diff --git a/src/plugins/debugger/cdb/cdbengine.cpp b/src/plugins/debugger/cdb/cdbengine.cpp
index b3623f42867..05708c6ca4b 100644
--- a/src/plugins/debugger/cdb/cdbengine.cpp
+++ b/src/plugins/debugger/cdb/cdbengine.cpp
@@ -1239,14 +1239,9 @@ void CdbEngine::updateAll()
     updateLocals();
 }
 
-void CdbEngine::selectThread(ThreadId threadId)
+void CdbEngine::selectThread(const Thread &thread)
 {
-    if (!threadId.isValid() || threadId == threadsHandler()->currentThread())
-        return;
-
-    threadsHandler()->setCurrentThread(threadId);
-
-    runCommand({'~' + QString::number(threadId.raw()) + " s", BuiltinCommand,
+    runCommand({'~' + thread->id() + " s", BuiltinCommand,
                [this](const DebuggerResponse &) { reloadFullStack(); }});
 }
 
@@ -1809,7 +1804,7 @@ void CdbEngine::processStop(const GdbMi &stopReason, bool conditionalBreakPointT
     // Further examine stop and report to user
     QString message;
     QString exceptionBoxMessage;
-    ThreadId forcedThreadId;
+    Thread forcedThread;
     const unsigned stopFlags = examineStopReason(stopReason, &message, &exceptionBoxMessage,
                                                  conditionalBreakPointTriggered);
     m_stopMode = NoStopRequested;
@@ -1847,7 +1842,7 @@ void CdbEngine::processStop(const GdbMi &stopReason, bool conditionalBreakPointT
         if (stopFlags & StopInArtificialThread) {
             showMessage(tr("Switching to main thread..."), LogMisc);
             runCommand({"~0 s", NoFlags});
-            forcedThreadId = ThreadId(0);
+            forcedThread = Thread();
             // Re-fetch stack again.
             reloadFullStack();
         } else {
@@ -1872,8 +1867,8 @@ void CdbEngine::processStop(const GdbMi &stopReason, bool conditionalBreakPointT
         const GdbMi threads = stopReason["threads"];
         if (threads.isValid()) {
             threadsHandler()->updateThreads(threads);
-            if (forcedThreadId.isValid())
-                threadsHandler()->setCurrentThread(forcedThreadId);
+            if (forcedThread)
+                threadsHandler()->setCurrentThread(forcedThread);
         } else {
             showMessage(stopReason["threaderror"].data(), LogError);
         }
diff --git a/src/plugins/debugger/cdb/cdbengine.h b/src/plugins/debugger/cdb/cdbengine.h
index cfc822c658f..e5b617eb437 100644
--- a/src/plugins/debugger/cdb/cdbengine.h
+++ b/src/plugins/debugger/cdb/cdbengine.h
@@ -80,7 +80,7 @@ public:
     void executeDebuggerCommand(const QString &command) override;
 
     void activateFrame(int index) override;
-    void selectThread(ThreadId threadId) override;
+    void selectThread(const Thread &thread) override;
 
     bool stateAcceptsBreakpointChanges() const override;
     bool acceptsBreakpoint(const BreakpointParameters &params) const override;
diff --git a/src/plugins/debugger/debuggerengine.cpp b/src/plugins/debugger/debuggerengine.cpp
index 028fa92211b..3717e502fd9 100644
--- a/src/plugins/debugger/debuggerengine.cpp
+++ b/src/plugins/debugger/debuggerengine.cpp
@@ -397,8 +397,12 @@ public:
 
     void selectThread(int index)
     {
-        ThreadId id = m_engine->threadsHandler()->threadAt(index);
-        m_engine->selectThread(id);
+        const Thread thread = m_engine->threadsHandler()->rootItem()->childAt(index);
+        QTC_ASSERT(thread, return);
+        // For immediate visual feedback.
+        m_engine->threadsHandler()->setCurrentThread(thread);
+        // Initiate the actual switching in the debugger backend.
+        m_engine->selectThread(thread);
     }
 
     void handleOperateByInstructionTriggered(bool on)
@@ -745,6 +749,7 @@ void DebuggerEnginePrivate::setupViews()
 
     m_threadBox = new QComboBox;
     m_threadBox->setSizeAdjustPolicy(QComboBox::AdjustToContents);
+    m_threadBox->setModel(m_threadsHandler.model());
     connect(m_threadBox, static_cast<void(QComboBox::*)(int)>(&QComboBox::activated),
             this, &DebuggerEnginePrivate::selectThread);
 
@@ -857,15 +862,6 @@ bool DebuggerEngine::isModulesWindowVisible() const
     return d->m_modulesWindow->isVisible();
 }
 
-void DebuggerEngine::setThreadBoxContents(const QStringList &list, int index)
-{
-    QSignalBlocker blocker(d->m_threadBox);
-    d->m_threadBox->clear();
-    for (const QString &item : list)
-        d->m_threadBox->addItem(item);
-    d->m_threadBox->setCurrentIndex(index);
-}
-
 void DebuggerEngine::frameUp()
 {
     int currentIndex = stackHandler()->currentIndex();
diff --git a/src/plugins/debugger/debuggerengine.h b/src/plugins/debugger/debuggerengine.h
index 14634085837..7b2bdbf7c9d 100644
--- a/src/plugins/debugger/debuggerengine.h
+++ b/src/plugins/debugger/debuggerengine.h
@@ -30,6 +30,7 @@
 #include "debuggeritem.h"
 #include "debuggerprotocol.h"
 #include "breakhandler.h"
+#include "threadshandler.h"
 
