diff --git a/gen.py b/gen.py
index 89a5451..b937e7f 100644
--- a/gen.py
+++ b/gen.py
@@ -38,8 +38,8 @@ def main(
     time_to_run: int = 60 * 60,
     ratio: float = 0.001,
     start_date: datetime.datetime = "2025-09-01",
-    weeks: int = 26,
-    bom: int = 1,
+    weeks: int = 16,
+    bom: int = 2,
 ):
     rota_start_date = start_date.date()
     suspend_on_finish = suspend
@@ -267,70 +267,20 @@ def main(
                     "name": "require_remote_site_presence_week",
                     "options": ("plymouth", 1),
                 },
-                {"name": "limit_grade_number", "options": {2: 1}},
+                {"name": "limit_grade_number", "options": {2: 2}},
                 {"name": "minimum_grade_number", "options": (4, 1)},
             ],
             #end_date=datetime.datetime.strptime("2025-06-01", "%Y-%m-%d").date(),
         ),
-        # SingleShift(
-        #    sites=sites,
-        #    name="night_weekday4",
-        #    length=12.25,
-        #    days=days[:4],
-        #    balance_offset=3.9,
-        #    balance_weighting=1,
-        #    # hard_constrain_shift=False,
-        #    workers_required=NIGHT_REGISTRAR_NUMBER,
-        #    force_as_block=True,
-        #    rota_on_nwds=True,
-        #    constraint=[
-        #        {"name": "night"},
-        #        {"name": "pre", "options": 2},
-        #        {"name": "post", "options": 2},
-        #        {
-        #            "name": "require_remote_site_presence_week",
-        #            "options": ("plymouth", 1),
-        #        },
-        #        {"name": "limit_grade_number", "options": {2: 1}},
-        #        {"name": "minimum_grade_number", "options": (4, 1)},
-        #    ],
-        #    start_date=datetime.datetime.strptime("2025-06-02", "%Y-%m-%d").date(),
-        # ),
-        # SingleShift(
-        #    sites=[
-        #        *sites,
-        #        "plymouth twilights, weekends and weekend nights",
-        #        "truro twilights and weekend nights",
-        #        "weekend nights",
-        #        "truro twilights, weekends and weekend nights",
-        #    ],
-        #    name="night_weekend4",
-        #    length=12.25,
-        #    days=days[4:],
-        #    balance_offset=2.9,
-        #    balance_weighting=1,
-        #    # hard_constrain_shift=False,
-        #    workers_required=NIGHT_REGISTRAR_NUMBER,
-        #    force_as_block=True,
-        #    rota_on_nwds=True,
-        #    constraint=[
-        #        {"name": "night"},
-        #        {"name": "pre", "options": 2},
-        #        {"name": "post", "options": 3},
-        #        {
-        #            "name": "require_remote_site_presence_week",
-        #            "options": ("plymouth", 1),
-        #        },
-        #        {"name": "limit_grade_number", "options": {2: 1}},
-        #        {"name": "minimum_grade_number", "options": (4, 1)},
-        #    ],
-        #    start_date=datetime.datetime.strptime("2025-06-02", "%Y-%m-%d").date(),
-        # ),
     )
 
-    # Rota.add_grade_constraint_by_week([2], [1, 2], ["night_weekday", "night_weekend"])
+    # Prevent shifts for ST2s for 2 weeks
+    Rota.add_grade_constraint_by_week([2], [1, 2], [shift.name for shift in Rota.shifts])
 
     Rota.add_min_summed_grade_by_shifts_per_day_constraint(["weekend_plymouth1", "weekend_plymouth2"], 6)
+    Rota.add_min_summed_grade_by_shifts_per_day_constraint(["plymouth_twilight", "plymouth_bank_holidays"], 6)
+
+    Rota.terminate_on_warning.remove("Worker/no valid shifts")
 
     load_leave = True
     Rota.build_shifts()
diff --git a/rota/shifts.py b/rota/shifts.py
index ceae404..493024a 100644
--- a/rota/shifts.py
+++ b/rota/shifts.py
@@ -1029,13 +1029,15 @@ class RotaBuilder(object):
                 for day in days_list:
                     # Only consider if all shifts are present that day
                     if all(shift in self.get_shift_names_by_week_day(week, day) for shift in constraint.shifts):
-                        self.model.constraints.add(
-                            sum(
-                                worker.grade * self.model.works[worker.id, week, day, shift]
-                                for shift in constraint.shifts
-                                for worker in self.get_workers_for_shift(self.get_shift_by_name(shift))
-                            ) >= constraint.min_grade_sum
-                        )
+                        expr_terms = [
+                            worker.grade * self.model.works[worker.id, week, day, shift]
+                            for shift in constraint.shifts
+                            for worker in self.get_workers_for_shift(self.get_shift_by_name(shift))
+                        ]
+                        if expr_terms:  # Only add constraint if there are eligible workers
+                            self.model.constraints.add(
+                                sum(expr_terms) >= constraint.min_grade_sum
+                            )
 
 
 
@@ -1783,6 +1785,15 @@ class RotaBuilder(object):
                             - adjusted_balance_offset * self.balance_offset_modifier
                         )
 
+                        # --- Store for export ---
+                        if not hasattr(worker, "hard_constrain_shift_limits"):
+                            worker.hard_constrain_shift_limits = {}
+                        worker.hard_constrain_shift_limits[shift.name] = {
+                            "min_shifts": min_shifts,
+                            "max_shifts": max_shifts,
+                            "target_shifts": target_shifts,
+                        }
+
                         self.model.constraints.add(
                             inequality(
                                 min_shifts,
@@ -1791,8 +1802,6 @@ class RotaBuilder(object):
                                     for week, day in self.get_week_day_combinations_for_shift(
                                         shift
                                     )
-                                    # for week, day in self.get_week_day_combinations()
-                                    # if shift.name in self.get_shift_names_by_week_day(week, day)
                                 ),
                                 max_shifts,
                             )
@@ -4190,6 +4199,15 @@ class RotaBuilder(object):
 
         joined_timetable = "\n".join(timetable)
 
+        hard_constrain_shift_info = []
+        for worker in self.workers:
+            for shift_name, limits in getattr(worker, "hard_constrain_shift_limits", {}).items():
+                hard_constrain_shift_info.append({
+                    "worker": worker.name,
+                    "shift": shift_name,
+                    **limits,
+                })
+
         html = f""" 
         <body>
         <div class="table-div" id="{table_name}">
@@ -4246,6 +4264,11 @@ class RotaBuilder(object):
         <br/>
         <div>
         </details>
+    <details><summary><h2>Hard Constrain Shift Min/Max</h2></summary>
+    <pre>
+     {json.dumps(hard_constrain_shift_info, indent=4)}
+     "</pre></details>
+
         </div
         </body>
         """