diff --git a/.github/workflows/windows-build.yml b/.github/workflows/windows-build.yml
new file mode 100644
index 0000000..8bba429
--- /dev/null
+++ b/.github/workflows/windows-build.yml
@@ -0,0 +1,122 @@
+name: Windows build
+
+# Builds the portable Windows x64 package so the translate fix can be tested
+# without a local Qt/MSVC toolchain. PDFium is vendored in third_party/;
+# OpenSSL, QPDF and ZLIB come from vcpkg; Tesseract is left out, so OCR is
+# disabled in this build (the app builds and runs fine without it).
+
+on:
+  push:
+    branches: ['**']
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  build:
+    runs-on: windows-2022
+
+    env:
+      VCPKG_BINARY_SOURCES: 'clear;x-gha,readwrite'
+      QT_VERSION: '6.8.1'
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Export GitHub Actions cache env for vcpkg
+        uses: actions/github-script@v7
+        with:
+          script: |
+            core.exportVariable('ACTIONS_CACHE_URL', process.env.ACTIONS_CACHE_URL || '');
+            core.exportVariable('ACTIONS_RUNTIME_TOKEN', process.env.ACTIONS_RUNTIME_TOKEN || '');
+
+      - name: Install Qt ${{ env.QT_VERSION }}
+        uses: jurplel/install-qt-action@v4
+        with:
+          version: ${{ env.QT_VERSION }}
+          host: windows
+          target: desktop
+          arch: win64_msvc2022_64
+          modules: 'qtimageformats'
+          cache: true
+
+      - name: Install vcpkg dependencies (OpenSSL, QPDF, ZLIB, Tesseract)
+        shell: pwsh
+        run: |
+          & "$env:VCPKG_INSTALLATION_ROOT\vcpkg.exe" install `
+            openssl:x64-windows qpdf:x64-windows zlib:x64-windows tesseract:x64-windows
+          if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
+
+      - name: Configure
+        shell: pwsh
+        run: |
+          cmake -B build -S . -G "Visual Studio 17 2022" -A x64 `
+            -DCMAKE_BUILD_TYPE=Release `
+            -DCMAKE_TOOLCHAIN_FILE="$env:VCPKG_INSTALLATION_ROOT\scripts\buildsystems\vcpkg.cmake" `
+            -DVCPKG_TARGET_TRIPLET=x64-windows 2>&1 | Tee-Object -Variable cfg
+          if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
+          # CMake only warns when Tesseract is missing and builds an OCR stub, which
+          # is far too quiet a way to ship a package with a headline feature gone.
+          if ($cfg -match 'Tesseract khong tim thay') {
+            throw "Tesseract was not found — OCR would be silently disabled in this build"
+          }
+
+      - name: Build
+        run: cmake --build build --config Release --parallel
+
+      - name: Deploy Qt runtime
+        shell: pwsh
+        run: |
+          $out = "build\bin\Release"
+          if (-not (Test-Path $out)) { $out = "build\bin" }
+          Get-ChildItem $out
+          & "$env:QT_ROOT_DIR\bin\windeployqt.exe" --release --no-translations "$out\TorReader.exe"
+          if ($LASTEXITCODE -ne 0) { exit $LASTEXITCODE }
+          # windeployqt's --compiler-runtime is a silent no-op on the runner, and
+          # the shipped portable build carries the CRT locally rather than assuming
+          # the VC++ redistributable is installed. Copy it in by hand.
+          $crt = Get-ChildItem "C:\Program Files*\Microsoft Visual Studio\2022\*\VC\Redist\MSVC" `
+                   -Directory -Filter 'Microsoft.VC*.CRT' -Recurse -ErrorAction SilentlyContinue |
+                 Where-Object { $_.FullName -match '\\x64\\' } |
+                 Sort-Object FullName -Descending | Select-Object -First 1
+          if (-not $crt) { throw "MSVC redistributable CRT not found on the runner" }
+          Write-Host "CRT from $($crt.FullName)"
+          Copy-Item "$($crt.FullName)\*.dll" $out -Force
+          # Vendored PDFium and the vcpkg runtime DLLs sit outside windeployqt's view.
+          Copy-Item third_party\pdfium\bin\pdfium.dll $out -Force
+          $vcbin = "$env:VCPKG_INSTALLATION_ROOT\installed\x64-windows\bin"
+          if (Test-Path $vcbin) {
+            Copy-Item "$vcbin\*.dll" $out -Force -ErrorAction SilentlyContinue
+          }
+          Get-ChildItem $out | Select-Object Name, Length
+
+      - name: Verify package contents
+        shell: pwsh
+        run: |
+          $out = "build\bin\Release"
+          if (-not (Test-Path $out)) { $out = "build\bin" }
+          $missing = @()
+          foreach ($f in 'TorReader.exe','Qt6Network.dll','pdfium.dll',
+                          'msvcp140.dll','vcruntime140.dll','tls\qschannelbackend.dll') {
+            if (-not (Test-Path "$out\$f")) { $missing += $f }
+          }
+          if (-not (Get-ChildItem "$out" -Filter 'tesseract*.dll' -ErrorAction SilentlyContinue)) {
+            $missing += 'tesseract*.dll'
+          }
+          $langs = @(Get-ChildItem "$out\tessdata" -Filter *.traineddata -ErrorAction SilentlyContinue)
+          Write-Host "tessdata language files: $($langs.Count)"
+          if ($langs.Count -lt 10) { $missing += "tessdata/*.traineddata (found $($langs.Count), expected 10+)" }
+          if ($missing) { throw "Incomplete package, missing: $($missing -join ', ')" }
+          Write-Host "Package verified."
+
+      - name: Package
+        shell: pwsh
+        run: |
+          $out = "build\bin\Release"
+          if (-not (Test-Path $out)) { $out = "build\bin" }
+          Compress-Archive -Path "$out\*" -DestinationPath TorReaderPDF-win64.zip -Force
+
+      - uses: actions/upload-artifact@v4
+        with:
+          name: TorReaderPDF-win64
+          path: TorReaderPDF-win64.zip
+          retention-days: 14
diff --git a/CMakeLists.txt b/CMakeLists.txt
index f29c80f..403b614 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -187,6 +187,7 @@ set(SOURCES
     src/ui/UpdateBanner.cpp
     src/ui/GateDialog.cpp
     src/ui/TranslationPopup.cpp
+    src/ui/LanguagePickerPopup.cpp
     src/ui/NotificationBar.cpp
     >
 )
@@ -231,6 +232,7 @@ set(HEADERS
     src/ui/UpdateBanner.h
     src/ui/GateDialog.h
     src/ui/TranslationPopup.h
+    src/ui/LanguagePickerPopup.h
     src/ui/NotificationBar.h
     >
 )
diff --git a/src/core/Translator.cpp b/src/core/Translator.cpp
index a4776fc..5fd9212 100755
--- a/src/core/Translator.cpp
+++ b/src/core/Translator.cpp
@@ -15,23 +15,60 @@
 #include <QMetaObject>
 #include <QSettings>
 #include <QTimer>
+#include <QSslSocket>
 #include <algorithm>
 
