diff --git a/.github/workflows/test_basic.yaml b/.github/workflows/test_basic.yaml
index fdc4e758f..f4fd3c18a 100644
--- a/.github/workflows/test_basic.yaml
+++ b/.github/workflows/test_basic.yaml
@@ -82,7 +82,7 @@ jobs:
     - uses: ./.github/actions/setup-ubuntu
     - name: Run examples
       run: |
-        python3 example.py --examples ntt_kyber_1_23_45_67_m55,ntt_dilithium_12_34_56_78_m55 --timeout=300
+        python3 example.py --examples ntt_kyber_1_23_45_67_m55,ntt_dilithium_12_34_56_78_m55 --timeout=1200
   examples_ntt_kyber_dilithium_neon_core:
     runs-on: ubuntu-latest
     steps:
@@ -90,7 +90,7 @@ jobs:
     - uses: ./.github/actions/setup-ubuntu
     - name: Run examples
       run: |
-        python3 example.py --examples ntt_kyber_123_4567_a55,ntt_dilithium_123_45678_a55 --timeout=300
+        python3 example.py --examples ntt_kyber_123_4567_a55,ntt_dilithium_123_45678_a55 --timeout=1200
   sqmag:
     runs-on: ubuntu-latest
     steps:
diff --git a/pyproject.toml b/pyproject.toml
index 462870efa..52106f1bc 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -44,12 +44,7 @@ classifiers = [
 ]
 requires-python = ">=3.10"
 dependencies = [
-    "ortools==9.7.2996; python_version < '3.12'",
-    # ortools depends on pandas, but 9.7 does not specify it as dependency
-    "pandas>=2.0.3; python_version < '3.12'",
-    # ortools 9.7 requires protobuf<=6.31.1
-    "protobuf<=6.31.1; python_version < '3.12'",
-    "ortools==9.15.6755; python_version >= '3.12'",
+    "ortools==9.15.6755",
     "sympy==1.14.0",
     "unicorn==2.1.4",
 ]
diff --git a/requirements.txt b/requirements.txt
index 740cd6b84..97a70a260 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,9 +1,4 @@
-ortools==9.7.2996 ; python_version < "3.12"
-ortools==9.15.6755 ; python_version >= "3.12"
-# ortools 9.7 requires protobuf<=6.31.1
-protobuf<=6.31.1 ; python_version < "3.12"
-# ortools depends on pandas, but 9.7 does not specify it as dependency
-pandas>=2.0.3 ; python_version < "3.12"
+ortools==9.15.6755
 sympy==1.14.0
 unicorn==2.1.4
 black==26.3.1
@@ -18,4 +13,3 @@ sphinx_mdinclude ; python_version >= "3.11"
 myst_parser ; python_version >= "3.11"
 sphinx-autobuild ; python_version >= "3.11"
 sphinx-autodoc2 ; python_version >= "3.11"
-
diff --git a/slothy/core/core.py b/slothy/core/core.py
index c255535da..a7c2d2615 100644
--- a/slothy/core/core.py
+++ b/slothy/core/core.py
@@ -1979,8 +1979,8 @@ def _add_register_usage(
 
         spill_ival_active = self._NewBoolVar("")
         self._AddMultiplicationEquality([var, spill_var], spill_ival_active)
-        spill_point_start = self._NewOptionalIntervalVar(
-            t.program_start_var, 1, t.program_start_var + 1, spill_ival_active, ""
+        spill_point_start = self._NewOptionalFixedIntervalVar(
+            t.program_start_var, 1, spill_ival_active, ""
         )
 
         interval = self._NewOptionalIntervalVar(
@@ -2649,15 +2649,15 @@ def _add_variables_functional_units(self):
                     # multiple execution units in use
                     for unit in units[0]:
                         t.exec_unit_choices = None
-                        t.exec = self._NewIntervalVar(
-                            t.cycle_start_var, cycles_unit_occupied, t.cycle_end_var, ""
+                        t.exec = self._NewFixedIntervalVar(
+                            t.cycle_start_var, cycles_unit_occupied, ""
                         )
                         self._model.intervals_for_unit[unit].append(t.exec)
                 else:
                     t.exec_unit_choices = None
                     unit = units[0]
-                    t.exec = self._NewIntervalVar(
-                        t.cycle_start_var, cycles_unit_occupied, t.cycle_end_var, ""
+                    t.exec = self._NewFixedIntervalVar(
+                        t.cycle_start_var, cycles_unit_occupied, ""
                     )
                     self._model.intervals_for_unit[unit].append(t.exec)
             else:
@@ -2669,10 +2669,9 @@ def _add_variables_functional_units(self):
                     for unit in unit_choices:
                         unit_var = self._NewBoolVar(f"[{t.inst}].unit_choice.{unit}")
                         t.exec_unit_choices[unit] = unit_var
-                        t.exec = self._NewOptionalIntervalVar(
+                        t.exec = self._NewOptionalFixedIntervalVar(
                             t.cycle_start_var,
                             cycles_unit_occupied,
-                            t.cycle_end_var,
                             unit_var,
                             f"{t.varname}_usage_{unit}",
                         )
@@ -4007,18 +4006,30 @@ def _init_external_model_and_solver(self):
         self._model.cp_solver = cp_model.CpSolver()
         self._model.cp_solver.random_seed = self.config.solver_random_seed
 
-    def _NewIntVar(self, minval, maxval, name=""):
+    def _NewIntVar(self, minval, maxval, name=""):  # pylint:disable=invalid-name
         r = self._model.cp_model.NewIntVar(minval, maxval, name)
         self._model.variables.append(r)
         return r
 
-    def _NewIntervalVar(self, base, dur, end, name=""):
+    def _NewFixedIntervalVar(self, base, dur, name=""):  # pylint:disable=invalid-name
+        return self._model.cp_model.new_fixed_size_interval_var(base, dur, name)
+
+    def _NewIntervalVar(self, base, dur, end, name=""):  # pylint:disable=invalid-name
         return self._model.cp_model.NewIntervalVar(base, dur, end, name)
 
-    def _NewOptionalIntervalVar(self, base, dur, end, cond, name=""):
+    def _NewOptionalFixedIntervalVar(
+        self, base, dur, cond, name=""
+    ):  # pylint:disable=invalid-name
+        return self._model.cp_model.new_optional_fixed_size_interval_var(
+            base, dur, cond, name
+        )
+
+    def _NewOptionalIntervalVar(
+        self, base, dur, end, cond, name=""
+    ):  # pylint:disable=invalid-name
         return self._model.cp_model.NewOptionalIntervalVar(base, dur, end, cond, name)
 
-    def _NewBoolVar(self, name=""):
+    def _NewBoolVar(self, name=""):  # pylint:disable=invalid-name
         r = self._model.cp_model.NewBoolVar(name)
         self._model.variables.append(r)
         return r