Merge branch 'delete-to-trash'

Delete moves mail into the account's trash folder instead of only tagging it,
with a Trash filter, Restore from trash, and a repeatable cleanup for the mail
the old behaviour stranded.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

11 files changed, 1783 insertions, 37 deletions

diff --git a/src/config.cpp b/src/config.cpp
index 600c558..a2d1cec 100644
--- a/src/config.cpp
+++ b/src/config.cpp
@@ -60,7 +60,8 @@ constexpr int kQueriesFormatVersion = 1;
 const QStringList kQueryGenerators = { QStringLiteral("unread"),
                                        QStringLiteral("inbox"),
                                        QStringLiteral("flagged"),
-                                       QStringLiteral("sent") };
+                                       QStringLiteral("sent"),
+                                       QStringLiteral("trash") };
 
 /// The tag a generator matches, for the three filters that are a plain tag
 /// query. Empty for "sent", which composes from each account's folder instead
@@ -137,6 +138,23 @@ QString Account::draftsQuery() const
     return folderQuery(maildir, drafts);
 }
 
+QString Account::trashQuery() const
+{
+    return folderQuery(maildir, trash);
+}
+
+QString Account::inboxFolder() const
+{
+    // Never empty: Restore needs a folder to name, and "Inbox" is both the
+    // Maildir convention and what mbsync's own Inbox directive defaults to.
+    return inbox.isEmpty() ? QStringLiteral("Inbox") : inbox;
+}
+
+QString Account::inboxQuery() const
+{
+    return folderQuery(maildir, inboxFolder());
+}
+
 QString Config::allSentQuery() const
 {
     return joinAccountQueries(m_accounts, &Account::sentQuery);
@@ -147,6 +165,11 @@ QString Config::allDraftsQuery() const
     return joinAccountQueries(m_accounts, &Account::draftsQuery);
 }
 
+QString Config::allTrashQuery() const
+{
+    return joinAccountQueries(m_accounts, &Account::trashQuery);
+}
+
 QString Config::defaultPath()
 {
     const QString base =
@@ -433,6 +456,19 @@ void Config::load(const QString &path)
         account.sent =
             settings.value(QStringLiteral("sent")).toString().trimmed();
 
+        // Mandatory, unlike sent: Delete moves a file into this folder, so an
+        // account without one cannot delete at all. Trimmed for the same
+        // reason as sent, above.
+        account.trash =
+            settings.value(QStringLiteral("trash")).toString().trimmed();
+
+        // Optional, unlike trash: inboxFolder() defaults it to "Inbox", which
+        // is right for any ordinary Maildir. Read so an account whose inbox is
+        // named otherwise can say so, rather than having Restore create a
+        // second folder under a name this program assumed.
+        account.inbox =
+            settings.value(QStringLiteral("inbox")).toString().trimmed();
+
         // Both optional, and both describe this account's chip in the thread
         // list. An account tag is a different taxonomy from a functional one,
         // saying which mailbox a thread arrived in rather than what state it
@@ -462,6 +498,21 @@ void Config::load(const QString &path)
                     .arg(account.key));
             continue;
         }
+
+        // Mandatory, unlike sent: Delete moves a file into this folder, so an
+        // account without one cannot delete at all. Reported rather than
+        // silently disabled, so the user finds out from a warning rather than
+        // from a Delete that quietly does nothing. The account still loads;
+        // only Delete is unusable, which does not warrant losing the rest of
+        // the account's mail.
+        if (account.trash.isEmpty()) {
+            addProblem(
+                tr("Account '%1' has no trash folder configured; add a "
+                   "'trash' key to its section. Delete will not work for "
+                   "this account until it does.")
+                    .arg(account.key));
+        }
+
         m_accounts.append(account);
     }
 
@@ -711,6 +762,8 @@ QString Config::resolvedQuery(const SavedQuery &query) const
     if (query.isGenerated()) {
         if (query.generated == QStringLiteral("sent"))
             return allSentQuery();
+        if (query.generated == QStringLiteral("trash"))
+            return allTrashQuery();
         // An unknown generator was reported on load. Empty rather than the
         // bare stored query, which for a generated entry is empty anyway and
         // would otherwise run as "match everything".
@@ -783,6 +836,11 @@ SavedQuery Config::builtinFilter(const QString &generator)
         // thread would fold the user's sent message back into the conversation
         // it belongs to, which is item 63's finding.
         filter.flat = true;
+    } else if (generator == QStringLiteral("trash")) {
+        filter.name = tr("Trash");
+        // NOT flat, unlike Sent. A deleted message still belongs to its
+        // conversation, and folding it back is what Sent had to avoid rather
+        // than something every folder filter wants.
     }
 
     return filter;
@@ -807,6 +865,10 @@ QString Config::resolvedQuery(const SavedQuery &query,
             const QString all = allSentQuery();
             return all.isEmpty() ? matchNothingQuery() : all;
         }
+        if (query.generated == QStringLiteral("trash")) {
+            const QString all = allTrashQuery();
+            return all.isEmpty() ? matchNothingQuery() : all;
+        }
         return QStringLiteral("tag:%1").arg(generatorTag(query.generated));
     }
 
@@ -827,6 +889,14 @@ QString Config::resolvedQuery(const SavedQuery &query,
         return sent.isEmpty() ? matchNothingQuery() : sent;
     }
 
+    if (query.generated == QStringLiteral("trash")) {
+        // The account's OWN trash query, for the reason spelled out above the
+        // sent case: wrapping the all-accounts query in this account's path
+        // works by accident of path: being hierarchical.
+        const QString trash = scope.trashQuery();
+        return trash.isEmpty() ? matchNothingQuery() : trash;
+    }
+
     // A tag filter carries no path of its own, so scoping is exactly what
     // scopedQuery() does. Its parentheses are load-bearing: `path:... and a or
     // b` binds as `(path:... and a) or b`.
diff --git a/src/config.h b/src/config.h
index 70f7181..ede5dea 100644
--- a/src/config.h
+++ b/src/config.h
@@ -58,6 +58,29 @@ struct Account
     /// one for the account that has none.
     QString sent;
 
+    /// The account's trash folder, relative to maildir.
+    ///
+    /// MANDATORY, unlike `sent` and `drafts`. Delete moves a file into this
+    /// folder, so an account without one cannot delete at all, and the user
+    /// chose a config error over a per-account disabled state: "it is
+    /// mandatory for the program to function properly". Config::load()
+    /// reports a missing key through the warnings path.
+    QString trash;
+
+    /// The account's inbox folder, relative to maildir. Optional.
+    ///
+    /// Only Restore reads it, as the destination for a message that carries no
+    /// `deleted-from:` origin, which is what mail trashed by another client
+    /// looks like. Defaults to "Inbox", the Maildir convention and mbsync's
+    /// own default.
+    ///
+    /// Configurable rather than hardcoded because the name is not ours to
+    /// assume: naming a folder that does not exist CREATES it, beside the real
+    /// one, and under mbsync's `Create Both` that folder reaches the server.
+    /// Unlike `trash` this is optional, since the default is right for every
+    /// ordinary Maildir and a wrong guess here only affects the fallback.
+    QString inbox;
+
     /// Chip colour in the thread list. Invalid when unset, in which case one
     /// is generated from the account tag's name.
     QColor color;
@@ -98,6 +121,20 @@ struct Account
     /// keys are independent, and one real account configures `drafts` with no
     /// `sent` at all.
     QString draftsQuery() const;
+
+    /// Matches this account's trash, or empty when `trash` is unset.
+    ///
+    /// Empty is a config error rather than a legitimate state, unlike
+    /// sentQuery(). The query helper still returns empty so callers compose
+    /// uniformly; it is Config::load() that reports the problem.
+    QString trashQuery() const;
+
+    /// Matches this account's inbox folder, using inboxFolder().
+    QString inboxQuery() const;
+
+    /// The inbox folder name, which is `inbox` when set and "Inbox"
+    /// otherwise. Never empty, so a caller always has a folder to name.
+    QString inboxFolder() const;
 };
 
 /// A named query, stored in queries.json.
@@ -275,6 +312,13 @@ public:
     /// open-coded at the call site.
     QString allSentQuery() const;
 
+    /// Matches every configured account's trash, or empty when none has one.
+    ///
+    /// Joins only the NON-EMPTY trashQuery() results, for the same reason
+    /// allSentQuery() does: notmuch accepts a bare "or" without complaint and
+    /// silently answers a different question.
+    QString allTrashQuery() const;
+
     /// Matches every configured account's drafts, or empty when none has one.
     ///
     /// Joins only the NON-EMPTY draftsQuery() results, for the same reason
diff --git a/src/keymap.cpp b/src/keymap.cpp
index c731bbb..76c6b60 100644
--- a/src/keymap.cpp
+++ b/src/keymap.cpp
@@ -31,6 +31,8 @@ QStringList KeyMap::knownActions()
         QStringLiteral("open_thread"),
         QStringLiteral("archive"),
         QStringLiteral("delete"),
+        QStringLiteral("restore"),
+        QStringLiteral("cleanup_stranded"),
         QStringLiteral("spam"),
         QStringLiteral("toggle_unread"),
         QStringLiteral("mark_all_read"),
@@ -97,7 +99,31 @@ QList<QPair<QString, QString>> KeyMap::defaultBindings()
         { QStringLiteral("Alt+Up"),        QStringLiteral("prev_thread") },
         { QStringLiteral("Return"),       QStringLiteral("open_thread") },
         { QStringLiteral("Ctrl+E"),       QStringLiteral("archive") },
+        // Del FIRST, and the order matters twice over. defaultSequenceFor()
+        // returns the first match, and sequenceFor() prefers any binding that
+        // is not that default, treating it as a user override; listing Del
+        // second therefore made it the "override" of Ctrl+D and left the two
+        // functions disagreeing about which key the menus should advertise.
+        // First also makes it the ADVERTISED one, which is the point: it is
+        // the key a user reaches for, and Ctrl+D is not a guess anyone makes.
+        //
+        // Bare, which is safe for a reason that does NOT generalise to other
+        // bare keys. Delete is not a letter, so Qt's protection for editable
+        // widgets does not cover it, but QLineEdit accepts the
+        // ShortcutOverride for Delete itself, because it is one of its own
+        // editing keys. Return is not, which is why that one needed an
+        // explicit filter in MainWindow::eventFilter() and this one does not.
+        // Measured both ways; see theDeleteKeyEditsTextInTheQueryBar().
+        { QStringLiteral("Del"),          QStringLiteral("delete") },
         { QStringLiteral("Ctrl+D"),       QStringLiteral("delete") },
+        // Restore is only enabled in the trash view, so its key is dead
+        // elsewhere rather than doing something surprising.
+        { QStringLiteral("Ctrl+R"),       QStringLiteral("restore") },
+        // Item 103's cleanup. A chord rather than a plain key: it replaces the
+        // whole view, and it is reached from a menu far more often than from
+        // the keyboard. Ctrl+Shift+D is message_details and Ctrl+Alt+D is
+        // delete_thread, so this takes the T of "trash".
+        { QStringLiteral("Ctrl+Alt+T"),   QStringLiteral("cleanup_stranded") },
         { QStringLiteral("Ctrl+Shift+S"), QStringLiteral("spam") },
         { QStringLiteral("Ctrl+U"),       QStringLiteral("toggle_unread") },
         // Shifted against Ctrl+U, which toggles unread on the selection: this
@@ -246,7 +272,7 @@ QKeySequence KeyMap::sequenceFor(const QString &action) const
         if (it.value() != action)
             continue;
 
-        const bool isBuiltIn = !builtIn.isEmpty() && it.key() == builtIn;
+        const bool isBuiltIn = isDefaultBinding(it.key(), action);
         if (best.isEmpty()) {
             best = it.key();
             bestIsBuiltIn = isBuiltIn;
@@ -256,6 +282,13 @@ QKeySequence KeyMap::sequenceFor(const QString &action) const
         if (bestIsBuiltIn && !isBuiltIn) {
             best = it.key();
             bestIsBuiltIn = false;
+        } else if (bestIsBuiltIn && isBuiltIn) {
+            // Both are defaults, so the ADVERTISED one is whichever
+            // defaultBindings() lists first: that order is the author's
+            // preference and is why Del is listed before Ctrl+D. Falling back
+            // to alphabetical here would advertise Ctrl+D instead.
+            if (it.key() == builtIn)
+                best = it.key();
         } else if (bestIsBuiltIn == isBuiltIn
                    && it.key().toString() < best.toString()) {
             best = it.key();
@@ -264,6 +297,27 @@ QKeySequence KeyMap::sequenceFor(const QString &action) const
     return best;
 }
 
