diff --git a/SUB Control/.gitignore b/SUB Control/.gitignore
index 6dbe475..c7bf4b4 100644
--- a/SUB Control/.gitignore	
+++ b/SUB Control/.gitignore	
@@ -3,3 +3,4 @@ __pycache__/
 *.py[cod]
 logs/
 model_settings.json
+runtime/
diff --git a/SUB Control/README.md b/SUB Control/README.md
index 86148ee..78e74d6 100644
--- a/SUB Control/README.md	
+++ b/SUB Control/README.md	
@@ -14,10 +14,10 @@ server, open a browser tab, or require an internet connection.
 The WebView is frameless and uses the compact title bar drawn by the interface.
 The vehicle rail includes a local STL viewer: choose **Load STL**, then drag to
 orbit, use the mouse wheel to zoom, or switch between shaded and edge-focused
-rendering. The chosen file is remembered in `model_settings.json`; only its
-local path is stored. STEP/STP CAD solids must first be tessellated/exported as
-STL because the embedded renderer intentionally does not include a full CAD
-kernel.
+rendering. A cached STL copy is stored locally under the ignored `runtime/`
+directory so the model can be restored on the next launch.
+STEP/STP CAD solids must first be tessellated/exported as STL because the
+embedded renderer intentionally does not include a full CAD kernel.
 
 ## Safety first
 
diff --git a/SUB Control/web/app.js b/SUB Control/web/app.js
index 4e73fdd..611d18c 100644
--- a/SUB Control/web/app.js	
+++ b/SUB Control/web/app.js	
@@ -25,7 +25,10 @@ addEventListener('blur',()=>{keys.clear();if(!joyDrag)easeJoy();if(!heaveDrag)ea
 
 function openModal(id){document.getElementById(id)?.showModal()}$$('[data-open]').forEach(b=>b.onclick=()=>openModal(b.dataset.open));$$('[data-close]').forEach(b=>b.onclick=()=>b.closest('dialog').close());
 $('#window-min').onclick=()=>api('minimize_window');$('#window-max').onclick=()=>api('toggle_maximize_window');$('#window-close').onclick=()=>api('close_window');$('.window-drag').ondblclick=()=>api('toggle_maximize_window');
-$('#load-model').onclick=async e=>{const button=e.currentTarget,old=button.textContent;try{button.disabled=true;button.textContent='Loading…';const model=await api('choose_model');if(!model)return;await new Promise(requestAnimationFrame);const result=window.rovModel.load(model);button.textContent='Replace STL';toast(`Loaded ${result.name} • ${result.triangles.toLocaleString()} triangles`)}catch(error){toast(`STL import failed: ${error.message}`,true)}finally{button.disabled=false;if(button.textContent==='Loading…')button.textContent=old}};$('#model-style').onclick=e=>{const edges=window.rovModel.toggleStyle();e.currentTarget.textContent=edges?'Shaded':'Edges'};
+const modelInput=$('#model-input'),modelButton=$('#load-model');
+modelButton.onclick=()=>{modelInput.value='';modelInput.click()};
+modelInput.onchange=async()=>{const file=modelInput.files?.[0],old=modelButton.textContent;if(!file)return;try{if(!file.name.toLowerCase().endsWith('.stl'))throw new Error('Choose an STL mesh');if(file.size>30*1024*1024)throw new Error('The STL is larger than 30 MB; export a lighter mesh');modelButton.disabled=true;modelButton.textContent='Loading…';await new Promise(requestAnimationFrame);const buffer=await file.arrayBuffer(),result=window.rovModel.loadBuffer(buffer,file.name);modelButton.textContent='Replace STL';toast(`Loaded ${result.name} • ${result.triangles.toLocaleString()} triangles`);if(bridgeReady){const dataUrl=await new Promise((resolve,reject)=>{const reader=new FileReader();reader.onload=()=>resolve(reader.result);reader.onerror=()=>reject(reader.error);reader.readAsDataURL(file)});api('save_model',file.name,String(dataUrl).split(',')[1]).catch(error=>toast(`Model loaded, but could not be saved: ${error.message}`,true))}}catch(error){toast(`STL import failed: ${error.message}`,true)}finally{modelButton.disabled=false;if(modelButton.textContent==='Loading…')modelButton.textContent=old}};
+$('#model-style').onclick=e=>{const edges=window.rovModel.toggleStyle();e.currentTarget.textContent=edges?'Shaded':'Edges'};
 $('#refresh').onclick=async()=>populatePorts(await api('refresh_ports'));$('#connect').onclick=async()=>{try{if(connected)await api('disconnect');else await api('connect',$('#port').value,+$('#baud').value,+$('#rate').value)}catch(e){toast(e.message,true)}};
 $('#manual').onclick=()=>api('command','manual').catch(e=>toast(e.message,true));$('#arm').onclick=()=>openModal('arm-dialog');$('#confirm-arm').onclick=()=>{api('command','arm').catch(e=>toast(e.message,true));$('#arm-dialog').close()};$('#disarm').onclick=()=>api('command','disarm').catch(e=>toast(e.message,true));$('#logs').onclick=()=>api('open_logs');
 $('#gain').oninput=e=>{$('#gain-value').textContent=`${e.target.value}%`;api('set_gain',+e.target.value)};
diff --git a/SUB Control/web/index.html b/SUB Control/web/index.html
index 116d5ca..ba232fc 100644
--- a/SUB Control/web/index.html	
+++ b/SUB Control/web/index.html	
@@ -46,6 +46,7 @@
         <div class="model-tools">
           <button id="load-model">Load STL</button>
           <button id="model-style" disabled>Edges</button>
+          <input id="model-input" type="file" accept=".stl,model/stl,application/sla" hidden>
         </div>
       </div>
       <div class="vehicle-name"><small>VEHICLE</small><strong id="vehicle">No heartbeat</strong><span>SimpleROV-3 • differential drive</span></div>
diff --git a/SUB Control/web/model-viewer.js b/SUB Control/web/model-viewer.js
index 3cb1692..6c67954 100644
--- a/SUB Control/web/model-viewer.js	
+++ b/SUB Control/web/model-viewer.js	
@@ -65,15 +65,18 @@
   addEventListener('resize',requestDraw);
 