-static constexpr const char* kTargetLang = "vi";
 static constexpr const char* kGeminiModel = "gemini-2.5-flash";
 static constexpr const char* kCacheFileName = "translate_cache.json";
 static constexpr int kMaxMemoryEntries = 500;
 static constexpr int kMaxDiskEntries = 2000;
 static constexpr int kCacheSaveDebounceMs = 2000;
+static constexpr int kRequestTimeoutMs = 15000;
 
-static QString makeCacheKey(const QString& lang, const QString& text) {
+static QString makeCacheKey(const QString& srcLang, const QString& dstLang,
+                            const QString& text) {
     return QString::fromLatin1(
         QCryptographicHash::hash(
-            (lang + QLatin1String("\x1f") + text).toUtf8(),
+            (srcLang + QLatin1String("\x1f") + dstLang +
+             QLatin1String("\x1f") + text).toUtf8(),
             QCryptographicHash::Sha1)
         .toHex());
 }
 
+const QList<QPair<QString, QString>>& Translator::languages() {
+    static const QList<QPair<QString, QString>> kLangs = {
+        { QStringLiteral("auto"), QStringLiteral("Detect language") },
+        { QStringLiteral("en"),   QStringLiteral("English") },
+        { QStringLiteral("vi"),   QStringLiteral("Vietnamese") },
+        { QStringLiteral("zh-CN"),QStringLiteral("Chinese (Simplified)") },
+        { QStringLiteral("zh-TW"),QStringLiteral("Chinese (Traditional)") },
+        { QStringLiteral("ja"),   QStringLiteral("Japanese") },
+        { QStringLiteral("ko"),   QStringLiteral("Korean") },
+        { QStringLiteral("fr"),   QStringLiteral("French") },
+        { QStringLiteral("de"),   QStringLiteral("German") },
+        { QStringLiteral("es"),   QStringLiteral("Spanish") },
+        { QStringLiteral("pt"),   QStringLiteral("Portuguese") },
+        { QStringLiteral("it"),   QStringLiteral("Italian") },
+        { QStringLiteral("ru"),   QStringLiteral("Russian") },
+        { QStringLiteral("th"),   QStringLiteral("Thai") },
+        { QStringLiteral("id"),   QStringLiteral("Indonesian") },
+        { QStringLiteral("ms"),   QStringLiteral("Malay") },
+        { QStringLiteral("hi"),   QStringLiteral("Hindi") },
+        { QStringLiteral("ar"),   QStringLiteral("Arabic") },
+        { QStringLiteral("nl"),   QStringLiteral("Dutch") },
+        { QStringLiteral("pl"),   QStringLiteral("Polish") },
+        { QStringLiteral("tr"),   QStringLiteral("Turkish") },
+    };
+    return kLangs;
+}
+
+QString Translator::languageName(const QString& code) {
+    for (const auto& p : languages())
+        if (p.first.compare(code, Qt::CaseInsensitive) == 0)
+            return p.second;
+    return code;
+}
+
 Translator::Translator(QObject* parent)
     : QObject(parent)
     , m_nam(new QNetworkAccessManager(this))
@@ -45,13 +82,15 @@ Translator::Translator(QObject* parent)
     m_diskCachePath = appData + QLatin1Char('/') + QLatin1String(kCacheFileName);
 }
 
-void Translator::translate(const QString& text) {
-    const QString lang = QString::fromLatin1(kTargetLang);
-    const QString key = makeCacheKey(lang, text);
+void Translator::translate(const QString& text, const QString& srcLangIn,
+                           const QString& dstLangIn) {
+    const QString srcLang = srcLangIn.isEmpty() ? QStringLiteral("auto") : srcLangIn;
+    const QString dstLang = dstLangIn.isEmpty() ? QStringLiteral("vi")   : dstLangIn;
+    const QString key = makeCacheKey(srcLang, dstLang, text);
 
-    auto emitCached = [this, text](const QString& translation) {
-        QMetaObject::invokeMethod(this, [this, text, translation]() {
-            emit finished(text, translation);
+    auto emitCached = [this, text, srcLang, dstLang](const QString& translation) {
+        QMetaObject::invokeMethod(this, [this, text, translation, srcLang, dstLang]() {
+            emit finished(text, translation, srcLang, dstLang);
         }, Qt::QueuedConnection);
     };
 
