diff --git a/frontend/src/components/simulator/FlashModal.tsx b/frontend/src/components/simulator/FlashModal.tsx
index 4fa14108..29fc882c 100644
--- a/frontend/src/components/simulator/FlashModal.tsx
+++ b/frontend/src/components/simulator/FlashModal.tsx
@@ -404,7 +404,10 @@ interface WebReadyProps {
 }
 
 const WebReadyView = ({ board, onFlash }: WebReadyProps) => {
-  const hasCompiled = !!board.compiledProgram;
+  // MicroPython boards carry the 'micropython-loaded' sentinel instead of
+  // a flash image — nothing to write. Arduino/ESP-IDF sketches only.
+  const isMpy = board.languageMode === 'micropython';
+  const hasCompiled = !!board.compiledProgram && !isMpy;
   return (
     <div>
       <div style={{ padding: 16, background: '#0c0c11', borderRadius: 4, marginBottom: 12 }}>
@@ -418,7 +421,14 @@ const WebReadyView = ({ board, onFlash }: WebReadyProps) => {
         </div>
       </div>
 
-      {!hasCompiled && (
+      {isMpy && (
+        <div style={{ padding: 10, background: '#3a2e1a', color: '#ffb84d', borderRadius: 4, fontSize: 12, marginBottom: 12 }}>
+          MicroPython projects cannot be flashed to a real board yet — only
+          compiled Arduino/ESP-IDF sketches.
+        </div>
+      )}
+
+      {!board.compiledProgram && !isMpy && (
         <div style={{ padding: 10, background: '#3a2e1a', color: '#ffb84d', borderRadius: 4, fontSize: 12, marginBottom: 12 }}>
           No compiled program for this board yet. Click Compile in the toolbar first.
         </div>
diff --git a/frontend/src/components/simulator/SimulatorCanvas.tsx b/frontend/src/components/simulator/SimulatorCanvas.tsx
index 975aab43..98444c93 100644
--- a/frontend/src/components/simulator/SimulatorCanvas.tsx
+++ b/frontend/src/components/simulator/SimulatorCanvas.tsx
@@ -3447,13 +3447,19 @@ export const SimulatorCanvas = ({ headerSlot }: SimulatorCanvasProps = {}) => {
           // on the web the pro overlay may install a Web Serial flasher
           // for this board kind (no-op in pure OSS builds).
           if (isTauriRuntime || webFlashAvailable(board.boardKind)) {
+            // MicroPython boards don't compile to a flash image — the store
+            // keeps the 'micropython-loaded' sentinel, which no flasher can
+            // write. Arduino/ESP-IDF sketches only.
+            const isMpy = board.languageMode === 'micropython';
             actions.push({
               id: 'flash',
               label: t('editor.canvas.flashToBoard'),
-              disabled: !board.compiledProgram,
-              title: board.compiledProgram
-                ? 'Flash the compiled sketch to a real USB-attached board'
-                : 'Compile the sketch first',
+              disabled: !board.compiledProgram || isMpy,
+              title: isMpy
+                ? 'MicroPython projects cannot be flashed yet — Arduino sketches only'
+                : board.compiledProgram
+                  ? 'Flash the compiled sketch to a real USB-attached board'
+                  : 'Compile the sketch first',
               onSelect: () => {
                 setFlashModalFor(boardContextMenu.boardId);
                 setBoardContextMenu(null);