feat(compose): wire the composer into the main window, item 123compose-and-send

The reply family is disabled on mail that arrived at an account with no
send_command, behind a ribbon in MessageView naming the account and the key
to add. save_message is deliberately never disabled: it is the escape hatch
for exactly that case.

The ribbon is a WIDGET in the pane's layout, never markup inside the web
view. Composing HTML from configuration into the one document that renders
input from strangers is the wrong direction, and the header row is already a
widget for the same reason.

Compose itself is disabled only when NO account can send, and that state is
not warned about at startup: an installation with no send_command anywhere
is a valid read-only installation.

Every reply resolves through messageScopeFor(), not threadFor(): a thread
row means the one message its card shows. Replying to a thread is
meaningless; a reply answers a message. The context is built from the
DATABASE rather than the model, the rule Restore already follows, because a
row whose state has not been re-queried carries stale values and a reply
built from one would carry the wrong recipients.

The mail root crosses from the worker as its own signal. There was no route
for it at all: mailRootOf() is file-static in notmuchworker.cpp, and item
124 records that composing a destination from database.path writes into the
Xapian tree under a split index. The test uses NotmuchFixture::splitIndex(),
the only layout where the two accessors disagree.

A thread row's path is RELATIVE to the mail root while a message row's is
absolute, so the account lookup matched nothing and the reply family was
dead on mail from an account that could send. Found by the positive guard
test rather than the negative one, which passed throughout for the wrong
reason.

The quit path checks the failed-save case FIRST. In the ordinary case
nothing is lost by saving; there, saving is what is already not working, so
the dialog says plainly that quitting loses that text rather than offering a
save that will fail again. Both dialogs name the composers, and the ordinary
one asks once whatever the count, because three modals in a row is worse
than a coarse answer. Its wording says drafts already saved stay in the
folder, so Discard cannot read as 'delete my three messages'.

The Save loop holds QPointers, not raw pointers. A deleteLater() posted
while a nested exec() runs IS processed by that nested loop, measured in a
standalone program: the guard nulls before the modal returns. Closing a
composer while the quit dialog is up therefore freed a window the loop then
called saveDraftNow() on, crashing at the exact moment the application
promised to preserve that text.

A compose request that matches nothing clears itself and says so. It was
cleared only on a match, so a message deleted between selection and Reply
left the request armed for the session: Reply did nothing, and the next
ordinary click on that message opened a composer nobody asked for while the
pane stayed blank.

Forward carries the original's attachments, which the context has always had
a field for and nothing ever filled, and seeds its HTML toggle from
[compose] send_html. Only Reply seeds that from the original.

save_message keeps its filename inside the chosen directory and no longer
overwrites a file already there. The check was correct and untested: the
test asserted through Attachment's helpers rather than through the function
production calls, so deleting the containment check outright left it green.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TvwDptMWxjqhbCmjxwcSZ2

1 files changed, 615 insertions, 10 deletions

diff --git a/src/mainwindow.cpp b/src/mainwindow.cpp
index 5155c09..0131959 100644
--- a/src/mainwindow.cpp
+++ b/src/mainwindow.cpp
@@ -26,6 +26,7 @@
 #include <QDialog>
 #include <QDialogButtonBox>
 #include <QDir>
+#include <QFileDialog>
 #include <QFileInfo>
 #include <QHBoxLayout>
 #include <QHeaderView>
@@ -47,6 +48,8 @@
 #include <QToolButton>
 #include <QVBoxLayout>
 
+#include "composecontext.h"
+#include "composewindow.h"
 #include "mailsync.h"
 #include "messageview.h"
 #include "mimeparser.h"
@@ -93,8 +96,42 @@ QString MainWindow::uiStatePath()
 namespace {
 /// Overridden only by setLocksPathForTesting(); "/proc/locks" in every real run.
 QString g_locksPath = QStringLiteral("/proc/locks");
+
 } // namespace
 