+bool KeyMap::isDefaultBinding(const QKeySequence &sequence,
+                             const QString &action)
+{
+    // ANY of the action's defaults, not just the first.
+    //
+    // An action can ship with more than one binding: `delete` has Del and
+    // Ctrl+D. sequenceFor() compares against defaultSequenceFor(), which
+    // returns only the first, so the second looked like a USER binding and
+    // won the "a user binding always beats the default" rule. The menus then
+    // advertised Ctrl+D for a user who had configured nothing, and
+    // sequenceFor() and defaultSequenceFor() disagreed about an untouched
+    // action.
+    for (const auto &binding : defaultBindings()) {
+        if (binding.second == action
+            && normalizeSequence(binding.first) == sequence) {
+            return true;
+        }
+    }
+    return false;
+}
+
 QKeySequence KeyMap::defaultSequenceFor(const QString &action)
 {
     for (const auto &binding : defaultBindings()) {
diff --git a/src/keymap.h b/src/keymap.h
index 81e1813..8774209 100644
--- a/src/keymap.h
+++ b/src/keymap.h
@@ -73,6 +73,14 @@ public:
     /// The built-in sequence for an action, ignoring any user override.
     static QKeySequence defaultSequenceFor(const QString &action);
 
+    /// Whether `sequence` is ANY of `action`'s default bindings.
+    ///
+    /// Not the same question as `sequence == defaultSequenceFor(action)`: an
+    /// action can ship several, and comparing against only the first makes the
+    /// others look like user overrides.
+    static bool isDefaultBinding(const QKeySequence &sequence,
+                                 const QString &action);
+
     /// Every action name carrying a built-in binding.
     static QStringList defaultActions();
 
diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
index 594535b..58c82ca 100644
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -214,7 +214,7 @@ void MainWindow::closeEvent(QCloseEvent *event)
             // Degrade to a warning rather than offering a sync that cannot run.
             const auto answer = QMessageBox::warning(
                 this, tr("Unsynced changes"),
-                tr("%n tag change(s) have not been synced, and no sync command "
+                tr("%n change(s) have not been synced, and no sync command "
                    "is configured. Quit anyway?", "", pendingEditCount()),
                 QMessageBox::Discard | QMessageBox::Cancel,
                 QMessageBox::Cancel);
@@ -228,7 +228,7 @@ void MainWindow::closeEvent(QCloseEvent *event)
             QMessageBox box(this);
             box.setIcon(QMessageBox::Question);
             box.setWindowTitle(tr("Unsynced changes"));
-            box.setText(tr("%n tag change(s) have not been synced.", "",
+            box.setText(tr("%n change(s) have not been synced.", "",
                            pendingEditCount()));
             box.setInformativeText(tr("Sync before quitting?"));
             QPushButton *sync =
@@ -309,6 +309,18 @@ bool MainWindow::eventFilter(QObject *watched, QEvent *event)
             keyEvent->accept();
             return true;
         }
+        // Delete needs NO entry here, and that is worth stating because the
+        // reasoning that says it does is nearly right. It is bound bare to
+        // `delete`, and Qt's protection for editable widgets covers plain
+        // LETTERS only, so by the same argument that made Return a problem it
+        // should trigger the action while the user edits a query.
+        //
+        // It does not, because QLineEdit accepts the ShortcutOverride for
+        // Delete itself: Delete is one of its own editing keys, which Return
+        // is not. Measured both ways, with this branch present and absent:
+        // the action fires 0 times either way and the text is edited either
+        // way. Adding a guard here would be dead code carrying a test that
+        // cannot fail.
     }
 
     return QMainWindow::eventFilter(watched, event);
@@ -841,10 +853,23 @@ void MainWindow::registerActions()
         // is about reading a message at all.
         const bool allDeleted = everySelectedRowHasTag(QStringLiteral("deleted"));
 
+        // Item 103. A MOVE now, not only a tag: Delete used to add `deleted`
+        // and leave the file exactly where it was, so deleted mail sat in the
+        // inbox indefinitely and only the chip said otherwise.
         if (allDeleted)
-            tagSelected({}, { QStringLiteral("deleted") }, tr("Undelete"));
+            restoreSelected();
         else
-            tagSelected({ QStringLiteral("deleted") }, {}, tr("Delete"));
+            trashSelected();
+    });
+    addAction(QStringLiteral("restore"), tr("&Restore from trash"),
+              tr("Move the selected messages out of the trash"), [this]() {
+        restoreSelectedFromTrash();
+    });
+    addAction(QStringLiteral("cleanup_stranded"),
+              tr("Find &stranded deleted mail"),
+              tr("Show mail tagged deleted that is not in a trash folder"),
+              [this]() {
+        showStrandedDeletedMail();
     });
     addAction(QStringLiteral("spam"), tr("Mark &spam"),
               tr("Add spam and remove inbox"), [this]() {
@@ -930,12 +955,19 @@ void MainWindow::registerActions()
     });
     addAction(QStringLiteral("delete_thread"), tr("&Delete thread"),
               tr("Add or remove the deleted tag on whole threads"), [this]() {
+        // A MOVE now, like its message-scoped twin. It tagged and moved
+        // nothing until item 103's follow-up, so "Delete thread" left a whole
+        // conversation sitting in the inbox wearing a `deleted` chip: exactly
+        // the half-deleted state Delete stopped producing.
+        //
+        // The direction is read per MESSAGE, not from the thread's tag union.
+        // A thread whose root was deleted on its own carries `deleted` in the
+        // union while its replies do not, and asking the union there ran
+        // Delete a second time on messages already in the trash.
         if (everySelectedRowHasTag(QStringLiteral("deleted"), TagScope::Thread)) {
-            tagSelected({}, { QStringLiteral("deleted") },
-                        tr("Undelete thread"), TagScope::Thread);
+            restoreSelectedThreads();
         } else {
-            tagSelected({ QStringLiteral("deleted") }, {}, tr("Delete thread"),
-                        TagScope::Thread);
+            trashSelectedThreads();
         }
     });
     addAction(QStringLiteral("spam_thread"), tr("Mark thread as &spam"),
@@ -1126,6 +1158,11 @@ void MainWindow::buildMenus()
     auto *messageMenu = menuBar()->addMenu(tr("&Message"));
     messageMenu->addAction(m_actions.value(QStringLiteral("archive")));
     messageMenu->addAction(m_actions.value(QStringLiteral("delete")));
+    // Beside Delete, whose inverse it is. Greyed outside the trash view
+    // rather than hidden: an action that vanishes teaches nothing, while a
+    // disabled entry with its shortcut beside it says both that it exists and
+    // where it applies.
+    messageMenu->addAction(m_actions.value(QStringLiteral("restore")));
     messageMenu->addAction(m_actions.value(QStringLiteral("spam")));
     messageMenu->addSeparator();
     messageMenu->addAction(m_actions.value(QStringLiteral("toggle_unread")));
@@ -1137,11 +1174,23 @@ void MainWindow::buildMenus()
     // Separated from the entries above: those act on the selection, this edits
     // a rule store shared with mailctl and changes nothing that is on screen.
     messageMenu->addSeparator();
+    // A MENU entry and nothing else, at the user's request: "the cleanup
+    // should be a menu entry only, not to be confused with the filter Trash".
+    // It replaces the whole view like a filter does, so a sixth button beside
+    // the five filters would read as one of them.
+    messageMenu->addAction(m_actions.value(QStringLiteral("cleanup_stranded")));
     messageMenu->addAction(m_actions.value(QStringLiteral("tag_rules")));
 
     auto *viewMenu = menuBar()->addMenu(tr("&View"));
     viewMenu->addAction(m_actions.value(QStringLiteral("prev_thread")));
     viewMenu->addAction(m_actions.value(QStringLiteral("next_thread")));
+    viewMenu->addAction(m_actions.value(QStringLiteral("open_thread")));
+    viewMenu->addSeparator();
+    // The two clears. Both shipped keyboard-only, which is what
+    // everyActionIsReachableFromAMenu() exists to stop: an action reachable
+    // only by a chord is an action nobody discovers.
+    viewMenu->addAction(m_actions.value(QStringLiteral("clear_pane")));
+    viewMenu->addAction(m_actions.value(QStringLiteral("clear_selection")));
     viewMenu->addSeparator();
     viewMenu->addAction(m_actions.value(QStringLiteral("toggle_html")));
     viewMenu->addAction(m_actions.value(QStringLiteral("load_remote")));
@@ -1183,6 +1232,13 @@ void MainWindow::buildMenus()
         // control: two buttons with different consequences looked identical.
         { QStringLiteral("archive"), QStringLiteral("mail-archive") },
         { QStringLiteral("delete"),  QStringLiteral("edit-delete") },
+        // The inverse of delete, and the theme's own name for it: the icon
+        // every desktop uses for taking something back out of the wastebasket.
+        { QStringLiteral("restore"), QStringLiteral("edit-undelete") },
+        // A SEARCH, not a delete. The action reports what it finds and moves
+        // nothing, so an icon from the delete family would promise the one
+        // thing it deliberately does not do.
+        { QStringLiteral("cleanup_stranded"), QStringLiteral("system-search") },
         { QStringLiteral("undo"),    QStringLiteral("edit-undo") },
         { QStringLiteral("spam"),    QStringLiteral("mail-mark-junk") },
         { QStringLiteral("flag"),    QStringLiteral("mail-mark-important") },
@@ -1249,6 +1305,7 @@ void MainWindow::buildMenus()
     m_threadContextMenu->setObjectName(QStringLiteral("threadContextMenu"));
     m_threadContextMenu->addAction(m_actions.value(QStringLiteral("archive")));
     m_threadContextMenu->addAction(m_actions.value(QStringLiteral("delete")));
+    m_threadContextMenu->addAction(m_actions.value(QStringLiteral("restore")));
     m_threadContextMenu->addAction(m_actions.value(QStringLiteral("spam")));
     m_threadContextMenu->addSeparator();
     m_threadContextMenu->addAction(m_actions.value(QStringLiteral("toggle_unread")));
@@ -1604,6 +1661,15 @@ void MainWindow::wireWorker()
     connect(m_worker, &NotmuchWorker::tagsApplied,
             this, &MainWindow::onTagsApplied);
 
+    // messagesMovedFrom rather than messagesMoved: the tags a move carries can
+    // only be resolved once the origins are known, and that signal is the one
+    // that reports them.
+    connect(m_worker, &NotmuchWorker::messagesMovedFrom,
+            this, &MainWindow::onMessagesMoved);
+
+    connect(m_worker, &NotmuchWorker::threadMessagesResolved,
+            this, &MainWindow::onThreadMessagesResolved);
+
     m_workerThread.start();
 
     // Queued behind the thread start, so the completer has real tags as soon
@@ -1893,6 +1959,7 @@ void MainWindow::buildSavedQueryRow(QWidget *parent, QVBoxLayout *layout)
             { QStringLiteral("inbox"),   QStringLiteral("mail-inbox") },
             { QStringLiteral("flagged"), QStringLiteral("starred") },
             { QStringLiteral("sent"),    QStringLiteral("mail-folder-sent") },
+            { QStringLiteral("trash"),   QStringLiteral("user-trash") },
         };
         button->setIcon(
             QIcon::fromTheme(filterIcons.value(filter.generated)));
@@ -2439,8 +2506,40 @@ void MainWindow::onQueryFinished(int total, quint64 generation)
     applyPendingRecovery();
 }
 
