diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 1462c5e09..fd0cdcd0c 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -258,11 +258,17 @@ jobs:
           $portableDir = Join-Path $portableRoot "DBX_${version}_${arch}"
           $zipName = "DBX_${version}_${arch}-portable.zip"
           $exePath = "target/${{ matrix.target }}/release/dbx.exe"
+          $cargoMetadata = cargo metadata --no-deps --format-version 1 | ConvertFrom-Json
+          $appVersion = ($cargoMetadata.packages | Where-Object { $_.name -eq "dbx" } | Select-Object -First 1).version
 
           if (!(Test-Path $exePath)) {
             Write-Error "Missing Windows executable: $exePath"
             exit 1
           }
+          if (!$appVersion -or $appVersion -ne $version) {
+            Write-Error "Release tag version $version does not match the built DBX package version $appVersion"
+            exit 1
+          }
 
           New-Item -ItemType Directory -Force -Path $portableDir | Out-Null
           Copy-Item $exePath (Join-Path $portableDir "DBX.exe") -Force
@@ -270,8 +276,26 @@ jobs:
           Copy-Item "README.md" (Join-Path $portableDir "README.md") -Force
           Set-Content -Path (Join-Path $portableDir "portable.dbx") -Value "" -NoNewline
 
+          $portableExe = Join-Path $portableDir "DBX.exe"
+          $manifest = [ordered]@{
+            schema_version = 1
+            version = $appVersion
+            arch = $arch
+            executable = "DBX.exe"
+            executable_sha256 = (Get-FileHash -LiteralPath $portableExe -Algorithm SHA256).Hash.ToLowerInvariant()
+          } | ConvertTo-Json
+          Set-Content -Path (Join-Path $portableDir "portable-update.json") -Value $manifest -Encoding utf8NoBOM
+
           Compress-Archive -Path (Join-Path $portableDir "*") -DestinationPath $zipName -Force
-          gh release upload "${env:GITHUB_REF_NAME}" $zipName --repo "${env:GITHUB_REPOSITORY}" --clobber
+          pnpm tauri signer sign $zipName
+
+          $signatureName = "${zipName}.sig"
+          if (!(Test-Path $signatureName)) {
+            Write-Error "Missing portable update signature: $signatureName"
+            exit 1
+          }
+
+          gh release upload "${env:GITHUB_REF_NAME}" $zipName $signatureName --repo "${env:GITHUB_REPOSITORY}" --clobber
 
       - name: Upload Windows WebView2 offline installer
         if: matrix.arch == 'x64' || matrix.arch == 'arm64'
@@ -317,7 +341,7 @@ jobs:
             gh release view "${GITHUB_REF_NAME}" \
               --repo "${GITHUB_REPOSITORY}" \
               --json assets \
-              --jq '.assets[].name | select(endswith(".sig"))'
+              --jq '.assets[].name | select(endswith(".sig") and (endswith("-portable.zip.sig") | not))'
           )
 
           if [ "${#SIG_ASSETS[@]}" -eq 0 ]; then
diff --git a/Cargo.lock b/Cargo.lock
index f4c050630..8cad18cf4 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1825,6 +1825,7 @@ dependencies = [
  "futures",
  "libloading 0.8.9",
  "log",
+ "minisign-verify",
  "mongodb",
  "objc2",
  "objc2-app-kit",
@@ -1836,8 +1837,10 @@ dependencies = [
  "russh",
  "rust_decimal",
  "rustls 0.23.40",
+ "semver",
  "serde",
  "serde_json",
+ "sha2 0.10.9",
  "tauri",
  "tauri-build",
  "tauri-plugin-clipboard-manager",
diff --git a/apps/desktop/src/components/layout/UpdateDialog.spec.ts b/apps/desktop/src/components/layout/UpdateDialog.spec.ts
index 298c86d11..3a53913b8 100644
--- a/apps/desktop/src/components/layout/UpdateDialog.spec.ts
+++ b/apps/desktop/src/components/layout/UpdateDialog.spec.ts
@@ -13,6 +13,7 @@ const mountedApps: App[] = [];
 
 interface DialogState {
   open: boolean;
+  portableMode: boolean;
   isDownloadingUpdate: boolean;
   downloadProgress: number;
   updateDownloaded: boolean;
@@ -28,6 +29,7 @@ async function flushDialog() {
 async function mountDialog(activeTaskCount: number, initialState: Partial<DialogState> = {}, installDownloaded = vi.fn(async () => {})) {
   const state = reactive<DialogState>({
     open: true,
+    portableMode: false,
     isDownloadingUpdate: false,
     downloadProgress: 0,
     updateDownloaded: false,
@@ -64,7 +66,7 @@ async function mountDialog(activeTaskCount: number, initialState: Partial<Dialog
               current_version: "0.5.60",
               latest_version: "0.5.61",
               update_available: true,
-              portable_mode: false,
+              portable_mode: state.portableMode,
               release_name: "DBX v0.5.61",
               release_url: "https://github.com/t8y2/dbx/releases/tag/v0.5.61",
               release_notes: "",
@@ -127,6 +129,13 @@ describe("UpdateDialog active task guard", () => {
     expect(downloadButton()?.disabled).toBe(false);
   });
 
+  it("offers automatic installation for portable builds", async () => {
+    await mountDialog(0, { portableMode: true });
+
+    expect(document.body.textContent).toContain("portable ZIP");
+    expect(downloadButton()?.disabled).toBe(false);
+  });
+
   it("retains the downloaded update and enables installation only after tasks finish", async () => {
     await mountDialog(1, { updateDownloaded: true, downloadProgress: 100 });
 
diff --git a/apps/desktop/src/components/layout/UpdateDialog.vue b/apps/desktop/src/components/layout/UpdateDialog.vue
index 93f658dda..fd37a6073 100644
--- a/apps/desktop/src/components/layout/UpdateDialog.vue
+++ b/apps/desktop/src/components/layout/UpdateDialog.vue
@@ -107,7 +107,7 @@ watch(
           {{ t("updates.toUpdate") }}
         </p>
         <p v-if="isDesktop && updateInfo?.update_available && updateInfo.portable_mode" class="text-xs text-muted-foreground">
-          {{ t("updates.portableManualUpdate") }}
+          {{ t("updates.portableAutomaticUpdate") }}
         </p>
         <div v-if="canDownloadAndInstallUpdate(updateInfo, isDesktop) && activeTaskCount > 0" role="alert" class="flex items-start gap-2 rounded-md border border-amber-500/40 bg-amber-500/10 px-3 py-2 text-xs text-amber-700 dark:text-amber-300">
           <AlertTriangle class="mt-0.5 h-4 w-4 shrink-0" />
diff --git a/apps/desktop/src/composables/useAppUpdater.ts b/apps/desktop/src/composables/useAppUpdater.ts
index 6ea017e6e..27b7daaa0 100644
--- a/apps/desktop/src/composables/useAppUpdater.ts
+++ b/apps/desktop/src/composables/useAppUpdater.ts
@@ -19,7 +19,7 @@ export function shouldOpenUpdateDialog(options: { silent?: boolean }) {
 }
 