+/// Doc comment on the declaration. Separators and control characters are
+/// replaced rather than stripped so a subject carrying one yields a readable
+/// name, instead of being truncated to its last segment by the basename
+/// reduction Attachment::safeFilename() performs afterwards.
+QString MainWindow::defaultMessageFilename(const QString &subject)
+{
+    QString name = subject.simplified();
+    for (QChar &c : name) {
+        if (c == QLatin1Char('/') || c == QLatin1Char('\\')
+            || c == QLatin1Char(':') || c.category() == QChar::Other_Control) {
+            c = QLatin1Char('-');
+        }
+    }
+    // Long subjects exist and many filesystems stop at 255 bytes. Truncated
+    // before the extension is added, so the cut cannot eat it.
+    name.truncate(120);
+    name = name.trimmed();
+
+    // A leading dot makes the file HIDDEN on every Unix desktop, and a subject
+    // beginning with one is ordinary ("...and another thing", or a traversal
+    // whose separators were just replaced above, leaving "..-..-etc-passwd").
+    // The write succeeds and the user cannot see the file they just saved.
+    // Measured: QDir::entryList omits it without QDir::Hidden, which is how
+    // this was found.
+    while (name.startsWith(QLatin1Char('.')))
+        name.remove(0, 1);
+    name = name.trimmed();
+
+    if (name.isEmpty())
+        name = QStringLiteral("message");
+    return name + QStringLiteral(".eml");
+}
+
 void MainWindow::setLocksPathForTesting(const QString &path)
 {
     g_locksPath = path;
@@ -202,6 +239,105 @@ void MainWindow::closeEvent(QCloseEvent *event)
         return;
     }
 
+    // Case 3 FIRST, because it is the one where saving is what is already not
+    // working: in case 2 nothing is lost by saving, here quitting loses that
+    // text, so the dialog must say so plainly rather than offering a save that
+    // will fail again.
+    QStringList failedSaves;
+    for (const QPointer<ComposeWindow> &composer : m_composers) {
+        if (composer && composer->lastSaveFailed())
+            failedSaves.append(composer->windowTitle());
+    }
+    if (!failedSaves.isEmpty()) {
+        // The titles, not merely the count. The spec requires the dialog to
+        // NAME what could not be saved: "2 messages could not be saved" tells
+        // a user with four composers open nothing about which two to rescue.
+        //
+        // The list is a separate paragraph rather than interpolated into the
+        // sentence. The count and the list combine differently across
+        // languages, and a translator given "%n message(s) ...: %1" has to
+        // keep an English clause order Italian does not share.
+        QMessageBox box(this);
+        box.setIcon(QMessageBox::Warning);
+        box.setWindowTitle(tr("A draft could not be saved"));
+        box.setText(tr("%n message(s) could not be saved to the drafts "
+                       "folder. Quitting now loses that text.", "",
+                       failedSaves.size()));
+        box.setInformativeText(failedSaves.join(QLatin1Char('\n')));
+        box.setStandardButtons(QMessageBox::Retry | QMessageBox::Discard
+                               | QMessageBox::Cancel);
+        box.setDefaultButton(QMessageBox::Cancel);
+        const int answer = box.exec();
+
+        if (answer == QMessageBox::Cancel) {
+            event->ignore();
+            return;
+        }
+        if (answer == QMessageBox::Retry) {
+            bool allSaved = true;
+            for (const QPointer<ComposeWindow> &composer : m_composers) {
+                if (composer && composer->lastSaveFailed()
+                    && !composer->saveDraftNow()) {
+                    allSaved = false;
+                }
+            }
+            if (!allSaved) {
+                // Still failing: stay open rather than quitting on a retry
+                // that did not work, which would lose exactly the text the
+                // user pressed Retry to keep.
+                event->ignore();
+                return;
+            }
+        }
+    }
+
+    // Case 2: ONE dialog whatever the count. Three modals in a row is worse
+    // than a coarse answer, so it applies to all of them and there is no
+    // per-draft choice.
+    const QList<QPointer<ComposeWindow>> blocking = composersBlockingQuit();
+    if (!blocking.isEmpty()) {
+        QStringList titles;
+        titles.reserve(blocking.size());
+        for (const QPointer<ComposeWindow> &composer : blocking)
+            titles.append(composer->windowTitle());
+
+        QMessageBox box(this);
+        box.setIcon(QMessageBox::Question);
+        box.setWindowTitle(tr("Messages still being composed"));
+        // "Discard" discards UNSAVED EDITS, not drafts: a draft already
+        // autosaved stays in the folder. The wording must not read as
+        // "delete my three messages".
+        box.setText(tr("%n message(s) are still being composed. Drafts "
+                       "already saved stay in the drafts folder either way.",
+                       "", blocking.size()));
+        box.setInformativeText(titles.join(QLatin1Char('\n')));
+        box.setStandardButtons(QMessageBox::Save | QMessageBox::Discard
+                               | QMessageBox::Cancel);
+        box.setDefaultButton(QMessageBox::Save);
+        const int answer = box.exec();
+
+        if (answer == QMessageBox::Cancel) {
+            event->ignore();
+            return;
+        }
+        if (answer == QMessageBox::Save) {
+            // Null-checked per iteration, because `blocking` was computed
+            // BEFORE exec() and a nested event loop processes deleteLater().
+            // The dialog is window-modal to this window only, so a user can
+            // close a composer while it is up; measured in a standalone Qt
+            // program, that composer is destroyed before exec() returns.
+            // Without this check the save runs on freed memory at the exact
+            // moment the application promised to preserve the text, and the
+            // remaining composers' drafts are never written because the crash
+            // happens mid-loop. Case 3's Retry loop above has always had the
+            // equivalent guard; this one had dropped it.
+            for (const QPointer<ComposeWindow> &composer : blocking) {
+                if (composer)
+                    composer->saveDraftNow();
+            }
+        }
+    }
+
     if (!m_closeApproved && pendingEditCount() > 0
         && m_config.syncOnExit() != Config::SyncOnExit::Never) {
 