+bool MainWindow::isShowingTrash() const
+{
+    // Compared against the trash GENERATOR's query, not against the word
+    // "trash" or against a tag. The trash view is path-based so that mail
+    // trashed by another client shows up in it; deciding this from
+    // `tag:deleted` instead would disable Restore on exactly the messages
+    // that most need it, which is the case Restore's fallback exists for.
+    //
+    // Both scopes, because the view composes with the account dropdown like
+    // every other filter: one account's trash, or all of them.
+    const QString query = m_lastQuery.trimmed();
+    if (query.isEmpty())
+        return false;
+
+    const QString all = m_config.allTrashQuery().trimmed();
+    if (!all.isEmpty() && query == all)
+        return true;
+
+    for (const Account &account : m_config.accounts()) {
+        const QString trash = account.trashQuery().trimmed();
+        if (!trash.isEmpty() && query == trash)
+            return true;
+    }
+    return false;
+}
+
 void MainWindow::updateViewWideActions()
 {
+    // Only meaningful on mail that is actually in a trash folder. An enabled
+    // action that does nothing is worse than an absent one, and Restore
+    // outside the trash has nothing to restore from.
+    if (QAction *action = m_actions.value(QStringLiteral("restore")))
+        action->setEnabled(isShowingTrash());
+
     // Threads arrive in batches of kBatchSize, so before the query reports its
     // total the model holds only what has landed. An action that says "all"
     // must not run against a partial set and silently skip the rest, and a
@@ -2921,6 +3020,21 @@ bool MainWindow::aSyncHoldsTheWriteLock() const
 
 void MainWindow::flushHeldEdits()
 {
+    // Moves first, and they are flushed even when no tag edit is waiting: the
+    // early return below used to be the whole guard, so a held move with an
+    // empty edit queue would never have been sent at all. That is item 106's
+    // data loss with a worse shape, since a dropped move leaves the file where
+    // the user asked it not to be.
+    if (!m_heldMoves.isEmpty()) {
+        const QVector<HeldMove> moves = m_heldMoves;
+        m_heldMoves.clear();
+        for (const HeldMove &move : moves) {
+            sendMove(move.messageIds, move.destFolder, move.add, move.remove,
+                     move.description, move.fromUndo);
+        }
+        updatePendingIndicator();
+    }
+
     if (m_heldEdits.isEmpty())
         return;
 
@@ -3731,7 +3845,15 @@ int MainWindow::pendingEditCount() const
     // Each held edit counts as one whatever its size, since it carries thread
     // ids rather than message ids and cannot be netted against the map.
     const int held = int(m_heldEdits.size());
-    return m_pendingTagEdits.size() + m_unnettablePendingEdits + held;
+    // Held MOVES count for exactly the same reason, and were missed. With no
+    // tag edit queued the count was 0, so the indicator stayed hidden and
+    // closeEvent()'s `pendingEditCount() > 0` guard never fired: a Delete
+    // pressed during a sync was discarded on quit with no prompt at all. That
+    // is item 106's data loss, and worse here, because a dropped move leaves
+    // the file in the folder the user asked it out of.
+    const int heldMoves = int(m_heldMoves.size());
+    return m_pendingTagEdits.size() + m_unnettablePendingEdits + held
+           + heldMoves;
 }
 
 void MainWindow::updatePendingIndicator()
@@ -3746,7 +3868,7 @@ void MainWindow::updatePendingIndicator()
     // they did, not the writes it became.
     m_pendingLabel->setText(tr("%n unsynced change(s)", "", pending));
     m_pendingLabel->setToolTip(
-        tr("Tag changes made here that a sync has not yet carried to the mail "
+        tr("Changes made here that a sync has not yet carried to the mail "
            "store. An external notmuch run can clear them without this count "
            "noticing."));
     m_pendingLabel->show();
@@ -3870,22 +3992,43 @@ bool MainWindow::everySelectedRowHasTag(const QString &tag,
         } else if (m_model->isMessageRow(index)) {
             tags = m_model->messageAt(index).tags;
         } else {
-            // The thread's summary, and this is a KNOWN approximation rather
-            // than an oversight. A thread row acts on the message its card
-            // displays, but that message's own tags are never in the model:
-            // setThreadMessages drops depth 0 because the root row stands for
-            // it, so there is no node to read and messageById() cannot find
-            // one. The summary is a union over the thread, so it answers
-            // "unread" while ANY message is.
+            // A thread row answers about the MESSAGE ITS CARD DISPLAYS, which
+            // is what it acts on. threadFor() already substitutes that
+            // message's own tags for the thread's union when they are known
+            // (item 110), so this reads the row's real state rather than a
+            // union over messages it does not stand for.
             //
-            // The consequence is bounded and only affects the DIRECTION a
-            // toggle picks, never what it writes: on a thread whose first
-            // message is read while a later one is not, Toggle unread reads
-            // the thread as unread and marks the first message read again, a
-            // no-op. Fixing it properly needs per-message state in
-            // ThreadSummary, which is the same thing item 87 needs; leave it
-            // for that item rather than guessing here.
-            tags = m_model->threadFor(index).tags;
+            // This used to read the union deliberately, with a comment
+            // calling the imprecision bounded because no per-message tags
+            // existed in the model. They do now: ThreadSummary carries
+            // firstMessageTags from the query, so an UNEXPANDED row already
+            // knows its own tags, and the comment outlived the fact.
+            //
+            // The cost of the union was not bounded once Delete became a
+            // MOVE. Deleting the root of a three-message thread left the two
+            // replies undeleted, so the union carried no `deleted`, so a
+            // second press read the row as not-deleted and deleted it AGAIN:
+            // the message was moved trash-to-trash and came out carrying
+            // `deleted`, `deleted-from:inbox` and `deleted-from:Trash` at
+            // once, with no way back. A tag toggle merely re-applied a tag it
+            // already had; a move re-applies the MOVE.
+            //
+            // Resolved through messageById() on the row's own message, which
+            // is the id messageScopeFor() will act on. Asking the same
+            // question the write asks is what keeps the direction and the
+            // write from disagreeing; the union answered a question about a
+            // conversation when the row stands for one message.
+            const ThreadSummary summary = m_model->threadFor(index);
+            const MessageNode own =
+                m_model->messageById(summary.firstMessageId);
+            // messageById() and NOT summary.firstMessageTags, which is the
+            // value the QUERY delivered and is not refreshed by an optimistic
+            // update: applyMessageTagChange() writes the row's node, so after
+            // a delete the node reads `deleted, deleted-from:inbox` while the
+            // summary still reads `inbox, unread`. Measured, and preferring
+            // the summary left this defect exactly as it was.
+            tags = own.messageId.isEmpty() ? summary.firstMessageTags
+                                           : own.tags;
         }
         if (!tags.contains(tag))
             return false;
@@ -4081,6 +4224,798 @@ void MainWindow::sendMessageTagChange(const QStringList &messageIds,
                               Q_ARG(TagChange, m_pendingChange));
 }
 
