feat(ai): pass chat history to prompt improver

- Force English output so improved prompts are always in a
  consistent language for downstream tooling.
- Thread recent chat history into the improver request so the
  LLM has context when rewriting the draft; budget-capped at
  ~4000 chars walking backwards from the most recent message.
- Replace SVG icon with a Unicode sparkle glyph to remove a
  palette-dependent repaint path on every theme change.
- Make the improve button a cancel toggle while streaming;
  Esc also cancels, removing the need to disable the button.
- Surface canImprove failure reason as a timed warning banner
  instead of silently doing nothing.
- Rename the Preferences group box to "AI Provider" and add a
  note listing which features share the configuration, since
  more than commit messages now depend on it.
- Improve canImprove error strings to be more actionable.

Author: nullmastermind

src/ai/PromptImprover.cpp

@@ -26,8 +26,8 @@ const QString kSystemTemplate = QStringLiteral(
     "- If the prompt starts with a slash command (e.g. /chore, /feat, /fix, "
     "/refactor), you MUST keep that command at the beginning. Never remove, "
     "rename, or reorder it.\n"
-    "- Preserve the user's language (if they write in Vietnamese, respond in "
-    "Vietnamese; English stays English).\n"
+    "- Always output the improved prompt in English, regardless of the input "
+    "language.\n"
     "- Do not add information the user did not mention. You may restructure, "
     "clarify ambiguity, add specificity where the intent is obvious, and "
     "improve phrasing.\n"
@@ -71,17 +71,18 @@ bool PromptImprover::canImprove(QString *whyNot) const
     if (m_state == State::Streaming)
         return fail(tr("Improvement already in progress"));
     if (m_settings->commitMessageProviderUrl().trimmed().isEmpty())
-        return fail(tr("Configure the AI provider URL in Preferences → AI"));
+        return fail(tr("AI provider not configured. Set the endpoint in Preferences → AI Provider."));
     if (m_settings->commitMessageModel().trimmed().isEmpty())
-        return fail(tr("Configure the AI model in Preferences → AI"));
+        return fail(tr("AI model not configured. Set the model in Preferences → AI Provider."));
     if (m_credStore && !m_credStore->isApiKeyAvailable())
-        return fail(tr("Configure the AI API key in Preferences → AI"));
+        return fail(tr("AI API key not configured. Save your key in Preferences → AI Provider."));
     return true;
 }
 
 void PromptImprover::trigger(const QString &userDraft,
                              const QString &workingDirectory,
-                             const QList<AcpProtocol::AcpCommandInfo> &commands)
+                             const QList<AcpProtocol::AcpCommandInfo> &commands,
+                             const QString &chatHistory)
 {
     QString why;
     if (!canImprove(&why)) {
@@ -104,12 +105,18 @@ void PromptImprover::trigger(const QString &userDraft,
 
     m_responseBuffer.clear();
 
+    QString userMessage;
+    if (!chatHistory.isEmpty()) {
+        userMessage += QStringLiteral("<chat_history>\n%1\n</chat_history>\n\n").arg(chatHistory);
+    }
+    userMessage += QStringLiteral("<user_draft>\n%1\n</user_draft>").arg(userDraft);
+
     ILlmHttpClient::Request req;
     req.url = QUrl(m_settings->commitMessageProviderUrl());
     req.model = m_settings->commitMessageModel();
     req.apiKey = apiKey;
     req.systemPrompt = systemPrompt;
-    req.prompt = QStringLiteral("<user_draft>\n%1\n</user_draft>").arg(userDraft);
+    req.prompt = userMessage;
     req.maxTokens = 4096;
     req.idleTimeoutSec = m_settings->commitMessageStreamIdleTimeoutSec();
 

src/ai/PromptImprover.h

@@ -34,7 +34,8 @@ class PromptImprover : public QObject
 
     void trigger(const QString &userDraft,
                  const QString &workingDirectory,
-                 const QList<AcpProtocol::AcpCommandInfo> &commands);
+                 const QList<AcpProtocol::AcpCommandInfo> &commands,
+                 const QString &chatHistory = {});
 
     void cancel();
 

src/dialogs/PreferencesDialog.cpp

@@ -282,7 +282,19 @@ PreferencesDialog::PreferencesDialog(ApplicationSettings *settings, QWidget *par
         offerRestart();
     });
 
