0.75, 0.80]]},
+                            "schema": {
+                                "fields": [
+                                    {"name": "Time"},
+                                    {
+                                        "name": "Value",
+                                        "labels": {"instance": "host:9100"},
+                                        "config": {"displayName": "CPU Usage"},
+                                    },
+                                ]
+                            },
+                        }
+                    ]
+                }
+            }
+        }
+        out = normalize_grafana_frames(raw)
+        assert out[0]["label"] == "CPU Usage"
+
+    def test_labels_fallback_when_no_display_name(self) -> None:
+        raw = {
+            "results": {
+                "A": {
+                    "frames": [
+                        {
+                            "data": {"values": [[100], [1.0]]},
+                            "schema": {
+                                "fields": [
+                                    {"name": "Time"},
+                                    {
+                                        "name": "Value",
+                                        "labels": {"__name__": "up", "instance": "h:9100"},
+                                    },
+                                ]
+                            },
+                        }
+                    ]
+                }
+            }
+        }
+        out = normalize_grafana_frames(raw)
+        assert out[0]["label"] == "instance=h:9100"
+
+    def test_falls_back_to_value_when_no_metadata(self) -> None:
+        raw = {
+            "results": {
+                "A": {
+                    "frames": [
+                        {
+                            "data": {"values": [[100], [1.0]]},
+                            "schema": {"fields": [{"name": "Time"}, {}]},
+                        }
+                    ]
+                }
+            }
+        }
+        out = normalize_grafana_frames(raw)
+        assert out[0]["label"] == "value"
+
+    def test_dedup_collisions(self) -> None:
+        raw = {
+            "results": {
+                "A": {
+                    "frames": [
+                        {
+                            "data": {"values": [[100], [1.0]]},
+                            "schema": {"fields": [{}, {"name": "Value"}]},
+                        },
+                        {
+                            "data": {"values": [[100], [2.0]]},
+                            "schema": {"fields": [{}, {"name": "Value"}]},
+                        },
+                    ]
+                }
+            }
+        }
+        out = normalize_grafana_frames(raw)
+        labels = [s["label"] for s in out]
+        assert labels == ["Value", "Value (1)"]
+
+    def test_skips_frames_with_insufficient_values(self) -> None:
+        raw = {
+            "results": {
+                "A": {
+                    "frames": [
+                        {"data": {"values": [[100]]}, "schema": {"fields": []}},
+                        {"data": {"values": [[100], [1.0]]}, "schema": {"fields": [{}, {}]}},
+                    ]
+                }
+            }
+        }
+        out = normalize_grafana_frames(raw)
+        assert len(out) == 1

backend/tests/test_services.py

@@ -117,7 +117,7 @@ def test_widget_kind_lookup():
 def test_service_config_schema_is_json_schema():
     schema = get_service_definition("prometheus").config_schema
     assert schema["type"] == "object"
-    assert "base_url" in schema["properties"]
+    assert "grafana_url" in schema["properties"]
 
 
 # ---------------------------------------------------------------------------
@@ -182,7 +182,7 @@ def test_list_service_types(client):
 def test_service_type_includes_secret_and_widget_metadata(client):
     response = client.get("/api/services/types")
     prom = next(item for item in response.json() if item["service_type"] == "prometheus")
-    assert [sf["key"] for sf in prom["secret_fields"]] == ["api_key"]
+    assert [sf["key"] for sf in prom["secret_fields"]] == ["grafana_api_key"]
     assert set(wk["kind"] for wk in prom["widget_kinds"]) == {"metric", "chart", "gauge", "mean"}
 