@@ -758,25 +894,407 @@ void MainWindow::buildUi()
     setWindowTitle(QStringLiteral("qtmaildir %1").arg(QTMAILDIR_VERSION));
 }
 
-// The six compose handlers, empty until the composer exists (item 123).
-//
-// Deliberately empty rather than absent. Registering the actions first means
-// everyKnownActionIsRegistered, everyActionCarriesAnIcon and
-// everyActionIsReachableFromAMenu cover them while the composer is being
-// built; a menu entry that does nothing yet is a smaller defect than an action
-// nobody can reach, which is what those tests exist to catch.
 void MainWindow::composeNew()
 {
+    // m_accountBox->currentData() is how the selected account is read
+    // everywhere else in this file; there is no currentAccountKey() accessor.
+    // Empty means the All accounts view, which falls through to rule 2.
+    const QString accountKey = ComposeContextBuilder::accountForNew(
+        m_config, m_accountBox->currentData().toString());
+    if (accountKey.isEmpty()) {
+        // Unreachable while the action is disabled, which is the only state
+        // this can be true in. Reported rather than returning silently: an
+        // action that runs and does nothing is the failure mode item 105
+        // records as "the key does nothing".
+        showTransientStatus(tr("No account is configured to send mail"));
+        return;
+    }
+
+    ComposeContext context;
+    context.kind = ComposeContext::Kind::New;
+    context.accountKey = accountKey;
+    context.seedHtml = m_config.compose().sendHtml;
+
+    openComposer(context);
 }
 
