diff --git a/electron-builder.yml b/electron-builder.yml
index d8f3b67..4abacd6 100644
--- a/electron-builder.yml
+++ b/electron-builder.yml
@@ -21,6 +21,11 @@ linux:
   target:
     - AppImage
     - deb
+    # tar.gz is what the in-app updater installs (pickAsset looks for a
+    # linux x86_64/amd64 tarball); arch must be x64 so the asset name ends
+    # in -linux-x86_64 like every published release.
+    - target: tar.gz
+      arch: x64
 
 # OS file associations: double-click / "Open with Folio" on Markdown and
 # plain-text files imports them as books (see folio:openPathOrImport and
diff --git a/package-lock.json b/package-lock.json
index 5c27704..6b4b766 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "folio",
-  "version": "0.1.8",
+  "version": "0.1.17",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "folio",
-      "version": "0.1.8",
+      "version": "0.1.17",
       "license": "MIT",
       "dependencies": {
         "@tiptap/core": "^2.27.2",
diff --git a/package.json b/package.json
index afb7897..3ffd369 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "folio",
-  "version": "0.1.10",
+  "version": "0.1.17",
   "description": "A simple, local, open-source desktop writing app.",
   "productName": "Folio",
   "author": "Folio Contributors",
@@ -15,6 +15,7 @@
     "dev": "concurrently -k \"npm run build:watch\" \"wait-on dist/main.js && npm run electron\"",
     "start": "npm run build && npm run electron",
     "lint": "tsc --noEmit",
+    "prepackage": "npm run build",
     "test": "node tests/run-project-test.mjs && node tests/run-chapters-test.mjs && node tests/run-wikilinks-test.mjs && node tests/run-office-export-test.mjs && node tests/run-migration-test.mjs && node tests/run-editor-test.mjs && node tests/run-fullbook-test.mjs && node tests/run-print-test.mjs && node tests/run-update-import-test.mjs && node tests/run-update-installer-test.mjs && node tests/run-snapshots-test.mjs && node tests/run-search-test.mjs",
     "package": "electron-builder"
   },
diff --git a/src/main/index.ts b/src/main/index.ts
index 80749cd..c9557a1 100644
--- a/src/main/index.ts
+++ b/src/main/index.ts
@@ -1220,46 +1220,100 @@ handleIpc("folio:performUpdate", async () => {
       app.getPath("temp"),
       `folio-update-${Date.now()}.tar.gz`
     );
-    // Downloads of the ~100MB asset have twice truncated near the end while
-    // the server copy stayed intact. The old 2-byte magic check could not
-    // see that, so the detached installer failed after the app had quit and
-    // the update silently no-oped. Now: retry the download up to 3 times,
-    // require the advertised byte count, and gunzip the whole file before
-    // handing off. A corrupt file is deleted and the user gets a real error.
-    const { Readable } = await import("stream");
-    const { createWriteStream } = await import("fs");
-    const { pipeline } = await import("stream/promises");
+    // Downloads go through curl, not Chromium's network stack: on flaky Wi-Fi
+    // the Electron net stack restarts requests mid-stream, producing a
+    // right-sized but corrupt gzip ("100% three times, then failed"). curl
+    // resumes with HTTP Range (-C -) so a dropped connection continues where
+    // it left off instead of restarting, and retries internally. We still
+    // verify the exact byte count and gunzip the whole file before handoff.
     const total = Number(asset.size) || 0;
     let lastError = "";
     let downloaded = false;
-    for (let attempt = 1; attempt <= 3 && !downloaded; attempt++) {
-      try {
-        const res = await fetch(asset.browser_download_url, {
-          redirect: "follow",
-          signal: AbortSignal.timeout(10 * 60 * 1000),
+    const { spawn } = await import("child_process");
+    const haveCurl = await new Promise<boolean>((resolve) => {
+      const p = spawn("curl", ["--version"], { stdio: "ignore" });
+      p.on("error", () => resolve(false));
+      p.on("close", (code) => resolve(code === 0));
+    });
+    if (haveCurl) {
+      for (let attempt = 1; attempt <= 3 && !downloaded; attempt++) {
+        const code = await new Promise<number>((resolve) => {
+          const c = spawn(
+            "curl",
+            [
+              "-fsSL",
+              "-C", "-", // resume a partial file
+              "--max-time", "900",
+              "--retry", "5", "--retry-delay", "2", "--retry-all-errors",
+              "--connect-timeout", "15",
+              "-o", tarball,
+              asset.browser_download_url,
+            ],
+            { stdio: "ignore" }
+          );
+          const timer = setInterval(() => {
+            try {
+              getWindow()?.webContents.send("folio:update-progress", {
+                received: fs.statSync(tarball).size,
+                total,
+              });
+            } catch {
+              /* file not created yet */
+            }
+          }, 1000);
+          c.on("error", () => { clearInterval(timer); resolve(-1); });
+          c.on("close", (rc) => { clearInterval(timer); resolve(rc ?? -1); });
         });
-        if (!res.ok || !res.body) {
-          lastError = `Download failed (HTTP ${res.status}).`;
+        if (code !== 0) {
+          lastError = `Download failed (curl exit ${code}).`;
           continue;
         }
-        let received = 0;
-        const source = Readable.fromWeb(res.body as never);
-        source.on("data", (chunk: Buffer) => {
-          received += chunk.length;
-          getWindow()?.webContents.send("folio:update-progress", { received, total });
-        });
-        await pipeline(source, createWriteStream(tarball));
-        if (looksTruncated(received, total)) {
-          lastError = `Download truncated (${received}/${total} bytes).`;
+        const size = fs.existsSync(tarball) ? fs.statSync(tarball).size : 0;
+        if (looksTruncated(size, total)) {
+          lastError = `Download truncated (${size}/${total} bytes).`;
           continue;
         }
         if (!(await verifyArchiveGzip(tarball))) {
           lastError = "Downloaded archive is corrupt (gzip stream incomplete).";
+          fs.rmSync(tarball, { force: true }); // corrupted resume file must not poison the next attempt
           continue;
         }
         downloaded = true;
-      } catch (e) {
-        lastError = `Download failed: ${(e as Error).message}`;
+      }
+    } else {
+      // No curl on PATH: fall back to the in-process fetch pipeline.
