diff --git a/python/rcs/_core/sim.pyi b/python/rcs/_core/sim.pyi
index fa5a8899..71f79cba 100644
--- a/python/rcs/_core/sim.pyi
+++ b/python/rcs/_core/sim.pyi
@@ -97,6 +97,7 @@ class Sim:
     def is_converged(self) -> bool: ...
     def reset(self) -> None: ...
     def set_config(self, cfg: SimConfig) -> bool: ...
+    def set_model_data(self, mjmdl: int, mjdata: int) -> None: ...
     def step(self, k: int) -> None: ...
     def step_until_convergence(self) -> None: ...
     def sync_gui(self) -> None: ...
diff --git a/python/rcs/envs/scenes.py b/python/rcs/envs/scenes.py
index b661204d..2c8c42b0 100644
--- a/python/rcs/envs/scenes.py
+++ b/python/rcs/envs/scenes.py
@@ -70,8 +70,9 @@ def add_task_mujoco(cfg: TaskConfig, composer: ModelComposer, env_cfg: "SimEnvCr
         """Add task-specific elements to the Mujoco scene."""
 
     @staticmethod
-    def add_task_env(_cfg: TaskConfig, env: gym.Env, _simulation: Sim, _env_cfg: "SimEnvCreatorConfig") -> gym.Env:
+    def add_task_env(cfg: TaskConfig, env: gym.Env, simulation: Sim, env_cfg: "SimEnvCreatorConfig") -> gym.Env:
         """Add task-specific wrappers to the environment."""
+        _ = (cfg, simulation, env_cfg)
         return env
 
 
diff --git a/python/rcs/sim/sim.py b/python/rcs/sim/sim.py
index 07963e4d..5bce943e 100644
--- a/python/rcs/sim/sim.py
+++ b/python/rcs/sim/sim.py
@@ -48,19 +48,7 @@ class Sim(_Sim):
     STATE_SPEC = mj.mjtState.mjSTATE_INTEGRATION
 
     def __init__(self, mjmdl: str | PathLike | ModelComposer, cfg: SimConfig | None = None):
-        if isinstance(mjmdl, ModelComposer):
-            self.model = mjmdl.get_model()
-        else:
-            mjmdl = Path(mjmdl)
-            if mjmdl.suffix == ".xml":
-                self.model = mj.MjModel.from_xml_path(str(mjmdl))
-            elif mjmdl.suffix == ".mjb":
-                self.model = mj.MjModel.from_binary_path(str(mjmdl))
-            else:
-                msg = f"Filetype {mjmdl.suffix} is unknown"
-                logger.error(msg)
-
-        self.data = mj.MjData(self.model)
+        self.model, self.data = self.get_model_data(mjmdl)
         super().__init__(self.model._address, self.data._address)
         self._mp_context = mp.get_context("spawn")
         self._gui_uuid: Optional[str] = None
@@ -71,6 +59,28 @@ def __init__(self, mjmdl: str | PathLike | ModelComposer, cfg: SimConfig | None
         if cfg is not None:
             self.set_config(cfg)
 
+    def get_model_data(self, mjmdl: str | PathLike | ModelComposer) -> tuple[mj.MjModel, mj.MjData]:
+        if isinstance(mjmdl, ModelComposer):
+            model = mjmdl.get_model()
+        else:
+            mjmdl = Path(mjmdl)
+            if mjmdl.suffix == ".xml":
+                model = mj.MjModel.from_xml_path(str(mjmdl))
+            elif mjmdl.suffix == ".mjb":
+                model = mj.MjModel.from_binary_path(str(mjmdl))
+            else:
+                msg = f"Filetype {mjmdl.suffix} is unknown"
+                logger.error(msg)
+        data = mj.MjData(model)
+        return model, data
+
+    def set_model_data(self, model: mj.MjModel, data: mj.MjData):
+        super().set_model_data(model._address, data._address)
+
+    def instantiate_new_sim(self, mjmdl: str | PathLike | ModelComposer):
+        self.model, self.data = self.get_model_data(mjmdl)
+        self.set_model_data(self.model, self.data)
+
     def get_state_spec(self) -> int:
         return int(self.STATE_SPEC)
 
diff --git a/src/pybind/rcs.cpp b/src/pybind/rcs.cpp
index ab7772c0..23e42944 100644
--- a/src/pybind/rcs.cpp
+++ b/src/pybind/rcs.cpp
@@ -735,6 +735,12 @@ PYBIND11_MODULE(_core, m) {
              return std::make_shared<rcs::sim::Sim>((mjModel*)m, (mjData*)d);
            }),
            py::arg("mjmdl"), py::arg("mjdata"))
+      .def(
+          "set_model_data",
+          [](rcs::sim::Sim& self, long model, long data) {
+            self.set_model_data((mjModel*)model, (mjData*)data);
+          },
+          py::arg("mjmdl"), py::arg("mjdata"))
       .def("step_until_convergence", &rcs::sim::Sim::step_until_convergence,
            py::call_guard<py::gil_scoped_release>())
       .def("is_converged", &rcs::sim::Sim::is_converged)
diff --git a/src/sim/sim.cpp b/src/sim/sim.cpp
index 8facd93d..bfecf014 100644
--- a/src/sim/sim.cpp
+++ b/src/sim/sim.cpp
@@ -25,7 +25,12 @@ bool get_last_return_value(ConditionCallback cb) {
   return cb.last_return_value;
 }
 
-Sim::Sim(mjModel* m, mjData* d) : m(m), d(d), renderer(m) {};
+Sim::Sim(mjModel* m, mjData* d) : m(m), d(d), renderer(m) {}
+
+void Sim::set_model_data(mjModel* model, mjData* data) {
+  this->m = model;
+  this->d = data;
+}
 
 bool Sim::set_config(const SimConfig& cfg) {
   this->cfg = cfg;
diff --git a/src/sim/sim.h b/src/sim/sim.h
index 4ed35e60..bcc364c1 100644
--- a/src/sim/sim.h
+++ b/src/sim/sim.h
@@ -76,6 +76,7 @@ class Sim {
   mjModel* m;
   mjData* d;
   Sim(mjModel* m, mjData* d);
+  void set_model_data(mjModel* model, mjData* data);
   bool set_config(const SimConfig& cfg);
   SimConfig get_config();
   bool is_converged();