 void MainWindow::composeReply(ComposeContext::Kind kind, bool quote)
 {
-    Q_UNUSED(kind);
-    Q_UNUSED(quote);
+    // messageScopeFor() semantics, NOT threadFor(): a thread row means the one
+    // message its card shows, a reply row means itself. Replying to a thread
+    // is meaningless; a reply answers a message.
+    //
+    // It takes a QModelIndexList, not a single index, so the current index is
+    // wrapped rather than passed bare.
+    const ActionScope scope =
+        m_model->messageScopeFor({ m_threadView->currentIndex() });
+    if (scope.messageIds.isEmpty()) {
+        showTransientStatus(tr("No message is selected"));
+        return;
+    }
+
+    // Built from the DATABASE, never from the model. The model's data comes
+    // from the query, so a row whose state has not been re-queried carries
+    // stale values, and a reply built from a stale row would carry the wrong
+    // recipients. This is the rule Restore already follows.
+    requestMessageForCompose(scope.messageIds.first(), kind, quote);
+}
+
+void MainWindow::requestMessageForCompose(const QString &messageId,
+                                          ComposeContext::Kind kind,
+                                          bool quote)
+{
+    if (messageId.isEmpty())
+        return;
+
+    m_pendingCompose = { messageId, kind, quote, true };
+
+    // The same generation every other worker request carries, so a reply that
+    // arrives after the query moved on is discarded rather than opening a
+    // composer on a message the user is no longer looking at.
+    QMetaObject::invokeMethod(m_worker, "loadMessage", Qt::QueuedConnection,
+                              Q_ARG(QString, messageId),
+                              Q_ARG(quint64, m_generation));
+}
+
+void MainWindow::openComposerFor(const MessageRef &ref,
+                                 ComposeContext::Kind kind, bool quote)
+{
+    MimeParser parser;
+    const ParsedMessage original = parser.parse(ref.filePath);
+    if (!original.ok) {
+        showTransientStatus(tr("That message could not be read"));
+        return;
+    }
+
+    ComposeContext context;
+    context.kind = kind;
+    context.originalPath = ref.filePath;
+
+    const bool replyAll = kind == ComposeContext::Kind::ReplyAll;
+    const bool forwarding = kind == ComposeContext::Kind::Forward;
+
+    if (!forwarding) {
+        ComposeContextBuilder::recipientsForReply(
+            original, replyAll, ComposeContextBuilder::ownAddresses(m_config),
+            &context.to, &context.cc);
+
+        // Threading headers on a reply only. A forward starts a new
+        // conversation: carrying In-Reply-To would file it under the thread it
+        // was forwarded out of, in the RECIPIENT's client.
+        context.inReplyTo = original.messageId;
+        context.references = ComposeContextBuilder::referencesForReply(original);
+    }
+
+    context.subject = forwarding
+                          ? ComposeContextBuilder::forwardSubject(original.subject)
+                          : ComposeContextBuilder::replySubject(original.subject);
+
+    if (quote)
+        context.quotedBody = ComposeContextBuilder::quoteBody(original);
+
+    // Forward seeds from the CONFIG, Reply from the original. The split is
+    // the spec's and Config::ComposeSettings::sendHtml states it too: an HTML
+    // part in the original is a fact about the SENDER's software, so it is the
+    // right seed when answering them and says nothing about a forward, which
+    // is a new message to somebody else. composeNew() already reads the config
+    // for the same reason.
+    context.seedHtml = forwarding ? m_config.compose().sendHtml
+                                  : original.hasHtml();
+
+    // accountForReply() takes messagePaths PLURAL because notmuch can return
+    // several filenames for one id, and it disambiguates between them by
+    // recipient. That disambiguation is INERT here, and the reason is upstream
+    // rather than a decision made at this call site: NotmuchWorker::loadMessage
+    // builds its MessageRef from notmuch_message_get_filename(), the SINGULAR
+    // accessor, so nothing in the pipeline ever carries more than one path and
+    // the list below can never hold more than one element. Backlog item 137
+    // carries the fix (MessageRef gains a filePaths list populated from
+    // notmuch_message_get_filenames()); until then a message that arrived at
+    // two accounts can open its reply from the wrong one.
+    const QStringList recipients = context.to + context.cc;
+    context.accountKey = ComposeContextBuilder::accountForReply(
+        m_config, { ref.filePath }, recipients, m_mailRoot);
+
+    if (context.accountKey.isEmpty()
+        || !m_config.account(context.accountKey).canSend()) {
+        // The enablement pass should already have stopped this, but it answers
+        // from the model's path while this answers from the database's, and
+        // the two can disagree on a row that has not been re-queried.
+        showTransientStatus(
+            tr("That message arrived at an account that cannot send"));
+        return;
+    }
+
+    openComposer(context);
+}
+
+void MainWindow::openComposer(const ComposeContext &context)
+{
+    if (m_mailRoot.isEmpty()) {
+        // Without the root a draft cannot be written anywhere, and a composer
+        // that silently cannot autosave is the state the quit path's honesty
+        // depends on not being in.
+        showTransientStatus(tr("The Maildir root is not known yet"));
+        return;
+    }
+
+    auto *composer = new ComposeWindow(context, m_config, m_mailRoot);
+    composer->setAttribute(Qt::WA_DeleteOnClose);
+    m_composers.append(QPointer<ComposeWindow>(composer));
+
+    // Compaction, and ONLY compaction. The QPointer above is what keeps
+    // composersBlockingQuit() safe against a destroyed window, since it nulls
+    // on destruction; this drops the entry so the list does not accumulate
+    // nulls for the session's lifetime. Neither replaces the other: without
+    // the signal the list leaks entries, without the QPointer it dangles.
+    connect(composer, &ComposeWindow::closed, this,
+            [this](ComposeWindow *which) {
+                m_composers.removeIf([which](const QPointer<ComposeWindow> &p) {
+                    return p.isNull() || p.data() == which;
+                });
+            });
+
+    composer->show();
+}
+
+QList<QPointer<ComposeWindow>> MainWindow::composersBlockingQuit() const
+{
+    QList<QPointer<ComposeWindow>> blocking;
+    for (const QPointer<ComposeWindow> &composer : m_composers) {
+        if (composer && composer->hasUnsavedEdits())
+            blocking.append(composer);
+    }
+    return blocking;
+}
+
+ComposeWindow *MainWindow::openComposerForTest()
+{
+    const QString accountKey =
+        ComposeContextBuilder::accountForNew(m_config, QString());
+    if (accountKey.isEmpty())
+        return nullptr;
+
+    ComposeContext context;
+    context.kind = ComposeContext::Kind::New;
+    context.accountKey = accountKey;
+
+    const int before = m_composers.size();
+    openComposer(context);
+    if (m_composers.size() == before)
+        return nullptr;
+    return m_composers.constLast().data();
 }
 