-    // --- AI commit-message settings ------------------------------------------
+    // --- AI provider settings --------------------------------------------------
+
+    // Add a note explaining which features use this configuration.
+    {
+        auto *noteLabel = new QLabel(
+            tr("Used by: AI Commit Message, Prompt Improver. "
+               "More features will use this provider in the future."),
+            this);
+        noteLabel->setWordWrap(true);
+        noteLabel->setStyleSheet(QStringLiteral(
+            "color: palette(placeholder-text); font-size: 11px; margin-bottom: 4px;"));
+        ui->formLayoutAi->insertRow(0, noteLabel);
+    }
 
     ui->lineEditAiUrl->setText(settings->commitMessageProviderUrl());
     connect(ui->lineEditAiUrl, &QLineEdit::editingFinished, this, [=]() {

src/dialogs/PreferencesDialog.ui

@@ -357,7 +357,7 @@
        <item>
         <widget class="QGroupBox" name="groupBoxAi">
          <property name="title">
-          <string>AI Commit Message</string>
+          <string>AI Provider</string>
          </property>
          <layout class="QFormLayout" name="formLayoutAi">
           <item row="0" column="0">

src/icons/sparkle.svg

@@ -47,7 +47,6 @@
         <file>icons/plus.svg</file>
         <file>icons/list_with_icons.svg</file>
         <file>icons/paperclip.svg</file>
-        <file>icons/sparkle.svg</file>
         <file>icons/markdown-preview.svg</file>
     </qresource>
 </RCC>

src/resources.qrc

@@ -205,6 +205,11 @@ AcpSessionView::AcpSessionView(AcpSessionModel *model,
 
 AcpSessionView::~AcpSessionView() = default;
 
+QSize AcpSessionView::sizeHint() const
+{
+    return QSize(420, 300);
+}
+
 QSize AcpSessionView::minimumSizeHint() const
 {
     return QSize(200, 100);
@@ -434,6 +439,13 @@ void AcpSessionView::buildUi()
     cb->onSubmit = [this]() { onSendClicked(); };
     cb->onRestart = [this]() { emit restartSessionRequested(); };
     cb->onKeyFilter = [this](QKeyEvent *ke) -> bool {
+        // Esc cancels prompt improvement if streaming.
+        if (ke->key() == Qt::Key_Escape
+            && m_promptImprover
+            && m_promptImprover->state() == ai::PromptImprover::State::Streaming) {
+            onImproveClicked(); // toggles to cancel
+            return true;
+        }
         if (!m_commandPopup || !m_commandPopup->isVisible())
             return false;
         switch (ke->key()) {
@@ -496,16 +508,16 @@ void AcpSessionView::buildUi()
     // 6b. Floating improve-prompt button (child of m_input, bottom-right).
     m_improveBtn = new QToolButton(m_input->viewport());
     m_improveBtn->setAutoRaise(true);
-    m_improveBtn->setToolButtonStyle(Qt::ToolButtonIconOnly);
+    m_improveBtn->setToolButtonStyle(Qt::ToolButtonTextOnly);
+    m_improveBtn->setText(QStringLiteral("✨"));
     m_improveBtn->setToolTip(tr("Improve prompt with AI (Ctrl+I)"));
     m_improveBtn->setAccessibleName(tr("Improve prompt with AI"));
     m_improveBtn->setAccessibleDescription(tr("Rewrite the current prompt to be clearer (Ctrl+I)"));
     m_improveBtn->setCursor(Qt::PointingHandCursor);
     m_improveBtn->setStyleSheet(QStringLiteral(
-        "QToolButton { background: transparent; border: none; padding: 2px; border-radius: 3px; }"
+        "QToolButton { background: transparent; border: none; padding: 2px; border-radius: 3px; font-size: 14px; }"
         "QToolButton:hover { background: palette(midlight); }"
         "QToolButton:disabled { opacity: 0.3; }"));
-    rebuildImproveIcon();
     m_improveBtn->hide();
     connect(m_improveBtn, &QToolButton::clicked, this, &AcpSessionView::onImproveClicked);
 
@@ -1751,7 +1763,6 @@ void AcpSessionView::changeEvent(QEvent *event)
     case QEvent::StyleChange:
     case QEvent::ApplicationPaletteChange:
         rebuildAttachIcon();
-        rebuildImproveIcon();
         break;
     default:
         break;
@@ -1765,13 +1776,6 @@ void AcpSessionView::rebuildAttachIcon()
                                     palette().color(QPalette::WindowText)));
 }
 
