diff --git a/web/standalone/vite.config.ts b/web/standalone/vite.config.ts
index 701d5a8..306652b 100644
--- a/web/standalone/vite.config.ts
+++ b/web/standalone/vite.config.ts
@@ -40,6 +40,11 @@ export default defineConfig({
     alias: {
       "@": path.resolve(__dirname, "./src"),
     },
+    // @pcbjam/shared is in a second pnpm workspace with its own `yjs`; dedupe so
+    // the bundled editor links ONE yjs (a mutable, instanceof-checked singleton).
+    // Without it shared's collab code (kicad-y) and the app's yjs are two
+    // instances → "Unexpected content type" the moment a doc is seeded.
+    dedupe: ["yjs"],
   },
   server: {
     // Default :3048. The closed `pnpm dev:gpl` runs a second editor instance on
diff --git a/web/standalone/vitest.config.ts b/web/standalone/vitest.config.ts
index 62549f3..968f811 100644
--- a/web/standalone/vitest.config.ts
+++ b/web/standalone/vitest.config.ts
@@ -7,6 +7,11 @@ import { defineConfig } from "vitest/config";
 export default defineConfig({
   resolve: {
     alias: { "@": path.resolve(__dirname, "./src") },
+    // @pcbjam/shared lives in a second pnpm workspace, so without this its `yjs`
+    // and the standalone's `yjs` resolve to two physical copies → a Y.Map from
+    // one instance rejects Y types from the other ("Unexpected content type").
+    // Force a single yjs (it's a shared mutable singleton — instanceof-checked).
+    dedupe: ["yjs"],
   },
   test: {
     environment: "node",