diff --git a/mu4e/mu4e-compose.el b/mu4e/mu4e-compose.el
index 3c5642c7..c1ec8d66 100644
--- a/mu4e/mu4e-compose.el
+++ b/mu4e/mu4e-compose.el
@@ -238,8 +238,8 @@ When enabled, this attempts to put mu4e's completions at the
 start of the buffer-local `completion-at-point-functions'. Other
 completion functions still apply."
   (when mu4e-compose-complete-addresses
-    (set (make-local-variable 'completion-ignore-case) t)
-    (set (make-local-variable 'completion-cycle-threshold) 7)
+    (setq-local completion-ignore-case t)
+    (setq-local completion-cycle-threshold 7)
     (add-to-list (make-local-variable 'completion-styles) 'substring)
     (add-hook 'completion-at-point-functions
               #'mu4e--compose-complete-contact-field -10 t)))
@@ -289,13 +289,13 @@ buffers; lets remap its faces so it uses the ones for mu4e."
   (when (eq major-mode 'mu4e-compose-mode)
     (mu4e-warn "Not available in mu4e")))
 
-(defun mu4e--neutralize-undesirables ()
-  "Beware Gnus commands that do not work with mu4e."
-  ;; the Field menu contains many items that don't apply.
-  (advice-add 'gnus-delay-article
-              :before #'mu4e--compose-unsupported) ;; # XXX does not work?!
-  (advice-add 'message-goto-newsgroups :before #'mu4e--compose-unsupported)
-  (advice-add 'message-insert-newsgroups :before #'mu4e--compose-unsupported))
+;; Neutralize Gnus commands that do not work with mu4e. The advice is a no-op
+;; outside mu4e-compose-mode (see `mu4e--compose-unsupported'), so it is safe
+;; to install unconditionally at load time.
+(advice-add 'gnus-delay-article
+            :before #'mu4e--compose-unsupported) ;; # XXX does not work?!
+(advice-add 'message-goto-newsgroups :before #'mu4e--compose-unsupported)
+(advice-add 'message-insert-newsgroups :before #'mu4e--compose-unsupported)
 
 (define-derived-mode mu4e-compose-mode message-mode "mu4e:compose"
   "Major mode for the mu4e message composition, derived from `message-mode'.
@@ -303,13 +303,12 @@ buffers; lets remap its faces so it uses the ones for mu4e."
   (progn
     (use-local-map mu4e-compose-mode-map)
     (mu4e-context-minor-mode)
-    (mu4e--neutralize-undesirables)
     (mu4e--compose-remap-faces)
     (setq-local nobreak-char-display nil)
     ;; set this to allow mu4e to work when gnus-agent is unplugged in gnus
-    (set (make-local-variable 'message-send-mail-real-function) nil)
+    (setq-local message-send-mail-real-function nil)
     ;; Set to nil to enable `electric-quote-local-mode' to work:
-    (set (make-local-variable 'comment-use-syntax) nil)
+    (setq-local comment-use-syntax nil)
     (mu4e--compose-setup-completion) ;; maybe offer address completion
     (if mu4e-compose-format-flowed   ;; format-flowed
         (progn
diff --git a/mu4e/mu4e-contacts.el b/mu4e/mu4e-contacts.el
index 3f7c2748..a4720ea4 100644
--- a/mu4e/mu4e-contacts.el
+++ b/mu4e/mu4e-contacts.el
@@ -280,7 +280,7 @@ case a phrase contains a quote, it will be escaped."
   "Get the full combination of name and email address from CONTACT."
   (let* ((email (mu4e-contact-email contact))
          (name (mu4e-contact-name contact)))
-    (if (and name (> (length name) 0))
+    (if (and name (not (string-empty-p name)))
         (format "%s <%s>" (mu4e--rfc822-quote-phrase name) email)
       email)))
 
diff --git a/mu4e/mu4e-headers.el b/mu4e/mu4e-headers.el
index f629cc67..dc3b8c04 100644
--- a/mu4e/mu4e-headers.el
+++ b/mu4e/mu4e-headers.el
@@ -1185,7 +1185,7 @@ The following specs are supported:
   (use-local-map mu4e-headers-mode-map)
   (make-local-variable 'mu4e~headers-proc)
   (make-local-variable 'mu4e~highlighted-docid)
-  (set (make-local-variable 'hl-line-face) 'mu4e-header-highlight-face)
+  (setq-local hl-line-face 'mu4e-header-highlight-face)
 
