diff --git a/apps/desktop/src/lib/mupdf/mupdf-worker.ts b/apps/desktop/src/lib/mupdf/mupdf-worker.ts
index f912051..3334a12 100644
--- a/apps/desktop/src/lib/mupdf/mupdf-worker.ts
+++ b/apps/desktop/src/lib/mupdf/mupdf-worker.ts
@@ -1,13 +1,43 @@
-import * as mupdf from "mupdf";
+import type { PDFDocument } from "mupdf";
 
-const documentMap = new Map<number, mupdf.PDFDocument>();
+type MupdfModule = typeof import("mupdf");
+
+type MupdfWasmModuleConfig = {
+  locateFile?: (path: string) => string;
+};
+
+const wasmModuleConfig = ((
+  globalThis as typeof globalThis & {
+    $libmupdf_wasm_Module?: MupdfWasmModuleConfig;
+  }
+).$libmupdf_wasm_Module ??= {});
+
+// In Vite dev, requests for /node_modules/.../mupdf-wasm.wasm can fall back to
+// index.html. Pointing MuPDF at Vite's @fs URL keeps worker startup on the
+// actual binary during local development without changing packaged builds.
+if (import.meta.env.DEV) {
+  const devWasmUrl = `/@fs/${__MUPDF_WASM_FS_PATH__}`;
+  wasmModuleConfig.locateFile = (path: string) => {
+    if (path.endsWith("mupdf-wasm.wasm")) {
+      return devWasmUrl;
+    }
+    return path;
+  };
+}
+
+const mupdf: MupdfModule = await import("mupdf");
+
+const documentMap = new Map<number, PDFDocument>();
 let nextDocId = 1;
 
 const methods: Record<string, (...args: any[]) => any> = {};
 
 methods.openDocument = (buffer: ArrayBuffer, magic: string): number => {
   const docId = nextDocId++;
-  const doc = mupdf.Document.openDocument(buffer, magic) as mupdf.PDFDocument;
+  const doc = mupdf.Document.openDocument(
+    buffer,
+    magic,
+  ) as unknown as PDFDocument;
   documentMap.set(docId, doc);
   return docId;
 };
diff --git a/apps/desktop/src/vite-env.d.ts b/apps/desktop/src/vite-env.d.ts
index 11f02fe..3e45f76 100644
--- a/apps/desktop/src/vite-env.d.ts
+++ b/apps/desktop/src/vite-env.d.ts
@@ -1 +1,3 @@
 /// <reference types="vite/client" />
+
+declare const __MUPDF_WASM_FS_PATH__: string;
diff --git a/apps/desktop/vite.config.ts b/apps/desktop/vite.config.ts
index 57e85b3..740f71b 100644
--- a/apps/desktop/vite.config.ts
+++ b/apps/desktop/vite.config.ts
@@ -4,6 +4,15 @@ import topLevelAwait from "vite-plugin-top-level-await";
 import path from "node:path";
 
 const host = process.env.TAURI_DEV_HOST;
+const mupdfWasmFile = path.resolve(
+  __dirname,
+  "..",
+  "..",
+  "node_modules",
+  "mupdf",
+  "dist",
+  "mupdf-wasm.wasm",
+);
 
 export default defineConfig({
   plugins: [react(), topLevelAwait()],
@@ -12,6 +21,9 @@ export default defineConfig({
       "@": path.resolve(__dirname, "src"),
     },
   },
+  define: {
+    __MUPDF_WASM_FS_PATH__: JSON.stringify(mupdfWasmFile.replace(/\\/g, "/")),
+  },
   worker: {
     format: "es",
   },