 #include <coreplugin/icontext.h>
 #include <projectexplorer/devicesupport/idevice.h>
@@ -37,7 +38,6 @@
 #include <texteditor/textmark.h>
 #include <utils/fileutils.h>
 
-#include <QObject>
 #include <QProcess>
 
 QT_BEGIN_NAMESPACE
@@ -74,13 +74,11 @@ class RegisterHandler;
 class StackHandler;
 class StackFrame;
 class SourceFilesHandler;
-class ThreadsHandler;
 class WatchHandler;
 class WatchTreeView;
 class DebuggerToolTipContext;
 class MemoryViewSetupData;
 class TerminalRunner;
-class ThreadId;
 
 class DebuggerRunParameters
 {
@@ -317,7 +315,7 @@ public:
 
     virtual void assignValueInDebugger(WatchItem *item,
         const QString &expr, const QVariant &value);
-    virtual void selectThread(Internal::ThreadId threadId) = 0;
+    virtual void selectThread(const Internal::Thread &thread) = 0;
 
     virtual void executeRecordReverse(bool) {}
     virtual void executeReverse(bool) {}
@@ -417,8 +415,6 @@ public:
     bool isRegistersWindowVisible() const;
     bool isModulesWindowVisible() const;
 
-    void setThreadBoxContents(const QStringList &list, int index);
-
     void openMemoryEditor();
 
     void handleExecDetach();
diff --git a/src/plugins/debugger/gdb/gdbengine.cpp b/src/plugins/debugger/gdb/gdbengine.cpp
index a5b80b7e7c1..fe64936e929 100644
--- a/src/plugins/debugger/gdb/gdbengine.cpp
+++ b/src/plugins/debugger/gdb/gdbengine.cpp
@@ -523,7 +523,7 @@ void GdbEngine::handleAsyncOutput(const QString &asyncClass, const GdbMi &result
         QString id = result["id"].data();
         showStatusMessage(tr("Thread %1 created.").arg(id), 1000);
         ThreadData thread;
-        thread.id = ThreadId(id.toLong());
+        thread.id = id;
         thread.groupId = result["group-id"].data();
         threadsHandler()->updateThread(thread);
     } else if (asyncClass == "thread-group-exited") {
@@ -537,7 +537,7 @@ void GdbEngine::handleAsyncOutput(const QString &asyncClass, const GdbMi &result
         QString groupid = result["group-id"].data();
         showStatusMessage(tr("Thread %1 in group %2 exited.")
                           .arg(id).arg(groupid), 1000);
-        threadsHandler()->removeThread(ThreadId(id.toLong()));
+        threadsHandler()->removeThread(id);
     } else if (asyncClass == "thread-selected") {
         QString id = result["id"].data();
         showStatusMessage(tr("Thread %1 selected.").arg(id), 1000);
@@ -2880,12 +2880,11 @@ void GdbEngine::reloadSourceFiles()
 //
 //////////////////////////////////////////////////////////////////////
 
-void GdbEngine::selectThread(ThreadId threadId)
+void GdbEngine::selectThread(const Thread &thread)
 {
-    threadsHandler()->setCurrentThread(threadId);
-    showStatusMessage(tr("Retrieving data for stack view thread 0x%1...")
-        .arg(threadId.raw(), 0, 16), 10000);
-    DebuggerCommand cmd("-thread-select " + QString::number(threadId.raw()), Discardable);
+    showStatusMessage(tr("Retrieving data for stack view thread %1...")
+        .arg(thread->id()), 10000);
+    DebuggerCommand cmd("-thread-select " + thread->id(), Discardable);
     cmd.callback = [this](const DebuggerResponse &) {
         QTC_CHECK(state() == InferiorUnrunnable || state() == InferiorStopOk);
         showStatusMessage(tr("Retrieving data for stack view..."), 3000);
@@ -2987,9 +2986,8 @@ void GdbEngine::handleThreadInfo(const DebuggerResponse &response)
         ThreadsHandler *handler = threadsHandler();
         handler->updateThreads(response.data);
         // This is necessary as the current thread might not be in the list.
-        if (!handler->currentThread().isValid()) {
-            ThreadId other = handler->threadAt(0);
-            if (other.isValid())
+        if (!handler->currentThread()) {
+            if (Thread other = handler->threadAt(0))
                 selectThread(other);
         }
         updateState(false); // Adjust Threads combobox.
@@ -3011,9 +3009,9 @@ void GdbEngine::handleThreadListIds(const DebuggerResponse &response)
     // In gdb 7.1+ additionally: current-thread-id="1"
     ThreadsHandler *handler = threadsHandler();
     const QVector<GdbMi> &items = response.data["thread-ids"].children();
-    for (int index = 0, n = items.size(); index != n; ++index) {
+    for (const GdbMi &item : items) {
         ThreadData thread;
-        thread.id = ThreadId(items.at(index).toInt());
+        thread.id = item.data();
         handler->updateThread(thread);
     }
     reloadStack(); // Will trigger register reload.
@@ -3027,7 +3025,7 @@ void GdbEngine::handleThreadNames(const DebuggerResponse &response)
         names.fromString(response.consoleStreamOutput);
         for (const GdbMi &name : names.children()) {
             ThreadData thread;
-            thread.id = ThreadId(name["id"].toInt());
+            thread.id = name["id"].data();
             thread.name = decodeData(name["value"].data(), name["valueencoded"].data());
             handler->updateThread(thread);
         }
diff --git a/src/plugins/debugger/gdb/gdbengine.h b/src/plugins/debugger/gdb/gdbengine.h
index dbd437ffd8a..c93178ee71b 100644
--- a/src/plugins/debugger/gdb/gdbengine.h
+++ b/src/plugins/debugger/gdb/gdbengine.h
@@ -219,7 +219,7 @@ private: ////////// General Interface //////////
 