-void MainWindow::saveDisplayedMessage()
+QList<ComposeWindow *> MainWindow::openComposersForTest() const
 {
+    QList<ComposeWindow *> live;
+    for (const QPointer<ComposeWindow> &composer : m_composers) {
+        if (composer)
+            live.append(composer.data());
+    }
+    return live;
+}
+
+int MainWindow::openComposerCount() const
+{
+    int live = 0;
+    for (const QPointer<ComposeWindow> &composer : m_composers) {
+        if (composer)
+            ++live;
+    }
+    return live;
+}
+
+void MainWindow::markComposersDirtyForTest()
+{
+    // Through the real edit path: the body editor's own textChanged is what
+    // ComposeWindow::markDirty() is connected to, so inserting text here
+    // exercises the same route typing does. Setting a dirty flag directly
+    // would pass against a composer that never notices an edit at all.
+    //
+    // QTextCursor rather than QTest::keyClicks, so production code does not
+    // have to link QtTest.
+    for (const QPointer<ComposeWindow> &composer : m_composers) {
+        if (!composer)
+            continue;
+        if (auto *body = composer->findChild<QPlainTextEdit *>(
+                QStringLiteral("body"))) {
+            body->textCursor().insertText(QStringLiteral("x"));
+        }
+    }
+}
+
+QString MainWindow::accountForCurrentMessage() const
+{
+    if (m_mailRoot.isEmpty())
+        return {};
+
+    const QModelIndex current = m_threadView->currentIndex();
+    if (!current.isValid())
+        return {};
+
+    // The model's path, deliberately. This decides whether a CONTROL is live,
+    // which a stale path answers well enough; the context that actually opens
+    // a composer resolves the account again from the database. Asking the
+    // worker here would make every selection change a round trip.
+    //
+    // The two sources are in DIFFERENT FORMS and normalising them is not
+    // tidying. ThreadSummary::firstMessagePath is RELATIVE to the mail root,
+    // because runQuery() reduces it with relativeFilePath() so the UI can
+    // compare it against an account's maildir; MessageNode::filePath is
+    // ABSOLUTE, because MimeParser opens it. accountOwning() builds an
+    // absolute prefix, so handing it the relative one matches no account at
+    // all and every thread row reports no account, which disables the reply
+    // family on mail from an account that can perfectly well send. Measured:
+    // it did exactly that until the guard test caught it.
+    QString path;
+    if (m_model->isMessageRow(current)) {
+        path = m_model->messageAt(current).filePath;
+    } else {
+        path = m_model->threadFor(current).firstMessagePath;
+    }
+    if (path.isEmpty())
+        return {};
+
+    const QString absolute = QDir::isAbsolutePath(path)
+                                 ? path
+                                 : QDir(m_mailRoot).absoluteFilePath(path);
+
+    return ComposeContextBuilder::accountForReply(m_config, { absolute },
+                                                  QStringList(), m_mailRoot);
+}
+
+void MainWindow::updateComposeActions()
+{
+    // The reply family is disabled on mail that arrived at an account which
+    // cannot send. save_message is deliberately NOT in this list: it is the
+    // escape hatch for exactly that case, writing the raw message to a file
+    // that can be attached to a new message from an account that can send.
+    const QString replyAccount = accountForCurrentMessage();
+    const bool canReply = !replyAccount.isEmpty()
+                          && m_config.account(replyAccount).canSend();
+
+    static const QStringList kReplyFamily = {
+        QStringLiteral("reply"), QStringLiteral("reply_all"),
+        QStringLiteral("reply_no_quote"), QStringLiteral("forward")
+    };
+    for (const QString &name : kReplyFamily) {
+        if (QAction *action = m_actions.value(name))
+            action->setEnabled(canReply);
+    }
+
+    // The ribbon appears only when an account was identified AND it cannot
+    // send. An unidentified account is not a receive-only one: it is a message
+    // whose file no account owns, and naming no account in a ribbon that
+    // exists to name one would be worse than staying quiet.
+    const bool receiveOnly =
+        !replyAccount.isEmpty() && !m_config.account(replyAccount).canSend();
+    m_messageView->setReceiveOnlyAccount(receiveOnly ? replyAccount
+                                                     : QString());
+
+    // compose is disabled only when NO account can send. A read-only
+    // installation is valid and is not warned about.