 export function canDownloadAndInstallUpdate(info: api.UpdateInfo | null, isDesktop: boolean) {
-  return isDesktop && info?.update_available === true && info.portable_mode !== true;
+  return isDesktop && info?.update_available === true;
 }
 
 export function normalizeUpdateDownloadSource(value: unknown): SettingsUpdateDownloadSource {
@@ -169,9 +169,11 @@ export function useAppUpdater(options: UseAppUpdaterOptions = {}) {
   async function installPendingUpdate() {
     isInstallingUpdate.value = true;
     try {
+      const portableMode = updateInfo.value?.portable_mode === true;
       await api.installDownloadedUpdate();
       updateDownloaded.value = false;
-      updateReady.value = true;
+      // The portable helper exits and relaunches DBX after the invoke response is delivered.
+      updateReady.value = !portableMode;
     } finally {
       isInstallingUpdate.value = false;
     }
diff --git a/apps/desktop/src/i18n/locales/en.ts b/apps/desktop/src/i18n/locales/en.ts
index 9c3f25cd1..a4662f712 100644
--- a/apps/desktop/src/i18n/locales/en.ts
+++ b/apps/desktop/src/i18n/locales/en.ts
@@ -70,7 +70,7 @@ export default {
     openRelease: "Open Release",
     downloadAndInstall: "Download & Install",
     activeTasksBlockUpdate: "{count} task(s) are still running. Wait for them to finish before updating DBX.",
-    portableManualUpdate: "Portable builds cannot use the in-app installer. Download the portable ZIP from the release page, then extract it over the current DBX folder to keep portable.dbx and data.",
+    portableAutomaticUpdate: "DBX will download the signed portable ZIP, replace only DBX.exe after exit, and restart automatically. portable.dbx and data will be kept.",
     downloading: "Downloading {progress}%",
     downloadFailed: "Update download failed: {error}",
     installing: "Installing update...",
diff --git a/apps/desktop/src/i18n/locales/es.ts b/apps/desktop/src/i18n/locales/es.ts
index bd7518002..4046c2cc1 100644
--- a/apps/desktop/src/i18n/locales/es.ts
+++ b/apps/desktop/src/i18n/locales/es.ts
@@ -72,7 +72,7 @@ export default withEnglishFallback({
     openRelease: "Abrir lanzamiento",
     downloadAndInstall: "Descargar e instalar",
     activeTasksBlockUpdate: "Hay {count} tarea(s) en ejecución. Espera a que terminen antes de actualizar DBX.",
-    portableManualUpdate: "Las versiones portables no pueden usar el instalador integrado. Descarga el ZIP portable desde la página de lanzamiento y extráelo sobre la carpeta actual de DBX para conservar portable.dbx y data.",
+    portableAutomaticUpdate: "DBX descargará el ZIP portable firmado, reemplazará solo DBX.exe después de salir y se reiniciará automáticamente. portable.dbx y data se conservarán.",
     downloading: "Descargando {progress}%",
     downloadFailed: "Error al descargar la actualización: {error}",
     installing: "Instalando actualización...",
diff --git a/apps/desktop/src/i18n/locales/it.ts b/apps/desktop/src/i18n/locales/it.ts
index c25874938..f34f2b77b 100644
--- a/apps/desktop/src/i18n/locales/it.ts
+++ b/apps/desktop/src/i18n/locales/it.ts
@@ -71,7 +71,7 @@ export default withEnglishFallback({
     openRelease: "Apri Release",
     downloadAndInstall: "Scarica e Installa",
     activeTasksBlockUpdate: "Ci sono {count} attività in esecuzione. Attendi che terminino prima di aggiornare DBX.",
-    portableManualUpdate: "Le build portatili non possono utilizzare l'installer in-app. Scarica lo ZIP portatile dalla pagina delle release, quindi estrailo nella cartella DBX corrente per mantenere portable.dbx e i dati.",
+    portableAutomaticUpdate: "DBX scaricherà lo ZIP portatile firmato, sostituirà solo DBX.exe dopo l'uscita e si riavvierà automaticamente. portable.dbx e i dati verranno mantenuti.",
     downloading: "Download in corso {progress}%",
     downloadFailed: "Download dell'aggiornamento non riuscito: {error}",
     installing: "Installazione dell'aggiornamento...",
diff --git a/apps/desktop/src/i18n/locales/ja.ts b/apps/desktop/src/i18n/locales/ja.ts
index 56d31a488..98a4fe597 100644
--- a/apps/desktop/src/i18n/locales/ja.ts
+++ b/apps/desktop/src/i18n/locales/ja.ts
@@ -72,7 +72,7 @@ export default withEnglishFallback({
     openRelease: "リリースページを開く",
     downloadAndInstall: "ダウンロード & インストール",
     activeTasksBlockUpdate: "{count} 件のタスクが実行中です。完了してから DBX を更新してください。",
-    portableManualUpdate: "ポータブル版はアプリ内インストーラーを使用できません。リリースページからポータブルZIPをダウンロードし、現在のDBXフォルダに上書き展開してください。portable.dbxとデータは保持されます。",
+    portableAutomaticUpdate: "DBX は署名済みのポータブル ZIP をダウンロードし、終了後に DBX.exe のみを置き換えて自動的に再起動します。portable.dbx とデータは保持されます。",
     downloading: "ダウンロード中 {progress}%",
     downloadFailed: "アップデートのダウンロードに失敗しました: {error}",
     installing: "アップデートをインストール中...",
diff --git a/apps/desktop/src/i18n/locales/pt-BR.ts b/apps/desktop/src/i18n/locales/pt-BR.ts
index 937d8c561..af5f318fe 100644
--- a/apps/desktop/src/i18n/locales/pt-BR.ts
+++ b/apps/desktop/src/i18n/locales/pt-BR.ts
@@ -72,7 +72,7 @@ export default withEnglishFallback({
     openRelease: "Abrir Lançamento",
     downloadAndInstall: "Baixar e Instalar",
     activeTasksBlockUpdate: "Há {count} tarefa(s) em execução. Aguarde a conclusão antes de atualizar o DBX.",
-    portableManualUpdate: "Versões portáteis não podem usar o instalador interno. Baixe o ZIP portátil da página de lançamento e extraia-o sobre a pasta atual do DBX para manter o portable.dbx e os dados.",
+    portableAutomaticUpdate: "O DBX baixará o ZIP portátil assinado, substituirá apenas o DBX.exe após sair e reiniciará automaticamente. O portable.dbx e os dados serão mantidos.",
     downloading: "Baixando {progress}%",
     downloadFailed: "Falha ao baixar a atualização: {error}",
     installing: "Instalando atualização...",
diff --git a/apps/desktop/src/i18n/locales/zh-CN.ts b/apps/desktop/src/i18n/locales/zh-CN.ts
index 90df59988..00f017447 100644
--- a/apps/desktop/src/i18n/locales/zh-CN.ts
+++ b/apps/desktop/src/i18n/locales/zh-CN.ts
@@ -72,7 +72,7 @@ export default withEnglishFallback({
     openRelease: "打开下载页",
     downloadAndInstall: "下载并安装",
     activeTasksBlockUpdate: "有 {count} 个任务正在执行，请等待任务完成后再更新 DBX。",
-    portableManualUpdate: "便携版不能使用应用内安装器更新。请从 release 下载便携版 ZIP，并解压覆盖当前 DBX 目录，以保留 portable.dbx 和 data。",
+    portableAutomaticUpdate: "DBX 将下载已签名的便携版 ZIP，退出后仅替换 DBX.exe 并自动重启。portable.dbx 和 data 会保留。",
     downloading: "下载中 {progress}%",
     downloadFailed: "更新下载失败：{error}",
     installing: "正在安装更新...",
diff --git a/apps/desktop/src/i18n/locales/zh-TW.ts b/apps/desktop/src/i18n/locales/zh-TW.ts
index 19794fc5e..e69a26658 100644
--- a/apps/desktop/src/i18n/locales/zh-TW.ts
+++ b/apps/desktop/src/i18n/locales/zh-TW.ts
@@ -72,7 +72,7 @@ export default withEnglishFallback({
     openRelease: "開啟下載頁",
     downloadAndInstall: "下載並安裝",
     activeTasksBlockUpdate: "有 {count} 個任務正在執行，請等待任務完成後再更新 DBX。",
-    portableManualUpdate: "可攜版無法使用應用程式內建安裝器更新。請從發行頁下載可攜版 ZIP，並解壓縮覆蓋目前的 DBX 目錄，以保留 portable.dbx 和 data。",
+    portableAutomaticUpdate: "DBX 將下載已簽署的可攜版 ZIP，結束後僅替換 DBX.exe 並自動重新啟動。portable.dbx 和 data 會保留。",
     downloading: "下載中 {progress}%",
     downloadFailed: "更新下載失敗：{error}",
     installing: "正在安裝更新...",
diff --git a/packages/app-tests/appUpdater.test.ts b/packages/app-tests/appUpdater.test.ts
index 16f9b8bde..a12f881f4 100644
--- a/packages/app-tests/appUpdater.test.ts
+++ b/packages/app-tests/appUpdater.test.ts
@@ -24,8 +24,8 @@ test("allows in-app update installation for installed desktop builds", () => {
   assert.equal(canDownloadAndInstallUpdate(updateInfo(), true), true);
 });
 