   ;; Eldoc support
   (when (and (featurep 'eldoc) mu4e-eldoc-support)
@@ -1198,8 +1198,8 @@ The following specs are supported:
                     #'mu4e-headers-eldoc-function)))
 
   ;; support bookmarks.
-  (set (make-local-variable 'bookmark-make-record-function)
-       'mu4e--make-bookmark-record)
+  (setq-local bookmark-make-record-function
+              #'mu4e--make-bookmark-record)
   ;; maybe update the current headers upon indexing changes
   (add-hook 'mu4e-index-updated-hook #'mu4e~headers-maybe-auto-update)
   (setq
diff --git a/mu4e/mu4e-helpers.el b/mu4e/mu4e-helpers.el
index c3cb04a6..7ccca16b 100644
--- a/mu4e/mu4e-helpers.el
+++ b/mu4e/mu4e-helpers.el
@@ -721,7 +721,7 @@ shorter keys in some cases where there are multiple bindings."
   ;; not a perfect heuristic: e.g. '<up>' is longer that 'C-p'
   (car-safe
    (seq-sort (lambda (b1 b2)
-               (< (length b1) (length b2)))
+               (length< b1 (length b2)))
              (seq-map #'key-description
                       (where-is-internal cmd)))))
 
diff --git a/mu4e/mu4e-main.el b/mu4e/mu4e-main.el
index ac6367e3..89b2ecdd 100644
--- a/mu4e/mu4e-main.el
+++ b/mu4e/mu4e-main.el
@@ -205,7 +205,7 @@ binding representation, remove that first letter."
   (let* ((bindstr (or bindstr (mu4e-key-description cmd) alt
                       (mu4e-error "No binding for %s" cmd)))
          (bindstr
-          (if (and alt (> (length bindstr) 1)) alt bindstr))
+          (if (and alt (length> bindstr 1)) alt bindstr))
          (title ;; remove first letter afrer [] if it equal last of binding
           (string-replace
            (concat "[@]" (substring bindstr -1)) "[@]" title))
diff --git a/mu4e/mu4e-mark.el b/mu4e/mu4e-mark.el
index 42ccfc21..37a8144d 100644
--- a/mu4e/mu4e-mark.el
+++ b/mu4e/mu4e-mark.el
@@ -106,7 +106,7 @@ is the target directory (for \"move\")")
 
 (defun mu4e--mark-initialize ()
   "Initialize the marks-subsystem."
-  (set (make-local-variable 'mu4e--mark-map) (make-hash-table))
+  (setq-local mu4e--mark-map (make-hash-table))
   ;; ask user when kill buffer / emacs with live marks.
   ;; (subject to mu4e-headers-leave-behavior)
   (add-hook 'kill-buffer-query-functions
diff --git a/mu4e/mu4e-mime-parts.el b/mu4e/mu4e-mime-parts.el
index 2ddea250..02514f95 100644
--- a/mu4e/mu4e-mime-parts.el
+++ b/mu4e/mu4e-mime-parts.el
@@ -72,6 +72,17 @@ See `mu4e--uniquify-file-name' for an example."
     (mm-destroy-parts mu4e--view-gnus-article-mime-handles)
     (setq mu4e--view-gnus-article-mime-handles nil)))
 
