diff --git a/lib/core/platform/open_directory.dart b/lib/core/platform/open_directory.dart
index 692b6fcb..4e8dd71f 100644
--- a/lib/core/platform/open_directory.dart
+++ b/lib/core/platform/open_directory.dart
@@ -9,8 +9,12 @@ Future<bool> openDirectoryInFileManager(
   Future<bool> Function(String path)? opener,
 }) async {
   final dir = Directory(directoryPath);
-  if (!await dir.exists()) {
-    await dir.create(recursive: true);
+  try {
+    if (!await dir.exists()) {
+      await dir.create(recursive: true);
+    }
+  } on FileSystemException {
+    return false;
   }
 
   final open = opener ?? _defaultOpener;
diff --git a/lib/core/security/ssl_certificate_support.dart b/lib/core/security/ssl_certificate_support.dart
index b51022f4..f4169753 100644
--- a/lib/core/security/ssl_certificate_support.dart
+++ b/lib/core/security/ssl_certificate_support.dart
@@ -167,36 +167,39 @@ Future<String?> resolveMongoTlsCertificateKeyFile({
 
   final certBytes = await File(certPath).readAsString();
   final keyBytes = await File(keyPath).readAsString();
-  final dir = await Directory.systemTemp.createTemp(kMongoTlsTempPrefix);
-  if (!Platform.isWindows) {
-    try {
-      await Process.run('chmod', ['700', dir.path]);
-    } catch (e) {
-      logIgnored('ssl_certificate_support', e);
-    }
-  }
+  // The pid in the name lets another instance's start-up cleanup see that this
+  // directory is in use.
+  final dir = await Directory.systemTemp
+      .createTemp('$kMongoTlsTempPrefix${pid}_');
   final merged = File('${dir.path}/client.pem');
-  await merged.writeAsString('$certBytes\n$keyBytes\n', flush: true);
-  if (!Platform.isWindows) {
-    // `Process.run` does not throw on a non-zero exit, so check it: a key
-    // file that stayed at the default mode must not be handed out silently.
-    try {
-      final result = await Process.run('chmod', ['600', merged.path]);
-      if (result.exitCode != 0) {
-        throw FileSystemException(
-          'Could not restrict permissions of the TLS client key file: '
-          '${result.stderr}'.trim(),
-          merged.path,
-        );
-      }
-    } catch (_) {
-      await cleanupMongoTlsTempFile(merged.path);
-      rethrow;
+  try {
+    if (!Platform.isWindows) {
+      await _chmod('700', dir.path, 'TLS temp directory');
+      // Empty and 0600 before the key goes in, so it is never readable with
+      // the default mode.
+      await merged.create();
+      await _chmod('600', merged.path, 'TLS client key file');
     }
+    await merged.writeAsString('$certBytes\n$keyBytes\n', flush: true);
+  } catch (_) {
+    await cleanupMongoTlsTempFile(merged.path);
+    rethrow;
   }
   return merged.path;
 }
 
+/// `Process.run` does not throw on a non-zero exit, so check it: a key file
+/// that stayed at the default mode must not be handed out silently.
+Future<void> _chmod(String mode, String path, String what) async {
+  final result = await Process.run('chmod', [mode, path]);
+  if (result.exitCode != 0) {
+    throw FileSystemException(
+      'Could not restrict permissions of the $what: ${result.stderr}'.trim(),
+      path,
+    );
+  }
+}
+
 /// Reliably deletes a temporary MongoDB TLS certificate file and its parent temp directory.
 Future<void> cleanupMongoTlsTempFile(String? filePath) async {
   if (filePath == null || filePath.trim().isEmpty) return;
@@ -220,8 +223,30 @@ Future<void> cleanupMongoTlsTempFile(String? filePath) async {
   }
 }
 