+const QString &MainWindow::kOriginTagPlaceholder()
+{
+    // Not wrapped in tr(). It is never displayed: onMessagesMoved() replaces
+    // it with a real tag before anything reaches the worker, and a translated
+    // placeholder would stop matching in the one locale that translated it,
+    // which is the trap CLAUDE.md records for startup_query.
+    static const QString placeholder =
+        QStringLiteral("\x01qtmaildir-origin-placeholder");
+    return placeholder;
+}
+
+Account MainWindow::accountForMessagePath(const QString &path) const
+{
+    // From the PATH, not from the thread's account tag. The tag is optional
+    // config, so resolving through it would silently disable Delete for an
+    // account that never set one; a message's maildir prefix is what makes it
+    // belong to an account at all.
+    //
+    // Longest maildir wins, so nested account maildirs (`mail` and
+    // `mail/work`) resolve to the more specific one rather than to whichever
+    // happens to be listed first.
+    //
+    // BOTH path shapes are accepted, and that is not defensive coding. A
+    // thread row's path comes from ThreadSummary::firstMessagePath and is
+    // database-RELATIVE; a reply row's comes from MessageNode::filePath and is
+    // ABSOLUTE, because MimeParser has to open it. Matching only the relative
+    // form resolved every reply to no account, so Delete on a reply reported
+    // "no trash folder configured" and moved nothing, which is exactly the
+    // thread-row/reply-row asymmetry this file has been bitten by before.
+    //
+    // A `/` is required after the maildir in both cases, so `acctX` cannot
+    // match an account whose maildir is `acct`.
+    Account best;
+    int bestLength = -1;
+    for (const Account &account : m_config.accounts()) {
+        if (account.maildir.isEmpty())
+            continue;
+        const QString segment = QLatin1Char('/') + account.maildir
+                                + QLatin1Char('/');
+        const bool matches =
+            path.startsWith(account.maildir + QLatin1Char('/'))
+            || path.contains(segment);
+        if (!matches)
+            continue;
+        if (account.maildir.length() > bestLength) {
+            best = account;
+            bestLength = account.maildir.length();
+        }
+    }
+    return best;
+}
+
+void MainWindow::trashSelected()
+{
+    const QModelIndexList rows =
+        m_threadView->selectionModel()->selectedRows();
+    if (rows.isEmpty())
+        return;
+
+    // Message scope, exactly as tagSelected() uses by default: a thread row
+    // stands for the ONE message its card displays. Escalating to the thread
+    // would move a whole conversation into the trash because the user deleted
+    // one reply.
+    const ActionScope scope = m_model->messageScopeFor(rows);
+    if (scope.messageIds.isEmpty())
+        return;
+
+    QHash<QString, QString> pathById;
+    for (const QString &messageId : scope.messageIds)
+        pathById.insert(messageId, m_model->messageById(messageId).filePath);
+
+    trashMessages(scope.messageIds, pathById, scope.messageCount);
+}
+
+void MainWindow::trashMessages(const QStringList &messageIds,
+                               const QHash<QString, QString> &pathById,
+                               int messageCount,
+                               const QStringList &wholeThreadIds)
+{
+    if (messageIds.isEmpty())
+        return;
+
+    // Grouped by destination, because moveMessages() takes one folder per call
+    // and a selection can span accounts with different trash folders.
+    //
+    // Paths are passed IN rather than read from the model, because the thread
+    // path arrives with messages the model has never seen: a thread the user
+    // never expanded holds no node for its replies, so a lookup there returns
+    // nothing and every message resolves to no account.
+    QHash<QString, QStringList> byTrash;
+    QStringList unconfigured;
+    for (const QString &messageId : messageIds) {
+        const Account account =
+            accountForMessagePath(pathById.value(messageId));
+        if (account.trash.isEmpty()) {
+            unconfigured.append(messageId);
+            continue;
+        }
+        byTrash[account.maildir + QLatin1Char('/') + account.trash]
+            .append(messageId);
+    }
+
+    // Task 2 warns at config load; this is the second line of defence, for a
+    // user who never fixed it. Reported rather than silently doing nothing,
+    // and NOT tagged either: a `deleted` tag on a file still in the inbox is
+    // precisely the half-done state this item removes.
+    if (!unconfigured.isEmpty()) {
+        m_statusLabel->setText(
+            tr("%n message(s) could not be deleted: no trash folder is "
+               "configured for their account.", "", int(unconfigured.size())));
+    }
+
+    if (byTrash.isEmpty())
+        return;
+
+    for (auto it = byTrash.cbegin(); it != byTrash.cend(); ++it) {
+        sendMove(it.value(), it.key(),
+                 { QStringLiteral("deleted"), kOriginTagPlaceholder() }, {},
+                 tr("Delete"), false, wholeThreadIds);
+    }
+
+    showTransientStatus(
+        tr("%1: %n message(s)", "", messageCount).arg(tr("Delete")));
+}
+
+QString MainWindow::originTagFor(const QString &dbRelativeFolder) const
+{
+    // `acct/inbox` becomes `deleted-from:inbox`. The tag stores the folder
+    // relative to the ACCOUNT, never to the database: the account prefix is
+    // recomposed from the message's own path when it is read back, so storing
+    // it would duplicate it and would go stale the day the user renames a
+    // maildir.
+    //
+    // Shared by the two sites that need the tag, rather than derived twice.
+    // They disagreed once already: onMessagesMoved() resolved a placeholder
+    // from the folder the worker reported, which on a RESTORE is the trash
+    // rather than the origin, so the restore stripped `deleted-from:Trash`
+    // and left the real tag in place.
+    const Account account =
+        accountForMessagePath(dbRelativeFolder + QLatin1Char('/'));
+    QString accountRelative = dbRelativeFolder;
+    if (!account.maildir.isEmpty()
+        && dbRelativeFolder.startsWith(account.maildir + QLatin1Char('/'))) {
+        accountRelative = dbRelativeFolder.mid(account.maildir.length() + 1);
+    }
+    if (accountRelative.isEmpty())
+        return QString();
+    return QStringLiteral("deleted-from:%1").arg(accountRelative);
+}
+
+QStringList MainWindow::selectedThreadIds() const
+{
+    // A THREAD action on a reply row means that reply's conversation.
+    //
+    // scopeFor() reports a reply under messageIds and leaves threadIds empty,
+    // which is right for the mixed selections it was built for and wrong as
+    // the only input to a thread-scoped action: the early return on an empty
+    // threadIds made Delete thread do nothing at all when the selected row
+    // happened to be a reply. threadFor() resolves either kind of row.
+    const QModelIndexList rows =
+        m_threadView->selectionModel()->selectedRows();
+    QStringList threadIds;
+    for (const QModelIndex &index : rows) {
+        const QString threadId = m_model->threadFor(index).threadId;
+        if (!threadId.isEmpty() && !threadIds.contains(threadId))
+            threadIds.append(threadId);
+    }
+    return threadIds;
+}
+
+void MainWindow::trashSelectedThreads()
+{
+    const QModelIndexList rows =
+        m_threadView->selectionModel()->selectedRows();
+    if (rows.isEmpty())
+        return;
+
+    const QStringList threadIds = selectedThreadIds();
+    if (threadIds.isEmpty())
+        return;
+
+    // Asked of the WORKER rather than resolved here. A thread the user never
+    // expanded has no nodes in the model for its replies, so the ids and the
+    // paths a move needs exist only in the database. applyTagsToThreads()
+    // solves the same problem the same way, for the same reason.
+    //
+    // Repainted HERE, synchronously, before the worker is asked.
+    //
+    // The move needs message ids and paths that only the database holds for an
+    // unexpanded thread, so the move itself is asynchronous. The DISPLAY must
+    // not wait for that round trip: the card is what the user watches, and
+    // holding it back is what made a deleted thread sit unchanged until it was
+    // clicked. It also keeps the toggle's direction readable immediately, so a
+    // second press restores rather than deleting again.
+    for (const QString &threadId : threadIds)
+        m_model->applyTagChange(threadId, { QStringLiteral("deleted") }, {});
+
+    m_pendingThreadScope = threadIds;
+    QMetaObject::invokeMethod(m_worker, "resolveThreadMessages",
+                              Qt::QueuedConnection,
+                              Q_ARG(QStringList, threadIds),
+                              Q_ARG(QString, QStringLiteral("delete_thread")));
+}
+
+void MainWindow::onThreadMessagesResolved(const QStringList &messageIds,
+                                          const QStringList &paths,
+                                          const QStringList &tags,
+                                          const QString &requestTag)
+{
+    if (messageIds.size() != paths.size() || messageIds.size() != tags.size())
+        return;
+
+    QHash<QString, QString> pathById;
+    for (int i = 0; i < messageIds.size(); ++i)
+        pathById.insert(messageIds.at(i), paths.at(i));
+
+    const QStringList threadScope = m_pendingThreadScope;
+    m_pendingThreadScope.clear();
+
+    if (requestTag == QStringLiteral("delete_thread")) {
+        trashMessages(messageIds, pathById, messageIds.size(), threadScope);
+        return;
+    }
+
+    if (requestTag == QStringLiteral("restore_messages")) {
+        restoreResolvedMessages(messageIds, paths, tags);
+        return;
+    }
+
+    if (requestTag != QStringLiteral("undelete_thread"))
+        return;
+
+    // Restore, resolved per message: each one goes back to the folder its own
+    // `deleted-from:` tag names, so a thread whose messages were deleted from
+    // different folders reassembles correctly rather than collapsing into one.
+    const QString prefix = QStringLiteral("deleted-from:");
+    QHash<QString, QStringList> byOrigin;
+    QStringList unknown;
+    for (int i = 0; i < messageIds.size(); ++i) {
+        // Split on TAB, matching resolveThreadMessages(). A space is not a
+        // safe separator: a folder name containing one produces a tag
+        // containing one, and splitting there silently truncates the origin
+        // to its first word.
+        const QStringList messageTags =
+            tags.at(i).split(QLatin1Char('\t'), Qt::SkipEmptyParts);
+        QString origin;
+        for (const QString &tag : messageTags) {
+            if (tag.startsWith(prefix)) {
+                origin = tag.mid(prefix.length());
+                break;
+            }
+        }
+        // A message with no `deleted` tag is not in the trash and has nothing
+        // to come back from. A thread-scoped restore reaches every message,
+        // including ones the user never deleted, and moving those would drag
+        // untouched mail out of whatever folder it legitimately sits in.
+        if (!messageTags.contains(QStringLiteral("deleted")))
+            continue;
+        const Account account =
+            accountForMessagePath(paths.at(i));
+        if (origin.isEmpty() || account.maildir.isEmpty()) {
+            unknown.append(messageIds.at(i));
+            continue;
+        }
+        byOrigin[account.maildir + QLatin1Char('/') + origin]
+            .append(messageIds.at(i));
+    }
+
+    if (!unknown.isEmpty()) {
+        // No origin recorded: deleted by an older version or tagged by hand.
+        // The tag comes off so the row stops claiming to be deleted, but no
+        // file moves, since guessing a folder would put the message somewhere
+        // the user never had it.
+        sendMessageTagChange(unknown, {}, { QStringLiteral("deleted") },
+                             tr("Undelete thread"));
+        m_undoStack.push(new MessageTagCommand(this, unknown, {},
+                                               { QStringLiteral("deleted") },
+                                               tr("Undelete thread")));
+    }
+
+    for (auto it = byOrigin.cbegin(); it != byOrigin.cend(); ++it) {
+        // The origin tag is named here, not left as the placeholder: on a
+        // restore the placeholder would resolve to the folder the message is
+        // coming FROM, which is the trash, and strip a tag never written.
+        const QString origin = originTagFor(it.key());
+        QStringList remove{ QStringLiteral("deleted") };
+        if (!origin.isEmpty())
+            remove.append(origin);
+        sendMove(it.value(), it.key(), {}, remove, tr("Undelete thread"),
+                 false, threadScope);
+    }
+
+    showTransientStatus(tr("%1: %n message(s)", "", messageIds.size())
+                            .arg(tr("Undelete thread")));
+}
+
+void MainWindow::restoreSelectedThreads()
+{
+    const QModelIndexList rows =
+        m_threadView->selectionModel()->selectedRows();
+    if (rows.isEmpty())
+        return;
+
+    const QStringList threadIds = selectedThreadIds();
+    if (threadIds.isEmpty())
+        return;
+
+    // Repainted synchronously, as the delete direction is.
+    for (const QString &threadId : threadIds)
+        m_model->applyTagChange(threadId, {}, { QStringLiteral("deleted") });
+
+    m_pendingThreadScope = threadIds;
+    QMetaObject::invokeMethod(
+        m_worker, "resolveThreadMessages", Qt::QueuedConnection,
+        Q_ARG(QStringList, threadIds),
+        Q_ARG(QString, QStringLiteral("undelete_thread")));
+}
+
+QString MainWindow::inboxFolderFor(const Account &account) const
+{
+    // Discovered from the account's OWN inbox query, never hardcoded.
+    //
+    // The casing is not ours to assume: the real Maildir has `Inbox` and a
+    // test fixture has `inbox`, and picking either would create a SECOND
+    // folder beside the real one on whichever side disagreed. That is exactly
+    // the failure a truncated origin folder caused on real mail this morning,
+    // and under mbsync's `Create Both` such a folder can reach the server.
+    //
+    // The inbox query is a generated `path:"<maildir>/<folder>/**"`, so the
+    // folder name is the part between the account prefix and the glob.
+    const QString query = account.inboxQuery();
+    const QString prefix =
+        QStringLiteral("path:\"") + account.maildir + QLatin1Char('/');
+    const QString suffix = QStringLiteral("/**\"");
+    if (query.startsWith(prefix) && query.endsWith(suffix)) {
+        const int from = prefix.length();
+        const int length = query.length() - from - suffix.length();
+        if (length > 0)
+            return query.mid(from, length);
+    }
+
+    // No inbox configured for this account. `Inbox` is the Maildir
+    // convention and is what mbsync's own `Inbox` directive defaults to.
+    return QStringLiteral("Inbox");
+}
+
+void MainWindow::restoreResolvedMessages(const QStringList &messageIds,
+                                         const QStringList &paths,
+                                         const QStringList &tags)
+{
+    if (messageIds.size() != paths.size() || messageIds.size() != tags.size())
+        return;
+
+    const QString prefix = QStringLiteral("deleted-from:");
+    QHash<QString, QStringList> byOrigin;
+    QHash<QString, QStringList> byInbox;
+    QStringList stranded;
+
+    for (int i = 0; i < messageIds.size(); ++i) {
+        const QStringList messageTags =
+            tags.at(i).split(QLatin1Char('\t'), Qt::SkipEmptyParts);
+        QString origin;
+        for (const QString &tag : messageTags) {
+            if (tag.startsWith(prefix)) {
+                origin = tag.mid(prefix.length());
+                break;
+            }
+        }
+
+        const Account account = accountForMessagePath(paths.at(i));
+        if (account.maildir.isEmpty()) {
+            stranded.append(messageIds.at(i));
+            continue;
+        }
+
+        if (origin.isEmpty()) {
+            // Trashed by another client, so there is no record of where it
+            // belongs. Inbox is the documented fallback, and it is reported:
+            // a guess the user is not told about is worse than the guess.
+            byInbox[account.maildir + QLatin1Char('/')
+                    + account.inboxFolder()]
+                .append(messageIds.at(i));
+            continue;
+        }
+        byOrigin[account.maildir + QLatin1Char('/') + origin]
+            .append(messageIds.at(i));
+    }
+
+    for (auto it = byOrigin.cbegin(); it != byOrigin.cend(); ++it) {
+        // The origin tag is named here rather than left as the placeholder,
+        // which onMessagesMoved() would resolve to the folder the message is
+        // coming FROM, namely the trash.
+        const QString origin = originTagFor(it.key());
+        QStringList remove{ QStringLiteral("deleted") };
+        if (!origin.isEmpty())
+            remove.append(origin);
+        sendMove(it.value(), it.key(), {}, remove, tr("Restore"));
+    }
+
+    for (auto it = byInbox.cbegin(); it != byInbox.cend(); ++it) {
+        sendMove(it.value(), it.key(), {}, { QStringLiteral("deleted") },
+                 tr("Restore"));
+    }
+
+    if (!byInbox.isEmpty()) {
+        m_statusLabel->setText(
+            tr("%n message(s) had no record of where they came from and were "
+               "moved to the inbox.", "", int(byInbox.size())));
+    }
+    if (!stranded.isEmpty()) {
+        m_statusLabel->setText(
+            tr("%n message(s) could not be restored: they belong to no "
+               "configured account.", "", int(stranded.size())));
+    }
+}
+
+void MainWindow::restoreSelectedFromTrash()
+{
+    const QModelIndexList rows =
+        m_threadView->selectionModel()->selectedRows();
+    if (rows.isEmpty())
+        return;
+
+    const ActionScope scope = m_model->messageScopeFor(rows);
+    if (scope.messageIds.isEmpty())
+        return;
+
+    // Resolved by the WORKER, not read from the model.
+    //
+    // The model's tags come from the QUERY, and a row whose delete has not yet
+    // been re-queried still carries its pre-delete tags: measured
+    // `[inbox,unread]` on a message already in the trash, one run in three.
+    // The origin tag is then not found, the message falls into the
+    // no-origin branch, and Restore sends it to the INBOX instead of the
+    // folder it came from, silently and irreversibly.
+    //
+    // A restore has to be right about the destination or it is worse than
+    // doing nothing, so it asks the database rather than trusting a view that
+    // may be a moment behind. restoreSelectedThreads() already worked this
+    // way; this is the same reasoning applied to the message-scoped path.
+    m_pendingRestoreIds = scope.messageIds;
+    QMetaObject::invokeMethod(
+        m_worker, "resolveMessages", Qt::QueuedConnection,
+        Q_ARG(QStringList, scope.messageIds),
+        Q_ARG(QString, QStringLiteral("restore_messages")));
+}
+
+void MainWindow::showStrandedDeletedMail()
+{
+    // Not scoped to the selected account, deliberately. The stranded mail is
+    // an artefact of an old version rather than a view of anything, and the
+    // user wants to see all of it at once; the account dropdown is still there
+    // to narrow it by hand afterwards.
+    const QString trash = m_config.allTrashQuery();
+
+    // No account configures a trash folder: everything tagged `deleted` is by
+    // definition stranded, since there is nowhere for it to have gone. An
+    // empty exclusion must never be written as `not ()`, which notmuch parses
+    // without complaint and matches nothing, reporting a clean database.
+    const QString query =
+        trash.isEmpty()
+            ? QStringLiteral("tag:deleted")
+            : QStringLiteral("tag:deleted and not (%1)").arg(trash);
+
+    // Into the bar, like a filter: what ran is visible and editable, and
+    // AlreadyScoped stops runQuery() wrapping it in the selected account's
+    // path, which would hide every other account's stranded mail.
+    m_queryEdit->setText(query);
+    runQuery(FlatResult::No, AccountScope::AlreadyScoped);
+
+    // After runQuery(), which sets "Searching...": set before it, this would
+    // be overwritten and the user would be told nothing about what they are
+    // looking at.
+    m_statusLabel->setText(tr("Mail tagged deleted but not in a trash folder. "
+                              "Select what should go and press Delete."));
+}
+
+void MainWindow::restoreSelected(bool fallbackToInbox)
+{
+    const QModelIndexList rows =
+        m_threadView->selectionModel()->selectedRows();
+    if (rows.isEmpty())
+        return;
+
+    const ActionScope scope = m_model->messageScopeFor(rows);
+    if (scope.messageIds.isEmpty())
+        return;
+
+    // Where each message came from, read back off its own tag. This is what
+    // the tag exists for: the file has moved, so nothing on disk and nothing
+    // in notmuch still records the original folder.
+    const QString prefix = QStringLiteral("deleted-from:");
+    QHash<QString, QStringList> byOrigin;
+    QStringList unknown;
+    for (const QString &messageId : scope.messageIds) {
+        const MessageNode node = m_model->messageById(messageId);
+        QString origin;
+        for (const QString &tag : node.tags) {
+            if (tag.startsWith(prefix)) {
+                origin = tag.mid(prefix.length());
+                break;
+            }
+        }
+        // An account prefix is needed to name a folder to the worker, which
+        // works in database-relative paths. The origin tag stores the folder
+        // relative to the ACCOUNT, so the two are recomposed here.
+        const Account account = accountForMessagePath(node.filePath);
+        if (origin.isEmpty() || account.maildir.isEmpty()) {
+            unknown.append(messageId);
+            continue;
+        }
+        byOrigin[account.maildir + QLatin1Char('/') + origin].append(messageId);
+    }
+
+    if (!unknown.isEmpty()) {
+        // No origin recorded. Two quite different situations reach here and
+        // they want opposite things, which is what `fallbackToInbox` selects.
+        //
+        // From the TRASH VIEW the message is demonstrably in the trash, put
+        // there by another client, and refusing to move it leaves the user
+        // looking at a message they cannot get out. Inbox is the documented
+        // fallback, and it is reported, because a guess the user is not told
+        // about is worse than the guess itself.
+        //
+        // From a second press of Delete the message is NOT in the trash: it is
+        // sitting wherever it always was, wearing a stale `deleted` tag from
+        // an older version or from a hand-written notmuch command. Moving it
+        // to the inbox there would relocate mail the user never asked to move.
+        // The tag comes off and the file stays put.
+        if (fallbackToInbox) {
+            QHash<QString, QStringList> byInbox;
+            QStringList stranded;
+            for (const QString &messageId : unknown) {
+                const Account account =
+                    accountForMessagePath(m_model->messageById(messageId).filePath);
+                if (account.maildir.isEmpty()) {
+                    stranded.append(messageId);
+                    continue;
+                }
+                byInbox[account.maildir + QLatin1Char('/')
+                        + inboxFolderFor(account)]
+                    .append(messageId);
+            }
+
+            for (auto it = byInbox.cbegin(); it != byInbox.cend(); ++it) {
+                sendMove(it.value(), it.key(), {},
+                         { QStringLiteral("deleted") }, tr("Restore"));
+            }
+
+            if (!byInbox.isEmpty()) {
+                m_statusLabel->setText(
+                    tr("%n message(s) had no record of where they came from "
+                       "and were moved to the inbox.", "",
+                       int(unknown.size() - stranded.size())));
+            }
+            if (!stranded.isEmpty()) {
+                m_statusLabel->setText(
+                    tr("%n message(s) could not be restored: they belong to no "
+                       "configured account.", "", int(stranded.size())));
+            }
+        } else {
+            sendMessageTagChange(unknown, {}, { QStringLiteral("deleted") },
+                                 tr("Undelete"));
+            m_undoStack.push(new MessageTagCommand(
+                this, unknown, {}, { QStringLiteral("deleted") },
+                tr("Undelete")));
+        }
+    }
+
+    for (auto it = byOrigin.cbegin(); it != byOrigin.cend(); ++it) {
+        // The origin tag is named HERE, not left as the placeholder.
+        //
+        // onMessagesMoved() resolves the placeholder from the origin the
+        // WORKER reports, which is where the message is coming FROM. On a
+        // delete that is the inbox and correct; on a restore it is the trash,
+        // so the placeholder resolved to `deleted-from:Trash` and asked to
+        // remove a tag that never existed, while the real `deleted-from:inbox`
+        // was never named. The message came home still claiming to have been
+        // deleted from somewhere, which then made Restore offer to move a
+        // message that was already back.
+        //
+        // A restore does not need the placeholder at all: the origin was just
+        // read off the message's own tag to decide where to send it, so the
+        // exact tag to strip is already known. Recomposed from the same
+        // account-relative form it was stored in.
+        const QString origin = originTagFor(it.key());
+        QStringList remove{ QStringLiteral("deleted") };
+        if (!origin.isEmpty())
+            remove.append(origin);
+        sendMove(it.value(), it.key(), {}, remove, tr("Undelete"));
+    }
+
+    showTransientStatus(
+        tr("%1: %n message(s)", "", scope.messageCount).arg(tr("Undelete")));
+}
+
+void MainWindow::sendMove(const QStringList &messageIds,
+                          const QString &destFolder, const QStringList &add,
+                          const QStringList &remove,
+                          const QString &description, bool fromUndo,
+                          const QStringList &wholeThreadIds)
+{
+    if (messageIds.isEmpty() || destFolder.isEmpty())
+        return;
+
+    // Held during a sync for the same reason every tag write is: the worker's
+    // read-write open BLOCKS on notmuch's exclusive lock rather than failing,
+    // so sending now would freeze the worker for the rest of the run.
+    //
+    // A move is held as the MOVE it is, not decomposed into a tag edit. The
+    // held-edit queue carries tag changes only, so a move pushed through it
+    // would apply the tags and never move the file, which is worse than
+    // waiting: the message would read as deleted and still be in the inbox.
+    if (aSyncHoldsTheWriteLock()) {
+        m_heldMoves.append(HeldMove{ messageIds, destFolder, add, remove,
+                                     description, fromUndo });
+        m_statusLabel->setText(
+            tr("A sync is running; your change will be applied when it "
+               "finishes."));
+        updatePendingIndicator();
+        return;
+    }
+
+    // Repainted NOW, before the worker is asked.
+    //
+    // The write itself waits for the move to be confirmed, and must: tagging
+    // the database first would leave a message marked deleted in a folder it
+    // never left if the rename failed. The DISPLAY has no such constraint, and
+    // holding it back until the round trip finished is what made a deleted row
+    // sit there unchanged until the user clicked it. The reply rows repainted
+    // and the root did not, because the replies were separately tagged while
+    // the root's card reads its thread's summary.
+    //
+    // Reverted by revertPendingTagChange() if the write is rejected, exactly
+    // as the tag path's optimistic update is.
+    //
+    // The placeholder is dropped rather than displayed: the real origin is not
+    // known until the worker answers, and a chip reading the placeholder's
+    // literal name would be worse than one chip arriving a moment late.
+    QStringList displayAdd;
+    for (const QString &tag : add) {
+        if (tag != kOriginTagPlaceholder())
+            displayAdd.append(tag);
+    }
+    QStringList displayRemove;
+    for (const QString &tag : remove) {
+        if (tag != kOriginTagPlaceholder())
+            displayRemove.append(tag);
+    }
+    // A thread-scoped move already repainted its rows in
+    // trashSelectedThreads() / restoreSelectedThreads(), synchronously, before
+    // the worker was asked to resolve the threads at all. Repeating it here
+    // would be harmless but redundant; more importantly the caller there needs
+    // the repaint to happen WITHOUT a worker round trip, which is the whole
+    // reason it is not done from this function.
+    //
+    // applyTagChange() is what those callers use, and applyMessageTagChange()
+    // is what this one uses, and the difference is not a style choice: the
+    // former moves the thread's SUMMARY, which a thread row's card draws from,
+    // while the latter deliberately leaves a multi-message thread's summary
+    // alone because one message's edit does not describe the conversation.
+    if (wholeThreadIds.isEmpty()) {
+        for (const QString &messageId : messageIds)
+            m_model->applyMessageTagChange(messageId, displayAdd, displayRemove);
+    }
+
+    // What to tag once the move is CONFIRMED. Tagging now would leave a
+    // message marked deleted in a folder it never left if the rename failed.
+    //
+    // A QUEUE, not a map keyed on the destination: two Deletes in the same
+    // account before the first confirmation arrives both name `acct/Trash`,
+    // so the second insert overwrote the first and the second confirmation
+    // took an empty PendingMove. That file landed in the trash carrying
+    // neither `deleted` nor `deleted-from:`, which makes it unrestorable and
+    // invisible to a `tag:deleted` query. The worker handles one move at a
+    // time on its own thread and emits in the order it was asked, so a plain
+    // FIFO matches confirmations to requests without needing a key at all.
+    m_pendingMoves.enqueue(PendingMove{ add, remove, description, fromUndo });
+
+    QMetaObject::invokeMethod(m_worker, "moveMessages", Qt::QueuedConnection,
+                              Q_ARG(QStringList, messageIds),
+                              Q_ARG(QString, destFolder));
+}
+
+void MainWindow::onMessagesMoved(const QMap<QString, QString> &originByMessageId,
+                                 const QString &destFolder)
+{
+    if (m_pendingMoves.isEmpty())
+        return;
+    const PendingMove pending = m_pendingMoves.dequeue();
+    if (originByMessageId.isEmpty())
+        return;
+
+    // The origin differs per message, so the tags do too: two messages deleted
+    // from different folders get different `deleted-from:` tags out of one
+    // gesture. Grouped by the resolved tag list so identical ones still travel
+    // as a single write.
+    QHash<QString, QStringList> byOrigin;
+    for (auto it = originByMessageId.cbegin(); it != originByMessageId.cend();
+         ++it) {
+        byOrigin[it.value()].append(it.key());
+    }
+
+    for (auto it = byOrigin.cbegin(); it != byOrigin.cend(); ++it) {
+        // The origin tag names the folder relative to the ACCOUNT, not to the
+        // database: `inbox`, never `acct/inbox`. Restore recomposes the
+        // account prefix from the message's own path, so storing it here would
+        // duplicate it, and a stored account prefix would go stale the day the
+        // user renames a maildir.
+        //
+        // The worker reports `acct/inbox`; the account's own maildir is
+        // `acct`, so the stored tag is `inbox`. Resolved through the first
+        // message's path, which is still the account's whichever folder it
+        // sits in now.
+        const QString originTag = originTagFor(it.key());
+
+        auto resolve = [&](const QStringList &tags) {
+            QStringList out;
+            for (const QString &tag : tags) {
+                if (tag != kOriginTagPlaceholder()) {
+                    out.append(tag);
+                    continue;
+                }
+                if (!originTag.isEmpty())
+                    out.append(originTag);
+            }
+            return out;
+        };
+
+        const QStringList resolvedAdd = resolve(pending.add);
+        const QStringList resolvedRemove = resolve(pending.remove);
+        sendMessageTagChange(it.value(), resolvedAdd, resolvedRemove,
+                             pending.description);
+
+        // The undo entry carries the RESOLVED tags, and is pushed per origin
+        // group rather than once for the batch.
+        //
+        // It used to be handed pending.add straight, which still holds the
+        // unresolved placeholder: undo then asked to remove a tag by that
+        // literal name, which no message carries, so the removal was a silent
+        // no-op and `deleted-from:inbox` survived the undo. The file came home
+        // still claiming to have been deleted from somewhere. Same defect as
+        // the one the second-Delete path had, reached through Ctrl+Z instead.
+        //
+        // Per group because the placeholder resolves to a DIFFERENT tag per
+        // origin: one command for a batch spanning two folders could only
+        // carry one of them, so the other would be the wrong tag rather than
+        // merely an unresolved one.
+        if (!pending.fromUndo) {
+            QMap<QString, QString> groupOrigins;
+            for (const QString &messageId : it.value())
+                groupOrigins.insert(messageId, originByMessageId.value(messageId));
+            m_undoStack.push(new MoveCommand(this, groupOrigins, destFolder,
+                                             resolvedAdd, resolvedRemove,
+                                             pending.description));
+        }
+    }
+
+    // A restore out of the TRASH VIEW leaves the row it came from showing a
+    // message that is no longer there, and only a refresh can say so.
+    //
+    // Reported from a hand test: the move was correct and the row sat in the
+    // list until the Trash filter was clicked again. The trash view is PATH
+    // based, so a restored message stops matching the query the list was built
+    // from, which is a state no tag change can express. Nothing else here
+    // removes a row, deliberately: in an ordinary view a deleted message's
+    // card should stay put, since one deleted reply does not doom the
+    // conversation.
+    //
+    // refreshCurrentQuery() rather than runCurrentQuery(): it clears nothing,
+    // so the selection, the expanded threads, the undo stack and the message
+    // being read all survive. Re-running the query outright would destroy the
+    // undo entry this function just pushed, which is the one thing a restore
+    // must leave intact.
+    //
+    // Gated on isShowingTrash() and not on the destination: a Delete is a move
+    // too and reaches this same slot, and refreshing after every delete would
+    // make a row vanish from under the user in every other view.
+    if (isShowingTrash())
+        refreshCurrentQuery();
+
+    // The undo entries are pushed inside the loop above, one per origin
+    // group, because the placeholder resolves per origin. Nothing is pushed
+    // for a move the undo stack itself started: a MoveCommand is confirmed
+    // through this same slot, so pushing unconditionally left the undo of a
+    // Delete putting a fresh command on the stack instead of consuming the
+    // one it undid, and a second press of undo re-deleted the message. The
+    // flag rides on PendingMove because the answer has to survive the queued
+    // round trip; a window-wide "am I undoing" flag would long since have
+    // been cleared by the time the worker replies.
+}
+
 void MainWindow::sendThreadTagChange(const QStringList &threadIds,
                                      const QStringList &add,
                                      const QStringList &remove,
diff --git a/src/mainwindow.h b/src/mainwindow.h
index e741416..5b1621f 100644
--- a/src/mainwindow.h
+++ b/src/mainwindow.h
@@ -21,6 +21,7 @@
 #include <QHash>
 #include <QSet>
 #include <QMainWindow>
+#include <QQueue>
 #include <QPointer>
 #include <QThread>
 #include <QUndoCommand>
@@ -739,6 +740,172 @@ private:
                               const QStringList &remove,
                               const QString &description);
 