@@ -70,26 +109,74 @@ void Translator::translate(const QString& text) {
         }
     }
 
-    QUrl url(QStringLiteral("https://translate.googleapis.com/translate_a/single"
-                            "?client=gtx&sl=auto&tl=%1&dt=t").arg(lang));
+    // A Qt build shipped without its TLS backend plugin cannot open *any* https
+    // connection, and the resulting reply error is opaque. Say so plainly.
+    if (!QSslSocket::supportsSsl()) {
+        emit failed(QStringLiteral(
+            "No TLS backend available, so https requests cannot be made. "
+            "The Qt 'tls' plugin folder is missing next to the executable "
+            "(re-run windeployqt on the build)."));
+        return;
+    }
 
-    QNetworkRequest req(url);
+    sendGoogleRequest(text, srcLang, dstLang, key, /*useGet=*/false);
+}
+
+// Google is asked twice before falling back to Gemini: first as the POST the
+// endpoint documents, then as a plain GET. Some proxies and captive networks
+// drop the POST body and hand back an empty 200, which used to look exactly
+// like "no response at all" from the UI.
+void Translator::sendGoogleRequest(const QString& text, const QString& srcLang,
+                                   const QString& dstLang, const QString& key,
+                                   bool useGet)
+{
+    QString urlStr = QStringLiteral("https://translate.googleapis.com/translate_a/single"
+                                    "?client=gtx&sl=%1&tl=%2&dt=t")
+                         .arg(QString::fromLatin1(QUrl::toPercentEncoding(srcLang)),
+                              QString::fromLatin1(QUrl::toPercentEncoding(dstLang)));
+    if (useGet)
+        urlStr += QStringLiteral("&q=") +
+                  QString::fromLatin1(QUrl::toPercentEncoding(text));
+
+    QNetworkRequest req((QUrl(urlStr)));
     req.setHeader(QNetworkRequest::ContentTypeHeader,
                   "application/x-www-form-urlencoded");
     req.setHeader(QNetworkRequest::UserAgentHeader,
                   "Mozilla/5.0 (compatible; TorReaderPDF/2.0.0)");
+    req.setAttribute(QNetworkRequest::RedirectPolicyAttribute,
+                     QNetworkRequest::NoLessSafeRedirectPolicy);
+    // Without a timeout a stalled connection never emits finished(), so the UI
+    // would sit on "Translating…" forever with no error.
+    req.setTransferTimeout(kRequestTimeoutMs);
+
+    QNetworkReply* rep = useGet
+        ? m_nam->get(req)
+        : m_nam->post(req, QByteArray("q=") + QUrl::toPercentEncoding(text));
+
+    connect(rep, &QNetworkReply::finished, this,
+            [this, rep, text, srcLang, dstLang, key, useGet]() {
+        rep->deleteLater();
 
-    QByteArray body = "q=" + QUrl::toPercentEncoding(text);
-    QNetworkReply* rep = m_nam->post(req, body);
+        const int http = rep->attribute(
+            QNetworkRequest::HttpStatusCodeAttribute).toInt();
+        const QByteArray raw = rep->readAll();
+
+        qWarning("Translator: %s %s -> http=%d qterr=%d(%s) bytes=%lld",
+                 useGet ? "GET" : "POST",
+                 qPrintable(QStringLiteral("%1->%2").arg(srcLang, dstLang)),
+                 http, int(rep->error()), qPrintable(rep->errorString()),
+                 qint64(raw.size()));
 
-    connect(rep, &QNetworkReply::finished, [this, rep, text, lang, key]() {
-        rep->deleteLater();
         if (rep->error() != QNetworkReply::NoError) {
-            tryGeminiFallback(text, lang, key, rep->errorString());
+            const QString why = QStringLiteral("%1 (HTTP %2)")
+                                    .arg(rep->errorString()).arg(http);
+            if (!useGet)
+                sendGoogleRequest(text, srcLang, dstLang, key, /*useGet=*/true);
+            else
+                tryGeminiFallback(text, srcLang, dstLang, key, why);
             return;
         }
 
-        QByteArray raw = rep->readAll();
         QJsonDocument doc = QJsonDocument::fromJson(raw);
         QString translation;
 
@@ -126,17 +213,26 @@ void Translator::translate(const QString& text) {
         }
 
         if (translation.trimmed().isEmpty()) {
-            tryGeminiFallback(text, lang, key,
-                              QStringLiteral("No translation returned"));
+            // An empty 200 usually means the body never reached Google; retry
+            // as a GET before giving up on the endpoint entirely.
+            if (!useGet) {
+                sendGoogleRequest(text, srcLang, dstLang, key, /*useGet=*/true);
+                return;
+            }
+            tryGeminiFallback(
+                text, srcLang, dstLang, key,
+                QStringLiteral("Google returned HTTP %1 with %2 bytes and no "
+                               "translation").arg(http).arg(raw.size()));
         } else {
             addToCache(key, translation.trimmed());
-            emit finished(text, translation.trimmed());
+            emit finished(text, translation.trimmed(), srcLang, dstLang);
         }
     });
 }
 
-void Translator::tryGeminiFallback(const QString& text, const QString& lang,
-                                   const QString& key, const QString& primaryError)
+void Translator::tryGeminiFallback(const QString& text, const QString& srcLang,
+                                   const QString& dstLang, const QString& key,
+                                   const QString& primaryError)
 {
     if (!m_geminiKeyChecked) {
         m_geminiApiKey = qEnvironmentVariable("GEMINI_API_KEY");
@@ -149,7 +245,7 @@ void Translator::tryGeminiFallback(const QString& text, const QString& lang,
 
     if (m_geminiApiKey.isEmpty()) {
         emit failed(primaryError +
-                    QStringLiteral(" (Gemini fallback: chưa cấu hình GEMINI_API_KEY)"));
+                    QStringLiteral(" (Gemini fallback unavailable: GEMINI_API_KEY is not configured)"));
         return;
     }
 
