diff --git a/scripts/model_ci.py b/scripts/model_ci.py
index d88696d..7cdf2a4 100644
--- a/scripts/model_ci.py
+++ b/scripts/model_ci.py
@@ -103,14 +103,32 @@ def validate_outputs(inputs, tables, zones):
     )
     require(trips.depart.between(1, 24).all(), "trips: invalid departure")
     require(trips.outbound.isin([True, False]).all(), "trips: invalid direction")
-    for (_, _), group in trips.groupby(["tour_id", "outbound"]):
-        group = group.sort_values("trip_num")
-        require(
-            group.trip_num.tolist() == list(range(1, len(group) + 1)),
-            "trips: broken sequence",
-        )
-        require(group.trip_count.eq(len(group)).all(), "trips: incorrect trip_count")
-        require(group.depart.is_monotonic_increasing, "trips: departure order")
+    for tour_id, group in trips.groupby("tour_id"):
+        require(set(group.outbound) == {True, False}, "trips: missing tour direction")
+        # ActivitySim 1.5.1 initialize_from_tours numbers/counts trips per
+        # (tour_id, outbound), so first_trip/last_trip describe each half-tour.
+        group = group.sort_values(["outbound", "trip_num"], ascending=[False, True])
+        tour = tours.loc[tour_id]
+        for outbound, leg in group.groupby("outbound"):
+            require(
+                leg.trip_num.tolist() == list(range(1, len(leg) + 1)),
+                "trips: broken sequence",
+            )
+            require(leg.trip_count.eq(len(leg)).all(), "trips: incorrect trip_count")
+            # The locked scheduler handles directions independently; their time
+            # ranges can overlap even when each leg is correctly ordered.
+            require(leg.depart.is_monotonic_increasing, "trips: departure order")
+            origin, destination = (
+                (tour.origin, tour.destination)
+                if outbound
+                else (tour.destination, tour.origin)
+            )
+            require(
+                leg.iloc[0].origin == origin
+                and leg.iloc[-1].destination == destination,
+                "trips: incorrect tour endpoints",
+            )
+        # Check the whole spatial path, including the outbound/inbound boundary.
         require(
             np.array_equal(
                 group.destination.to_numpy()[:-1], group.origin.to_numpy()[1:]
diff --git a/tests/test_model_ci.py b/tests/test_model_ci.py
index 3d42888..757e1bd 100644
--- a/tests/test_model_ci.py
+++ b/tests/test_model_ci.py
@@ -62,6 +62,62 @@ def test_valid_outputs(population, outputs):
     ci.validate_outputs(population, outputs, [1, 2])
 
 
+@pytest.fixture
+def multistop_outputs(outputs):
+    # Two outbound trips and three inbound trips; numbering restarts on return.
+    trips = outputs["trips"].iloc[[0, 0, 1, 1, 1]].copy()
+    trips.index = [40, 41, 42, 43, 44]
+    trips["origin"] = [1, 3, 2, 4, 3]
+    trips["destination"] = [3, 2, 4, 3, 1]
+    trips["trip_num"] = [1, 2, 1, 2, 3]
+    trips["trip_count"] = [2, 2, 3, 3, 3]
+    trips["depart"] = [8, 9, 17, 18, 19]
+    outputs["trips"] = trips
+    return outputs
+
+
+def test_valid_multistop_round_trip(population, multistop_outputs):
+    # Neither table order nor trip IDs define travel order.
+    multistop_outputs["trips"] = multistop_outputs["trips"].iloc[[3, 1, 4, 0, 2]]
+    ci.validate_outputs(population, multistop_outputs, [1, 2, 3, 4])
+
+
+def test_allows_independently_scheduled_directions(population, multistop_outputs):
+    # ActivitySim 1.5.1 can produce overlapping leg schedules. Preserve the
+    # per-leg time contract rather than turning this existing behavior blocking.
+    multistop_outputs["trips"].loc[[42, 43, 44], "depart"] = [8, 9, 10]
+    ci.validate_outputs(population, multistop_outputs, [1, 2, 3, 4])
+
+
+@pytest.mark.parametrize(
+    "row,column,value,message",
+    [
+        (42, "trip_num", 3, "broken sequence"),
+        (44, "trip_num", 2, "broken sequence"),
+        (42, "trip_count", 5, "incorrect trip_count"),
+        (40, "origin", 3, "incorrect tour endpoints"),
+        (41, "destination", 3, "incorrect tour endpoints"),
+        (42, "origin", 3, "incorrect tour endpoints"),
+        (44, "destination", 3, "incorrect tour endpoints"),
+        (43, "origin", 1, "disconnected path"),
+        (43, "depart", 16, "departure order"),
+    ],
+)
+def test_rejects_corrupt_round_trip(
+    population, multistop_outputs, row, column, value, message
+):
+    multistop_outputs["trips"].loc[row, column] = value
+    with pytest.raises(ValueError, match=message):
+        ci.validate_outputs(population, multistop_outputs, [1, 2, 3, 4])
+
+
+@pytest.mark.parametrize("outbound", [True, False])
+def test_rejects_missing_direction(population, outputs, outbound):
+    outputs["trips"] = outputs["trips"].loc[outputs["trips"].outbound == outbound]
+    with pytest.raises(ValueError, match="missing tour direction"):
+        ci.validate_outputs(population, outputs, [1, 2])
+
+
 @pytest.mark.parametrize(
     "table,column,value,message",
     [