+    /// Moves messages into `destFolder` and applies the tags that go with it.
+    ///
+    /// The counterpart to sendMessageTagChange() for the one action that is
+    /// not purely a tag change. Both trashSelected() and MoveCommand route
+    /// through this.
+    ///
+    /// The tags are NOT applied here: they are applied when the worker
+    /// confirms the move, in onMessagesMoved(). Tagging first would leave a
+    /// message marked `deleted` in a folder it never left if the rename
+    /// failed, which is the half-done state item 103 exists to remove.
+    ///
+    /// `add` may contain the placeholder kOriginTagPlaceholder, which
+    /// onMessagesMoved() replaces with `deleted-from:<origin>` per message.
+    /// The origin is not known until the worker reports it, and it differs per
+    /// message in a multi-row selection.
+    /// `fromUndo` marks a move the undo stack itself started, which must NOT
+    /// push a command of its own when it is confirmed. See onMessagesMoved().
+    /// `wholeThreadIds`, when non-empty, says this move covers every message
+    /// of those threads, so the optimistic repaint updates each thread's
+    /// SUMMARY rather than each message's node. A thread row's card reads the
+    /// summary, so a thread-scoped move that updated only nodes repainted the
+    /// replies and left the root card stale until the next query.
+    void sendMove(const QStringList &messageIds, const QString &destFolder,
+                  const QStringList &add, const QStringList &remove,
+                  const QString &description, bool fromUndo = false,
+                  const QStringList &wholeThreadIds = {});
+
+    /// Moves each selected row's message to its account's trash, tagging it
+    /// `deleted` and recording where it came from.
+    void trashSelected();
+
+    /// The half of trashSelected() that does the work, given the messages and
+    /// their paths.
+    ///
+    /// Paths are passed in rather than looked up, because the thread-scoped
+    /// caller has messages the MODEL has never seen: an unexpanded thread
+    /// holds no node for its replies, so a model lookup resolves them to no
+    /// account and the move is silently dropped. The worker supplies them.
+    void trashMessages(const QStringList &messageIds,
+                       const QHash<QString, QString> &pathById,
+                       int messageCount,
+                       const QStringList &wholeThreadIds = {});
+
+    /// Moves every message of each selected THREAD to its account's trash.
+    ///
+    /// Asynchronous, unlike its message-scoped twin: the ids and paths of an
+    /// unexpanded thread's messages live only in the database, so this asks
+    /// the worker and finishes in onThreadMessagesResolved().
+    void trashSelectedThreads();
+
+    /// The thread ids the selection covers, resolving a reply row to its own
+    /// thread. scopeFor() reports a reply under messageIds instead, which left
+    /// a thread action on a reply row doing nothing at all.
+    QStringList selectedThreadIds() const;
+
+    /// The inverse of trashSelectedThreads(): moves every message of each
+    /// selected thread back where it came from.
+    void restoreSelectedThreads();
+
+    /// Runs the thread-scoped delete once the worker has resolved the
+    /// threads to messages.
+    void onThreadMessagesResolved(const QStringList &messageIds,
+                                  const QStringList &paths,
+                                  const QStringList &tags,
+                                  const QString &requestTag);
+
+    /// The inverse: moves each selected row's message back to the folder its
+    /// `deleted-from:` tag names, stripping both tags.
+    ///
+    /// `fallbackToInbox` decides what happens to a message with NO origin tag,
+    /// and the two callers want opposite things. From the trash view the
+    /// message is demonstrably in the trash, trashed by another client, and
+    /// must still come out: it goes to the inbox, reported. From a second
+    /// press of Delete it is not in the trash at all and merely wears a stale
+    /// tag, so the tag comes off and the file stays where it is.
+    void restoreSelected(bool fallbackToInbox = false);
+
+    /// Restore as reached from the TRASH VIEW: resolves each selected
+    /// message against the database first, then moves it.
+    ///
+    /// Asynchronous, unlike restoreSelected(), and that is the point. The
+    /// model's tags come from the query, so a row whose delete has not been
+    /// re-queried still carries its pre-delete tags; reading the origin from
+    /// there found none and sent the message to the INBOX instead of the
+    /// folder it came from, one run in three.
+    void restoreSelectedFromTrash();
+
+    /// Runs the query that finds mail tagged `deleted` whose file never left
+    /// its original folder, which is what every version before item 103 left
+    /// behind. It REPORTS and moves nothing: acting on its own would be a bulk
+    /// delete with no selection behind it, and the user asked for something
+    /// they could come back to and review.
+    ///
+    /// Repeatable rather than a one-time startup migration, for the same
+    /// reason: mail reaches this state again whenever another client tags
+    /// without moving.
+    void showStrandedDeletedMail();
+
+    /// Moves each resolved message home, using the tags and paths the WORKER
+    /// reported rather than anything the model holds.
+    void restoreResolvedMessages(const QStringList &messageIds,
+                                 const QStringList &paths,
+                                 const QStringList &tags);
+
+    /// The messages a resolveMessages() request was made for.
+    QStringList m_pendingRestoreIds;
+
+    /// The account's inbox FOLDER name, discovered from its inbox query.
+    ///
+    /// Never hardcoded: the real Maildir has `Inbox` and a fixture has
+    /// `inbox`, and assuming either would create a second folder beside the
+    /// real one on the side that disagreed.
+    QString inboxFolderFor(const Account &account) const;
+
+    /// Whether the current query IS a trash view, for either scope.
+    ///
+    /// Compared against the trash generator's own query rather than against a
+    /// tag: the view is path-based so mail trashed by another client appears
+    /// in it, and such a message carries no tag of ours.
+    bool isShowingTrash() const;
+
+    /// The `deleted-from:` tag naming `dbRelativeFolder`, or empty when no
+    /// account owns it.
+    ///
+    /// One rule for both sites that need the tag: the delete that writes it
+    /// and the restore that strips it. Deriving it twice let them disagree,
+    /// and a restore stripped a tag that had never been written.
+    QString originTagFor(const QString &dbRelativeFolder) const;
+
+    /// The account whose maildir contains `path`, or an invalid account when
+    /// no configured maildir does.
+    ///
+    /// Resolved from the PATH rather than from the thread's account tag. The
+    /// tag is optional config, so an account without one would resolve to
+    /// nothing and silently disable Delete; the maildir prefix is what makes
+    /// a message belong to an account in the first place.
+    Account accountForMessagePath(const QString &path) const;
+
+    /// Confirms a move: applies the tags the move was asked to carry, with the
+    /// origin placeholder resolved per message.
+    void onMessagesMoved(const QMap<QString, QString> &originByMessageId,
+                         const QString &destFolder);
+
+    /// What a move asked to be tagged, held until the worker confirms it.
+    ///
+    /// A FIFO and not a map keyed on the destination: two Deletes in one
+    /// account before the first confirmation arrives name the same folder, so
+    /// a keyed map dropped the first entry and left the second confirmation
+    /// with nothing to apply. That file reached the trash carrying neither
+    /// `deleted` nor `deleted-from:`, unrestorable and invisible to a
+    /// `tag:deleted` query. The worker moves one batch at a time and emits in
+    /// request order, so position alone matches a confirmation to its request.
+    struct PendingMove {
+        QStringList add;
+        QStringList remove;
+        QString description;
+        /// Set for a move the undo stack started, which must not push again.
+        bool fromUndo = false;
+    };
+    QQueue<PendingMove> m_pendingMoves;
+
+    /// The threads a resolveThreadMessages() request was made for, held until
+    /// the answer arrives so the optimistic repaint knows the move is
+    /// thread-scoped.
+    QStringList m_pendingThreadScope;
+
     /// Undoes the optimistic model update for a write the worker rejected.
     void revertPendingTagChange();
 