 
@@ -195,8 +195,8 @@ def _prometheus_payload(**overrides):
     payload = {
         "service_type": "prometheus",
         "name": "Production Prometheus",
-        "config": {"base_url": "https://prometheus.example.com"},
-        "secrets": {"api_key": "secret-token"},
+        "config": {"grafana_url": "https://grafana.example.com", "datasource_uid": "prometheus"},
+        "secrets": {"grafana_api_key": "secret-token"},
         "enabled": True,
     }
     payload.update(overrides)
@@ -208,10 +208,10 @@ def test_create_and_list_service(client):
     assert response.status_code == 201
     created = response.json()
     assert created["service_type"] == "prometheus"
-    assert created["config"]["base_url"] == "https://prometheus.example.com"
+    assert created["config"]["grafana_url"] == "https://grafana.example.com"
     # Plaintext secrets are never returned.
     assert "secrets" not in created
-    assert created["secrets_set"] == {"api_key": True}
+    assert created["secrets_set"] == {"grafana_api_key": True}
 
     response = client.get("/api/services/instances")
     assert response.status_code == 200
@@ -242,11 +242,11 @@ def test_update_service_preserves_unsent_secrets(client):
         json={
             "service_type": "prometheus",
             "name": "Renamed Prometheus",
-            "config": {"base_url": "https://prometheus.example.com", "timeout_seconds": 10},
+            "config": {"grafana_url": "https://grafana.example.com", "timeout_seconds": 10},
         },
     ).json()
     assert updated["name"] == "Renamed Prometheus"
-    assert updated["secrets_set"] == {"api_key": True}
+    assert updated["secrets_set"] == {"grafana_api_key": True}
 
 
 def test_update_service_can_clear_secret(client):
@@ -256,11 +256,11 @@ def test_update_service_can_clear_secret(client):
         json={
             "service_type": "prometheus",
             "name": "Production Prometheus",
-            "config": {"base_url": "https://prometheus.example.com"},
-            "secrets": {"api_key": ""},
+            "config": {"grafana_url": "https://grafana.example.com"},
+            "secrets": {"grafana_api_key": ""},
         },
     ).json()
-    assert updated["secrets_set"] == {"api_key": False}
+    assert updated["secrets_set"] == {"grafana_api_key": False}
 
 
 def test_unknown_service_type_rejected(client):
@@ -274,7 +274,7 @@ def test_unknown_service_type_rejected(client):
 def test_invalid_config_rejected(client):
     response = client.post(
         "/api/services/instances",
-        json={"service_type": "prometheus", "name": "x", "config": {"base_url": ""}},
+        json={"service_type": "prometheus", "name": "x", "config": {"grafana_url": ""}},
     )
     assert response.status_code == 422
     # Force a real validation error via bad type.
@@ -292,10 +292,10 @@ def test_service_base_url_requires_http_schema(bad_url):
     """Every service base_url must include an http:// or https:// schema."""
     model = get_service_definition("prometheus").config_model
     with pytest.raises(ValidationError):
-        model.model_validate({"base_url": bad_url, "timeout_seconds": 5})
+        model.model_validate({"grafana_url": bad_url, "timeout_seconds": 5})
 
 
-@pytest.mark.parametrize("service_type", ["prometheus", "alertmanager", "jellyfin", "authentik", "nextcloud"])
+@pytest.mark.parametrize("service_type", ["alertmanager", "jellyfin", "authentik", "nextcloud"])
 def test_service_base_url_accepts_absolute_urls(service_type):
     model = get_service_definition(service_type).config_model
     instance = model.model_validate({"base_url": "https://example.com"})
@@ -308,7 +308,7 @@ def test_unknown_secret_field_rejected(client):
         json={
             "service_type": "prometheus",
             "name": "x",
-            "config": {"base_url": "https://prometheus.example.com"},
+            "config": {"grafana_url": "https://grafana.example.com"},
             "secrets": {"password": "leak"},
         },
     )
@@ -321,7 +321,7 @@ def test_credential_key_in_config_rejected(client):
         json={
             "service_type": "prometheus",
             "name": "x",
-            "config": {"base_url": "https://prometheus.example.com", "api_key": "leak"},
+            "config": {"grafana_url": "https://grafana.example.com", "api_key": "leak"},
         },
     )
     assert response.status_code == 422
@@ -369,7 +369,7 @@ def test_delete_service_cascades_to_widgets(client, tmp_path):
     """
     store = app.dependency_overrides[get_settings_store]()
     service = store.upsert_service(
-        {"service_type": "prometheus", "name": "Prometheus", "config": {"base_url": "u"}, "enabled": True}
+        {"service_type": "prometheus", "name": "Prometheus", "config": {"grafana_url": "u"}, "enabled": True}
     )
 