     ////////// View & Data Stuff //////////
 
-    void selectThread(ThreadId threadId) final;
+    void selectThread(const Thread &thread) final;
     void activateFrame(int index) final;
 
     //
diff --git a/src/plugins/debugger/lldb/lldbengine.cpp b/src/plugins/debugger/lldb/lldbengine.cpp
index 952505e51fc..3e5b88d5187 100644
--- a/src/plugins/debugger/lldb/lldbengine.cpp
+++ b/src/plugins/debugger/lldb/lldbengine.cpp
@@ -444,17 +444,18 @@ void LldbEngine::activateFrame(int frameIndex)
 
     DebuggerCommand cmd("activateFrame");
     cmd.arg("index", frameIndex);
-    cmd.arg("thread", threadsHandler()->currentThread().raw());
+    cmd.arg("thread", threadsHandler()->currentThread()->id());
     runCommand(cmd);
 
     updateLocals();
     reloadRegisters();
 }
 
-void LldbEngine::selectThread(ThreadId threadId)
+void LldbEngine::selectThread(const Thread &thread)
 {
+    QTC_ASSERT(thread, return);
     DebuggerCommand cmd("selectThread");
-    cmd.arg("id", threadId.raw());
+    cmd.arg("id", thread->id());
     cmd.callback = [this](const DebuggerResponse &) {
         fetchStack(action(MaximalStackDepth)->value().toInt());
     };
diff --git a/src/plugins/debugger/lldb/lldbengine.h b/src/plugins/debugger/lldb/lldbengine.h
index a6487de3bc0..907a5c2bdfa 100644
--- a/src/plugins/debugger/lldb/lldbengine.h
+++ b/src/plugins/debugger/lldb/lldbengine.h
@@ -82,7 +82,7 @@ private:
     void executeJumpToLine(const ContextData &data) override;
 
     void activateFrame(int index) override;
-    void selectThread(ThreadId threadId) override;
+    void selectThread(const Thread &thread) override;
     void fetchFullBacktrace();
 
     // This should be always the last call in a function.
diff --git a/src/plugins/debugger/pdb/pdbengine.cpp b/src/plugins/debugger/pdb/pdbengine.cpp
index 981951894d6..5089365f7b5 100644
--- a/src/plugins/debugger/pdb/pdbengine.cpp
+++ b/src/plugins/debugger/pdb/pdbengine.cpp
@@ -240,9 +240,9 @@ void PdbEngine::activateFrame(int frameIndex)
     updateLocals();
 }
 
-void PdbEngine::selectThread(ThreadId threadId)
+void PdbEngine::selectThread(const Thread &thread)
 {
-    Q_UNUSED(threadId)
+    Q_UNUSED(thread)
 }
 
 bool PdbEngine::acceptsBreakpoint(const BreakpointParameters &bp) const
diff --git a/src/plugins/debugger/pdb/pdbengine.h b/src/plugins/debugger/pdb/pdbengine.h
index 09966f229ed..420e0639c7b 100644
--- a/src/plugins/debugger/pdb/pdbengine.h
+++ b/src/plugins/debugger/pdb/pdbengine.h
@@ -69,7 +69,7 @@ private:
     void executeJumpToLine(const ContextData &data) override;
 
     void activateFrame(int index) override;
-    void selectThread(ThreadId threadId) override;
+    void selectThread(const Thread &thread) override;
 
     bool acceptsBreakpoint(const BreakpointParameters &bp) const override;
     void insertBreakpoint(const Breakpoint &bp) override;
diff --git a/src/plugins/debugger/qml/qmlengine.cpp b/src/plugins/debugger/qml/qmlengine.cpp
index 8f8816ff449..91bd3e2e552 100644
--- a/src/plugins/debugger/qml/qmlengine.cpp
+++ b/src/plugins/debugger/qml/qmlengine.cpp
@@ -684,9 +684,9 @@ void QmlEngine::activateFrame(int index)
     d->updateLocals();
 }
 