@@ -791,10 +958,38 @@ private:
     /// it. Order matters: two edits touching one thread must reach the database
     /// in the order they were made, or the later one does not win.
     QVector<HeldEdit> m_heldEdits;
+
+    /// A MOVE not yet sent, for the same reason a tag edit is held.
+    ///
+    /// A separate queue rather than an entry in m_heldEdits, because a move is
+    /// not a tag change and cannot be replayed as one: pushing it through the
+    /// edit queue would apply `deleted` and never move the file, leaving the
+    /// message reading as deleted while still sitting in the inbox. Item 106
+    /// recorded what a dropped held edit costs, and a move dropped the same
+    /// way is worse: the tag lands and the file does not.
+    struct HeldMove {
+        QStringList messageIds;
+        QString destFolder;
+        QStringList add;
+        QStringList remove;
+        QString description;
+        /// Carried through the hold, or a move undone during a sync would
+        /// push a command when it is finally flushed.
+        bool fromUndo = false;
+    };
+    QVector<HeldMove> m_heldMoves;
+
     quint64 m_flushGeneration = 0;
 
     friend class ThreadTagCommand;
     friend class MessageTagCommand;
+    friend class MoveCommand;
+
+    /// Stands in for `deleted-from:<origin>` between asking for a move and
+    /// learning where each message actually came from. Not a tag anyone ever
+    /// sees: onMessagesMoved() substitutes the real one per message before
+    /// anything is written.
+    static const QString &kOriginTagPlaceholder();
 