+    if (QAction *compose = m_actions.value(QStringLiteral("compose")))
+        compose->setEnabled(!m_config.sendingAccounts().isEmpty());
+}
+
+void MainWindow::saveDisplayedMessage(const QString &chosenDirectory)
+{
+    const QModelIndex current = m_threadView->currentIndex();
+    const ActionScope scope = m_model->messageScopeFor({ current });
+    if (scope.messageIds.isEmpty()) {
+        showTransientStatus(tr("No message is selected"));
+        return;
+    }
+
+    // The path from the model, which is what the pane is rendering. Unlike a
+    // reply, a copy of the wrong file is visible to the user the moment they
+    // open it, so this does not need the database round trip a reply does.
+    QString sourcePath;
+    QString subject;
+    if (m_model->isMessageRow(current)) {
+        const MessageNode node = m_model->messageAt(current);
+        sourcePath = node.filePath;
+        subject = node.subject;
+    } else {
+        const ThreadSummary thread = m_model->threadFor(current);
+        sourcePath = thread.firstMessagePath;
+        subject = thread.subject;
+    }
+    if (sourcePath.isEmpty()) {
+        showTransientStatus(tr("That message's file could not be found"));
+        return;
+    }
+
+    // Relative for a thread row, absolute for a message row. The same
+    // asymmetry accountForCurrentMessage() documents at length.
+    if (!QDir::isAbsolutePath(sourcePath) && !m_mailRoot.isEmpty())
+        sourcePath = QDir(m_mailRoot).absoluteFilePath(sourcePath);
+
+    if (!QFileInfo::exists(sourcePath)) {
+        showTransientStatus(tr("That message's file could not be found"));
+        return;
+    }
+
+    // The dialog only when no directory was supplied. A test supplies one,
+    // because the modal cannot be driven under the offscreen platform and the
+    // containment check below is the only line guarding the write.
+    const QString directory =
+        chosenDirectory.isEmpty()
+            ? QFileDialog::getExistingDirectory(
+                  this, tr("Save message to"),
+                  QStandardPaths::writableLocation(
+                      QStandardPaths::DownloadLocation))
+            : chosenDirectory;
+    if (directory.isEmpty())
+        return;  // cancelled
+
+    // The default name is derived from the SUBJECT, which is input from a
+    // stranger: it may carry path separators, "..", or nothing usable. The
+    // same rules the attachment path follows, and the same helpers, rather
+    // than a second implementation that has to be kept correct separately.
+    Attachment naming;
+    naming.filename = defaultMessageFilename(subject);
+    const QString safeName = naming.safeFilename();
+
+    // Disambiguated rather than overwritten, matching what the attachment bar
+    // does. Attachment::saveWithoutOverwriting() is the same rule and cannot
+    // be reused here because it writes an Attachment's own bytes, while this
+    // COPIES a file; the naming is duplicated, the behaviour is not.
+    //
+    // The earlier version deleted an existing same-named file, on the
+    // reasoning that a save the user just confirmed a location for should not
+    // silently do nothing. That is right about the failure and wrong about the
+    // remedy: two messages very often share a subject, so the second save
+    // would destroy the first, and QFile::copy's refusal is a reason to pick
+    // another name rather than to delete somebody's file.
+    const QFileInfo naming_info(safeName);
+    const QString base = naming_info.completeBaseName();
+    const QString suffix = naming_info.suffix().isEmpty()
+                               ? QString()
+                               : QLatin1Char('.') + naming_info.suffix();
+    const QDir dir(directory);
+    QString candidate = safeName;
+    for (int n = 2; dir.exists(candidate); ++n)
+        candidate = QStringLiteral("%1 (%2)%3").arg(base).arg(n).arg(suffix);
+
+    const QString target = dir.absoluteFilePath(candidate);
+
+    // Compared as PATHS, never with startsWith(): "/tmp/safe-evil" passes a
+    // startsWith("/tmp/safe") check while being a sibling directory.
+    if (!Attachment::isPathInsideDirectory(directory, target)) {
+        showTransientStatus(tr("Refusing to write outside %1")
+                                .arg(QDir::cleanPath(
+                                    QDir(directory).absolutePath())));
+        return;
+    }
+
+    if (!QFile::copy(sourcePath, target)) {
+        showTransientStatus(tr("Could not write %1").arg(target));
+        return;
+    }
+    showTransientStatus(tr("Saved %1").arg(target));
 }
 