-void QmlEngine::selectThread(ThreadId threadId)
+void QmlEngine::selectThread(const Thread &thread)
 {
-    Q_UNUSED(threadId)
+    Q_UNUSED(thread)
 }
 
 void QmlEngine::insertBreakpoint(const Breakpoint &bp)
diff --git a/src/plugins/debugger/qml/qmlengine.h b/src/plugins/debugger/qml/qmlengine.h
index 76b0452c160..8d407b11ae1 100644
--- a/src/plugins/debugger/qml/qmlengine.h
+++ b/src/plugins/debugger/qml/qmlengine.h
@@ -93,7 +93,7 @@ private:
     void executeJumpToLine(const ContextData &data) override;
 
     void activateFrame(int index) override;
-    void selectThread(ThreadId threadId) override;
+    void selectThread(const Thread &thread) override;
 
     bool acceptsBreakpoint(const BreakpointParameters &bp) const final;
     void insertBreakpoint(const Breakpoint &bp) final;
diff --git a/src/plugins/debugger/threaddata.h b/src/plugins/debugger/threaddata.h
index e54d0f37716..5d7a4a25805 100644
--- a/src/plugins/debugger/threaddata.h
+++ b/src/plugins/debugger/threaddata.h
@@ -31,28 +31,6 @@
 namespace Debugger {
 namespace Internal {
 
-////////////////////////////////////////////////////////////////////////
-//
-// ThreadId
-//
-////////////////////////////////////////////////////////////////////////
-
-/*! A typesafe identifier. */
-class ThreadId
-{
-public:
-    ThreadId() = default;
-    explicit ThreadId(qint64 id) : m_id(id) {}
-
-    bool isValid() const { return m_id != -1; }
-    qint64 raw() const { return m_id; }
-    bool operator==(const ThreadId other) const { return m_id == other.m_id; }
-    bool operator!=(const ThreadId other) const { return m_id != other.m_id; }
-
-private:
-    qint64 m_id = -1;
-};
-
 ////////////////////////////////////////////////////////////////////////
 //
 // ThreadData
@@ -77,12 +55,10 @@ struct ThreadData
         CoreColumn,
         ComboNameColumn,
         ColumnCount = CoreColumn,
-
-        IdRole = Qt::UserRole
     };
 
     // Permanent data.
-    ThreadId id;
+    QString id;
     QString groupId;
     QString targetId;
     QString core;
diff --git a/src/plugins/debugger/threadshandler.cpp b/src/plugins/debugger/threadshandler.cpp
index a4fd57dad61..acb3c4f35b7 100644
--- a/src/plugins/debugger/threadshandler.cpp
+++ b/src/plugins/debugger/threadshandler.cpp
@@ -53,168 +53,156 @@ namespace Internal {
 //
 ///////////////////////////////////////////////////////////////////////
 
-class ThreadItem : public TreeItem
+// ThreadItem
+
+ThreadItem::ThreadItem(const ThreadsHandler *handler, const ThreadData &data)
+    : threadData(data), handler(handler)
+{}
+
+QVariant ThreadItem::data(int column, int role) const
 {
-    Q_DECLARE_TR_FUNCTIONS(Debugger::Internal::ThreadsHandler)
-
-public:
-    ThreadItem(const ThreadsHandler *handler, const ThreadData &data = ThreadData())
-        : threadData(data), handler(handler)
-    {}
-
-    QVariant data(int column, int role) const override
-    {
-        switch (role) {
-        case Qt::DisplayRole:
-            return threadPart(column);
-        case Qt::ToolTipRole:
-            return threadToolTip();
-        case Qt::DecorationRole:
-            // Return icon that indicates whether this is the active stack frame.
-            if (column == 0)
-                return threadData.id == handler->currentThread() ? Icons::LOCATION.icon()
-                                                                 : Icons::EMPTY.icon();
-            break;
-        case ThreadData::IdRole:
-            return threadData.id.raw();
-        default:
-            break;
-        }
-        return QVariant();
+    switch (role) {
+    case Qt::DisplayRole:
+        if (column == 0)
+            return QString("#%1 %2").arg(threadData.id).arg(threadData.name);
+        return threadPart(column);
+    case Qt::ToolTipRole:
+        return threadToolTip();
+    case Qt::DecorationRole:
+        // Return icon that indicates whether this is the active stack frame.
+        if (column == 0)
+            return this == handler->currentThread() ? Icons::LOCATION.icon()
+                                                    : Icons::EMPTY.icon();
+        break;
+    default:
+        break;
     }
+    return QVariant();
+}
 
-    Qt::ItemFlags flags(int column) const override
-    {
-        return threadData.stopped ? TreeItem::flags(column) : Qt::ItemFlags({});
+Qt::ItemFlags ThreadItem::flags(int column) const
+{
+    return threadData.stopped ? TreeItem::flags(column) : Qt::ItemFlags({});
+}
+
+QString ThreadItem::threadToolTip() const
+{
+    const char start[] = "<tr><td>";
+    const char sep[] = "</td><td>";
+    const char end[] = "</td>";
+    QString rc;
+    QTextStream str(&rc);
+    str << "<html><head/><body><table>"
+        << start << ThreadsHandler::tr("Thread&nbsp;id:")
+        << sep << threadData.id << end;
+    if (!threadData.targetId.isEmpty())
+        str << start << ThreadsHandler::tr("Target&nbsp;id:")
+            << sep << threadData.targetId << end;
+    if (!threadData.groupId.isEmpty())
+        str << start << ThreadsHandler::tr("Group&nbsp;id:")
+            << sep << threadData.groupId << end;
+    if (!threadData.name.isEmpty())
+        str << start << ThreadsHandler::tr("Name:")
+            << sep << threadData.name << end;
+    if (!threadData.state.isEmpty())
+        str << start << ThreadsHandler::tr("State:")
+            << sep << threadData.state << end;
+    if (!threadData.core.isEmpty())
+        str << start << ThreadsHandler::tr("Core:")
+            << sep << threadData.core << end;
+    if (threadData.address) {
+        str << start << ThreadsHandler::tr("Stopped&nbsp;at:") << sep;
+        if (!threadData.function.isEmpty())
+            str << threadData.function << "<br>";
+        if (!threadData.fileName.isEmpty())
+            str << threadData.fileName << ':' << threadData.lineNumber << "<br>";
+        str << formatToolTipAddress(threadData.address);
     }
+    str << "</table></body></html>";
+    return rc;
+}
 