-test("blocks in-app update installation for portable builds", () => {
-  assert.equal(canDownloadAndInstallUpdate(updateInfo({ portable_mode: true }), true), false);
+test("allows portable builds to use the portable update installer", () => {
+  assert.equal(canDownloadAndInstallUpdate(updateInfo({ portable_mode: true }), true), true);
 });
 
 test("blocks in-app update installation outside desktop runtime or without an update", () => {
diff --git a/src-tauri/Cargo.toml b/src-tauri/Cargo.toml
index a36f000c2..cdba2f333 100644
--- a/src-tauri/Cargo.toml
+++ b/src-tauri/Cargo.toml
@@ -53,6 +53,9 @@ reqwest = { version = "0.12", features = ["json", "stream"] }
 futures = "0.3"
 mongodb = "3.2.5"
 percent-encoding = "2"
+minisign-verify = "0.2.5"
+semver = "1"
+sha2 = "0.10"
 russh = "0.60"
 csv = "1.4.0"
 calamine = "0.30.1"
diff --git a/src-tauri/src/commands/mod.rs b/src-tauri/src/commands/mod.rs
index 537599094..de493f245 100644
--- a/src-tauri/src/commands/mod.rs
+++ b/src-tauri/src/commands/mod.rs
@@ -47,6 +47,7 @@ pub mod text_export;
 pub mod transfer;
 pub mod tunnel_profiles;
 pub mod update;
+mod update_portable;
 pub mod window_controls;
 pub mod xlsx_export;
 pub mod zookeeper_cmd;
diff --git a/src-tauri/src/commands/update.rs b/src-tauri/src/commands/update.rs
index 95aaf8702..8ffa3098a 100644
--- a/src-tauri/src/commands/update.rs
+++ b/src-tauri/src/commands/update.rs
@@ -2,10 +2,13 @@ use std::sync::{
     atomic::{AtomicU64, Ordering},
     Arc, Mutex,
 };
+use std::time::Duration;
 
+use super::update_portable;
 pub use dbx_core::update::UpdateInfo;
+use semver::Version;
 use serde::{Deserialize, Serialize};
-use tauri::{AppHandle, Emitter};
+use tauri::{AppHandle, Emitter, Manager};
 use tauri_plugin_updater::{Update, UpdaterExt};
 
 const OFFICIAL_UPDATE_ENDPOINTS: [&str; 2] = [
@@ -16,6 +19,8 @@ const R2_LATEST_RELEASE_DOWNLOAD_PREFIX: &str = "https://dl.dbxio.com/releases/l
 const CNB_RELEASE_DOWNLOAD_PREFIX: &str = "https://cnb.cool/dbxio.com/dbx/-/releases/download/";
 const GITHUB_RELEASE_DOWNLOAD_PREFIX: &str = "https://github.com/t8y2/dbx/releases/download/";
 const UPDATE_DOWNLOAD_PROGRESS_EVENT: &str = "update-download-progress";
+const MAX_PORTABLE_ARCHIVE_BYTES: usize = 512 * 1024 * 1024;
+const MAX_PORTABLE_SIGNATURE_BYTES: usize = 64 * 1024;
 
 #[derive(Debug, Deserialize)]
 #[serde(rename_all = "lowercase")]
@@ -32,7 +37,19 @@ pub struct UpdateDownloadProgress {
 
 enum PendingUpdate {
     Downloading,
-    Ready { update: Box<Update>, bytes: Vec<u8> },
+    Installing,
+    Ready(ReadyUpdate),
+}
+
+enum ReadyUpdate {
+    Installer { update: Box<Update>, bytes: Vec<u8> },
+    Portable { archive: Vec<u8>, version: Version },
+}
+
+#[derive(Clone, Debug, Eq, PartialEq)]
+struct PortableAssetCandidate {
+    archive_url: String,
+    signature_url: String,
 }
 