+;; Temp directories created to hand attachments to external openers; cleaned up
+;; when the view buffer is killed.
+(defvar-local mu4e--view-temp-dirs nil)
+(put 'mu4e--view-temp-dirs 'permanent-local t)
+
+(defun mu4e--view-kill-temp-dirs ()
+  "Delete temp dirs created for opening MIME-parts externally."
+  (dolist (dir mu4e--view-temp-dirs)
+    (ignore-errors (delete-directory dir)))
+  (setq mu4e--view-temp-dirs nil))
+
 ;;; MIME-parts
 (defvar-local mu4e--view-mime-parts nil
   "Cached MIME parts for this message.")
@@ -229,7 +240,7 @@ COMPLETIONS is the list of completion strings to affixate."
                    'face 'mu4e-system-face))
             (target (propertize (or (plist-get part :target-dir) "")
                                 'face 'mu4e-system-face))
-            (icon (or (and (> (length raw-filename) 0)
+            (icon (or (and (not (string-empty-p raw-filename))
                            (mu4e-file-name-to-icon raw-filename))
                       (mu4e-mime-type-to-icon
                        (plist-get part :mime-type))))
@@ -430,32 +441,33 @@ Each of the actions is a plist with keys
 The filename is deduced from the MIME-part's filename, or
 otherwise random; the result is placed in a temporary directory
 with a unique name. Returns the full path for the file created.
-The directory and file are self-destructed."
+The directory is registered for cleanup when the current view
+buffer is killed (see `mu4e--view-kill-temp-dirs')."
   (let* ((tmpdir (make-temp-file "mu4e-temp-" t))
          (fname (mm-handle-filename handle))
          (fname (and fname
                      (gnus-map-function mm-file-name-rewrite-functions
                                         (file-name-nondirectory fname))))
          (fname (if fname
-                    (concat tmpdir "/" (replace-regexp-in-string "/" "-" fname))
+                    (mu4e-join-paths
+                     tmpdir (replace-regexp-in-string "/" "-" fname))
                   (let ((temporary-file-directory tmpdir))
                     (make-temp-file "mimepart")))))
     (mm-save-part-to-file handle fname)
-    (run-at-time "30 sec" nil
-                 (lambda () (ignore-errors (delete-directory tmpdir t))))
+    (push tmpdir mu4e--view-temp-dirs)
     fname))
 
 (defun mu4e--view-open-file (file &optional force-ask)
   "Open FILE with default handler, if any.
-Otherwise, or if FORCE-ASK is set, ask user for the program to
-open with."
+Otherwise, or if FORCE-ASK is set, ask user for the shell command
+to open with."
   (if (and (not force-ask)
            (functionp mu4e-view-open-program))
       (funcall mu4e-view-open-program file)
     (let ((opener
            (or (and (not force-ask) mu4e-view-open-program
                     (executable-find mu4e-view-open-program))
-               (read-shell-command "Open MIME-part with: "))))
+               (read-shell-command "Open MIME-part with shell command: "))))
       (call-process opener nil 0 nil file))))
 
 (defun mu4e-view-mime-part-action (&optional n)
@@ -515,17 +527,16 @@ the third MIME-part."
                     (cond
                      ((eq receives 'index)
                       (shell-command
-                       (concat handler " " (shell-quote-argument id))))
+                       (concat handler " " id)))
                      ((eq receives 'pipe)
                       (progn
                         (mm-pipe-part handle handler)))
                      ((eq receives 'temp)
                       (shell-command
-                       (shell-command
-                        (concat
-                         handler " "
-                         (shell-quote-argument
-                          (mu4e--view-mime-part-to-temp-file handle))))))
+                       (concat
+                        handler " "
+                        (shell-quote-argument
+                         (mu4e--view-mime-part-to-temp-file handle)))))
                      (t (mu4e-error "Invalid action %S" action))))))))
             ids)))
 