-    QString threadToolTip() const
-    {
-        const char start[] = "<tr><td>";
-        const char sep[] = "</td><td>";
-        const char end[] = "</td>";
-        QString rc;
-        QTextStream str(&rc);
-        str << "<html><head/><body><table>"
-            << start << ThreadsHandler::tr("Thread&nbsp;id:")
-            << sep << threadData.id.raw() << end;
-        if (!threadData.targetId.isEmpty())
-            str << start << ThreadsHandler::tr("Target&nbsp;id:")
-                << sep << threadData.targetId << end;
-        if (!threadData.groupId.isEmpty())
-            str << start << ThreadsHandler::tr("Group&nbsp;id:")
-                << sep << threadData.groupId << end;
-        if (!threadData.name.isEmpty())
-            str << start << ThreadsHandler::tr("Name:")
-                << sep << threadData.name << end;
-        if (!threadData.state.isEmpty())
-            str << start << ThreadsHandler::tr("State:")
-                << sep << threadData.state << end;
-        if (!threadData.core.isEmpty())
-            str << start << ThreadsHandler::tr("Core:")
-                << sep << threadData.core << end;
-        if (threadData.address) {
-            str << start << ThreadsHandler::tr("Stopped&nbsp;at:") << sep;
-            if (!threadData.function.isEmpty())
-                str << threadData.function << "<br>";
-            if (!threadData.fileName.isEmpty())
-                str << threadData.fileName << ':' << threadData.lineNumber << "<br>";
-            str << formatToolTipAddress(threadData.address);
-        }
-        str << "</table></body></html>";
-        return rc;
+QVariant ThreadItem::threadPart(int column) const
+{
+    switch (column) {
+    case ThreadData::IdColumn:
+        return threadData.id;
+    case ThreadData::FunctionColumn:
+        return threadData.function;
+    case ThreadData::FileColumn:
+        return threadData.fileName.isEmpty() ? threadData.module : threadData.fileName;
+    case ThreadData::LineColumn:
+        return threadData.lineNumber >= 0
+                ? QString::number(threadData.lineNumber) : QString();
+    case ThreadData::AddressColumn:
+        return threadData.address > 0
+                ? QLatin1String("0x") + QString::number(threadData.address, 16)
+                : QString();
+    case ThreadData::CoreColumn:
+        return threadData.core;
+    case ThreadData::StateColumn:
+        return threadData.state;
+    case ThreadData::TargetIdColumn:
+        if (threadData.targetId.startsWith(QLatin1String("Thread ")))
+            return threadData.targetId.mid(7);
+        return threadData.targetId;
+    case ThreadData::NameColumn:
+        return threadData.name;
+    case ThreadData::DetailsColumn:
+        return threadData.details;
+    case ThreadData::ComboNameColumn:
+        return QString::fromLatin1("#%1 %2").arg(threadData.id).arg(threadData.name);
     }
+    return QVariant();
+}
 
-    QVariant threadPart(int column) const
-    {
-        switch (column) {
-        case ThreadData::IdColumn:
-            return threadData.id.raw();
-        case ThreadData::FunctionColumn:
-            return threadData.function;
-        case ThreadData::FileColumn:
-            return threadData.fileName.isEmpty() ? threadData.module : threadData.fileName;
-        case ThreadData::LineColumn:
-            return threadData.lineNumber >= 0
-                    ? QString::number(threadData.lineNumber) : QString();
-        case ThreadData::AddressColumn:
-            return threadData.address > 0
-                    ? QLatin1String("0x") + QString::number(threadData.address, 16)
-                    : QString();
-        case ThreadData::CoreColumn:
-            return threadData.core;
-        case ThreadData::StateColumn:
-            return threadData.state;
-        case ThreadData::TargetIdColumn:
-            if (threadData.targetId.startsWith(QLatin1String("Thread ")))
-                return threadData.targetId.mid(7);
-            return threadData.targetId;
-        case ThreadData::NameColumn:
-            return threadData.name;
-        case ThreadData::DetailsColumn:
-            return threadData.details;
-        case ThreadData::ComboNameColumn:
-            return QString::fromLatin1("#%1 %2").arg(threadData.id.raw()).arg(threadData.name);
-        }
-        return QVariant();
-    }
+void ThreadItem::notifyRunning() // Clear state information.
+{
+    threadData.address = 0;
+    threadData.function.clear();
+    threadData.fileName.clear();
+    threadData.frameLevel = -1;
+    threadData.state.clear();
+    threadData.lineNumber = -1;
+    threadData.stopped = false;
+    update();
+}
 