 QAction *MainWindow::addAction(const QString &name, const QString &text,
@@ -1184,6 +1702,10 @@ void MainWindow::registerActions()
     // and offering "Mark all read" against nothing is a live control that does
     // nothing.
     updateViewWideActions();
+
+    // Compose and the reply family, for the same reason: QAction starts
+    // enabled, so a window with nothing selected would offer a live Reply.
+    updateComposeActions();
 }
 
 void MainWindow::buildMenus()
@@ -1725,6 +2247,8 @@ void MainWindow::wireWorker()
             this, &MainWindow::onWorkerError);
     connect(m_worker, &NotmuchWorker::allTagsReady,
             this, &MainWindow::onAllTagsReady);
+    connect(m_worker, &NotmuchWorker::mailRootReady,
+            this, &MainWindow::onMailRootReady);
     connect(m_worker, &NotmuchWorker::countsReady,
             this, &MainWindow::onCountsReady);
     connect(m_worker, &NotmuchWorker::databaseStatsReady,
@@ -1761,6 +2285,11 @@ void MainWindow::wireWorker()
     // as the database can be read. Nothing waits on the answer: requestAllTags
     // stays silent when the database cannot be opened.
     requestAllTags();
+
+    // The Maildir root, which this window cannot derive (item 124). Asked once:
+    // it does not change while the application runs. Nothing waits on it
+    // either; the reply family is gated on send_command, not on this.
+    QMetaObject::invokeMethod(m_worker, "requestMailRoot", Qt::QueuedConnection);
 }
 
 void MainWindow::requestAllTags()
@@ -1781,6 +2310,17 @@ void MainWindow::onAllTagsReady(const QStringList &tags)
     m_queryCompleter->setTags(tags);
 }
 