@@ -161,12 +257,17 @@ void Translator::tryGeminiFallback(const QString& text, const QString& lang,
     req.setHeader(QNetworkRequest::ContentTypeHeader, "application/json");
     req.setHeader(QNetworkRequest::UserAgentHeader,
                   "Mozilla/5.0 (compatible; TorReaderPDF/2.0.0)");
-    req.setTransferTimeout(15000);
+    req.setTransferTimeout(kRequestTimeoutMs);
+
+    const QString fromPart = (srcLang == QLatin1String("auto"))
+        ? QString()
+        : QStringLiteral("from %1 ").arg(languageName(srcLang));
 
     QJsonObject partObj;
     partObj[QStringLiteral("text")] =
-        QStringLiteral("Translate the following text to %1. Return ONLY the translation, no explanations:\n\n%2")
-            .arg(lang, text);
+        QStringLiteral("Translate the following text %1to %2. "
+                       "Return ONLY the translation, no explanations:\n\n%3")
+            .arg(fromPart, languageName(dstLang), text);
 
     QJsonArray parts;
     parts.append(partObj);
@@ -183,8 +284,16 @@ void Translator::tryGeminiFallback(const QString& text, const QString& lang,
     QByteArray body = QJsonDocument(bodyObj).toJson(QJsonDocument::Compact);
     QNetworkReply* rep = m_nam->post(req, body);
 
-    connect(rep, &QNetworkReply::finished, [this, rep, text, key, primaryError]() {
+    connect(rep, &QNetworkReply::finished, this,
+            [this, rep, text, srcLang, dstLang, key, primaryError]() {
         rep->deleteLater();
+        const int http = rep->attribute(
+            QNetworkRequest::HttpStatusCodeAttribute).toInt();
+        QByteArray raw = rep->readAll();
+        qWarning("Translator: Gemini -> http=%d qterr=%d(%s) bytes=%lld",
+                 http, int(rep->error()), qPrintable(rep->errorString()),
+                 qint64(raw.size()));
+
         if (rep->error() != QNetworkReply::NoError) {
             emit failed(primaryError +
                         QStringLiteral(" (Gemini fallback: ") + rep->errorString() +
@@ -192,7 +301,6 @@ void Translator::tryGeminiFallback(const QString& text, const QString& lang,
             return;
         }
 
-        QByteArray raw = rep->readAll();
         QJsonDocument doc = QJsonDocument::fromJson(raw);
         QString translation;
 
@@ -214,7 +322,7 @@ void Translator::tryGeminiFallback(const QString& text, const QString& lang,
                         QStringLiteral(" (Gemini fallback: empty response)"));
         } else {
             addToCache(key, translation);
-            emit finished(text, translation);
+            emit finished(text, translation, srcLang, dstLang);
         }
     });
 }
diff --git a/src/core/Translator.h b/src/core/Translator.h
index a82cd2e..6f34fb2 100755
--- a/src/core/Translator.h
+++ b/src/core/Translator.h
@@ -2,6 +2,8 @@
 #include <QObject>
 #include <QString>
 #include <QHash>
+#include <QList>
+#include <QPair>
 
 class QNetworkAccessManager;
 class QTimer;
@@ -15,18 +17,31 @@ class Translator : public QObject {
     Q_OBJECT
 public:
     explicit Translator(QObject* parent = nullptr);
-    void translate(const QString& text);
+
+    // srcLang may be "auto"; dstLang must be a concrete language code.
+    void translate(const QString& text,
+                   const QString& srcLang = QStringLiteral("en"),
+                   const QString& dstLang = QStringLiteral("vi"));
+
+    // Shared language table: <code, display name>. "auto" is the first entry.
+    static const QList<QPair<QString, QString>>& languages();
+    static QString languageName(const QString& code);
 
 signals:
-    void finished(const QString& original, const QString& translation);
+    void finished(const QString& original, const QString& translation,
+                  const QString& srcLang, const QString& dstLang);
     void failed(const QString& error);
 
 private:
+    void sendGoogleRequest(const QString& text, const QString& srcLang,
+                           const QString& dstLang, const QString& key,
+                           bool useGet);
     void addToCache(const QString& key, const QString& translation);
     void loadCacheFromDisk();
     void saveCacheToDisk();
-    void tryGeminiFallback(const QString& text, const QString& lang,
-                           const QString& key, const QString& primaryError);
+    void tryGeminiFallback(const QString& text, const QString& srcLang,
+                           const QString& dstLang, const QString& key,
+                           const QString& primaryError);
 
     QNetworkAccessManager* m_nam;
     QHash<QString, CacheEntry> m_cache;
diff --git a/src/ui/ContinuousView.cpp b/src/ui/ContinuousView.cpp
index 1152bb0..5f3b68f 100755
--- a/src/ui/ContinuousView.cpp
+++ b/src/ui/ContinuousView.cpp
@@ -1347,8 +1347,10 @@ void ContinuousView::wheelEvent(QWheelEvent* event)
 