   window.rovModel = {
+    loadBuffer(buffer, name) {
+      vertices=parseStl(buffer);stage.classList.add('model-loaded');
+      document.querySelector('#model-style').disabled=false;
+      document.querySelector('#model-file-name').textContent=name;
+      yaw=-.55;pitch=-.42;zoom=1;requestDraw();
+      return {name,triangles:vertices.length/9};
+    },
     load(payload) {
       if (!payload?.data) throw new Error('The selected STL returned no mesh data');
       const binary=atob(payload.data),bytes=new Uint8Array(binary.length);
       for(let i=0;i<binary.length;i++)bytes[i]=binary.charCodeAt(i);
-      vertices=parseStl(bytes.buffer);stage.classList.add('model-loaded');
-      document.querySelector('#model-style').disabled=false;
-      document.querySelector('#model-file-name').textContent=payload.name;
-      yaw=-.55;pitch=-.42;zoom=1;requestDraw();
-      return {name:payload.name,triangles:vertices.length/9};
+      return this.loadBuffer(bytes.buffer,payload.name);
     },
     toggleStyle() { edgesOnly=!edgesOnly;requestDraw();return edgesOnly; }
   };
diff --git a/SUB Control/web_ui.py b/SUB Control/web_ui.py
index 0eaa2a9..f27c29e 100644
--- a/SUB Control/web_ui.py	
+++ b/SUB Control/web_ui.py	
@@ -35,6 +35,8 @@ class ControlApi:
         self.motor_directions: dict[int, int] = {}
         self.battery_path = Path(__file__).resolve().parent / "battery_settings.json"
         self.model_path = Path(__file__).resolve().parent / "model_settings.json"
+        self.model_cache = Path(__file__).resolve().parent / "runtime" / "vehicle_model.stl"
+        self.model_cache_name = Path(__file__).resolve().parent / "runtime" / "vehicle_model_name.txt"
         # Leading underscore keeps the native WebView object out of js_api
         # serialization. Only the small public methods below are exposed.
         self._window = None
@@ -79,29 +81,28 @@ class ControlApi:
             self._window.destroy()
         return True
 
-    def choose_model(self):
-        if not self._window:
-            raise RuntimeError("Window is not ready")
-        selected = self._window.create_file_dialog(
-            webview.OPEN_DIALOG,
-            allow_multiple=False,
-            file_types=("STL mesh (*.stl)", "STEP model (*.step;*.stp)"),
-        )
-        if not selected:
-            return None
-        path = Path(selected[0])
-        if path.suffix.lower() in (".step", ".stp"):
-            raise ValueError(
-                "STEP is a CAD solid and must be tessellated first. Export it as a binary STL, then load that file."
-            )
-        if path.suffix.lower() != ".stl":
+    def save_model(self, name, data):
+        safe_name = Path(str(name)).name
+        if not safe_name.lower().endswith(".stl"):
             raise ValueError("Choose an STL mesh")
-        if path.stat().st_size > 30 * 1024 * 1024:
-            raise ValueError("The STL is larger than 30 MB; export a lighter mesh")
-        self.model_path.write_text(json.dumps({"path": str(path)}, indent=2) + "\n", encoding="utf-8")
-        return self._model_payload(path)
+        try:
+            content = base64.b64decode(data, validate=True)
+        except (ValueError, TypeError) as exc:
+            raise ValueError("Invalid STL data") from exc
+        if not content or len(content) > 30 * 1024 * 1024:
+            raise ValueError("STL must be between 1 byte and 30 MB")
+        self.model_cache.parent.mkdir(exist_ok=True)
+        self.model_cache.write_bytes(content)
+        self.model_cache_name.write_text(safe_name, encoding="utf-8")
+        return True
 
     def saved_model(self):
+        try:
+            if self.model_cache.is_file() and self.model_cache.stat().st_size <= 30 * 1024 * 1024:
+                name = self.model_cache_name.read_text(encoding="utf-8").strip() or "vehicle_model.stl"
+                return {"name": name, "data": base64.b64encode(self.model_cache.read_bytes()).decode("ascii")}
+        except (OSError, ValueError):
+            pass
         try:
             path = Path(json.loads(self.model_path.read_text(encoding="utf-8"))["path"])
             if path.is_file() and path.suffix.lower() == ".stl" and path.stat().st_size <= 30 * 1024 * 1024: