diff --git a/main.js b/main.js
index 1f0972a7..f397d77d 100644
--- a/main.js
+++ b/main.js
@@ -3232,15 +3232,22 @@ 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"). Launches the setup with
+// /S (silent, skips the wizard) and --force-run (electron-builder's NSIS
+// convention for "start the app when the install finishes"), then quits
+// Theseus so the installer can overwrite it. The user sees the browser
+// disappear for a couple of seconds and come back on the new version —
+// no manual relaunch needed. Verified E2E on 0.3.33 → 0.3.34 in the
+// 2026-09-08 session; the 0.3.37 → 0.3.39 update ran WITHOUT --force-run
+// (the flag was dropped in the 0.3.31 rewrite once it was clear /S alone
+// installs correctly) and the user reported the missing relaunch — this
+// commit puts --force-run back on so the auto-restart is part of the
+// standard flow again. --updated stays out: the earlier E2E showed it
+// wasn't load-bearing correctness for our NSIS config.
 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, ["/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.
diff --git a/package.json b/package.json
index b5555d46..9a17f7e8 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "theseus-navigator",
-  "version": "0.3.39",
+  "version": "0.3.40",
   "description": "Theseus Navigator — a browser that follows the thread. By Silent Mode, a Deviant project.",
   "author": "Silent Mode",
   "main": "main.js",