 void ContinuousView::mousePressEvent(QMouseEvent* event)
 {
-    // Ctrl+Left drag = text selection for translation (giu nguyen, SPEC phan 2).
-    if ((event->modifiers() & Qt::ControlModifier)
+    // Ctrl+Left (or Alt+Left) drag = text selection for translation.
+    // Both modifiers are accepted so the gesture matches PdfGpuView and still
+    // works when the window manager eats Alt+drag.
+    if ((event->modifiers() & (Qt::ControlModifier | Qt::AltModifier))
         && event->button() == Qt::LeftButton)
     {
         m_selecting = true;
diff --git a/src/ui/LanguagePickerPopup.cpp b/src/ui/LanguagePickerPopup.cpp
new file mode 100644
index 0000000..1c9276c
--- /dev/null
+++ b/src/ui/LanguagePickerPopup.cpp
@@ -0,0 +1,184 @@
+#include "LanguagePickerPopup.h"
+#include "../core/Translator.h"
+
+#include <QComboBox>
+#include <QLabel>
+#include <QPushButton>
+#include <QToolButton>
+#include <QCheckBox>
+#include <QVBoxLayout>
+#include <QHBoxLayout>
+#include <QGridLayout>
+#include <QPainter>
+#include <QSettings>
+#include <QScreen>
+#include <QGuiApplication>
+#include <QFontMetrics>
+
+static constexpr const char* kKeySrc      = "translate/srcLang";
+static constexpr const char* kKeyDst      = "translate/dstLang";
+static constexpr const char* kKeyRemember = "translate/rememberLangs";
+
+QString LanguagePickerPopup::savedSource() {
+    QSettings s;
+    return s.value(QLatin1String(kKeySrc), QStringLiteral("en")).toString();
+}
+
+QString LanguagePickerPopup::savedTarget() {
+    QSettings s;
+    return s.value(QLatin1String(kKeyDst), QStringLiteral("vi")).toString();
+}
+
+bool LanguagePickerPopup::rememberChoice() {
+    QSettings s;
+    return s.value(QLatin1String(kKeyRemember), false).toBool();
+}
+
+LanguagePickerPopup::LanguagePickerPopup(QWidget* parent)
+    : QDialog(parent, Qt::Tool | Qt::FramelessWindowHint)
+{
+    setAttribute(Qt::WA_TranslucentBackground);
+    setWindowTitle(tr("Translate"));
+    setFixedWidth(360);
+
+    auto* title = new QLabel(tr("Translate selection"), this);
+    title->setStyleSheet("font-weight:bold; font-size:11pt; color:#1a1a1a;");
+
+    m_lblPreview = new QLabel(this);
+    m_lblPreview->setWordWrap(true);
+    m_lblPreview->setStyleSheet("color:#666; font-size:9pt; font-style:italic;");
+
+    m_cbFrom = new QComboBox(this);
+    m_cbTo   = new QComboBox(this);
+    for (const auto& lang : Translator::languages()) {
+        m_cbFrom->addItem(lang.second, lang.first);
+        if (lang.first != QLatin1String("auto"))   // no "auto" as a target
+            m_cbTo->addItem(lang.second, lang.first);
+    }
+    selectCode(m_cbFrom, savedSource());
+    selectCode(m_cbTo,   savedTarget());
+
+    m_btnSwap = new QToolButton(this);
+    m_btnSwap->setText(QString::fromUtf8("\xE2\x87\x84"));   // ⇄
+    m_btnSwap->setToolTip(tr("Swap languages"));
+    m_btnSwap->setCursor(Qt::PointingHandCursor);
+    m_btnSwap->setAutoRaise(true);
+
+    auto* lblFrom = new QLabel(tr("From"), this);
+    auto* lblTo   = new QLabel(tr("Into"), this);
+    lblFrom->setStyleSheet("color:#444; font-size:9pt;");
+    lblTo->setStyleSheet("color:#444; font-size:9pt;");
+
+    auto* grid = new QGridLayout;
+    grid->setHorizontalSpacing(8);
+    grid->setVerticalSpacing(4);
+    grid->addWidget(lblFrom,  0, 0);
+    grid->addWidget(lblTo,    0, 2);
+    grid->addWidget(m_cbFrom, 1, 0);
+    grid->addWidget(m_btnSwap,1, 1);
+    grid->addWidget(m_cbTo,   1, 2);
+    grid->setColumnStretch(0, 1);
+    grid->setColumnStretch(2, 1);
+
+    m_chkRemember = new QCheckBox(tr("Always use this pair (don't ask again)"), this);
+    m_chkRemember->setStyleSheet("color:#444; font-size:9pt;");
+    m_chkRemember->setChecked(rememberChoice());
+
+    m_btnTranslate = new QPushButton(tr("Translate"), this);
+    m_btnTranslate->setDefault(true);
+    m_btnTranslate->setCursor(Qt::PointingHandCursor);
+    m_btnCancel = new QPushButton(tr("Cancel"), this);
+    m_btnCancel->setCursor(Qt::PointingHandCursor);
+
+    auto* btns = new QHBoxLayout;
+    btns->addStretch();
+    btns->addWidget(m_btnCancel);
+    btns->addWidget(m_btnTranslate);
+
+    auto* layout = new QVBoxLayout(this);
+    layout->setContentsMargins(14, 12, 14, 12);
+    layout->setSpacing(8);
+    layout->addWidget(title);
+    layout->addWidget(m_lblPreview);
+    layout->addLayout(grid);
+    layout->addWidget(m_chkRemember);
+    layout->addLayout(btns);
+
+    connect(m_btnSwap,      &QToolButton::clicked, this, &LanguagePickerPopup::onSwap);
+    connect(m_btnTranslate, &QPushButton::clicked, this, &LanguagePickerPopup::onTranslate);
+    connect(m_btnCancel,    &QPushButton::clicked, this, &QDialog::reject);
+}
+
+void LanguagePickerPopup::selectCode(QComboBox* box, const QString& code) {
+    int idx = box->findData(code);
+    if (idx < 0)