+void MainWindow::onMailRootReady(const QString &mailRoot)
+{
+    m_mailRoot = mailRoot;
+
+    // The enablement pass reads m_mailRoot to resolve which account owns the
+    // displayed message, so it answers "no account" until this arrives. A
+    // window that had already selected a row would otherwise keep the reply
+    // family greyed out until the next selection change.
+    updateComposeActions();
+}
+
 QList<MainWindow::PlaceholderLine> MainWindow::placeholderLines() const
 {
     // One list of (query, label-maker) pairs rather than two arrays indexed in
@@ -2734,6 +3274,11 @@ void MainWindow::onSelectionChanged()
             if (changed)
                 onThreadSelected(current, QModelIndex());
         }
+
+        // Which account owns the displayed message decides whether the reply
+        // family is live and whether the ribbon shows, so it is re-answered
+        // whenever the displayed message can have changed.
+        updateComposeActions();
         return;
     }
 
@@ -2745,6 +3290,7 @@ void MainWindow::onSelectionChanged()
         if (m_statusLabel->text() == m_selectionMessage)
             m_statusLabel->clear();
         m_selectionMessage.clear();
+        updateComposeActions();
         return;
     }
 
@@ -2786,6 +3332,10 @@ void MainWindow::onSelectionChanged()
     m_currentMessageThreadId.clear();
     m_messageView->clear();
     showPlaceholderPane();
+
+    // A multi-row selection displays no message, so there is no account to
+    // reply from and no ribbon to show.
+    updateComposeActions();
 }
 
 void MainWindow::onThreadSelected(const QModelIndex &current,
@@ -2923,6 +3473,61 @@ void MainWindow::onThreadSelected(const QModelIndex &current,
 void MainWindow::onMessageLoaded(const QVector<MessageRef> &messages,
                                  quint64 generation)
 {
+    // A compose request comes through this same signal rather than through a
+    // worker signal of its own, so it is answered before the render guards
+    // below: those exist to protect the PANE, and none of them applies to
+    // opening a composer.
+    //
+    // Matched by MESSAGE ID, not merely by a pending flag. The compose request
+    // and the pane share one loadMessage slot and one messageLoaded signal, so
+    // a pane load already in flight when the user presses Reply arrives FIRST
+    // and carries a different message: consuming it on the flag alone would
+    // open a composer on whichever message the pane happened to be loading.
+    // A non-matching reply falls through to the pane, which is what it is.
+    if (m_pendingCompose.active) {
+        const auto it = std::find_if(
+            messages.cbegin(), messages.cend(),
+            [this](const MessageRef &ref) {
+                return ref.messageId == m_pendingCompose.messageId;
+            });
+        if (it != messages.cend()) {
+            const PendingCompose request = m_pendingCompose;
+            m_pendingCompose = {};
+
+            // The generation guard still applies: a query that moved on means
+            // the row the user asked from is gone.
+            if (generation == m_generation)
+                openComposerFor(*it, request.kind, request.quote);
+
+            // A compose load carries no pane update: m_currentMessageId is
+            // untouched by requestMessageForCompose(), so falling through
+            // would repaint the pane with a message it did not select.
+            return;
+        }
+
+        // No match, and the request is DISARMED rather than left waiting.
+        //
+        // Leaving it armed was a two-stage defect. The immediate half is that
+        // Reply silently does nothing when the message is not in the index,
+        // which is item 105's "the key does nothing". The delayed half is
+        // worse: the request stays armed with a specific message id, and the
+        // pane's own loads are the traffic being matched against, so merely
+        // SELECTING that message later would match, open a composer nobody
+        // asked for, and return before renderMessages() leaving the pane blank
+        // on the row just clicked.
+        //
+        // Only an EMPTY reply disarms it, and that asymmetry is the point.
+        // loadMessage() emits an empty list precisely when the id resolved to
+        // nothing, so that reply belongs to this request and says it failed.
+        // A NON-empty reply naming other messages is the pane's own load
+        // crossing ours, which is the race the id match exists to survive;
+        // disarming on it would reintroduce that race from the other side.
+        if (messages.isEmpty()) {
+            m_pendingCompose = {};
+            showTransientStatus(tr("That message is no longer indexed"));
+        }
+    }
+
     // A stale generation means the query moved on. A reply landing after the
     // selection grew past one row would paint a message back over a pane that
     // was deliberately blanked: loadMessage crosses to the worker on a queued