     Config m_config;
     KeyMap m_keyMap;
@@ -1192,3 +1387,73 @@ private:
     QString m_description;
     bool m_firstRedo = true;
 };
+
+/// Undo entry for a message MOVE, which is a file rename plus a tag change.
+///
+/// The destination is CARRIED rather than derived, and that is the whole
+/// reason `deleted-from:` exists at all. A Maildir filename does not record
+/// where a message came from, and once the file has moved notmuch cannot
+/// answer either, so an undo that recomputed the origin would have nothing to
+/// recompute it from. Each message carries its own, since one selection can
+/// span folders and accounts.
+///
+/// Grouped by destination: undoing a delete of five messages from three
+/// folders is three moves, not five, because moveMessages() takes one folder
+/// per call.
+class MoveCommand : public QUndoCommand
+{
+public:
+    /// `originByMessageId` names where each message came FROM, and
+    /// `destFolder` where they all went.
+    MoveCommand(MainWindow *window,
+                const QMap<QString, QString> &originByMessageId,
+                const QString &destFolder, const QStringList &add,
+                const QStringList &remove, const QString &description)
+        : QUndoCommand(description), m_window(window),
+          m_origins(originByMessageId), m_dest(destFolder), m_add(add),
+          m_remove(remove), m_description(description) {}
+
+    /// The stack calls redo() when the command is pushed, by which point the
+    /// move has already been sent, so the first call is skipped. Same shape as
+    /// the two tag commands above.
+    void redo() override
+    {
+        if (m_firstRedo) {
+            m_firstRedo = false;
+            return;
+        }
+        // Also fromUndo: a redo replays a command that is ALREADY on the
+        // stack, so confirming it must not push a duplicate either.
+        m_window->sendMove(m_origins.keys(), m_dest, m_add, m_remove,
+                           m_description, true);
+    }
+
+    void undo() override
+    {
+        // Back to each message's OWN folder, one call per distinct
+        // destination. The tags invert with the direction: what the delete
+        // added, the undo removes.
+        QHash<QString, QStringList> byOrigin;
+        for (auto it = m_origins.cbegin(); it != m_origins.cend(); ++it) {
+            if (!it.value().isEmpty())
+                byOrigin[it.value()].append(it.key());
+        }
+        for (auto it = byOrigin.cbegin(); it != byOrigin.cend(); ++it) {
+            // fromUndo: this move is the undo, so its confirmation must not
+            // push a command of its own. Without it the stack grew on every
+            // press and a second undo re-deleted the message.
+            m_window->sendMove(it.value(), it.key(), m_remove, m_add,
+                               QStringLiteral("Undo %1").arg(m_description),
+                               true);
+        }
+    }
+
+private:
+    MainWindow *m_window;
+    QMap<QString, QString> m_origins;
+    QString m_dest;
+    QStringList m_add;
+    QStringList m_remove;
+    QString m_description;
+    bool m_firstRedo = true;
+};
diff --git a/src/notmuchworker.cpp b/src/notmuchworker.cpp
index b152830..2c03226 100644
--- a/src/notmuchworker.cpp
+++ b/src/notmuchworker.cpp
@@ -160,6 +160,39 @@ void walkReplies(notmuch_messages_t *messages, int depth,
     }
 }
 
+/// The Maildir FOLDER a message file sits in, relative to the database root.
+///
+/// `<root>/acct/inbox/cur/12345` becomes `acct/inbox`: the `cur`/`new` segment
+/// is stripped because it is Maildir's read-state bookkeeping rather than part
+/// of the folder's name, and moveMessages() takes a folder without one. That
+/// makes the value round-trip: what comes out here can be handed straight back
+/// to move a message home.
+///
+/// Empty when the file is not under the root at all, which the caller treats as
+/// "origin unknown" rather than guessing. A wrong folder here would send a
+/// restored message somewhere the user never had it.
+QString folderOfMessageFile(const QString &root, const QString &filePath)
+{
+    const QString rootPath = QDir(root).absolutePath();
+    const QString dir = QFileInfo(filePath).absolutePath();
+
+    const QString relative = QDir(rootPath).relativeFilePath(dir);
+    // relativeFilePath happily walks upwards, so a path outside the root comes
+    // back as `../something` rather than as a failure.
+    if (relative.isEmpty() || relative == QStringLiteral(".")
+        || relative.startsWith(QStringLiteral("../"))) {
+        return QString();
+    }
+
+    QStringList parts = relative.split(QLatin1Char('/'), Qt::SkipEmptyParts);
+    if (!parts.isEmpty()
+        && (parts.last() == QStringLiteral("cur")
+            || parts.last() == QStringLiteral("new"))) {
+        parts.removeLast();
+    }
+    return parts.join(QLatin1Char('/'));
+}
+
 } // namespace
 
 /// Registers SortOrder for queued calls, once, before main() runs.
@@ -254,6 +287,13 @@ void NotmuchWorker::runQuery(const QString &query, quint64 generation,
     }
     NmThreads threads(rawThreads);
 
+    // Message paths are reported RELATIVE to this. An absolute path would be
+    // useless to the UI, which knows accounts only by their maildir, a
+    // database-relative prefix: comparing the two never matched and left every
+    // row resolving to no account at all.
+    const QString dbRoot =
+        QDir(QString::fromUtf8(notmuch_database_get_path(m_db))).absolutePath();
+
     QVector<ThreadSummary> batch;
     batch.reserve(kBatchSize);
     int total = 0;
@@ -317,6 +357,10 @@ void NotmuchWorker::runQuery(const QString &query, quint64 generation,
                     // The card's own tags, beside the thread's union above.
                     // Same walk, same index read, no extra query.
                     summary.firstMessageTags = tagsOf(message);
+                    // Which account this belongs to, for Delete's destination.
+                    summary.firstMessagePath = QDir(dbRoot).relativeFilePath(
+                        QString::fromUtf8(
+                            notmuch_message_get_filename(message)));
                     break;
                 }
             }
@@ -329,6 +373,10 @@ void NotmuchWorker::runQuery(const QString &query, quint64 generation,
                     // The card's own tags, beside the thread's union above.
                     // Same walk, same index read, no extra query.
                     summary.firstMessageTags = tagsOf(first);
+                    // Which account this belongs to, for Delete's destination.
+                    summary.firstMessagePath = QDir(dbRoot).relativeFilePath(
+                        QString::fromUtf8(
+                            notmuch_message_get_filename(first)));
                 }
             }
         }
@@ -614,6 +662,205 @@ void NotmuchWorker::applyTags(const TagChange &change)
     emit tagsApplied(change);
 }
 
+void NotmuchWorker::moveMessages(const QStringList &messageIds,
+                                 const QString &destFolder)
+{
+    if (messageIds.isEmpty() || destFolder.isEmpty())
+        return;
+
+    // The read-only handle must be closed first: notmuch allows only one open
+    // handle per process. Same ordering as applyTags, for the same reason.
+    close();
+
+    const QByteArray configPath = configPathArg();
+    notmuch_database_t *db = nullptr;
+    char *error = nullptr;
+    const notmuch_status_t status = notmuch_database_open_with_config(
+        nullptr,
+        NOTMUCH_DATABASE_MODE_READ_WRITE,
+        configPath.isEmpty() ? nullptr : configPath.constData(),
+        nullptr,
+        &db,
+        &error);
+
+    if (status != NOTMUCH_STATUS_SUCCESS) {
+        emit errorOccurred(
+            QStringLiteral("Cannot open database for writing: %1")
+                .arg(QString::fromUtf8(error ? error
+                                             : notmuch_status_to_string(status))));
+        free(error);
+        return;
+    }
+
+    const QString root = QString::fromUtf8(notmuch_database_get_path(db));
+    const QString destDir =
+        root + QLatin1Char('/') + destFolder + QStringLiteral("/cur");
+
+    QStringList moved;
+    QMap<QString, QString> origins;
+    for (const QString &id : messageIds) {
+        notmuch_message_t *raw = nullptr;
+        // find_message reports SUCCESS with a null message when the id is not
+        // in the database, so both have to be checked. A stale id must not
+        // abort the batch: the live ids alongside it still need moving.
+        if (notmuch_database_find_message(db, id.toUtf8().constData(), &raw)
+                != NOTMUCH_STATUS_SUCCESS || !raw) {
+            continue;
+        }
+        NmMessage message(raw);
+
+        const char *rawName = notmuch_message_get_filename(message.get());
+        if (!rawName)
+            continue;
+        const QString from = QString::fromUtf8(rawName);
+        // The handle is released before the file moves under it.
+        message.reset();
+
+        // Where it is coming FROM, captured here because this is the only
+        // moment the old filename exists. See messagesMovedFrom().
+        const QString origin = folderOfMessageFile(root, from);
+
+        // cur/, never new/. A file dropped in new/ is re-announced as fresh
+        // mail by every reader of the Maildir.
+        if (!QDir().mkpath(destDir)) {
+            emit errorOccurred(QStringLiteral("Cannot create folder %1")
+                                   .arg(destDir));
+            continue;
+        }
+
+        const QString to = destDir + QLatin1Char('/') + QFileInfo(from).fileName();
+        if (from == to) {
+            // Already where it was asked to go. Reported as moved, since the
+            // caller's request is satisfied.
+            moved.append(id);
+            origins.insert(id, origin);
+            continue;
+        }
+
+        if (!QFile::rename(from, to)) {
+            emit errorOccurred(QStringLiteral("Cannot move %1 to %2")
+                                   .arg(QFileInfo(from).fileName(), destFolder));
+            continue;
+        }
+
+        // Index the NEW path BEFORE dropping the old one. The reverse order
+        // removes the last filename for this message id, which deletes the
+        // database entry and every tag on it; the file then reindexes as a
+        // brand new message with default tags, silently.
+        notmuch_message_t *indexed = nullptr;
+        const notmuch_status_t added = notmuch_database_index_file(
+            db, to.toUtf8().constData(), nullptr, &indexed);
+        if (indexed)
+            notmuch_message_destroy(indexed);
+
+        // DUPLICATE_MESSAGE_ID is success here: it means the id was already
+        // known, which is exactly the case for a file this just moved.
+        if (added != NOTMUCH_STATUS_SUCCESS
+            && added != NOTMUCH_STATUS_DUPLICATE_MESSAGE_ID) {
+            QFile::rename(to, from);
+            emit errorOccurred(QStringLiteral("Cannot index %1 at its new path: %2")
+                                   .arg(id, QString::fromUtf8(
+                                                notmuch_status_to_string(added))));
+            continue;
+        }
+
+        notmuch_database_remove_message(db, from.toUtf8().constData());
+        moved.append(id);
+        origins.insert(id, origin);
+    }
+
+    notmuch_database_close(db);
+    notmuch_database_destroy(db);
+
+    emit messagesMoved(moved, destFolder);
+    emit messagesMovedFrom(origins, destFolder);
+}
+
+void NotmuchWorker::resolveMessages(const QStringList &messageIds,
+                                   const QString &requestTag)
+{
+    if (messageIds.isEmpty())
+        return;
+
+    QStringList terms;
+    terms.reserve(messageIds.size());
+    for (const QString &id : messageIds)
+        terms.append(QStringLiteral("id:%1").arg(id));
+
+    resolveQuery(terms.join(QStringLiteral(" or ")), requestTag);
+}
+
+void NotmuchWorker::resolveThreadMessages(const QStringList &threadIds,
+                                          const QString &requestTag)
+{
+    if (threadIds.isEmpty())
+        return;
+
+    // One combined query, for the reason applyTagsToThreads() gives: a query
+    // per thread reopens the same Xapian cursor once per selected row.
+    QStringList terms;
+    terms.reserve(threadIds.size());
+    for (const QString &id : threadIds)
+        terms.append(QStringLiteral("thread:%1").arg(id));
+
+    resolveQuery(terms.join(QStringLiteral(" or ")), requestTag);
+}
+
+void NotmuchWorker::resolveQuery(const QString &query,
+                                 const QString &requestTag)
+{
+    if (!openReadOnly())
+        return;
+
+    NmQuery nmQuery(notmuch_query_create(m_db, query.toUtf8().constData()));
+    if (!nmQuery) {
+        emit errorOccurred(QStringLiteral("Cannot resolve selected threads"));
+        return;
+    }
+
+    notmuch_messages_t *raw = nullptr;
+    if (notmuch_query_search_messages(nmQuery.get(), &raw)
+        != NOTMUCH_STATUS_SUCCESS) {
+        emit errorOccurred(QStringLiteral("Cannot resolve selected threads"));
+        return;
+    }
+
+    // Paths are reported RELATIVE to the database root, matching
+    // ThreadSummary::firstMessagePath: the UI knows accounts only by their
+    // maildir, itself a database-relative prefix.
+    const QString dbRoot =
+        QDir(QString::fromUtf8(notmuch_database_get_path(m_db))).absolutePath();
+
+    QStringList messageIds;
+    QStringList paths;
+    QStringList tags;
+    NmMessages messages(raw);
+    for (; notmuch_messages_valid(messages.get());
+           notmuch_messages_move_to_next(messages.get())) {
+        NmMessage message(notmuch_messages_get(messages.get()));
+        if (!message)
+            continue;
+        const char *rawName = notmuch_message_get_filename(message.get());
+        if (!rawName)
+            continue;
+        messageIds.append(
+            QString::fromUtf8(notmuch_message_get_message_id(message.get())));
+        paths.append(
+            QDir(dbRoot).relativeFilePath(QString::fromUtf8(rawName)));
+        // Joined by a TAB, not a space. A notmuch tag may absolutely contain
+        // a space: a Maildir folder named "Inbox/SlackBuilds users" produces
+        // `deleted-from:Inbox/SlackBuilds users`, and splitting that on spaces
+        // truncated the folder to "Inbox/SlackBuilds". Restore then moved the
+        // messages into a folder of that name, CREATING it, so four real
+        // messages ended up in a directory mbsync does not sync and the user
+        // could not find them. A tab cannot appear in a tag, because notmuch's
+        // own dump/restore format is whitespace-delimited by line.
+        tags.append(tagsOf(message.get()).join(QLatin1Char('\t')));
+    }
+
+    emit threadMessagesResolved(messageIds, paths, tags, requestTag);
+}
+
 void NotmuchWorker::requestAllTags(quint64 generation)
 {
     if (!openReadOnly())
diff --git a/src/notmuchworker.h b/src/notmuchworker.h
index f07e563..9932e59 100644
--- a/src/notmuchworker.h
+++ b/src/notmuchworker.h
@@ -18,6 +18,7 @@
 