+        idx = box->findData(box == m_cbTo ? QStringLiteral("vi") : QStringLiteral("en"));
+    if (idx >= 0)
+        box->setCurrentIndex(idx);
+}
+
+void LanguagePickerPopup::onSwap() {
+    const QString from = m_cbFrom->currentData().toString();
+    const QString to   = m_cbTo->currentData().toString();
+    // "auto" cannot be a target, so swapping out of it falls back to English.
+    selectCode(m_cbTo, from == QLatin1String("auto") ? QStringLiteral("en") : from);
+    selectCode(m_cbFrom, to);
+}
+
+void LanguagePickerPopup::onTranslate() {
+    const QString src = m_cbFrom->currentData().toString();
+    const QString dst = m_cbTo->currentData().toString();
+
+    QSettings s;
+    s.setValue(QLatin1String(kKeySrc), src);
+    s.setValue(QLatin1String(kKeyDst), dst);
+    s.setValue(QLatin1String(kKeyRemember), m_chkRemember->isChecked());
+    s.sync();
+
+    hide();
+    emit translateRequested(m_text, src, dst);
+}
+
+void LanguagePickerPopup::askFor(const QString& selectedText, const QPoint& globalPos) {
+    m_text = selectedText;
+
+    QString preview = selectedText.simplified();
+    if (preview.size() > 160)
+        preview = preview.left(157) + QStringLiteral("...");
+    // Escaped rather than literal so the file stays ASCII, like the rest of the UI code.
+    m_lblPreview->setText(QString::fromUtf8("\xE2\x80\x9C%1\xE2\x80\x9D").arg(preview));
+
+    // Re-read persisted defaults in case they changed elsewhere.
+    selectCode(m_cbFrom, savedSource());
+    selectCode(m_cbTo,   savedTarget());
+    m_chkRemember->setChecked(rememberChoice());
+
+    adjustSize();
+
+    // Place near the cursor, clamped to the screen the cursor is actually on.
+    QScreen* scr = QGuiApplication::screenAt(globalPos);
+    if (!scr) scr = QGuiApplication::primaryScreen();
+    const QRect avail = scr ? scr->availableGeometry() : QRect(0, 0, 1920, 1080);
+
+    // qBound asserts when min > max, which happens if the popup is wider than
+    // the screen — clamp the upper bound first.
+    const int xMax = qMax(avail.left(), avail.right() - width());
+    int x = qBound(avail.left(), globalPos.x() - width() / 2, xMax);
+    int y = globalPos.y() + 14;
+    if (y + height() > avail.bottom())
+        y = qMax(avail.top(), globalPos.y() - height() - 14);
+    move(x, y);
+
+    show();
+    raise();
+    activateWindow();
+    m_btnTranslate->setFocus();
+}
+
+void LanguagePickerPopup::paintEvent(QPaintEvent*) {
+    QPainter p(this);
+    p.setRenderHint(QPainter::Antialiasing);
+    p.setBrush(QColor(255, 255, 255, 250));
+    p.setPen(QPen(QColor(190, 190, 190), 1));
+    p.drawRoundedRect(rect().adjusted(1, 1, -1, -1), 8, 8);
+}
diff --git a/src/ui/LanguagePickerPopup.h b/src/ui/LanguagePickerPopup.h
new file mode 100644
index 0000000..60eccb6
--- /dev/null
+++ b/src/ui/LanguagePickerPopup.h
@@ -0,0 +1,49 @@
+#pragma once
+#include <QDialog>
+#include <QString>
+
+class QComboBox;
+class QLabel;
+class QPushButton;
+class QToolButton;
+class QCheckBox;
+
+// Small floating panel shown right after the user marquee-selects text.
+// Lets them confirm "translate FROM <lang> INTO <lang>" before the request
+// goes out. Defaults to English -> Vietnamese and remembers the last choice.
+class LanguagePickerPopup : public QDialog {
+    Q_OBJECT
+public:
+    explicit LanguagePickerPopup(QWidget* parent = nullptr);
+
+    // Shows the panel near globalPos with a preview of the selected text.
+    void askFor(const QString& selectedText, const QPoint& globalPos);
+
+    static QString savedSource();
+    static QString savedTarget();
+    // True when the user ticked "don't ask again" - callers should then
+    // translate straight away using savedSource()/savedTarget().
+    static bool rememberChoice();
+
+signals:
+    // Emitted when the user confirms. src may be "auto".
+    void translateRequested(const QString& text, const QString& srcLang,
+                            const QString& dstLang);
+
+protected:
+    void paintEvent(QPaintEvent* event) override;
+
+private:
+    void selectCode(QComboBox* box, const QString& code);
+    void onSwap();
+    void onTranslate();
+
+    QLabel*      m_lblPreview;
+    QComboBox*   m_cbFrom;
+    QComboBox*   m_cbTo;
+    QToolButton* m_btnSwap;
+    QCheckBox*   m_chkRemember;
+    QPushButton* m_btnTranslate;
+    QPushButton* m_btnCancel;
+    QString      m_text;
+};
diff --git a/src/ui/MainWindow.cpp b/src/ui/MainWindow.cpp
index 2f49570..3146fd9 100755
--- a/src/ui/MainWindow.cpp
+++ b/src/ui/MainWindow.cpp
@@ -26,6 +26,7 @@
 #include "core/GoogleAuth.h"
 #include "core/Translator.h"
 #include "TranslationPopup.h"
+#include "LanguagePickerPopup.h"
 #include "NoteInputDialog.h"
 #include "core/UpdateChecker.h"
 #include "GateDialog.h"
@@ -785,7 +786,7 @@ MainWindow::MainWindow(QWidget* parent) : QMainWindow(parent) {
 
