diff --git a/apps/desktop/README.md b/apps/desktop/README.md
index 1003caa..4812616 100644
--- a/apps/desktop/README.md
+++ b/apps/desktop/README.md
@@ -36,7 +36,7 @@ pnpm desktop:build
 `beforeBuildCommand`:
 
 1. Bundles `@prm/api` into `src-tauri/sidecars/prm-api.mjs` (esbuild) and copies a portable **Node** binary + `better-sqlite3` next to it
-2. Builds the UI into `apps/ui/dist`
+2. Builds the UI into `apps/ui/dist` (Tauri `frontendDist` is `../../ui/dist` from `src-tauri`)
 
 At runtime the shell resolves `sidecars/` from the app resource dir (or `PRM_API_SIDECAR_DIR`), spawns bundled Node with the API entry, sets `PRM_LAUNCH_TOKEN` / `PRM_DATA_DIR`, and kills the child on exit — one process from the user’s point of view.
 
diff --git a/apps/desktop/src-tauri/run-hook.mjs b/apps/desktop/src-tauri/run-hook.mjs
index 36fc721..fe60fb8 100644
--- a/apps/desktop/src-tauri/run-hook.mjs
+++ b/apps/desktop/src-tauri/run-hook.mjs
@@ -5,21 +5,32 @@
  * when cwd is apps/desktop (CI / tauri-action).
  */
 import { spawnSync } from "node:child_process";
+import { existsSync } from "node:fs";
 import { dirname, join } from "node:path";
 import { fileURLToPath } from "node:url";
 
 const srcTauri = dirname(fileURLToPath(import.meta.url));
 const desktopRoot = join(srcTauri, "..");
 const repoRoot = join(desktopRoot, "../..");
+const uiDist = join(repoRoot, "apps/ui/dist");
 const hook = process.argv[2] ?? "build";
 
 function run(command, args, opts = {}) {
-  const result = spawnSync(command, args, {
-    stdio: "inherit",
-    cwd: opts.cwd ?? desktopRoot,
-    shell: process.platform === "win32",
-    env: process.env,
-  });
+  const isWin = process.platform === "win32";
+  // On Windows, prefer a single shell command string so args are not dropped.
+  const result = isWin && opts.shell !== false
+    ? spawnSync([command, ...args].map((a) => (/\s/.test(a) ? `"${a}"` : a)).join(" "), {
+        stdio: "inherit",
+        cwd: opts.cwd ?? desktopRoot,
+        shell: true,
+        env: process.env,
+      })
+    : spawnSync(command, args, {
+        stdio: "inherit",
+        cwd: opts.cwd ?? desktopRoot,
+        shell: false,
+        env: process.env,
+      });
   if (result.status !== 0) process.exit(result.status ?? 1);
 }
 
@@ -31,4 +42,9 @@ if (hook === "dev") {
     shell: false,
   });
   run("pnpm", ["--dir", repoRoot, "--filter", "@prm/ui", "build"], { cwd: desktopRoot });
+  if (!existsSync(join(uiDist, "index.html"))) {
+    console.error("UI build missing — expected", join(uiDist, "index.html"));
+    process.exit(1);
+  }
+  console.log("UI dist ready:", uiDist);
 }
diff --git a/apps/desktop/src-tauri/tauri.conf.json b/apps/desktop/src-tauri/tauri.conf.json
index 552bf3c..909dd26 100644
--- a/apps/desktop/src-tauri/tauri.conf.json
+++ b/apps/desktop/src-tauri/tauri.conf.json
@@ -7,7 +7,7 @@
     "beforeDevCommand": "pnpm prepare:dev",
     "devUrl": "http://localhost:5173",
     "beforeBuildCommand": "pnpm prepare:build",
-    "frontendDist": "../ui/dist"
+    "frontendDist": "../../ui/dist"
   },
   "app": {
     "windows": [],