diff --git a/frontend/src/__tests__/multi-board-integration.test.ts b/frontend/src/__tests__/multi-board-integration.test.ts
index 42e26c1b..e0f433cd 100644
--- a/frontend/src/__tests__/multi-board-integration.test.ts
+++ b/frontend/src/__tests__/multi-board-integration.test.ts
@@ -49,6 +49,11 @@ vi.mock('../simulation/PinManager', () => ({
     this.onPinChange = vi.fn().mockReturnValue(() => {});
     this.getListenersCount = vi.fn().mockReturnValue(0);
     this.resetPinStates = vi.fn();
+    // Added by upstream commit d64eebc (Stop semantics): the simulator
+    // store's stopBoard() invokes hardResetPinStates on the active pin
+    // manager. The mock has to expose it or test calls explode with
+    // "is not a function" even though the optional chain looks safe.
+    this.hardResetPinStates = vi.fn();
   }),
 }));
 
diff --git a/frontend/vitest.config.ts b/frontend/vitest.config.ts
index f7c97fba..cc41fdab 100644
--- a/frontend/vitest.config.ts
+++ b/frontend/vitest.config.ts
@@ -1,4 +1,5 @@
 import { defineConfig } from 'vitest/config';
+import path from 'path';
 
 /**
  * Vitest configuration — split out from `vite.config.ts` (Phase 1d-tests J).
@@ -15,8 +16,19 @@ import { defineConfig } from 'vitest/config';
  *     isolation, state leaks between tests sharing the same worker.
  *   - Coverage excludes the WASM bundle (large binary, irrelevant lcov)
  *     and the test files themselves.
+ *
+ *   - `resolve.alias` mirrors `vite.config.ts` — vitest's defineConfig
+ *     does NOT auto-inherit from vite.config.ts, so the @velxio alias
+ *     used by overlay tests (e.g. pro/.../snapshot.test.ts importing
+ *     `@velxio/store/useEditorStore`) must be declared here too or
+ *     test files explode with "Cannot find package '@velxio/...'".
  */
 export default defineConfig({
+  resolve: {
+    alias: {
+      '@velxio': path.resolve(__dirname, 'src'),
+    },
+  },
   // Allow vitest to import test files / sources from outside this
   // project root - specifically `../../pro/frontend/src/pro/...` for
   // velxio-prod overlay tests. Without this, Vite's fs sandbox blocks