     // Permanent hint bar — shows shortcut hints on the right side of the status bar
     auto* hintLabel = new QLabel(
-        "Ctrl+Scroll: Zoom  ·  Alt+Drag: Translate  "
+        "Ctrl+Scroll: Zoom  ·  Ctrl/Alt+Drag: Translate  "
         "·  Scroll: Flip page  ·  Right-click thumbnail: Page options");
     m_hintLabel = hintLabel;
     hintLabel->setStyleSheet(QStringLiteral("color:%1; font-size:10px; padding-right:8px;")
@@ -798,14 +799,36 @@ MainWindow::MainWindow(QWidget* parent) : QMainWindow(parent) {
     m_googleAuth = new GoogleAuth(this);
     m_translator = new Translator(this);
     m_transPopup = new TranslationPopup(nullptr); // top-level floating window
+    m_langPicker = new LanguagePickerPopup(nullptr);
+
+    // The picker asks "from X into Y" before anything goes over the network.
+    connect(m_langPicker, &LanguagePickerPopup::translateRequested,
+            this, [this](const QString& text, const QString& src, const QString& dst) {
+        statusBar()->showMessage("Translating\xE2\x80\xA6", 2000);
+        m_translator->translate(text, src, dst);
+    });
 
     connect(m_translator, &Translator::finished,
-            this, [this](const QString& orig, const QString& trans) {
-        m_transPopup->showTranslation(orig, trans, m_lastTransPos);
+            this, [this](const QString& orig, const QString& trans,
+                         const QString& src, const QString& dst) {
+        const QString pair = QStringLiteral("%1 \xE2\x86\x92 %2")
+                                 .arg(Translator::languageName(src),
+                                      Translator::languageName(dst));
+        m_transPopup->showTranslation(orig, trans, m_lastTransPos, pair);
     });
     connect(m_translator, &Translator::failed,
             this, [this](const QString& err) {
-        statusBar()->showMessage("Translation failed: " + err, 4000);
+        // A 4-second status flash was too easy to miss, which made every
+        // failure look like "nothing happened". Show the reason where the
+        // translation itself would have appeared.
+        statusBar()->showMessage("Translation failed: " + err, 10000);
+        m_transPopup->showTranslation(
+            QString(),
+            QStringLiteral("<span style='color:#B91C1C;'>Translation failed</span>"
+                           "<br><span style='font-weight:normal; font-size:9pt;'>%1</span>")
+                .arg(err.toHtmlEscaped()),
+            m_lastTransPos,
+            QStringLiteral("Error"));
     });
 
     connect(m_continuousView, &ContinuousView::textRegionSelected,
@@ -1231,7 +1254,8 @@ void MainWindow::setupActionBar() {
     // Translate — nut tren toolbar (giua About va Share app).
     m_translateAct = new QAction("Translate", this);
     m_translateAct->setToolTip(
-        "Enable Google Translate — hold Ctrl and drag over text to select & translate\n"
+        "Enable Google Translate — hold Ctrl (or Alt) and drag over text to select & translate\n"
+        "A pop-up asks which language to translate from and into (English \xE2\x86\x92 Vietnamese by default)\n"
         "Works in both Single and Continuous modes\n"
         "Right-click to reset consent");
     m_translateAct->setShortcut(QKeySequence("Ctrl+Shift+T"));
@@ -1241,9 +1265,11 @@ void MainWindow::setupActionBar() {
             mb.setWindowTitle("Google Translate Enabled");
             mb.setText(
                 "<b>Translation is enabled.</b><br><br>"
-                "Hold <b>Ctrl</b> and drag over text to select it.<br>"
+                "Hold <b>Ctrl</b> (or <b>Alt</b>) and drag over text to select it.<br>"
                 "Works in both <b>Single page</b> and <b>Continuous</b> modes.<br>"
-                "Release to automatically translate the selected text to Vietnamese.<br><br>"
+                "On release a pop-up asks which language to translate "
+                "<b>from</b> and <b>into</b> \xE2\x80\x94 English \xE2\x86\x92 Vietnamese by default.<br>"
+                "Tick <i>Always use this pair</i> there to skip the pop-up next time.<br><br>"
                 "<i>To disable/reset: right-click the Translate button.</i>");
             mb.setIcon(QMessageBox::Information);
             mb.setStandardButtons(QMessageBox::Ok);
@@ -4533,16 +4559,25 @@ void MainWindow::onTextRegionSelected(int pageIdx, QRectF rectPts, QPoint global
 
     FPDF_DOCUMENT rawDoc = t->doc->raw();
     m_lastTransPos = globalPos;
-    statusBar()->showMessage("Translating…", 3000);
+    statusBar()->showMessage("Extracting text…", 3000);
 