 #[derive(Default)]
@@ -50,9 +67,9 @@ impl PendingUpdateState {
         Ok(())
     }
 
-    fn finish_download(&self, update: Update, bytes: Vec<u8>) -> Result<(), String> {
+    fn finish_download(&self, update: ReadyUpdate) -> Result<(), String> {
         let mut pending = self.pending.lock().map_err(|_| "Update state is unavailable.".to_string())?;
-        *pending = Some(PendingUpdate::Ready { update: Box::new(update), bytes });
+        *pending = Some(PendingUpdate::Ready(update));
         Ok(())
     }
 
@@ -63,6 +80,32 @@ impl PendingUpdateState {
             }
         }
     }
+
+    fn take_ready(&self) -> Result<ReadyUpdate, String> {
+        let mut pending = self.pending.lock().map_err(|_| "Update state is unavailable.".to_string())?;
+        match pending.take() {
+            Some(PendingUpdate::Ready(update)) => {
+                *pending = Some(PendingUpdate::Installing);
+                Ok(update)
+            }
+            other => {
+                *pending = other;
+                Err("No downloaded update is ready to install.".to_string())
+            }
+        }
+    }
+
+    fn restore_ready(&self, update: ReadyUpdate) -> Result<(), String> {
+        let mut pending = self.pending.lock().map_err(|_| "Update state is unavailable.".to_string())?;
+        *pending = Some(PendingUpdate::Ready(update));
+        Ok(())
+    }
+
+    fn finish_install(&self) -> Result<(), String> {
+        let mut pending = self.pending.lock().map_err(|_| "Update state is unavailable.".to_string())?;
+        *pending = None;
+        Ok(())
+    }
 }
 
 impl UpdateDownloadSource {
@@ -120,6 +163,30 @@ impl UpdateDownloadSource {
             .ok_or_else(|| format!("Unsupported update download URL for {} source: {url}", self.label()))?;
         Ok(Some(format!("{R2_LATEST_RELEASE_DOWNLOAD_PREFIX}{filename}")))
     }
+
+    fn portable_asset_candidates(
+        &self,
+        latest_version: &str,
+        arch: &str,
+    ) -> Result<Vec<PortableAssetCandidate>, String> {
+        let normalized_version = latest_version.trim().trim_start_matches('v');
+        let filename = update_portable::portable_asset_name(normalized_version, arch)?;
+        let tag = tag_version(normalized_version);
+        let archive_urls = match self {
+            Self::Official => vec![
+                format!("{R2_LATEST_RELEASE_DOWNLOAD_PREFIX}{filename}"),
+                format!("{GITHUB_RELEASE_DOWNLOAD_PREFIX}{tag}/{filename}"),
+            ],
+            Self::Cnb => vec![
+                format!("{CNB_RELEASE_DOWNLOAD_PREFIX}{tag}/{filename}"),
+                format!("{R2_LATEST_RELEASE_DOWNLOAD_PREFIX}{filename}"),
+            ],
+        };
+        Ok(archive_urls
+            .into_iter()
+            .map(|archive_url| PortableAssetCandidate { signature_url: format!("{archive_url}.sig"), archive_url })
+            .collect())
+    }
 }
 
 fn tag_version(version: &str) -> String {
@@ -162,14 +229,25 @@ pub async fn download_update(
     source: UpdateDownloadSource,
     latest_version: Option<String>,
 ) -> Result<(), String> {
-    if crate::data_dir::is_portable_mode() {
-        return Err("Portable builds cannot use the in-app installer.".to_string());
-    }
-
+    let portable_version = if crate::data_dir::is_portable_mode() {
+        let requested_version =
+            latest_version.as_deref().ok_or_else(|| "Latest version is required for portable updates.".to_string())?;
+        Some(update_portable::validate_requested_portable_version(requested_version, env!("CARGO_PKG_VERSION"))?)
+    } else {
+        None
+    };
     state.begin_download()?;
-    let result = download_update_inner(&app, &source, latest_version.as_deref()).await;
+    let result = if let Some(version) = portable_version {
+        download_portable_update_inner(&app, &source, &version)
+            .await
+            .map(|archive| ReadyUpdate::Portable { archive, version })
+    } else {
+        download_update_inner(&app, &source, latest_version.as_deref())
+            .await
+            .map(|(update, bytes)| ReadyUpdate::Installer { update: Box::new(update), bytes })
+    };
     match result {
-        Ok((update, bytes)) => state.finish_download(update, bytes),
+        Ok(update) => state.finish_download(update),
         Err(error) => {
             state.cancel_download();
             Err(error)
@@ -234,17 +312,123 @@ async fn download_update_inner(
     Ok((update, bytes))
 }
 