     # Ensure the service_id column exists and seed a referencing widget.

backend/tests/test_widgets.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 from types import SimpleNamespace
+from typing import Any
 from unittest.mock import patch
 
 import pytest
@@ -42,7 +43,7 @@ def client(tmp_path):
 
 
 def _make_prometheus_service(client, name="Production Prometheus", **config_overrides):
-    config = {"base_url": "https://prometheus.example.com"}
+    config = {"grafana_url": "https://grafana.example.com", "datasource_uid": "prometheus"}
     config.update(config_overrides)
     return client.post(
         "/api/services/instances",
@@ -302,7 +303,7 @@ def test_fetch_widget_service_disabled(client):
         json={
             "service_type": "prometheus",
             "name": service["name"],
-            "config": {"base_url": "https://prometheus.example.com"},
+            "config": {"grafana_url": "https://grafana.example.com", "datasource_uid": "prometheus"},
             "enabled": False,
         },
     )
@@ -469,39 +470,45 @@ def test_jellyfin_definition_has_now_playing_widget():
 
 @pytest.mark.asyncio
 async def test_prometheus_chart_adapter_runs_range_query():
-    """SC-101: chart kind hits /api/v1/query_range and returns {series}."""
-    from media_library_viewer_api.widgets.sources import PrometheusWidgetSource
+    """GM-106: chart kind hits /api/ds/query and returns {series}."""
+    from media_library_viewer_api.widgets.sources import MetricSource
 
-    adapter = PrometheusWidgetSource()
+    adapter = MetricSource()
     service = ServiceRecord(
         id="s",
         service_type="prometheus",
         name="p",
-        config={"base_url": "http://p:9090", "timeout_seconds": 5},
+        config={"grafana_url": "http://grafana:3000", "datasource_uid": "prometheus", "timeout_seconds": 5},
+        secrets={"grafana_api_key": "key"},
     )
     payload = SimpleNamespace(
         raise_for_status=lambda: None,
         json=lambda: {
-            "data": {
-                "result": [
-                    {
-                        "metric": {"__name__": "up", "instance": "h:9100"},
-                        "values": [[100, "1"], [130, "1"]],
-                    }
-                ]
+            "results": {
+                "A": {
+                    "frames": [
+                        {
+                            "data": {"values": [[100, 130], [1.0, 1.0]]},
+                            "schema": {
+                                "fields": [
+                                    {"name": "Time"},
+                                    {"name": "Value", "labels": {"__name__": "up", "instance": "h:9100"}},
+                                ]
+                            },
+                        }
+                    ]
+                }
             }
         },
     )
-    with patch("media_library_viewer_api.widgets.sources.requests.get", return_value=payload) as mock_get:
+    with patch("media_library_viewer_api.widgets.sources.requests.post", return_value=payload) as mock_post:
         result = await adapter.fetch(service, "chart", {"promql": "up", "window": "1h"})
 