diff --git a/mu4e/mu4e-search.el b/mu4e/mu4e-search.el
index ac1b1d96..d7a8c516 100644
--- a/mu4e/mu4e-search.el
+++ b/mu4e/mu4e-search.el
@@ -281,7 +281,7 @@ limit the stack size."
     (unless (and stack (string= (car stack) query))
       (push query stack)
       ;; limit the stack to `mu4e--search-query-stack-size' elements
-      (when (> (length stack) mu4e--search-query-stack-size)
+      (when (length> stack mu4e--search-query-stack-size)
         (setq stack (cl-subseq stack 0 mu4e--search-query-stack-size)))
       ;; remove all duplicates of the new element
       (seq-remove (lambda (elm) (string= elm (car stack))) (cdr stack))
@@ -607,24 +607,30 @@ query before submitting it."
          (longest-query
           (seq-max (seq-map (lambda (c) (length (plist-get (cdr c) :query)))
                             candidates)))
-
-         (annotation-func
-          (lambda (candidate)
-            (let* ((item (cdr-safe (assoc candidate candidates)))
-                   (name (propertize (or  (plist-get item :name) "")
-                                     'face 'mu4e-header-key-face))
-                   (query (propertize (or (plist-get item :query) "")
-                                      'face 'mu4e-header-value-face)))
-              (concat
-               "  "
-               (make-string (- longest-name (length name)) ?\s)
-               query
-               (make-string (- longest-query (length query)) ?\s)
-               "  "
-               (mu4e--query-item-display-counts item)))))
-         (completion-extra-properties
-          `(:annotation-function ,annotation-func))
-         (chosen (completing-read "Query: " candidates))
+         (affixation-func
+          (lambda (completions)
+            (mapcar
+             (lambda (candidate)
+               (let* ((item (cdr-safe (assoc candidate candidates)))
+                      (query (propertize (or (plist-get item :query) "")
+                                         'face 'mu4e-header-value-face))
+                      (suffix
+                       (concat
+                        "  "
+                        (make-string (- longest-name (length candidate)) ?\s)
+                        query
+                        (make-string (- longest-query (length query)) ?\s)
+                        "  "
+                        (mu4e--query-item-display-counts item))))
+                 (list candidate "" suffix)))
+             completions)))
+         (table (lambda (string pred action)
+                  (if (eq action 'metadata)
+                      `(metadata
+                        (category . mu4e-query)
+                        (affixation-function . ,affixation-func))
+                    (complete-with-action action candidates string pred))))
+         (chosen (completing-read "Query: " table))
          (query (or (plist-get (cdr-safe (assoc chosen candidates)) :query)
                     (mu4e-warn "No query for %s" chosen))))
     (mu4e-search-bookmark query edit)))
diff --git a/mu4e/mu4e-view.el b/mu4e/mu4e-view.el
index 56653125..04948e21 100644
--- a/mu4e/mu4e-view.el
+++ b/mu4e/mu4e-view.el
@@ -651,10 +651,11 @@ activates URLs (in plain-text mode only)."
           (unless (mu4e--view-html-displayed-p)
             (mu4e--view-activate-urls))
           (kill-local-variable 'bookmark-make-record-function)
-          (setq mu4e--gnus-article-mime-handles gnus-article-mime-handles
+          (setq mu4e--view-gnus-article-mime-handles gnus-article-mime-handles
                 gnus-article-decoded-p gnus-article-decode-hook)
           (set-buffer-modified-p nil)
-          (add-hook 'kill-buffer-hook #'mu4e--view-kill-mime-handles))
+          (add-hook 'kill-buffer-hook #'mu4e--view-kill-mime-handles)
+          (add-hook 'kill-buffer-hook #'mu4e--view-kill-temp-dirs))
       (epg-error
        (mu4e-message "EPG error: %s; fall back to raw view"
                      (error-message-string err))))))
@@ -789,7 +790,7 @@ filename."
                   ;; (e.g. :user-agent): derive from the keyword name.
                   (capitalize (substring (symbol-name field) 1))))
          (help (plist-get info :help)))
-    (if (and val (> (length val) 0))
+    (if (and val (not (string-empty-p val)))
         (insert (propertize (concat key ":") 'help-echo help)
                 " " val "\n"))))
 
@@ -803,7 +804,7 @@ filename."
                                field info)))
          (val (funcall func msg))
          (help (plist-get info :help)))
-    (when (and val (> (length val) 0))
+    (when (and val (not (string-empty-p val)))
       (insert (propertize (concat key ":") 'help-echo help) " " val "\n"))))
 
 (define-advice gnus-icalendar-event-from-handle
diff --git a/mu4e/mu4e-window.el b/mu4e/mu4e-window.el
index d6e90827..aa9407ef 100644
--- a/mu4e/mu4e-window.el
+++ b/mu4e/mu4e-window.el
@@ -103,7 +103,11 @@ A symbol:
 
 For backward compatibility with `mu4e-compose-in-new-frame', t is
 treated as =\\'frame."
-  :type 'symbol
+  :type '(choice (const :tag "New buffer" nil)
+                 (const :tag "New window" window)
+                 (const :tag "New frame" frame)
+                 (const :tag "New frame (compat)" t)
+                 (const :tag "Use display-buffer" display-buffer))
   :group 'mu4e-compose)
 
 (declare-function mu4e-view-mode "mu4e-view")
@@ -252,7 +256,7 @@ being created if CREATE is non-nil."
         ;; Required. The call chain of `mu4e-view-mode' ends up
         ;; calling `kill-all-local-variables', which destroys the
         ;; local binding.
-        (set (make-local-variable 'mu4e-linked-headers-buffer) headers-buffer))
+        (setq-local mu4e-linked-headers-buffer headers-buffer))
       buffer)))
 
 ;; backward compat: `display-buffer-full-frame' only appears in emacs 29.