     auto* watcher = new QFutureWatcher<QString>(this);
     connect(watcher, &QFutureWatcher<QString>::finished, this,
-            [this, watcher]() {
+            [this, watcher, globalPos]() {
         watcher->deleteLater();
         QString text = watcher->result();
-        if (!text.isEmpty())
-            m_translator->translate(text);
-        else
+        if (!text.isEmpty()) {
+            // Ask "from X into Y" first, unless the user ticked "don't ask again".
+            if (LanguagePickerPopup::rememberChoice()) {
+                statusBar()->showMessage("Translating…", 2000);
+                m_translator->translate(text,
+                                        LanguagePickerPopup::savedSource(),
+                                        LanguagePickerPopup::savedTarget());
+            } else {
+                statusBar()->clearMessage();
+                m_langPicker->askFor(text, globalPos);
+            }
+        } else
             statusBar()->showMessage(
                 "No selectable text in this area. "
                 "Scanned pages may require OCR.", 4000);
diff --git a/src/ui/MainWindow.h b/src/ui/MainWindow.h
index 3c79724..d3b631f 100755
--- a/src/ui/MainWindow.h
+++ b/src/ui/MainWindow.h
@@ -34,6 +34,7 @@ class ContinuousView;
 class QSplitter;
 class Translator;
 class TranslationPopup;
+class LanguagePickerPopup;
 class GoogleAuth;
 class UpdateChecker;
 class QTimer;
@@ -246,6 +247,7 @@ private slots:
     // Translation feature
     Translator*        m_translator  = nullptr;
     TranslationPopup*  m_transPopup  = nullptr;
+    LanguagePickerPopup* m_langPicker = nullptr;
     GoogleAuth*        m_googleAuth  = nullptr;
     UpdateChecker*     m_updateChecker = nullptr;
     QPoint             m_lastTransPos;
diff --git a/src/ui/PdfGpuView.cpp b/src/ui/PdfGpuView.cpp
index 45827e3..d865753 100755
--- a/src/ui/PdfGpuView.cpp
+++ b/src/ui/PdfGpuView.cpp
@@ -1441,6 +1441,18 @@ void PdfGpuView::mousePressEvent(QMouseEvent* e) {
         update();
         return;
     }
+    // Ctrl/Alt + Left drag = marquee selection for translation. Checked here,
+    // before every tool branch below: those branches return unconditionally,
+    // so anywhere further down the gesture would simply never arm.
+    if ((e->modifiers() & (Qt::AltModifier | Qt::ControlModifier))
+        && e->button() == Qt::LeftButton && m_hasImage) {
+        m_selecting = true;
+        m_selStart  = e->position();
+        m_selEnd    = e->position();
+        setCursor(Qt::IBeamCursor);
+        update();
+        return;
+    }
     // Link: chi khi tool la Pan hoac Select, khong bat Ctrl. Bam vao link thi
     // di theo link truoc khi bat dau pan/chon chu (SPEC_PDF_LINKS muc 3).
     if ((m_tool == ViewTool::Pan || m_tool == ViewTool::SelectText)
@@ -1507,15 +1519,6 @@ void PdfGpuView::mousePressEvent(QMouseEvent* e) {
         beginTextSelection(e->position(), 1);
         return;
     }
-    // Alt+Left drag = text selection for translation
-    if ((e->modifiers() & Qt::AltModifier) && e->button() == Qt::LeftButton) {
-        m_selecting = true;
-        m_selStart  = e->position();
-        m_selEnd    = e->position();
-        setCursor(Qt::IBeamCursor);
-        update();
-        return;
-    }
     if (e->button() == Qt::LeftButton || e->button() == Qt::MiddleButton) {
         m_panning      = true;
         m_lastMousePos = e->position();
diff --git a/src/ui/TranslationPopup.cpp b/src/ui/TranslationPopup.cpp
index 4c8ce03..e81e879 100755
--- a/src/ui/TranslationPopup.cpp
+++ b/src/ui/TranslationPopup.cpp
@@ -18,6 +18,10 @@ TranslationPopup::TranslationPopup(QWidget* parent)
     setAttribute(Qt::WA_ShowWithoutActivating);
     setFixedWidth(340);
 
+    m_lblLangPair = new QLabel(this);
+    m_lblLangPair->setStyleSheet("color:#2563EB; font-size:8pt; font-weight:bold;");
+    m_lblLangPair->setVisible(false);
+
     m_lblOriginal = new QLabel(this);
     m_lblOriginal->setWordWrap(true);
     m_lblOriginal->setStyleSheet("color:#666; font-size:9pt; font-style:italic;");
@@ -52,6 +56,7 @@ TranslationPopup::TranslationPopup(QWidget* parent)
     auto* layout = new QVBoxLayout(this);
     layout->setContentsMargins(14, 12, 14, 12);
     layout->setSpacing(6);
+    layout->addWidget(m_lblLangPair);
     layout->addWidget(m_lblOriginal);
     layout->addWidget(m_lblTranslated);
     layout->addLayout(hdr);
@@ -66,9 +71,13 @@ TranslationPopup::TranslationPopup(QWidget* parent)
 
 void TranslationPopup::showTranslation(const QString& original,
                                         const QString& translation,
-                                        const QPoint& globalPos)
+                                        const QPoint& globalPos,
+                                        const QString& langPair)
 {
+    m_lblLangPair->setText(langPair);
+    m_lblLangPair->setVisible(!langPair.isEmpty());
     m_lblOriginal->setText(original);
+    m_lblOriginal->setVisible(!original.isEmpty());
     m_lblTranslated->setText(translation.isEmpty()
                              ? "<i>(no translation)</i>" : translation);
     m_translation = translation;
@@ -76,7 +85,9 @@ void TranslationPopup::showTranslation(const QString& original,
 
     adjustSize();
 
-    QRect screen = QGuiApplication::primaryScreen()->availableGeometry();
+    QScreen* scr = QGuiApplication::screenAt(globalPos);
+    if (!scr) scr = QGuiApplication::primaryScreen();
+    QRect screen = scr ? scr->availableGeometry() : QRect(0, 0, 1920, 1080);
     int x = qBound(screen.left(), globalPos.x() - width() / 2,
                    screen.right()  - width());
     int y = globalPos.y() - height() - 12;
diff --git a/src/ui/TranslationPopup.h b/src/ui/TranslationPopup.h
index 100e16a..5b53414 100755
--- a/src/ui/TranslationPopup.h
+++ b/src/ui/TranslationPopup.h
@@ -11,7 +11,8 @@ class TranslationPopup : public QWidget {
 public:
     explicit TranslationPopup(QWidget* parent = nullptr);
     void showTranslation(const QString& original, const QString& translation,
-                         const QPoint& globalPos);
+                         const QPoint& globalPos,
+                         const QString& langPair = QString());
 
 protected:
     void paintEvent(QPaintEvent* event) override;
@@ -20,6 +21,7 @@ private slots:
     void onCopy();
 
 private:
+    QLabel*       m_lblLangPair;
     QLabel*       m_lblOriginal;
     QLabel*       m_lblTranslated;
     QLabel*       m_lblCopied;