-    # query_range endpoint + window-derived start/end/step params.
-    call = mock_get.call_args
-    assert call.args[0].endswith("/api/v1/query_range")
-    params = call.kwargs["params"]
-    assert params["query"] == "up"
-    assert {"start", "end", "step"}.issubset(params)
-    # {series} shape with the shared normalization (label drops __name__).
+    call = mock_post.call_args
+    assert call.args[0].endswith("/api/ds/query")
+    body = call.kwargs["json"]
+    assert body["queries"][0]["expr"] == "up"
+    assert body["queries"][0]["datasource"]["uid"] == "prometheus"
     assert "series" in result
     assert result["series"][0]["label"] == "instance=h:9100"
     assert result["series"][0]["points"] == [{"t": 100, "v": 1.0}, {"t": 130, "v": 1.0}]
@@ -509,26 +516,43 @@ async def test_prometheus_chart_adapter_runs_range_query():
 
 @pytest.mark.asyncio
 async def test_prometheus_chart_adapter_requires_promql():
-    from media_library_viewer_api.widgets.sources import PrometheusWidgetSource
+    from media_library_viewer_api.widgets.sources import MetricSource
 
-    adapter = PrometheusWidgetSource()
-    service = ServiceRecord(id="s", service_type="prometheus", name="p", config={"base_url": "http://p:9090"})
+    adapter = MetricSource()
+    service = ServiceRecord(
+        id="s",
+        service_type="prometheus",
+        name="p",
+        config={"grafana_url": "http://grafana:3000", "datasource_uid": "prometheus"},
+        secrets={"grafana_api_key": "key"},
+    )
     result = await adapter.fetch(service, "chart", {"promql": ""})
     assert result == {"error": "promql is required"}
 
 
 @pytest.mark.asyncio
 async def test_prometheus_chart_adapter_degrades_on_http_error():
-    """SC-103: a connection error returns {error} rather than raising."""
+    """GM-103: a connection error returns {error} rather than raising."""
     import requests as req_mod
 
-    from media_library_viewer_api.widgets.sources import PrometheusWidgetSource
+    from media_library_viewer_api.widgets.sources import MetricSource
 
-    adapter = PrometheusWidgetSource()
+    adapter = MetricSource()
     service = ServiceRecord(
-        id="s", service_type="prometheus", name="p", config={"base_url": "http://p:9090", "timeout_seconds": 2}
+        id="s",
+        service_type="prometheus",
+        name="p",
+        config={
+            "grafana_url": "http://grafana:3000",
+            "datasource_uid": "prometheus",
+            "timeout_seconds": 2,
+        },
+        secrets={"grafana_api_key": "key"},
     )
-    with patch("media_library_viewer_api.widgets.sources.requests.get", side_effect=req_mod.ConnectionError("refused")):
+    with patch(
+        "media_library_viewer_api.widgets.sources.requests.post",
+        side_effect=req_mod.ConnectionError("refused"),
+    ):
         result = await adapter.fetch(service, "chart", {"promql": "up", "window": "1h"})
     assert "error" in result
     assert "failed" in result["error"].lower()
@@ -632,7 +656,7 @@ def test_widget_reference_lifecycle(widget_ref_client):
         {
             "service_type": "prometheus",
             "name": "Prometheus",
-            "config": {"base_url": "https://prometheus.example.com"},
+            "config": {"grafana_url": "https://grafana.example.com", "datasource_uid": "prometheus"},
             "secrets": {"api_key": "tok"},
             "enabled": True,
         },
@@ -690,7 +714,7 @@ def test_widget_reference_detach(widget_ref_client):
         {
             "service_type": "prometheus",
             "name": "Prometheus",
-            "config": {"base_url": "https://prometheus.example.com"},
+            "config": {"grafana_url": "https://grafana.example.com", "datasource_uid": "prometheus"},
             "secrets": {"api_key": "tok"},
             "enabled": True,
         },
@@ -794,46 +818,57 @@ def test_widget_reference_update_sort_order(widget_ref_client):
 
 
 # ---------------------------------------------------------------------------
-# Prometheus gauge + mean adapter tests (SC-109..SC-114)
+# Prometheus gauge + mean adapter tests (GM-107..GM-108)
 # ---------------------------------------------------------------------------
 