-    void notifyRunning() // Clear state information.
-    {
-        threadData.address = 0;
-        threadData.function.clear();
-        threadData.fileName.clear();
-        threadData.frameLevel = -1;
-        threadData.state.clear();
-        threadData.lineNumber = -1;
-        threadData.stopped = false;
-        update();
-    }
+void ThreadItem::notifyStopped()
+{
+    threadData.stopped = true;
+    update();
+}
 
-    void notifyStopped()
-    {
-        threadData.stopped = true;
-        update();
-    }
-
-    void mergeThreadData(const ThreadData &other)
-    {
-        if (!other.core.isEmpty())
-            threadData.core = other.core;
-        if (!other.fileName.isEmpty())
-            threadData.fileName = other.fileName;
-        if (!other.targetId.isEmpty())
-            threadData.targetId = other.targetId;
-        if (!other.name.isEmpty())
-            threadData.name = other.name;
-        if (other.frameLevel != -1)
-            threadData.frameLevel = other.frameLevel;
-        if (!other.function.isEmpty())
-            threadData.function = other.function;
-        if (other.address)
-            threadData.address = other.address;
-        if (!other.module.isEmpty())
-            threadData.module = other.module;
-        if (!other.details.isEmpty())
-            threadData.details = other.details;
-        if (!other.state.isEmpty())
-            threadData.state = other.state;
-        if (other.lineNumber != -1)
-            threadData.lineNumber = other.lineNumber;
-        update();
-    }
+void ThreadItem::mergeThreadData(const ThreadData &other)
+{
+    if (!other.core.isEmpty())
+        threadData.core = other.core;
+    if (!other.fileName.isEmpty())
+        threadData.fileName = other.fileName;
+    if (!other.targetId.isEmpty())
+        threadData.targetId = other.targetId;
+    if (!other.name.isEmpty())
+        threadData.name = other.name;
+    if (other.frameLevel != -1)
+        threadData.frameLevel = other.frameLevel;
+    if (!other.function.isEmpty())
+        threadData.function = other.function;
+    if (other.address)
+        threadData.address = other.address;
+    if (!other.module.isEmpty())
+        threadData.module = other.module;
+    if (!other.details.isEmpty())
+        threadData.details = other.details;
+    if (!other.state.isEmpty())
+        threadData.state = other.state;
+    if (other.lineNumber != -1)
+        threadData.lineNumber = other.lineNumber;
+    update();
+}
 
 
-public:
-    ThreadData threadData;
-    const ThreadsHandler * const handler;
-};
-
-////////////////////////////////////////////////////////////////////////
-//
 // ThreadsHandler
-//
-///////////////////////////////////////////////////////////////////////
 
 /*!
     \class Debugger::Internal::ThreadData
@@ -235,17 +223,17 @@ ThreadsHandler::ThreadsHandler(DebuggerEngine *engine)
 {
     setObjectName(QLatin1String("ThreadsModel"));
     setHeader({
-        QLatin1String("  ") + tr("ID") + QLatin1String("  "),
-        tr("Address"), tr("Function"), tr("File"), tr("Line"), tr("State"),
-        tr("Name"), tr("Target ID"), tr("Details"), tr("Core"),
-    });
+                  QLatin1String("  ") + tr("ID") + QLatin1String("  "),
+                  tr("Address"), tr("Function"), tr("File"), tr("Line"), tr("State"),
+                  tr("Name"), tr("Target ID"), tr("Details"), tr("Core"),
+              });
 }
 
 bool ThreadsHandler::setData(const QModelIndex &idx, const QVariant &data, int role)
 {
     if (role == BaseTreeView::ItemActivatedRole) {
-        ThreadId id = ThreadId(idx.data(ThreadData::IdRole).toLongLong());
-        m_engine->selectThread(id);
+        const Thread thread = itemForIndexAtLevel<1>(idx);
+        m_engine->selectThread(thread);
         return true;
     }
 
@@ -263,21 +251,9 @@ bool ThreadsHandler::setData(const QModelIndex &idx, const QVariant &data, int r
     return false;
 }
 
-static ThreadItem *itemForThreadId(const ThreadsHandler *handler, ThreadId threadId)
-{
-    const auto matcher = [threadId](ThreadItem *item) { return item->threadData.id == threadId; };
-    return handler->findItemAtLevel<1>(matcher);
-}
-
-static int indexForThreadId(const ThreadsHandler *handler, ThreadId threadId)
-{
-    ThreadItem *item = itemForThreadId(handler, threadId);
-    return item ? handler->rootItem()->indexOf(item) : -1;
-}
-
 int ThreadsHandler::currentThreadIndex() const
 {
-    return indexForThreadId(this, m_currentId);
+    return rootItem()->indexOf(m_currentThread);
 }
 
 void ThreadsHandler::sort(int column, Qt::SortOrder order)
@@ -294,36 +270,29 @@ void ThreadsHandler::sort(int column, Qt::SortOrder order)
     });
 }
 
-ThreadId ThreadsHandler::currentThread() const
+Thread ThreadsHandler::currentThread() const
 {
-    return m_currentId;
+    return m_currentThread;
 }
 
