diff --git a/main.js b/main.js
index 71bba56..f0077dc 100644
--- a/main.js
+++ b/main.js
@@ -3073,15 +3073,26 @@ ipcMain.handle("recheck-update", async () => {
   return { updateAvailable, currentVersion: app.getVersion() };
 });
 // One-click "Install & restart". Requires the silent pre-fetch to have
-// finished (updateDownloadState === "ready"). Launches the setup with /S
-// (skips the wizard; our nsis/installer.nsh's Ariadne prompt is bypassed
-// too on upgrades because the Ariadne registry key is already present),
-// then quits Theseus so the installer can overwrite it. When the installer
-// finishes, the user re-launches Theseus and lands on the new version.
+// finished (updateDownloadState === "ready").
+//
+// CRITICAL — spawning the setup with just ["/S"] uninstalls Theseus but
+// then FAILS to reinstall on our config (oneClick:false + perMachine:false
+// + allowToChangeInstallationDirectory:true). In wizard mode NSIS expects
+// UI for the install-path picker, and in silent mode with the registry
+// path wiped by the just-run uninstaller, it exits without installing.
+// Users hit this in 0.3.31: browser gone, nothing left.
+//
+// Fix: pass --updated alongside /S. electron-builder's NSIS template
+// treats --updated as "this is an auto-update, reuse the existing install
+// directory from registry, don't re-run the uninstaller". --force-run
+// tells it to relaunch the app after install so the user isn't stranded
+// even if the wizard-mode path somehow trips again.
 ipcMain.handle("install-update-now", () => {
   if (updateDownloadState !== "ready" || !updateDownloadPath) return false;
   try {
-    const p = spawn(updateDownloadPath, ["/S"], { detached: true, stdio: "ignore" });
+    const p = spawn(updateDownloadPath,
+      ["--updated", "/S", "--force-run"],
+      { detached: true, stdio: "ignore" });
     p.unref();
   } catch (e) { console.warn("update spawn failed:", e?.message); return false; }
   // Give the child a moment to inherit our arguments before we exit.