+async fn download_portable_update_inner(
+    app: &AppHandle,
+    source: &UpdateDownloadSource,
+    latest_version: &Version,
+) -> Result<Vec<u8>, String> {
+    let latest_version_text = latest_version.to_string();
+    let candidates = source.portable_asset_candidates(&latest_version_text, std::env::consts::ARCH)?;
+    let client = portable_update_http_client()?;
+    let mut failures = Vec::new();
+
+    for candidate in candidates {
+        println!("[DBX updater] downloading portable update from {}", candidate.archive_url);
+        let result = async {
+            let signature =
+                download_bounded_bytes(&client, &candidate.signature_url, MAX_PORTABLE_SIGNATURE_BYTES, None).await?;
+            let signature = String::from_utf8(signature)
+                .map_err(|error| format!("Portable update signature is not valid UTF-8: {error}"))?;
+            let archive =
+                download_bounded_bytes(&client, &candidate.archive_url, MAX_PORTABLE_ARCHIVE_BYTES, Some(app)).await?;
+            update_portable::verify_portable_archive(&archive, &signature, latest_version, std::env::consts::ARCH)?;
+            Ok::<Vec<u8>, String>(archive)
+        }
+        .await;
+
+        match result {
+            Ok(archive) => return Ok(archive),
+            Err(error) => {
+                println!("[DBX updater] portable update candidate failed: {error}");
+                failures.push(format!("{}: {error}", candidate.archive_url));
+            }
+        }
+    }
+
+    Err(format!("Failed to download a verified portable update. {}", failures.join("; ")))
+}
+
+fn portable_update_http_client() -> Result<reqwest::Client, String> {
+    let mut builder =
+        reqwest::Client::builder().connect_timeout(Duration::from_secs(15)).timeout(Duration::from_secs(15 * 60));
+    if let Some(proxy_url) = dbx_core::update::system_proxy_url() {
+        let proxy = reqwest::Proxy::all(&proxy_url).map_err(|error| format!("Invalid system proxy URL: {error}"))?;
+        builder = builder.proxy(proxy);
+    }
+    builder.build().map_err(|error| format!("Failed to create portable update client: {error}"))
+}
+
+async fn download_bounded_bytes(
+    client: &reqwest::Client,
+    url: &str,
+    max_bytes: usize,
+    progress_app: Option<&AppHandle>,
+) -> Result<Vec<u8>, String> {
+    let mut response = client
+        .get(url)
+        .send()
+        .await
+        .map_err(|error| format!("Failed to request {url}: {error}"))?
+        .error_for_status()
+        .map_err(|error| format!("Failed to download {url}: {error}"))?;
+    let total = response.content_length();
+    if total.is_some_and(|total| total > max_bytes as u64) {
+        return Err(format!("Update asset exceeds the {max_bytes} byte limit."));
+    }
+
+    if let Some(app) = progress_app {
+        let _ = app.emit(UPDATE_DOWNLOAD_PROGRESS_EVENT, UpdateDownloadProgress { downloaded: 0, total });
+    }
+    let mut bytes = Vec::with_capacity(total.unwrap_or(0).min(max_bytes as u64) as usize);
+    while let Some(chunk) =
+        response.chunk().await.map_err(|error| format!("Failed while downloading {url}: {error}"))?
+    {
+        if bytes.len().saturating_add(chunk.len()) > max_bytes {
+            return Err(format!("Update asset exceeds the {max_bytes} byte limit."));
+        }
+        bytes.extend_from_slice(&chunk);
+        if let Some(app) = progress_app {
+            let _ = app
+                .emit(UPDATE_DOWNLOAD_PROGRESS_EVENT, UpdateDownloadProgress { downloaded: bytes.len() as u64, total });
+        }
+    }
+    Ok(bytes)
+}
+
 #[tauri::command]
-pub fn install_downloaded_update(state: tauri::State<'_, PendingUpdateState>) -> Result<(), String> {
-    let mut pending = state.pending.lock().map_err(|_| "Update state is unavailable.".to_string())?;
-    let Some(PendingUpdate::Ready { update, bytes }) = pending.as_ref() else {
-        return Err("No downloaded update is ready to install.".to_string());
+pub fn install_downloaded_update(app: AppHandle, state: tauri::State<'_, PendingUpdateState>) -> Result<(), String> {
+    let ready = state.take_ready()?;
+    let portable = matches!(&ready, ReadyUpdate::Portable { .. });
+    let install_result = match &ready {
+        ReadyUpdate::Installer { update, bytes } => {
+            update.install(bytes).map_err(|error| format!("Failed to install update: {error}"))
+        }
+        ReadyUpdate::Portable { archive, version } => {
+            update_portable::ensure_portable_version_is_newer(version, env!("CARGO_PKG_VERSION"))
+                .and_then(|_| update_portable::launch_portable_update_helper(archive, version))
+        }
     };
-    update.install(bytes).map_err(|e| format!("Failed to install update: {e}"))?;
-    *pending = None;
+    if let Err(error) = install_result {
+        state.restore_ready(ready)?;
+        return Err(error);
+    }
+    state.finish_install()?;
+    if portable {
+        schedule_portable_update_exit(app);
+    }
     Ok(())
 }
 
+fn schedule_portable_update_exit(app: AppHandle) {
+    tauri::async_runtime::spawn(async move {
+        tokio::time::sleep(Duration::from_millis(150)).await;
+        if let Some(state) = app.try_state::<crate::CloseBehaviorState>() {
+            state.allow_next_exit();
+        }
+        app.exit(0);
+    });
+}
+
 async fn update_url_is_available(url: &str) -> bool {
     let client = match reqwest::Client::builder().timeout(std::time::Duration::from_secs(10)).build() {
         Ok(client) => client,
@@ -262,8 +446,8 @@ async fn update_url_is_available(url: &str) -> bool {
 #[cfg(test)]
 mod tests {
     use super::{
-        tag_version, UpdateDownloadSource, CNB_RELEASE_DOWNLOAD_PREFIX, OFFICIAL_UPDATE_ENDPOINTS,
-        R2_LATEST_RELEASE_DOWNLOAD_PREFIX,
+        tag_version, UpdateDownloadSource, CNB_RELEASE_DOWNLOAD_PREFIX, GITHUB_RELEASE_DOWNLOAD_PREFIX,
+        OFFICIAL_UPDATE_ENDPOINTS, R2_LATEST_RELEASE_DOWNLOAD_PREFIX,
     };
 