 
+def _grafana_single_frame(values, labels=None, display_name=None):
+    """Build a Grafana /api/ds/query frames response for a single series."""
+    field: dict[str, Any] = {"name": "Value"}
+    if labels:
+        field["labels"] = labels
+    if display_name:
+        field["config"] = {"displayName": display_name}
+    return {
+        "results": {
+            "A": {
+                "frames": [
+                    {
+                        "data": {"values": values},
+                        "schema": {"fields": [{"name": "Time"}, field]},
+                    }
+                ]
+            }
+        }
+    }
+
+
 @pytest.mark.asyncio
 async def test_prometheus_gauge_adapter_returns_scalar():
-    """SC-109: gauge kind hits /api/v1/query and returns {value, thresholds}."""
-    from media_library_viewer_api.widgets.sources import PrometheusWidgetSource
+    """GM-107: gauge kind hits /api/ds/query and returns {value, thresholds}."""
+    from media_library_viewer_api.widgets.sources import MetricSource
 
-    adapter = PrometheusWidgetSource()
+    adapter = MetricSource()
     service = ServiceRecord(
         id="s",
         service_type="prometheus",
         name="p",
-        config={"base_url": "http://p:9090", "timeout_seconds": 5},
+        config={"grafana_url": "http://grafana:3000", "datasource_uid": "prometheus", "timeout_seconds": 5},
+        secrets={"grafana_api_key": "key"},
     )
     payload = SimpleNamespace(
         raise_for_status=lambda: None,
-        json=lambda: {
-            "data": {
-                "result": [
-                    {"metric": {"__name__": "cpu"}, "value": [100, "0.75"]},
-                ]
-            }
-        },
+        json=lambda: _grafana_single_frame([[100], [0.75]]),
     )
-    with patch("media_library_viewer_api.widgets.sources.requests.get", return_value=payload) as mock_get:
+    with patch("media_library_viewer_api.widgets.sources.requests.post", return_value=payload) as mock_post:
         result = await adapter.fetch(
             service,
             "gauge",
-            {
-                "promql": "cpu_usage",
-                "warn_at": 0.8,
-                "crit_at": 0.95,
-                "unit": "%",
-            },
+            {"promql": "cpu_usage", "warn_at": 0.8, "crit_at": 0.95, "unit": "%"},
         )
-    call = mock_get.call_args
-    assert call.args[0].endswith("/api/v1/query")
-    assert call.kwargs["params"]["query"] == "cpu_usage"
+    call = mock_post.call_args
+    assert call.args[0].endswith("/api/ds/query")
+    assert call.kwargs["json"]["queries"][0]["expr"] == "cpu_usage"
     assert result["value"] == 0.75
     assert result["warn_at"] == 0.8
     assert result["crit_at"] == 0.95
@@ -842,28 +877,31 @@ async def test_prometheus_gauge_adapter_returns_scalar():
 
 @pytest.mark.asyncio
 async def test_prometheus_gauge_adapter_rejects_multi_series():
-    """SC-111: gauge must be scalar-only; multi-series returns error."""
-    from media_library_viewer_api.widgets.sources import PrometheusWidgetSource
+    """GM-107: gauge must be scalar-only; multi-series returns error."""
+    from media_library_viewer_api.widgets.sources import MetricSource
 
