feat(qt): add /clearhistory command

src/qt/rpcconsole.cpp

@@ -24,6 +24,7 @@
 #endif // ENABLE_WALLET
 #include <rpc/client.h>
 #include <rpc/server.h>
+#include <support/cleanse.h>
 #include <util/strencodings.h>
 #include <util/string.h>
 #include <util/time.h>
@@ -691,6 +692,85 @@ void RPCConsole::WriteCommandHistory()
     settings.endArray();
 }
 
+void RPCConsole::ClearCommandHistory()
+{
+    // Best-effort attempt to securely overwrite command history in memory.
+    // Note: Complete memory sanitization cannot be guaranteed with QString due to
+    // Qt's implicit sharing (copy-on-write) and internal memory management.
+    for (QString& cmd : history) {
+        if (cmd.isEmpty()) continue;
+
+        // Attempt to cleanse QString's internal buffer using Bitcoin Core's
+        // secure memory_cleanse function (uses platform-specific secure zeroing)
+        QChar* data = cmd.data();  // Get pointer to mutable internal buffer
+        size_t byte_size = cmd.size() * sizeof(QChar);
+
+        // First pass: overwrite with 'x' and cleanse
+        cmd.fill('x');
+        if (data == cmd.data()) {  // Verify we still have the same buffer
+            memory_cleanse(cmd.data(), byte_size);
+        }
+
+        // Second pass: overwrite with null and cleanse
+        cmd.fill('\0');
+        if (data == cmd.data()) {  // Verify we still have the same buffer
+            memory_cleanse(cmd.data(), byte_size);
+        }
+    }
+
+    // Overwrite saved history in settings with dummy data
+    QSettings settings;
+
+    // First pass: read existing commands and overwrite with dummy data of same length
+    QStringList dummy_commands;
+    int size = settings.beginReadArray("nRPCConsoleWindowHistory");
+    for (int i = 0; i < size; ++i) {
+        settings.setArrayIndex(i);
+        QString cmd = settings.value("cmd").toString();
+        // Store dummy command with same length as original (don't leak length info)
+        dummy_commands.append(QString(cmd.size(), 'x'));
+    }
+    settings.endArray();
+
+    // Write dummy data to overwrite the original commands
+    if (!dummy_commands.empty()) {
+        settings.beginWriteArray("nRPCConsoleWindowHistory");
+        for (int i = 0; i < dummy_commands.size(); ++i) {
+            settings.setArrayIndex(i);
+            settings.setValue("cmd", dummy_commands[i]);
+        }
+        settings.endArray();
+        settings.sync(); // Force to disk
+    }
+
+    // Clear the history list
+    history.clear();
+    historyPtr = 0;
+
+    // Also cleanse cmdBeforeBrowsing which may contain command data
+    if (!cmdBeforeBrowsing.isEmpty()) {
+        QChar* data = cmdBeforeBrowsing.data();
+        size_t byte_size = cmdBeforeBrowsing.size() * sizeof(QChar);
+        cmdBeforeBrowsing.fill('x');
+        if (data == cmdBeforeBrowsing.data()) {
+            memory_cleanse(cmdBeforeBrowsing.data(), byte_size);
+        }
+        cmdBeforeBrowsing.fill('\0');
+        if (data == cmdBeforeBrowsing.data()) {
+            memory_cleanse(cmdBeforeBrowsing.data(), byte_size);
+        }
+    }
+    cmdBeforeBrowsing.clear();
+
+    // Second pass: write empty history to settings
+    settings.beginWriteArray("nRPCConsoleWindowHistory");
+    // Empty array - no entries written
+    settings.endArray();
+
+    // Force settings to sync to disk
+    settings.sync();
+}
+
 RPCConsole::~RPCConsole()
 {
     QSettings settings;
@@ -1182,6 +1262,26 @@ void RPCConsole::on_lineEdit_returnPressed()
         return;
     }
 
+    // Special command to clear command history
+    if (cmd == QLatin1String("/clearhistory")) {
+        QMessageBox::StandardButton reply = QMessageBox::question(this,
+            tr("Clear Command History"),
+            tr("This will permanently clear your command history and console output.<br><br>"
+               "While this action is irreversible, complete removal from memory and disk "
+               "cannot be guaranteed due to system and Qt framework limitations.<br><br>"
+               "Are you sure you want to proceed?"),
+            QMessageBox::Yes | QMessageBox::No,
+            QMessageBox::No);
+
+        if (reply == QMessageBox::Yes) {
+            ClearCommandHistory();
+            clear(false); // Clear console output too
+            message(CMD_REPLY, tr("Command history and console output cleared."));
+        }
+        ui->lineEdit->clear();
+        return;
+    }
+
     if (m_is_executing) {
         return;
     }

src/qt/rpcconsole.h

@@ -166,6 +166,7 @@ public Q_SLOTS:
     void startExecutor();
     void setTrafficGraphRange(int mins);
     void WriteCommandHistory();
+    void ClearCommandHistory();
 
     enum ColumnWidths
     {