diff --git a/frontend/src/components/DynamicComponent.tsx b/frontend/src/components/DynamicComponent.tsx
index a33a8c9c..0e045b3d 100644
--- a/frontend/src/components/DynamicComponent.tsx
+++ b/frontend/src/components/DynamicComponent.tsx
@@ -204,28 +204,50 @@ export const DynamicComponent: React.FC<DynamicComponentProps> = ({
 
     let cleanupSimulationEvents: (() => void) | undefined;
     if (logic && logic.attachEvents && simulator) {
-      // Helper to find Arduino pin connected to a component pin
+      // Helper to find Arduino pin connected to a component pin.
+      // Traces through passive components (resistors) so that a circuit like
+      //   LED-cathode → resistor → GND  returns -1 (GND) instead of null.
       const getArduinoPin = (componentPinName: string): number | null => {
         const state = useSimulatorStore.getState();
-        const wires = state.wires.filter(
-          w => (w.start.componentId === id && w.start.pinName === componentPinName) ||
-            (w.end.componentId === id && w.end.pinName === componentPinName)
-        );
 
-        for (const w of wires) {
-          // Find which endpoint connects to a board component
-          const boardEndpoint = isBoardComponent(w.start.componentId) ? w.start :
-            isBoardComponent(w.end.componentId) ? w.end : null;
-          if (boardEndpoint) {
-            // Use the board's actual kind for pin mapping (instance ID may differ from kind,
-            // e.g. board ID 'arduino-uno' after switching to 'raspberry-pi-pico')
-            const boardKind = state.boards.find((b) => b.id === boardEndpoint.componentId)?.boardKind
-              ?? boardEndpoint.componentId;
-            const pin = boardPinToNumber(boardKind, boardEndpoint.pinName);
-            if (pin !== null) return pin;
+        // Passive component metadataIds that are electrically transparent.
+        const PASSIVE = new Set(['resistor', 'resistor-us']);
+
+        // Depth-limited BFS: trace from (fromId, fromPin) through wires,
+        // traversing through passive components to reach a board pin.
+        const trace = (fromId: string, fromPin: string, depth: number): number | null => {
+          if (depth > 6) return null;
+
+          const wires = state.wires.filter(
+            w => (w.start.componentId === fromId && w.start.pinName === fromPin) ||
+              (w.end.componentId === fromId && w.end.pinName === fromPin)
+          );
+
+          for (const w of wires) {
+            const selfEp  = (w.start.componentId === fromId && w.start.pinName === fromPin) ? w.start : w.end;
+            const otherEp = selfEp === w.start ? w.end : w.start;
+
+            if (isBoardComponent(otherEp.componentId)) {
+              // Direct board connection
+              const boardKind = state.boards.find((b) => b.id === otherEp.componentId)?.boardKind
+                ?? otherEp.componentId;
+              const pin = boardPinToNumber(boardKind, otherEp.pinName);
+              if (pin !== null) return pin;
+            } else {
+              // Intermediate passive component — traverse through it
+              const comp = state.components.find(c => c.id === otherEp.componentId);
+              if (comp && PASSIVE.has(comp.metadataId)) {
+                // Resistors have two pins; find the other one to continue tracing
+                const otherPin = otherEp.pinName === '1' ? '2' : '1';
+                const result = trace(otherEp.componentId, otherPin, depth + 1);
+                if (result !== null) return result;
+              }
+            }
           }
-        }
-        return null;
+          return null;
+        };
+
+        return trace(id, componentPinName, 0);
       };
 
       cleanupSimulationEvents = logic.attachEvents(el, simulator, getArduinoPin, id);
diff --git a/frontend/src/simulation/MicroPythonLoader.ts b/frontend/src/simulation/MicroPythonLoader.ts
index d8b9d4dd..737e1be0 100644
--- a/frontend/src/simulation/MicroPythonLoader.ts
+++ b/frontend/src/simulation/MicroPythonLoader.ts
@@ -8,6 +8,11 @@
 
 import { get as idbGet, set as idbSet } from 'idb-keyval';
 import createLittleFS from 'littlefs';
+// ?url tells Vite to return the correct asset URL for the WASM binary
+// (without this, Emscripten fetches 'littlefs.wasm' relative to the bundle
+//  which resolves to the SPA index.html — causing the "expected magic word" error)
+// @ts-ignore — Vite ?url import, no type declaration needed
+import littlefsWasmUrl from 'littlefs/dist/littlefs.wasm?url';
 
 // Flash geometry (matches rp2040js and MicroPython defaults)
 const FLASH_START_ADDRESS = 0x10000000;
@@ -68,8 +73,9 @@ export async function loadUserFiles(
   // Create a backing buffer for the LittleFS filesystem
   const fsBuffer = new Uint8Array(MICROPYTHON_FS_BLOCK_COUNT * MICROPYTHON_FS_BLOCK_SIZE);
 
-  // Initialize the littlefs WASM module
-  const lfs = await createLittleFS({});
+  // Initialize the littlefs WASM module.
+  // locateFile redirects Emscripten's internal fetch to the Vite-resolved asset URL.
+  const lfs = await createLittleFS({ locateFile: () => littlefsWasmUrl });
 
   // Register flash read/write callbacks for the WASM module
   const flashRead = lfs.addFunction(
diff --git a/frontend/vite.config.ts b/frontend/vite.config.ts
index 42881531..8d34bd91 100644
--- a/frontend/vite.config.ts
+++ b/frontend/vite.config.ts
@@ -20,6 +20,7 @@ export default defineConfig({
       },
     },
   },
+  assetsInclude: ['**/*.wasm'],
   optimizeDeps: {
     include: ['avr8js', 'rp2040js', '@wokwi/elements', 'littlefs'],
   },