     #[test]
@@ -311,4 +495,32 @@ mod tests {
             .unwrap();
         assert_eq!(fallback, Some(format!("{R2_LATEST_RELEASE_DOWNLOAD_PREFIX}DBX_0.5.44_x64.dmg")));
     }
+
+    #[test]
+    fn builds_signed_official_portable_asset_candidates() {
+        let candidates = UpdateDownloadSource::Official.portable_asset_candidates("0.5.64", "x86_64").unwrap();
+        assert_eq!(candidates.len(), 2);
+        assert_eq!(
+            candidates[0].archive_url,
+            format!("{R2_LATEST_RELEASE_DOWNLOAD_PREFIX}DBX_0.5.64_x64-portable.zip")
+        );
+        assert_eq!(
+            candidates[1].archive_url,
+            format!("{GITHUB_RELEASE_DOWNLOAD_PREFIX}v0.5.64/DBX_0.5.64_x64-portable.zip")
+        );
+        assert!(candidates.iter().all(|candidate| candidate.signature_url == format!("{}.sig", candidate.archive_url)));
+    }
+
+    #[test]
+    fn builds_cnb_portable_asset_candidate_with_r2_fallback() {
+        let candidates = UpdateDownloadSource::Cnb.portable_asset_candidates("v0.5.64", "aarch64").unwrap();
+        assert_eq!(
+            candidates[0].archive_url,
+            format!("{CNB_RELEASE_DOWNLOAD_PREFIX}v0.5.64/DBX_0.5.64_arm64-portable.zip")
+        );
+        assert_eq!(
+            candidates[1].archive_url,
+            format!("{R2_LATEST_RELEASE_DOWNLOAD_PREFIX}DBX_0.5.64_arm64-portable.zip")
+        );
+    }
 }
diff --git a/src-tauri/src/commands/update_portable.rs b/src-tauri/src/commands/update_portable.rs
new file mode 100644
index 000000000..f544869aa
--- /dev/null
+++ b/src-tauri/src/commands/update_portable.rs
@@ -0,0 +1,405 @@
+use base64::{engine::general_purpose::STANDARD as BASE64_STANDARD, Engine as _};
+use minisign_verify::{PublicKey, Signature};
+use semver::Version;
+use serde::Deserialize;
+use sha2::{Digest, Sha256};
+use std::io::{Cursor, Read};
+
+const MAX_PORTABLE_EXECUTABLE_BYTES: usize = 256 * 1024 * 1024;
+const MAX_PORTABLE_MANIFEST_BYTES: usize = 16 * 1024;
+const EMBEDDED_TAURI_CONFIG: &str = include_str!("../../tauri.conf.json");
+const PORTABLE_EXECUTABLE_NAME: &str = "DBX.exe";
+const PORTABLE_UPDATE_MANIFEST_NAME: &str = "portable-update.json";
+const PORTABLE_UPDATE_MANIFEST_SCHEMA_VERSION: u32 = 1;
+
+#[derive(Debug, Deserialize)]
+struct PortableUpdateManifest {
+    schema_version: u32,
+    version: String,
+    arch: String,
+    executable: String,
+    executable_sha256: String,
+}
+
+pub(super) fn validate_requested_portable_version(
+    requested_version: &str,
+    current_version: &str,
+) -> Result<Version, String> {
+    let requested = parse_portable_version(requested_version, "requested")?;
+    ensure_portable_version_is_newer(&requested, current_version)?;
+    Ok(requested)
+}
+
+pub(super) fn ensure_portable_version_is_newer(
+    requested_version: &Version,
+    current_version: &str,
+) -> Result<(), String> {
+    let current = parse_portable_version(current_version, "current app")?;
+    if requested_version <= &current {
+        return Err(format!(
+            "Portable update version {requested_version} must be newer than the current version {current}."
+        ));
+    }
+    Ok(())
+}
+
+fn parse_portable_version(value: &str, label: &str) -> Result<Version, String> {
+    let value = value.trim();
+    let value = value.strip_prefix('v').unwrap_or(value);
+    Version::parse(value).map_err(|error| format!("Invalid {label} portable update version: {error}"))
+}
+
+fn portable_arch_label(arch: &str) -> Result<&'static str, String> {
+    match arch {
+        "x86_64" => Ok("x64"),
+        "aarch64" => Ok("arm64"),
+        other => Err(format!("Portable updates are not available for architecture {other}.")),
+    }
+}
+
+pub(super) fn portable_asset_name(version: &str, arch: &str) -> Result<String, String> {
+    let version = parse_portable_version(version, "requested")?;
+    let arch = portable_arch_label(arch)?;
+    Ok(format!("DBX_{version}_{arch}-portable.zip"))
+}
+
+pub(super) fn verify_portable_archive(
+    archive: &[u8],
+    encoded_signature: &str,
+    expected_version: &Version,
+    expected_arch: &str,
+) -> Result<(), String> {
+    let config: serde_json::Value = serde_json::from_str(EMBEDDED_TAURI_CONFIG)
+        .map_err(|error| format!("Failed to read embedded updater configuration: {error}"))?;
+    let encoded_public_key = config
+        .pointer("/plugins/updater/pubkey")
+        .and_then(serde_json::Value::as_str)
+        .ok_or_else(|| "Embedded updater public key is missing.".to_string())?;
+    let public_key_text = decode_tauri_text(encoded_public_key, "public key")?;
+    let signature_text = decode_tauri_text(encoded_signature.trim(), "signature")?;
+    let public_key = PublicKey::decode(&public_key_text)
+        .map_err(|error| format!("Failed to decode portable update public key: {error}"))?;
+    let signature = Signature::decode(&signature_text)
+        .map_err(|error| format!("Failed to decode portable update signature: {error}"))?;
+    public_key
+        .verify(archive, &signature, true)
+        .map_err(|error| format!("Portable update signature verification failed: {error}"))?;
+    // The manifest lives inside the signed ZIP and hashes DBX.exe, binding the
+    // requested version and architecture to the exact executable we install.
+    validated_portable_executable(archive, expected_version, expected_arch).map(|_| ())
+}
+
+fn decode_tauri_text(value: &str, label: &str) -> Result<String, String> {
+    let decoded =
+        BASE64_STANDARD.decode(value).map_err(|error| format!("Invalid updater {label} encoding: {error}"))?;
+    String::from_utf8(decoded).map_err(|error| format!("Updater {label} is not valid UTF-8: {error}"))
+}
+
+fn validated_portable_executable(
+    archive: &[u8],
+    expected_version: &Version,
+    expected_arch: &str,
+) -> Result<Vec<u8>, String> {
+    let reader = Cursor::new(archive);
+    let mut archive = zip::ZipArchive::new(reader).map_err(|error| format!("Invalid portable update ZIP: {error}"))?;
+    let manifest = {
+        let mut manifest_file = archive
+            .by_name(PORTABLE_UPDATE_MANIFEST_NAME)
+            .map_err(|_| format!("Portable update ZIP does not contain {PORTABLE_UPDATE_MANIFEST_NAME}."))?;
+        if manifest_file.is_dir() || manifest_file.size() > MAX_PORTABLE_MANIFEST_BYTES as u64 {
+            return Err("Portable update manifest is unexpectedly large or invalid.".to_string());
+        }
+        let mut manifest_bytes = Vec::with_capacity(manifest_file.size() as usize);