-ThreadId ThreadsHandler::threadAt(int index) const
+Thread ThreadsHandler::threadAt(int index) const
 {
-    QTC_ASSERT(index >= 0 && index < rootItem()->childCount(), return ThreadId());
-    return rootItem()->childAt(index)->threadData.id;
+    QTC_ASSERT(index >= 0 && index < rootItem()->childCount(), return Thread());
+    return rootItem()->childAt(index);
 }
 
-void ThreadsHandler::setCurrentThread(ThreadId id)
+void ThreadsHandler::setCurrentThread(const Thread &thread)
 {
-    if (id == m_currentId)
+    if (thread == m_currentThread)
         return;
 
-    ThreadItem *newItem = itemForThreadId(this, id);
-    if (!newItem) {
-        qWarning("ThreadsHandler::setCurrentThreadId: No such thread %d.", int(id.raw()));
+    if (!threadForId(thread->id())) {
+        qWarning("ThreadsHandler::setCurrentThreadId: No such thread %s.", qPrintable(thread->id()));
         return;
     }
 
-    ThreadItem *oldItem = itemForThreadId(this, m_currentId);
-    m_currentId = id;
-    if (oldItem)
-        oldItem->update();
-
-    newItem->update();
-
-    updateThreadBox();
+    m_currentThread = thread;
+    thread->update();
 }
 
 QString ThreadsHandler::pidForGroupId(const QString &groupId) const
@@ -338,43 +307,16 @@ void ThreadsHandler::notifyGroupCreated(const QString &groupId, const QString &p
 
 void ThreadsHandler::updateThread(const ThreadData &threadData)
 {
-    if (ThreadItem *item = itemForThreadId(this, threadData.id))
-        item->mergeThreadData(threadData);
+    if (Thread thread = threadForId(threadData.id))
+        thread->mergeThreadData(threadData);
     else
         rootItem()->appendChild(new ThreadItem(this, threadData));
 }
 
-void ThreadsHandler::removeThread(ThreadId threadId)
+void ThreadsHandler::removeThread(const QString &id)
 {
-    if (ThreadItem *item = itemForThreadId(this, threadId))
-        destroyItem(item);
-}
-
-void ThreadsHandler::setThreads(const Threads &threads)
-{
-    auto root = new ThreadItem(this);
-    for (int i = 0, n = threads.size(); i < n; ++i)
-        root->appendChild(new ThreadItem(this, threads.at(i)));
-    rootItem()->removeChildren();
-    setRootItem(root);
-    m_resetLocationScheduled = false;
-    updateThreadBox();
-}
-
-void ThreadsHandler::updateThreadBox()
-{
-    QStringList list;
-    forItemsAtLevel<1>([&list](ThreadItem *item) {
-        list.append(QString::fromLatin1("#%1 %2").arg(item->threadData.id.raw()).arg(item->threadData.name));
-    });
-    m_engine->setThreadBoxContents(list, indexForThreadId(this, m_currentId));
-}
-
-ThreadData ThreadsHandler::thread(ThreadId id) const
-{
-    if (ThreadItem *item = itemForThreadId(this, id))
-        return item->threadData;
-    return ThreadData();
+    if (Thread thread = threadForId(id))
+        destroyItem(thread);
 }
 
 void ThreadsHandler::removeAll()
@@ -396,54 +338,27 @@ bool ThreadsHandler::notifyGroupExited(const QString &groupId)
     return m_pidForGroupId.isEmpty();
 }
 
-void ThreadsHandler::notifyRunning(const QString &data)
+Thread ThreadsHandler::threadForId(const QString &id) const
 {
-    if (data.isEmpty() || data == "all") {
-        notifyAllRunning();
-    } else {
-        bool ok;
-        qlonglong id = data.toLongLong(&ok);
-        if (ok)
-            notifyRunning(ThreadId(id));
-        else // FIXME
-            notifyAllRunning();
-    }
+    return findItemAtLevel<1>([id](const Thread &item) {
+        return item->threadData.id == id;
+    });
 }
 
-void ThreadsHandler::notifyAllRunning()
+void ThreadsHandler::notifyRunning(const QString &id)
 {
-    forItemsAtLevel<1>([](ThreadItem *item) { item->notifyRunning(); });
+    if (id.isEmpty() || id == "all")
+        forItemsAtLevel<1>([](const Thread &thread) { thread->notifyRunning(); });
+    else if (Thread thread = threadForId(id))
+        thread->notifyRunning();
 }
 
