diff --git a/src/app/utils/updateErrors.test.ts b/src/app/utils/updateErrors.test.ts
index 85574044d..780917a46 100644
--- a/src/app/utils/updateErrors.test.ts
+++ b/src/app/utils/updateErrors.test.ts
@@ -69,13 +69,23 @@ test('install kinds: anything unknown keeps the in-app updater', async () => {
 test('package installs get their package manager’s command, not an Install button', async () => {
   const { packageUpdateHelp, isPackageManagedError } = await import('./updateErrors');
   const pacman = packageUpdateHelp('pacman')!;
-  // Not `pacman -U <url>`: that also wants `<url>.sig`, which we don't publish.
-  assert.equal(
-    pacman.command,
-    'curl -LO https://code.lotusguild.org/LotusGuild/cinny-desktop/releases/download/latest/LotusChat-x86_64.pkg.tar.zst && sudo pacman -U ./LotusChat-x86_64.pkg.tar.zst',
+  // [cinny-desktop #36] signature, then checksum, then install, in that order;
+  // a local `pacman -U ./file` (not `<url>`, which also wants `<url>.sig`).
+  const steps = pacman.command!.split(' && ');
+  assert.equal(steps[0], 'cd "$(mktemp -d)"');
+  assert.match(
+    steps[1],
+    /-fLO \S+\/LotusChat-x86_64\.pkg\.tar\.zst -fLO \S+\/SHA256SUMS\.txt -fLO \S+\/SHA256SUMS\.txt\.minisig$/,
   );
+  assert.equal(
+    steps[2],
+    'minisign -Vm SHA256SUMS.txt -P RWRZZdyii05/NUcz337A5SAbiZK+NPVDWuiL2mM5Jk1p/LfRmNfiZ/6l',
+  );
+  assert.equal(steps[3], 'sha256sum -c --ignore-missing SHA256SUMS.txt');
+  assert.equal(steps[4], 'sudo pacman -U ./LotusChat-x86_64.pkg.tar.zst');
   assert.match(pacman.url, /LotusChat-x86_64\.pkg\.tar\.zst$/);
   const deb = packageUpdateHelp('deb')!;
+  assert.match(deb.command!, /minisign -Vm SHA256SUMS\.txt/);
   assert.match(deb.command!, /sudo apt install \.\/LotusChat-x86_64\.deb$/);
   assert.equal(packageUpdateHelp('manual')?.command, undefined);
   assert.equal(packageUpdateHelp('in-app'), undefined);
diff --git a/src/app/utils/updateErrors.ts b/src/app/utils/updateErrors.ts
index e45201e22..f3e2f5a7e 100644
--- a/src/app/utils/updateErrors.ts
+++ b/src/app/utils/updateErrors.ts
@@ -64,23 +64,38 @@ export const toInstallKind = (value: unknown): InstallKind =>
 
 export type PackageUpdateHelp = { command?: string; url: string; download: string };
 
+/** The desktop updater's minisign public key (cinny-desktop tauri.conf.json). */
+export const RELEASE_MINISIGN_KEY = 'RWRZZdyii05/NUcz337A5SAbiZK+NPVDWuiL2mM5Jk1p/LfRmNfiZ/6l';
+
+/**
+ * [cinny-desktop #36] Download a Linux package and install it only after
+ * checking the release's minisign-signed SHA256SUMS.txt. Runs in a fresh temp
+ * directory so a stale SHA256SUMS.txt can't be picked up.
+ */
+const verifiedInstall = (file: string, install: string): string =>
+  [
+    `cd "$(mktemp -d)"`,
+    `curl -fLO ${RELEASE_DOWNLOAD}/${file} -fLO ${RELEASE_DOWNLOAD}/SHA256SUMS.txt -fLO ${RELEASE_DOWNLOAD}/SHA256SUMS.txt.minisig`,
+    `minisign -Vm SHA256SUMS.txt -P ${RELEASE_MINISIGN_KEY}`,
+    `sha256sum -c --ignore-missing SHA256SUMS.txt`,
+    `${install} ./${file}`,
+  ].join(' && ');
+
 export const packageUpdateHelp = (kind: InstallKind): PackageUpdateHelp | undefined => {
   if (kind === 'pacman') {
-    const url = `${RELEASE_DOWNLOAD}/LotusChat-x86_64.pkg.tar.zst`;
-    // Download first, then install the local file: `pacman -U <url>` also
-    // fetches `<url>.sig` and fails without it (we don't sign packages),
-    // while a local file falls under LocalFileSigLevel (signature optional).
+    // Install the local file: `pacman -U <url>` also fetches `<url>.sig` and
+    // fails without it (packages aren't signed for pacman), while a local file
+    // falls under LocalFileSigLevel. Integrity comes from SHA256SUMS.txt.
     return {
-      command: `curl -LO ${url} && sudo pacman -U ./LotusChat-x86_64.pkg.tar.zst`,
-      url,
+      command: verifiedInstall('LotusChat-x86_64.pkg.tar.zst', 'sudo pacman -U'),
+      url: `${RELEASE_DOWNLOAD}/LotusChat-x86_64.pkg.tar.zst`,
       download: 'Download package',
     };
   }
   if (kind === 'deb') {
-    const url = `${RELEASE_DOWNLOAD}/LotusChat-x86_64.deb`;
     return {
-      command: `curl -LO ${url} && sudo apt install ./LotusChat-x86_64.deb`,
-      url,
+      command: verifiedInstall('LotusChat-x86_64.deb', 'sudo apt install'),
+      url: `${RELEASE_DOWNLOAD}/LotusChat-x86_64.deb`,
       download: 'Download package',
     };
   }