+        manifest_file
+            .by_ref()
+            .take((MAX_PORTABLE_MANIFEST_BYTES + 1) as u64)
+            .read_to_end(&mut manifest_bytes)
+            .map_err(|error| format!("Failed to read portable update manifest: {error}"))?;
+        if manifest_bytes.len() > MAX_PORTABLE_MANIFEST_BYTES {
+            return Err("Portable update manifest is unexpectedly large.".to_string());
+        }
+        serde_json::from_slice::<PortableUpdateManifest>(&manifest_bytes)
+            .map_err(|error| format!("Invalid portable update manifest: {error}"))?
+    };
+
+    if manifest.schema_version != PORTABLE_UPDATE_MANIFEST_SCHEMA_VERSION {
+        return Err(format!("Unsupported portable update manifest schema version {}.", manifest.schema_version));
+    }
+    let manifest_version = parse_portable_version(&manifest.version, "manifest")?;
+    if &manifest_version != expected_version {
+        return Err(format!(
+            "Portable update manifest version {manifest_version} does not match requested version {expected_version}."
+        ));
+    }
+    let expected_arch = portable_arch_label(expected_arch)?;
+    if manifest.arch != expected_arch {
+        return Err(format!(
+            "Portable update manifest architecture {} does not match the current architecture {expected_arch}.",
+            manifest.arch
+        ));
+    }
+    if manifest.executable != PORTABLE_EXECUTABLE_NAME {
+        return Err(format!("Portable update manifest executable must be {PORTABLE_EXECUTABLE_NAME}."));
+    }
+
+    let mut file = archive
+        .by_name(PORTABLE_EXECUTABLE_NAME)
+        .map_err(|_| format!("Portable update ZIP does not contain {PORTABLE_EXECUTABLE_NAME}."))?;
+    if file.size() > MAX_PORTABLE_EXECUTABLE_BYTES as u64 {
+        return Err("Portable update executable is unexpectedly large.".to_string());
+    }
+    let mut executable = Vec::with_capacity(file.size() as usize);
+    file.by_ref()
+        .take((MAX_PORTABLE_EXECUTABLE_BYTES + 1) as u64)
+        .read_to_end(&mut executable)
+        .map_err(|error| format!("Failed to extract DBX.exe from update ZIP: {error}"))?;
+    if executable.len() > MAX_PORTABLE_EXECUTABLE_BYTES {
+        return Err("Portable update executable is unexpectedly large.".to_string());
+    }
+    if !executable.starts_with(b"MZ") {
+        return Err("Portable update executable is not a valid Windows executable.".to_string());
+    }
+    let executable_sha256 = sha256_hex(&executable);
+    if !executable_sha256.eq_ignore_ascii_case(manifest.executable_sha256.trim()) {
+        return Err("Portable update executable hash does not match the signed manifest.".to_string());
+    }
+    Ok(executable)
+}
+
+fn sha256_hex(bytes: &[u8]) -> String {
+    Sha256::digest(bytes).iter().map(|byte| format!("{byte:02x}")).collect()
+}
+
+#[cfg(target_os = "windows")]
+pub(super) fn launch_portable_update_helper(archive: &[u8], version: &Version) -> Result<(), String> {
+    use std::fs::{self, OpenOptions};
+    use std::io::Write;
+    use std::os::windows::process::CommandExt;
+    use std::process::Command;
+    use std::time::{SystemTime, UNIX_EPOCH};
+
+    const CREATE_NO_WINDOW: u32 = 0x0800_0000;
+    const CREATE_NEW_PROCESS_GROUP: u32 = 0x0000_0200;
+
+    let current_exe =
+        std::env::current_exe().map_err(|error| format!("Failed to locate the portable executable: {error}"))?;
+    let exe_dir = current_exe.parent().ok_or_else(|| "Portable executable directory is unavailable.".to_string())?;
+    if !exe_dir.join("portable.dbx").is_file() {
+        return Err("Portable update marker is missing beside DBX.exe.".to_string());
+    }
+
+    let timestamp = SystemTime::now()
+        .duration_since(UNIX_EPOCH)
+        .map_err(|error| format!("System clock is unavailable: {error}"))?
+        .as_nanos();
+    let update_id = format!("{}-{timestamp}", std::process::id());
+    let write_probe = exe_dir.join(format!(".dbx-update-{update_id}.probe"));
+    OpenOptions::new()
+        .create_new(true)
+        .write(true)
+        .open(&write_probe)
+        .map_err(|error| format!("The portable DBX directory is not writable: {error}"))?;
+    fs::remove_file(&write_probe)
+        .map_err(|error| format!("Failed to finish portable directory write check: {error}"))?;
+
+    let staging_dir = std::env::temp_dir().join(format!("dbx-portable-update-{update_id}"));
+    fs::create_dir(&staging_dir)
+        .map_err(|error| format!("Failed to create portable update staging directory: {error}"))?;
+    let staged_exe = staging_dir.join("DBX.exe.new");
+    let script_path = staging_dir.join("apply-update.ps1");
+    let backup_exe = exe_dir.join(format!(".DBX-{update_id}.old.exe"));
+
+    let prepare_result = (|| -> Result<(), String> {
+        let executable = validated_portable_executable(archive, version, std::env::consts::ARCH)?;
+        let mut staged_file = OpenOptions::new()
+            .create_new(true)
+            .write(true)
+            .open(&staged_exe)
+            .map_err(|error| format!("Failed to stage portable DBX executable: {error}"))?;
+        staged_file
+            .write_all(&executable)
+            .and_then(|_| staged_file.sync_all())
+            .map_err(|error| format!("Failed to write portable DBX executable: {error}"))?;
+        fs::write(&script_path, PORTABLE_UPDATE_SCRIPT)
+            .map_err(|error| format!("Failed to create portable update helper: {error}"))?;
+
+        Command::new("powershell.exe")
+            .args(["-NoLogo", "-NoProfile", "-NonInteractive", "-ExecutionPolicy", "Bypass", "-File"])
+            .arg(&script_path)
+            .arg("-ParentProcessId")
+            .arg(std::process::id().to_string())
+            .arg("-SourceExe")
+            .arg(&staged_exe)
+            .arg("-TargetExe")
+            .arg(&current_exe)
+            .arg("-BackupExe")
+            .arg(&backup_exe)
+            .arg("-StagingDir")
+            .arg(&staging_dir)
+            .creation_flags(CREATE_NO_WINDOW | CREATE_NEW_PROCESS_GROUP)
+            .spawn()
+            .map_err(|error| format!("Failed to start portable update helper: {error}"))?;
+        Ok(())
+    })();
+
+    if prepare_result.is_err() {
+        let _ = fs::remove_dir_all(&staging_dir);
+    }
+    prepare_result
+}
+
+#[cfg(not(target_os = "windows"))]
+pub(super) fn launch_portable_update_helper(_archive: &[u8], _version: &Version) -> Result<(), String> {