-/// Cleans up any stale temporary MongoDB TLS directories left from previous sessions.
-Future<void> cleanupStaleMongoTlsTempFiles() async {
+final _tlsTempOwnerPid = RegExp('^$kMongoTlsTempPrefix(\\d+)_');
+
+Future<bool> _isProcessAlive(int owner) async {
+  if (owner == pid) return true;
+  try {
+    if (Platform.isWindows) {
+      final result =
+          await Process.run('tasklist', ['/FI', 'PID eq $owner', '/NH']);
+      return result.exitCode != 0 || '${result.stdout}'.contains('$owner');
+    }
+    return (await Process.run('kill', ['-0', '$owner'])).exitCode == 0;
+  } catch (_) {
+    // Cannot tell: leave the directory alone.
+    return true;
+  }
+}
+
+/// Cleans up stale temporary MongoDB TLS directories left from previous
+/// sessions. A directory named for a process that is still running belongs to
+/// another Querya instance and is kept; [isProcessAlive] is for tests.
+Future<void> cleanupStaleMongoTlsTempFiles({
+  Future<bool> Function(int pid)? isProcessAlive,
+}) async {
+  final alive = isProcessAlive ?? _isProcessAlive;
   try {
     final tempDir = Directory.systemTemp;
     if (!await tempDir.exists()) return;
@@ -230,6 +255,8 @@ Future<void> cleanupStaleMongoTlsTempFiles() async {
         final name =
             entity.uri.pathSegments.where((s) => s.isNotEmpty).lastOrNull ?? '';
         if (name.startsWith(kMongoTlsTempPrefix)) {
+          final owner = _tlsTempOwnerPid.firstMatch(name)?.group(1);
+          if (owner != null && await alive(int.parse(owner))) continue;
           try {
             await entity.delete(recursive: true);
           } catch (e) {
diff --git a/test/core/platform/open_directory_test.dart b/test/core/platform/open_directory_test.dart
index b458ebeb..d69bbc16 100644
--- a/test/core/platform/open_directory_test.dart
+++ b/test/core/platform/open_directory_test.dart
@@ -31,6 +31,23 @@ void main() {
       expect(await Directory(target).exists(), isTrue);
     });
 
+    test('returns false when the directory cannot be created (#1768)',
+        () async {
+      final root = await Directory.systemTemp
+          .createTemp('querya_open_directory_blocked_test_');
+      addTearDown(() => root.delete(recursive: true));
+      final file = File(p.join(root.path, 'a_file'))..writeAsStringSync('x');
+      var called = false;
+
+      final opened = await openDirectoryInFileManager(
+        p.join(file.path, 'child'),
+        opener: (_) async => called = true,
+      );
+
+      expect(opened, isFalse);
+      expect(called, isFalse);
+    });
+
     test('returns false when opener reports failure', () async {
       final root = await Directory.systemTemp
           .createTemp('querya_open_directory_fail_test_');
diff --git a/test/core/security/ssl_certificate_support_test.dart b/test/core/security/ssl_certificate_support_test.dart
index 239e5450..5f57f02c 100644
--- a/test/core/security/ssl_certificate_support_test.dart
+++ b/test/core/security/ssl_certificate_support_test.dart
@@ -110,6 +110,42 @@ void main() {
       expect(await orphanDir.exists(), isFalse);
     });
 
+    test('cleanup keeps the directory of a process that is still running (#1768)',
+        () async {
+      final live = await Directory.systemTemp
+          .createTemp('${kMongoTlsTempPrefix}4242_');
+      final dead = await Directory.systemTemp
+          .createTemp('${kMongoTlsTempPrefix}4243_');
+      addTearDown(() async {
+        if (await live.exists()) await live.delete(recursive: true);
+        if (await dead.exists()) await dead.delete(recursive: true);
+      });
+
+      await cleanupStaleMongoTlsTempFiles(
+        isProcessAlive: (pid) async => pid == 4242,
+      );
+
+      expect(await live.exists(), isTrue);
+      expect(await dead.exists(), isFalse);
+    });
+
+    test('the merged key is created in a directory named for this process (#1768)',
+        () async {
+      final input = await Directory.systemTemp.createTemp('querya_test_input_');
+      addTearDown(() => input.delete(recursive: true));
+      await File('${input.path}/c.pem').writeAsString('CERT');
+      await File('${input.path}/k.pem').writeAsString('KEY');
+
+      final path = await resolveMongoTlsCertificateKeyFile(
+        clientCert: '${input.path}/c.pem',
+        clientKey: '${input.path}/k.pem',
+      );
+      addTearDown(() => cleanupMongoTlsTempFile(path));
+
+      expect(File(path!).parent.path, contains('$kMongoTlsTempPrefix$pid'));
+      expect(await File(path).readAsString(), contains('KEY'));
+    });
+
     test('buildSecurityContext returns null when paths.hasAny is false', () {
       const paths = SslCertificatePaths();
       final ctx = buildSecurityContext(paths);