-    adapter = PrometheusWidgetSource()
+    adapter = MetricSource()
     service = ServiceRecord(
         id="s",
         service_type="prometheus",
         name="p",
-        config={"base_url": "http://p:9090"},
+        config={"grafana_url": "http://grafana:3000", "datasource_uid": "prometheus"},
+        secrets={"grafana_api_key": "key"},
     )
     payload = SimpleNamespace(
         raise_for_status=lambda: None,
         json=lambda: {
-            "data": {
-                "result": [
-                    {"metric": {"instance": "a"}, "value": [100, "1"]},
-                    {"metric": {"instance": "b"}, "value": [100, "2"]},
-                ]
+            "results": {
+                "A": {
+                    "frames": [
+                        {"data": {"values": [[100], [1.0]]}, "schema": {"fields": [{}, {"name": "A"}]}},
+                        {"data": {"values": [[100], [2.0]]}, "schema": {"fields": [{}, {"name": "A"}]}},
+                    ]
+                }
             }
         },
     )
-    with patch("media_library_viewer_api.widgets.sources.requests.get", return_value=payload):
+    with patch("media_library_viewer_api.widgets.sources.requests.post", return_value=payload):
         result = await adapter.fetch(service, "gauge", {"promql": "up"})
     assert "error" in result
     assert "single-series" in result["error"].lower()
@@ -871,14 +909,15 @@ async def test_prometheus_gauge_adapter_rejects_multi_series():
 
 @pytest.mark.asyncio
 async def test_prometheus_gauge_adapter_requires_promql():
-    from media_library_viewer_api.widgets.sources import PrometheusWidgetSource
+    from media_library_viewer_api.widgets.sources import MetricSource
 
-    adapter = PrometheusWidgetSource()
+    adapter = MetricSource()
     service = ServiceRecord(
         id="s",
         service_type="prometheus",
         name="p",
-        config={"base_url": "http://p:9090"},
+        config={"grafana_url": "http://grafana:3000", "datasource_uid": "prometheus"},
+        secrets={"grafana_api_key": "key"},
     )
     result = await adapter.fetch(service, "gauge", {"promql": ""})
     assert result == {"error": "promql is required"}
@@ -886,30 +925,22 @@ async def test_prometheus_gauge_adapter_requires_promql():
 
 @pytest.mark.asyncio
 async def test_prometheus_mean_adapter_computes_average():
-    """SC-112: mean kind averages non-null values over the window."""
-    from media_library_viewer_api.widgets.sources import PrometheusWidgetSource
+    """GM-108: mean kind averages non-null values over the window."""
+    from media_library_viewer_api.widgets.sources import MetricSource
 
-    adapter = PrometheusWidgetSource()
+    adapter = MetricSource()
     service = ServiceRecord(
         id="s",
         service_type="prometheus",
         name="p",
-        config={"base_url": "http://p:9090", "timeout_seconds": 5},
+        config={"grafana_url": "http://grafana:3000", "datasource_uid": "prometheus", "timeout_seconds": 5},
+        secrets={"grafana_api_key": "key"},
     )
     payload = SimpleNamespace(
         raise_for_status=lambda: None,
-        json=lambda: {
-            "data": {
-                "result": [
-                    {
-                        "metric": {"__name__": "cpu"},
-                        "values": [[100, "1.0"], [130, "2.0"], [160, "3.0"]],
-                    }
-                ]
-            }
-        },
+        json=lambda: _grafana_single_frame([[100, 130, 160], [1.0, 2.0, 3.0]]),
     )
-    with patch("media_library_viewer_api.widgets.sources.requests.get", return_value=payload):
+    with patch("media_library_viewer_api.widgets.sources.requests.post", return_value=payload):
         result = await adapter.fetch(service, "mean", {"promql": "cpu", "window": "1h"})
     assert result["value"] == 2.0
     assert result["unit"] is None
@@ -917,28 +948,31 @@ async def test_prometheus_mean_adapter_computes_average():
 
 @pytest.mark.asyncio
 async def test_prometheus_mean_adapter_rejects_multi_series():
-    """SC-114: mean must be scalar-only; multi-series returns error."""
-    from media_library_viewer_api.widgets.sources import PrometheusWidgetSource
+    """GM-108: mean must be scalar-only; multi-series returns error."""
+    from media_library_viewer_api.widgets.sources import MetricSource
 
