bug#81630: 32.0.50; completions-format 'vertical scrolls the completion window on TAB tapping

Hi.

When setting completions-format to 'vertical

and start TAB tapping the completions window starts scrolling up and
down even though all the candidates can be seen in the window.

To reproduce do:
emacs -Q --eval "(setq completions-format 'vertical)"
`M-x 5x5`  and start tapping TAB key or `M-x minibuffer-`

Workaround: set (completion-auto-select 'second-tab) or
(completion-auto-select t) or just don't tap TAB.

This behaviour isn't noticed with 'horizontal or 'one-column

Best regards.





In GNU Emacs 32.0.50 (build 1, x86_64-apple-darwin21.6.0, NS
appkit-2113.65 Version 12.7.6 (Build 21H1320)) of 2026-08-10 built on
mcbata
Windowing system distributor 'Apple', version 10.3.2113
System Description:  macOS 12.7.6

Configured using:
'configure --prefix=/opt/local --disable-silent-rules --without-dbus
--without-gconf --without-libotf --without-m17n-flt --with-libgmp
--with-gnutls --with-xml2 --with-modules --with-sqlite3 --with-webp
--with-native-compilation=aot --infodir /opt/local/share/info/emacs
--disable-gc-mark-trace --with-ns --with-lcms2 --without-harfbuzz
--without-xaw3d --with-imagemagick --with-rsvg --with-xwidgets
--with-tree-sitter 'CFLAGS=-pipe -Os -Wno-attributes
-isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk -arch
x86_64' 'CPPFLAGS=-isystem/opt/local/include
-isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk'
'LDFLAGS=-L/opt/local/lib -Wl,-headerpad_max_install_names -Wl,-no_pie
-Wl,-rpath /opt/local/lib/gcc15 -Wl,-rpath /opt/local/lib
-Wl,-syslibroot,/Library/Developer/CommandLineTools/SDKs/MacOSX12.sdk
-arch x86_64''

Configured features:
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NATIVE_COMP NOTIFY KQUEUE NS PDUMPER PNG RSVG SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER WEBP XIM XWIDGETS ZLIB

Important settings:
  value of $LC_ALL: en_US.UTF-8
  value of $LC_CTYPE: UTF-8
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
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  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  minibuffer-nonselected-mode: t
  minibuffer-regexp-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
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Load-path shadows:
None found.

Features:
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emacs)

Memory information:
((conses 16 57043 18395) (symbols 48 6196 0) (strings 32 15236 2279)
(string-bytes 1 545364) (vectors 16 9845)
(vector-slots 8 143839 4739) (floats 8 22 2) (intervals 56 307 23)
(buffers 1064 11))