-void ThreadsHandler::notifyRunning(ThreadId threadId)
+void ThreadsHandler::notifyStopped(const QString &id)
 {
-    if (ThreadItem *item = itemForThreadId(this, threadId))
-        item->notifyRunning();
-}
-
-void ThreadsHandler::notifyStopped(const QString &data)
-{
-    if (data.isEmpty() || data == "all") {
-        notifyAllStopped();
-    } else {
-        bool ok;
-        qlonglong id = data.toLongLong(&ok);
-        if (ok)
-            notifyRunning(ThreadId(id));
-        else // FIXME
-            notifyAllStopped();
-    }
-}
-
-void ThreadsHandler::notifyAllStopped()
-{
-    forItemsAtLevel<1>([](ThreadItem *item) { item->notifyStopped(); });
-}
-
-void ThreadsHandler::notifyStopped(ThreadId threadId)
-{
-    if (ThreadItem *item = itemForThreadId(this, threadId))
-        item->notifyStopped();
+    if (id.isEmpty() || id == "all")
+        forItemsAtLevel<1>([](const Thread &thread) { thread->notifyStopped(); });
+    else if (Thread thread = threadForId(id))
+        thread->notifyStopped();
 }
 
 void ThreadsHandler::updateThreads(const GdbMi &data)
@@ -453,13 +368,11 @@ void ThreadsHandler::updateThreads(const GdbMi &data)
     // file="/.../app.cpp",fullname="/../app.cpp",line="1175"},
     // state="stopped",core="0"}],current-thread-id="1"
 
-    const QVector<GdbMi> items = data["threads"].children();
-    const int n = int(items.size());
-    for (int index = 0; index != n; ++index) {
-        const GdbMi item = items[index];
-        const GdbMi frame = item["frame"];
+    const QVector<GdbMi> &items = data["threads"].children();
+    for (const GdbMi &item : items) {
+        const GdbMi &frame = item["frame"];
         ThreadData thread;
-        thread.id = ThreadId(item["id"].toInt());
+        thread.id = item["id"].data();
         thread.targetId = item["target-id"].data();
         thread.details = item["details"].data();
         thread.core = item["core"].data();
@@ -474,10 +387,8 @@ void ThreadsHandler::updateThreads(const GdbMi &data)
         updateThread(thread);
     }
 
-    const GdbMi current = data["current-thread-id"];
-    m_currentId = current.isValid() ? ThreadId(current.data().toLongLong()) : ThreadId();
-
-    updateThreadBox();
+    const QString &currentId = data["current-thread-id"].data();
+    m_currentThread = threadForId(currentId);
 }
 
 void ThreadsHandler::scheduleResetLocation()
diff --git a/src/plugins/debugger/threadshandler.h b/src/plugins/debugger/threadshandler.h
index 8f0b662afea..d071d02fac1 100644
--- a/src/plugins/debugger/threadshandler.h
+++ b/src/plugins/debugger/threadshandler.h
@@ -29,6 +29,8 @@
 
 #include <utils/treemodel.h>
 
+#include <QPointer>
+
 ////////////////////////////////////////////////////////////////////////
 //
 // ThreadsHandler
@@ -40,7 +42,33 @@ namespace Internal {
 
 class DebuggerEngine;
 class GdbMi;
-class ThreadItem;
+class ThreadsHandler;
+
+class ThreadItem : public QObject, public Utils::TreeItem
+{
+    Q_OBJECT
+
+public:
+    ThreadItem(const ThreadsHandler *handler, const ThreadData &data = ThreadData());
+
+    QVariant data(int column, int role) const override;
+    Qt::ItemFlags flags(int column) const override;
+
+    QString threadToolTip() const;
+    QVariant threadPart(int column) const;
+
+    void notifyRunning();
+    void notifyStopped();
+
+    void mergeThreadData(const ThreadData &other);
+    QString id() const { return threadData.id; }
+
+public:
+    ThreadData threadData;
+    const ThreadsHandler * const handler;
+};
+
+using Thread = QPointer<ThreadItem>;
 
 class ThreadsHandler : public Utils::TreeModel<Utils::TypedTreeItem<ThreadItem>, ThreadItem>
 {
@@ -50,43 +78,34 @@ public:
     explicit ThreadsHandler(DebuggerEngine *engine);
 
     int currentThreadIndex() const;
-    ThreadId currentThread() const;
-    ThreadId threadAt(int index) const;
-    void setCurrentThread(ThreadId id);
+    Thread currentThread() const;
+    Thread threadAt(int index) const;
+    Thread threadForId(const QString &id) const;
+    void setCurrentThread(const Thread &thread);
     QString pidForGroupId(const QString &groupId) const;
 
     void updateThread(const ThreadData &threadData);
     void updateThreads(const GdbMi &data);
 
-    void removeThread(ThreadId threadId);
-    void setThreads(const Threads &threads);
+    void removeThread(const QString &id);
     void removeAll();
-    ThreadData thread(ThreadId id) const;
     QAbstractItemModel *model();
 
     void notifyGroupCreated(const QString &groupId, const QString &pid);
     bool notifyGroupExited(const QString &groupId); // Returns true when empty.
 
-    // Clear out all frame information
-    void notifyRunning(const QString &data);
-    void notifyRunning(ThreadId threadId);
-    void notifyAllRunning();
-
-    void notifyStopped(const QString &data);
-    void notifyStopped(ThreadId threadId);
-    void notifyAllStopped();
+    void notifyRunning(const QString &id);
+    void notifyStopped(const QString &id);
 
     void resetLocation();
     void scheduleResetLocation();
 
 private:
-    void updateThreadBox();
-
     void sort(int column, Qt::SortOrder order) override;
     bool setData(const QModelIndex &idx, const QVariant &data, int role) override;
 
     DebuggerEngine *m_engine;
-    ThreadId m_currentId;
+    Thread m_currentThread;
     bool m_resetLocationScheduled = false;
     QHash<QString, QString> m_pidForGroupId;
 };