 #pragma once
 
+#include <QMap>
 #include <QObject>
 #include <QStringList>
 #include <QVector>
@@ -120,6 +121,19 @@ public slots:
     /// it would block the user's cron `notmuch new`.
     void applyTags(const TagChange &change);
 
+    /// Moves messages into `destFolder`, relative to the database path.
+    ///
+    /// A folder NAME rather than a "move to trash" call, because v2's Send
+    /// needs exactly this operation for Drafts and Sent. Nothing
+    /// trash-specific belongs here.
+    ///
+    /// The first mutation in this class that is not a notmuch tag: a rename on
+    /// disk plus a reindex. Ordering is rename, index the new path, drop the
+    /// old one. Indexing first is required, not stylistic: removing the last
+    /// filename for a message id deletes the database entry and every tag on
+    /// it, so removing before indexing loses the message's tags.
+    void moveMessages(const QStringList &messageIds, const QString &destFolder);
+
     /// Batch tagging over whole threads. The UI holds thread ids, not message
     /// ids, for rows it has not opened, so the resolution happens here where
     /// the database handle lives. This is the path the archive/flag/delete
@@ -129,6 +143,39 @@ public slots:
                             const QStringList &remove,
                             const QString &description);
 
+    /// Resolves whole threads to the message ids and file paths they contain.
+    ///
+    /// Delete thread MOVES every message, and a move needs message ids, which
+    /// the UI does not hold for a thread it never expanded. The resolution
+    /// happens here for the same reason applyTagsToThreads() does it here:
+    /// the database handle lives on this thread, and one combined query beats
+    /// reopening the cursor per thread.
+    ///
+    /// Paths come back beside the ids because the destination is per ACCOUNT
+    /// and the UI resolves an account from a message's path. Without them the
+    /// caller would know which messages to move and not where any of them
+    /// belongs.
+    void resolveThreadMessages(const QStringList &threadIds,
+                               const QString &requestTag);
+
+    /// The same walk for a set of MESSAGE ids rather than thread ids.
+    ///
+    /// Restore needs each message's tags and path to decide where to send it,
+    /// and must not read them from the model: the model's tags come from the
+    /// query, so a row whose delete has not been re-queried still carries its
+    /// pre-delete tags and the origin tag is missing. A restore that guesses
+    /// the destination is worse than one that does nothing.
+    void resolveMessages(const QStringList &messageIds,
+                         const QString &requestTag);
+
+private:
+    /// The shared walk behind resolveMessages() and resolveThreadMessages():
+    /// runs `query` and emits threadMessagesResolved() with each match's id,
+    /// database-relative path and tab-joined tags.
+    void resolveQuery(const QString &query, const QString &requestTag);
+
+public slots:
+
     /// Every tag in the database, sorted. Feeds query bar completion, which
     /// cannot offer tag names it has no way to enumerate. Called at startup,
     /// after a sync, and after a tag mutation introduces an unknown tag.
@@ -184,6 +231,42 @@ signals:
                           quint64 generation);
     void messageLoaded(const QVector<MessageRef> &messages, quint64 generation);
     void tagsApplied(const TagChange &change);
+
+    /// Carries the ids that ACTUALLY moved, which may be fewer than requested.
+    /// A stale id, a missing folder or a failed rename drops out here rather
+    /// than aborting the batch.
+    void messagesMoved(const QStringList &messageIds, const QString &destFolder);
+
+    /// The same move, reported per message with the folder it came FROM.
+    ///
+    /// Emitted alongside messagesMoved rather than replacing it: that signal's
+    /// shape is what test_notmuchworker asserts on, and a caller wanting only
+    /// "did it move" should not have to unpack a map.
+    ///
+    /// The origin has to be reported from HERE because nowhere else knows it.
+    /// A Maildir filename does not record the folder a message came from, and
+    /// once the file has moved notmuch cannot answer either; the UI holds no
+    /// path at all for a thread row it has not expanded. This is the one
+    /// moment the old filename exists, so it is the only place the origin can
+    /// be derived.
+    ///
+    /// Folders are relative to the database path and carry no `cur`/`new`
+    /// segment, matching the `destFolder` moveMessages() takes, so a value
+    /// from here can be passed straight back to move a message home.
+    void messagesMovedFrom(const QMap<QString, QString> &originByMessageId,
+                           const QString &destFolder);
+    /// The answer to resolveThreadMessages(), as parallel lists: `messageIds`
+    /// and the database-relative `paths` of the same messages, in the same
+    /// order. `requestTag` is echoed back so a caller can tell which request
+    /// this answers.
+    /// `tags` carries each message's tags joined by a space, in the same
+    /// order. Needed because Restore reads a message's `deleted-from:` tag to
+    /// decide where to send it, and an unexpanded thread's messages have no
+    /// node in the model to read tags from.
+    void threadMessagesResolved(const QStringList &messageIds,
+                                const QStringList &paths,
+                                const QStringList &tags,
+                                const QString &requestTag);
     void allTagsReady(const QStringList &tags, quint64 generation);
 
     /// One entry per requested query, in the order they were asked for. A query
diff --git a/src/tagdialog.cpp b/src/tagdialog.cpp
index 1fb3f18..fb2c629 100644
--- a/src/tagdialog.cpp
+++ b/src/tagdialog.cpp
@@ -268,16 +268,25 @@ void TagDialog::accept()
     QStringList add = splitTags(m_addEdit->text());
     QStringList remove = splitTags(m_removeEdit->text());
 
-    // Validate before applying anything: a partial change is worse than none,
-    // since the user cannot tell which half landed.
-    for (const QStringList &list : { add, remove }) {
-        for (const QString &tag : list) {
-            const TagNameProblem problem = validateTagName(tag);
-            if (problem != TagNameProblem::Ok) {
-                QMessageBox::warning(this, tr("Invalid tag"),
-                                     tagNameProblemText(problem, tag));
-                return;   // Stay open, with the text still there to fix.
-            }
+    // Validate what is being ADDED. A partial change is worse than none, since
+    // the user cannot tell which half landed, so this runs before anything is
+    // applied.
+    //
+    // REMOVAL is deliberately not validated. The rules here exist to stop a
+    // troublesome tag being CREATED; a tag that already exists is a fact, and
+    // refusing to remove it because it breaks a rule leaves the user with a
+    // tag they can see, cannot type, and cannot get rid of. That happened with
+    // `deleted-from:Inbox/SlackBuilds users`: an origin tag naming a Maildir
+    // folder whose name contains a space, rejected by the space rule, so the
+    // one dialog that could have cleared it refused the only text that names
+    // it. Whether such a tag SHOULD exist is a separate question from whether
+    // the user may delete it, and the answer to the second is always yes.
+    for (const QString &tag : add) {
+        const TagNameProblem problem = validateTagName(tag);
+        if (problem != TagNameProblem::Ok) {
+            QMessageBox::warning(this, tr("Invalid tag"),
+                                 tagNameProblemText(problem, tag));
+            return;   // Stay open, with the text still there to fix.
         }
     }
 
diff --git a/src/threadlistmodel.cpp b/src/threadlistmodel.cpp
index 6ddd85c..6162a5f 100644
--- a/src/threadlistmodel.cpp
+++ b/src/threadlistmodel.cpp
@@ -696,6 +696,10 @@ ThreadListModel::nodeFor(const ThreadSummary &summary)
         node.first.messageId = summary.firstMessageId;
         node.first.threadId = summary.threadId;
         node.first.tags = summary.firstMessageTags;
+        // Carried alongside the tags, for the same reason messageById()
+        // carries it onto a synthesised root: an unexpanded row has to know
+        // which account it belongs to before Delete can name a folder.
+        node.first.filePath = summary.firstMessagePath;
     }
     return node;
 }
@@ -984,6 +988,12 @@ MessageNode ThreadListModel::messageById(const QString &messageId) const
             root.subject = node.summary.subject;
             root.date = node.summary.date;
             root.tags = node.summary.tags;
+            // Carried from the query, so an UNEXPANDED row still knows which
+            // account it belongs to. Delete needs that to name a trash folder,
+            // and an unexpanded row is the ordinary case rather than an edge
+            // one: without this every thread row resolved to no account and
+            // Delete reported "no trash folder configured" for all of them.
+            root.filePath = node.summary.firstMessagePath;
             return root;
         }
 
@@ -1198,6 +1208,7 @@ void ThreadListModel::applyMessageTagChange(const QString &messageId,
                 node.first.messageId = node.summary.firstMessageId;
                 node.first.threadId = node.summary.threadId;
                 node.first.tags = node.summary.tags;
+                node.first.filePath = node.summary.firstMessagePath;
             }
             retag(node.first.tags);
 
diff --git a/src/types.h b/src/types.h
index 409ce79..f4d387a 100644
--- a/src/types.h
+++ b/src/types.h
@@ -62,6 +62,26 @@ struct ThreadSummary
     /// file. Do not move it behind a flag by analogy with `recipients`.
     QStringList firstMessageTags;
 
+    /// That message's file, RELATIVE to the database path, which is what says
+    /// which ACCOUNT it belongs to.
+    ///
+    /// Relative and not absolute, deliberately. The UI knows an account only
+    /// by its `maildir`, itself a database-relative prefix, so an absolute
+    /// path here matches no account and silently resolves every row to none.
+    ///
+    /// Needed because Delete moves the file (item 103) and the destination is
+    /// per account, so the action has to resolve an account before it can name
+    /// a trash folder. Resolving through the thread's account TAG instead is
+    /// not equivalent: that tag is optional config, so an account without one
+    /// would silently be undeletable, while a maildir prefix is what makes a
+    /// message belong to an account in the first place.
+    ///
+    /// Free for the same reason firstMessageId and firstMessageTags are: the
+    /// walk that finds that message is already happening, and this reads the
+    /// INDEX rather than the message file. Do not move it behind a flag by
+    /// analogy with `recipients`.
+    QString firstMessagePath;
+
     /// Who the thread's messages were sent TO, summarised for one line.
     ///
     /// Empty unless the query asked for it, and that is a performance