refactor: drop changepoint legacy fallback paths

Author: stefankumarasinghe

api/routes/metrics.py

@@ -55,15 +55,12 @@ async def metric_changepoints(req: ChangepointRequest) -> list[ChangePoint]:
     results: list[ChangePoint] = []
     for metric_name, ts, vals in anomaly.iter_series(raw, query_hint=req.query):
         threshold_sigma = float(req.threshold_sigma)
-        try:
-            results.extend(
-                changepoint_detect(
-                    ts,
-                    vals,
-                    threshold_sigma=threshold_sigma,
-                    metric_name=metric_name,
-                )
+        results.extend(
+            changepoint_detect(
+                ts,
+                vals,
+                threshold_sigma=threshold_sigma,
+                metric_name=metric_name,
             )
-        except TypeError:
-            results.extend(changepoint_detect(ts, vals, threshold_sigma))
+        )
     return sorted(results, key=lambda c: c.timestamp)

engine/analyze/helpers.py

@@ -530,16 +530,12 @@ async def _process_one_metric_series(
         else float(settings.cusum_threshold_sigma)
     )
     sigma_multiplier = max(1.0, sigma_multiplier)
-    try:
-        change_points = changepoint_detect(
-            job.ts,
-            job.vals,
-            threshold_sigma=sigma_multiplier,
-            metric_name=metric_name,
-        )
-    except TypeError:
-        # Backward-compatible path for monkeypatched/legacy detector signatures.
-        change_points = changepoint_detect(job.ts, job.vals, sigma_multiplier)
+    change_points = changepoint_detect(
+        job.ts,
+        job.vals,
+        threshold_sigma=sigma_multiplier,
+        metric_name=metric_name,
+    )
 
     threshold = next((v for k, v in FORECAST_THRESHOLDS.items() if k in job.query_string), None)
     if threshold and job.analysis_window_seconds >= float(

tests/test_analyze_helpers_filters_edges.py

@@ -295,10 +295,11 @@ async def _raise_compute(*_args, **_kwargs):
     monkeypatch.setattr(helpers, "baseline_compute", lambda *_a, **_k: called.__setitem__("baseline_fallback", 1))
     monkeypatch.setattr(helpers.anomaly, "detect", lambda *_a, **_k: [_anomaly("m", 1.0, 1.0)])
 
-    def _legacy_cp(ts, vals, sigma):
-        return [_cp("m", 1.0, sigma)]
+    def _cp_detector(ts, vals, threshold_sigma=None, metric_name=None):
+        assert metric_name == "m"
+        return [_cp("m", 1.0, float(threshold_sigma or 0.0))]
 
-    monkeypatch.setattr(helpers, "changepoint_detect", _legacy_cp)
+    monkeypatch.setattr(helpers, "changepoint_detect", _cp_detector)
     monkeypatch.setattr(helpers.settings, "cusum_threshold_sigma", 2.0)
     monkeypatch.setattr(helpers.settings, "analyzer_forecast_min_window_seconds", 10.0)
     monkeypatch.setattr(helpers.settings, "analyzer_degradation_min_window_seconds", 10.0)

tests/test_api_route_surface_edges.py

@@ -249,9 +249,7 @@ async def fake_safe_call(awaitable):
     captured = []
 
     def fake_changepoint_detect(ts, vals, threshold_sigma=None, metric_name=None):
-        if metric_name is not None:
-            raise TypeError("legacy signature")
-        captured.append((tuple(ts), tuple(vals), threshold_sigma))
+        captured.append((tuple(ts), tuple(vals), threshold_sigma, metric_name))
         return [types.SimpleNamespace(timestamp=2)]
 
     monkeypatch.setattr(metrics_route, "changepoint_detect", fake_changepoint_detect)
@@ -260,7 +258,10 @@ def fake_changepoint_detect(ts, vals, threshold_sigma=None, metric_name=None):
     )
 
     assert [item.timestamp for item in changepoints] == [2, 2]
-    assert captured == [((1,), (2.0,), 6.0), ((2,), (3.0,), 6.0)]
+    assert captured == [
+        ((1,), (2.0,), 6.0, "metric-b"),
+        ((2,), (3.0,), 6.0, "metric-a"),
+    ]
 
 
 @pytest.mark.asyncio