+    Err("Portable updates are only supported on Windows.".to_string())
+}
+
+#[cfg(target_os = "windows")]
+const PORTABLE_UPDATE_SCRIPT: &str = r#"param(
+    [Parameter(Mandatory = $true)][int]$ParentProcessId,
+    [Parameter(Mandatory = $true)][string]$SourceExe,
+    [Parameter(Mandatory = $true)][string]$TargetExe,
+    [Parameter(Mandatory = $true)][string]$BackupExe,
+    [Parameter(Mandatory = $true)][string]$StagingDir
+)
+
+$ErrorActionPreference = 'Stop'
+Remove-Item -LiteralPath $PSCommandPath -Force -ErrorAction SilentlyContinue
+try { Wait-Process -Id $ParentProcessId -Timeout 120 -ErrorAction SilentlyContinue } catch {}
+
+$installed = $false
+for ($attempt = 0; $attempt -lt 120; $attempt++) {
+    try {
+        if (Test-Path -LiteralPath $TargetExe) {
+            if (Test-Path -LiteralPath $BackupExe) {
+                Remove-Item -LiteralPath $BackupExe -Force
+            }
+            Move-Item -LiteralPath $TargetExe -Destination $BackupExe -Force
+        }
+
+        if (-not (Test-Path -LiteralPath $BackupExe)) {
+            throw 'The existing DBX executable could not be backed up.'
+        }
+
+        Move-Item -LiteralPath $SourceExe -Destination $TargetExe -Force
+        $installed = $true
+        break
+    } catch {
+        if (-not (Test-Path -LiteralPath $TargetExe) -and (Test-Path -LiteralPath $BackupExe)) {
+            try { Copy-Item -LiteralPath $BackupExe -Destination $TargetExe -Force } catch {}
+        }
+        Start-Sleep -Seconds 1
+    }
+}
+
+if (-not $installed) {
+    if (-not (Test-Path -LiteralPath $TargetExe) -and (Test-Path -LiteralPath $BackupExe)) {
+        try { Copy-Item -LiteralPath $BackupExe -Destination $TargetExe -Force } catch {}
+    }
+    exit 1
+}
+
+try {
+    Start-Process -FilePath $TargetExe -WorkingDirectory (Split-Path -Parent $TargetExe)
+} catch {
+    try {
+        if (Test-Path -LiteralPath $TargetExe) { Remove-Item -LiteralPath $TargetExe -Force }
+        if (Test-Path -LiteralPath $BackupExe) { Move-Item -LiteralPath $BackupExe -Destination $TargetExe -Force }
+        Start-Process -FilePath $TargetExe -WorkingDirectory (Split-Path -Parent $TargetExe)
+    } catch {}
+    exit 1
+}
+
+Remove-Item -LiteralPath $BackupExe -Force -ErrorAction SilentlyContinue
+Remove-Item -LiteralPath $StagingDir -Recurse -Force -ErrorAction SilentlyContinue
+exit 0
+"#;
+
+#[cfg(test)]
+mod tests {
+    use super::{
+        decode_tauri_text, portable_asset_name, sha256_hex, validate_requested_portable_version,
+        validated_portable_executable, PORTABLE_EXECUTABLE_NAME, PORTABLE_UPDATE_MANIFEST_NAME,
+        PORTABLE_UPDATE_MANIFEST_SCHEMA_VERSION,
+    };
+    use base64::{engine::general_purpose::STANDARD as BASE64_STANDARD, Engine as _};
+    use semver::Version;
+    use std::io::{Cursor, Write};
+
+    fn portable_zip(version: &str, arch: &str, executable: &[u8], executable_sha256: Option<&str>) -> Vec<u8> {
+        let cursor = Cursor::new(Vec::new());
+        let mut zip = zip::ZipWriter::new(cursor);
+        let options = zip::write::SimpleFileOptions::default().compression_method(zip::CompressionMethod::Stored);
+        let manifest = serde_json::json!({
+            "schema_version": PORTABLE_UPDATE_MANIFEST_SCHEMA_VERSION,
+            "version": version,
+            "arch": arch,
+            "executable": PORTABLE_EXECUTABLE_NAME,
+            "executable_sha256": executable_sha256.map(ToOwned::to_owned).unwrap_or_else(|| sha256_hex(executable)),
+        });
+        zip.start_file(PORTABLE_UPDATE_MANIFEST_NAME, options).unwrap();
+        zip.write_all(&serde_json::to_vec(&manifest).unwrap()).unwrap();
+        zip.start_file(PORTABLE_EXECUTABLE_NAME, options).unwrap();
+        zip.write_all(executable).unwrap();
+        zip.finish().unwrap().into_inner()
+    }
+
+    #[test]
+    fn builds_portable_asset_names_for_windows_architectures() {
+        assert_eq!(portable_asset_name("0.5.64", "x86_64").unwrap(), "DBX_0.5.64_x64-portable.zip");
+        assert_eq!(portable_asset_name("v0.5.64-beta.1", "aarch64").unwrap(), "DBX_0.5.64-beta.1_arm64-portable.zip");
+        assert!(portable_asset_name("0.5.64", "x86").is_err());
+        assert!(portable_asset_name("../../0.5.64", "x86_64").is_err());
+    }
+
+    #[test]
+    fn accepts_newer_portable_update_requests() {
+        assert_eq!(validate_requested_portable_version("0.5.64", "0.5.63").unwrap(), Version::parse("0.5.64").unwrap());
+    }
+
+    #[test]
+    fn rejects_equal_version_requests() {
+        let error = validate_requested_portable_version("0.5.63", "0.5.63").unwrap_err();
+        assert!(error.contains("must be newer"));
+    }
+
+    #[test]
+    fn rejects_downgrade_requests() {
+        let error = validate_requested_portable_version("0.5.62", "0.5.63").unwrap_err();
+        assert!(error.contains("must be newer"));
+    }
+
+    #[test]
+    fn decodes_tauri_base64_text() {
+        let encoded = BASE64_STANDARD.encode("untrusted comment: test\nAAAA");
+        assert_eq!(decode_tauri_text(&encoded, "test").unwrap(), "untrusted comment: test\nAAAA");
+    }
+
+    #[test]
+    fn extracts_the_executable_bound_to_the_signed_manifest() {
+        let archive = portable_zip("0.5.64", "x64", b"MZportable executable", None);
+        assert_eq!(
+            validated_portable_executable(&archive, &Version::parse("0.5.64").unwrap(), "x86_64").unwrap(),
+            b"MZportable executable"
+        );
+    }
+
+    #[test]
+    fn rejects_archives_without_a_windows_executable() {
+        let archive = portable_zip("0.5.64", "x64", b"not a PE file", None);
+        assert!(validated_portable_executable(&archive, &Version::parse("0.5.64").unwrap(), "x86_64").is_err());
+    }
+
+    #[test]
+    fn rejects_an_archive_whose_manifest_version_differs_from_the_request() {
+        let archive = portable_zip("0.5.62", "x64", b"MZolder executable", None);
+        let error = validated_portable_executable(&archive, &Version::parse("0.5.64").unwrap(), "x86_64").unwrap_err();
+        assert!(error.contains("does not match requested version"));
+    }
+
+    #[test]
+    fn rejects_an_executable_not_matching_the_signed_manifest_hash() {
+        let archive = portable_zip("0.5.64", "x64", b"MZportable executable", Some(&"0".repeat(64)));
+        let error = validated_portable_executable(&archive, &Version::parse("0.5.64").unwrap(), "x86_64").unwrap_err();
+        assert!(error.contains("hash does not match"));
+    }
+}