-void AcpSessionView::rebuildImproveIcon()
-{
-    if (!m_improveBtn) return;
-    m_improveBtn->setIcon(tintedIcon(QStringLiteral(":/icons/sparkle.svg"),
-                                     palette().color(QPalette::WindowText)));
-}
-
 void AcpSessionView::applyChatFont()
 {
     auto *settings = appSettings();
@@ -1914,16 +1918,29 @@ void AcpSessionView::updateImproveButtonState()
 
     m_improveBtn->show();
     positionImproveButton();
-
-    // Disable when streaming or LLM not configured.
-    const bool canFire = m_promptImprover && m_promptImprover->canImprove();
-    m_improveBtn->setEnabled(canFire);
+    m_improveBtn->setEnabled(true);
 }
 
 void AcpSessionView::onImproveClicked()
 {
     if (!m_promptImprover || !m_input) return;
-    if (!m_promptImprover->canImprove()) return;
+
+    // If already streaming, cancel.
+    if (m_promptImprover->state() == ai::PromptImprover::State::Streaming) {
+        m_promptImprover->cancel();
+        m_input->setReadOnly(false);
+        m_improveBtn->setText(QStringLiteral("✨"));
+        m_improveBtn->setToolTip(tr("Improve prompt with AI (Ctrl+I)"));
+        updateImproveButtonState();
+        return;
+    }
+
+    QString whyNot;
+    if (!m_promptImprover->canImprove(&whyNot)) {
+        setBanner(whyNot, BannerKind::Warning);
+        QTimer::singleShot(5000, this, &AcpSessionView::clearBanner);
+        return;
+    }
 
     const QString draft = m_input->toPlainText().trimmed();
     if (draft.isEmpty()) return;
@@ -1940,12 +1957,43 @@ void AcpSessionView::onImproveClicked()
     const QList<AcpProtocol::AcpCommandInfo> commands =
         m_model ? m_model->availableCommands() : QList<AcpProtocol::AcpCommandInfo>{};
 
+    // Build a condensed chat history from recent messages (budget: ~4000 chars).
+    QString chatHistory;
+    if (m_model) {
+        constexpr int kHistoryBudget = 4000;
+        const auto &msgs = m_model->messages();
+        int totalChars = 0;
+        // Walk backwards to get the most recent messages first.
+        for (int i = msgs.size() - 1; i >= 0; --i) {
+            const auto &msg = msgs[i];
+            if (msg.role != QLatin1String("user") && msg.role != QLatin1String("assistant"))
+                continue;
+            QString text;
+            for (const auto &block : msg.content) {
+                if (block.kind == AcpProtocol::AcpContentBlock::Kind::Text)
+                    text += block.text;
+            }
+            text = text.trimmed();
+            if (text.isEmpty()) continue;
+            // Truncate individual messages that are too long.
+            if (text.size() > 800)
+                text = text.left(800) + QStringLiteral("...");
+            const QString entry = QStringLiteral("[%1]: %2\n").arg(msg.role, text);
+            if (totalChars + entry.size() > kHistoryBudget)
+                break;
+            chatHistory.prepend(entry);
+            totalChars += entry.size();
+        }
+        chatHistory = chatHistory.trimmed();
+    }
+
     m_originalDraftBeforeImprove = m_input->toPlainText();
     m_input->setReadOnly(true);
-    m_improveBtn->setEnabled(false);
-    m_improveBtn->setToolTip(tr("Improving prompt..."));
+    m_improveBtn->setText(QStringLiteral("■"));
+    m_improveBtn->setToolTip(tr("Stop improving (Esc)"));
+    m_improveBtn->setEnabled(true);
 
-    m_promptImprover->trigger(draft, workingDir, commands);
+    m_promptImprover->trigger(draft, workingDir, commands, chatHistory);
 }
 
 void AcpSessionView::onImproveFinished(const QString &improvedText)
@@ -1961,6 +2009,7 @@ void AcpSessionView::onImproveFinished(const QString &improvedText)
     cursor.endEditBlock();
 
     m_input->setReadOnly(false);
+    m_improveBtn->setText(QStringLiteral("✨"));
     m_improveBtn->setToolTip(tr("Improve prompt with AI (Ctrl+I)"));
     m_input->setFocus();
     updateImproveButtonState();
@@ -1971,6 +2020,7 @@ void AcpSessionView::onImproveError(const QString &message)
     if (!m_input) return;
 
     m_input->setReadOnly(false);
+    m_improveBtn->setText(QStringLiteral("✨"));
     m_improveBtn->setToolTip(tr("Improve prompt with AI (Ctrl+I)"));
     updateImproveButtonState();
 

src/widgets/AcpSessionView.cpp

@@ -103,6 +103,7 @@ class AcpSessionView : public QWidget
 private slots:
     void onShowDebugLogClicked();
 
+    QSize sizeHint() const override;
     QSize minimumSizeHint() const override;
 
 protected:
@@ -144,7 +145,6 @@ private slots:
     void buildUi();
     void wireSignals();
     void rebuildAttachIcon();
-    void rebuildImproveIcon();
     void hydrateFromModel();
     void appendMessageWidget(int idx);
     // Insert a widget into the transcript timeline at the tail, just above