-    adapter = PrometheusWidgetSource()
+    adapter = MetricSource()
     service = ServiceRecord(
         id="s",
         service_type="prometheus",
         name="p",
-        config={"base_url": "http://p:9090"},
+        config={"grafana_url": "http://grafana:3000", "datasource_uid": "prometheus"},
+        secrets={"grafana_api_key": "key"},
     )
     payload = SimpleNamespace(
         raise_for_status=lambda: None,
         json=lambda: {
-            "data": {
-                "result": [
-                    {"metric": {"instance": "a"}, "values": [[100, "1"]]},
-                    {"metric": {"instance": "b"}, "values": [[100, "2"]]},
-                ]
+            "results": {
+                "A": {
+                    "frames": [
+                        {"data": {"values": [[100], [1.0]]}, "schema": {"fields": [{}, {"name": "A"}]}},
+                        {"data": {"values": [[100], [2.0]]}, "schema": {"fields": [{}, {"name": "A"}]}},
+                    ]
+                }
             }
         },
     )
-    with patch("media_library_viewer_api.widgets.sources.requests.get", return_value=payload):
+    with patch("media_library_viewer_api.widgets.sources.requests.post", return_value=payload):
         result = await adapter.fetch(service, "mean", {"promql": "up", "window": "1h"})
     assert "error" in result
     assert "single-series" in result["error"].lower()
@@ -946,45 +980,46 @@ async def test_prometheus_mean_adapter_rejects_multi_series():
 
 @pytest.mark.asyncio
 async def test_prometheus_mean_adapter_skips_nan_values():
-    """SC-112: NaN / Inf values are excluded from the mean computation."""
-    from media_library_viewer_api.widgets.sources import PrometheusWidgetSource
+    """GM-108: NaN values are excluded from the mean computation."""
+    from media_library_viewer_api.widgets.sources import MetricSource
 
-    adapter = PrometheusWidgetSource()
+    adapter = MetricSource()
     service = ServiceRecord(
         id="s",
         service_type="prometheus",
         name="p",
-        config={"base_url": "http://p:9090"},
+        config={"grafana_url": "http://grafana:3000", "datasource_uid": "prometheus"},
+        secrets={"grafana_api_key": "key"},
     )
+    # Grafana frames shape with NaN — normalize_grafana_frames converts string "NaN" to None
     payload = SimpleNamespace(
         raise_for_status=lambda: None,
         json=lambda: {
-            "data": {
-                "result": [
-                    {
-                        "metric": {},
-                        "values": [[100, "2.0"], [130, "NaN"], [160, "4.0"]],
-                    }
-                ]
+            "results": {
+                "A": {
+                    "frames": [
+                        {"data": {"values": [[100, 130, 160], [2.0, "NaN", 4.0]]}, "schema": {"fields": [{}, {}]}}
+                    ]
+                }
             }
         },
     )
-    with patch("media_library_viewer_api.widgets.sources.requests.get", return_value=payload):
+    with patch("media_library_viewer_api.widgets.sources.requests.post", return_value=payload):
         result = await adapter.fetch(service, "mean", {"promql": "up", "window": "1h"})
-    # (2.0 + 4.0) / 2 = 3.0 (NaN excluded)
     assert result["value"] == 3.0
 
 
 @pytest.mark.asyncio
 async def test_prometheus_mean_adapter_requires_promql():
-    from media_library_viewer_api.widgets.sources import PrometheusWidgetSource
+    from media_library_viewer_api.widgets.sources import MetricSource
 
-    adapter = PrometheusWidgetSource()
+    adapter = MetricSource()
     service = ServiceRecord(
         id="s",
         service_type="prometheus",
         name="p",
-        config={"base_url": "http://p:9090"},
+        config={"grafana_url": "http://grafana:3000", "datasource_uid": "prometheus"},
+        secrets={"grafana_api_key": "key"},
     )
     result = await adapter.fetch(service, "mean", {"promql": ""})
     assert result == {"error": "promql is required"}