+      const { Readable } = await import("stream");
+      const { createWriteStream } = await import("fs");
+      const { pipeline } = await import("stream/promises");
+      for (let attempt = 1; attempt <= 3 && !downloaded; attempt++) {
+        try {
+          const res = await fetch(asset.browser_download_url, {
+            redirect: "follow",
+            signal: AbortSignal.timeout(10 * 60 * 1000),
+          });
+          if (!res.ok || !res.body) {
+            lastError = `Download failed (HTTP ${res.status}).`;
+            continue;
+          }
+          let received = 0;
+          const source = Readable.fromWeb(res.body as never);
+          source.on("data", (chunk: Buffer) => {
+            received += chunk.length;
+            getWindow()?.webContents.send("folio:update-progress", { received, total });
+          });
+          await pipeline(source, createWriteStream(tarball));
+          if (looksTruncated(received, total)) {
+            lastError = `Download truncated (${received}/${total} bytes).`;
+            continue;
+          }
+          if (!(await verifyArchiveGzip(tarball))) {
+            lastError = "Downloaded archive is corrupt (gzip stream incomplete).";
+            continue;
+          }
+          downloaded = true;
+        } catch (e) {
+          lastError = `Download failed: ${(e as Error).message}`;
+        }
       }
     }
     if (!downloaded) {
@@ -1294,13 +1348,17 @@ handleIpc("folio:performUpdate", async () => {
     // systemd-run puts the script in its own transient unit that outlives us;
     // verified to survive on this machine. Fall back to a detached spawn for
     // non-systemd sessions.
-    const { spawn } = await import("child_process");
     let handedOff = false;
     try {
       const { execFileSync } = await import("child_process");
       execFileSync("systemd-run", [
         "--user", "--quiet", "--collect",
         `--description=Folio updater handoff`,
+        // Default KillMode=control-group means the unit's cgroup is swept
+        // when the script exits — that killed the backgrounded relaunch
+        // before Electron got to start (v0.1.15 update: swap OK, app died).
+        // KillMode=process lets the script exit while its child app lives.
+        "--property=KillMode=process",
         "/bin/sh", script,
       ], { timeout: 10_000, stdio: "ignore" });
       handedOff = true;
@@ -1370,4 +1428,8 @@ if (app.requestSingleInstanceLock()) {
     }
     if (f) openFromArg(f);
   });
+} else {
+  // Lost the lock: another Folio is already running. Without this quit the
+  // second process falls through to whenReady() and opens a duplicate window.
+  app.quit();
 }
diff --git a/src/main/update.ts b/src/main/update.ts
index 738245b..9493643 100644
--- a/src/main/update.ts
+++ b/src/main/update.ts
@@ -224,7 +224,14 @@ export function buildInstallerScript(spec: InstallerSpec): string {
     '  rm -rf "$NEW"',
     "fi",
     'say "relaunching"',
-    '"$RELAUNCH" >/dev/null 2>&1 &',
+    // Detach fully: setsid moves the relaunch into its own session so it
+    // survives this script's exit and any cgroup sweep of the transient
+    // unit (systemd KillMode). Fallback chain for missing setsid.
+    'if command -v setsid >/dev/null 2>&1; then',
+    '  setsid "$RELAUNCH" >/dev/null 2>&1 < /dev/null &',
+    'else',
+    '  nohup "$RELAUNCH" >/dev/null 2>&1 < /dev/null &',
+    "fi",
     "",
   ].join("\n");
 }