Emacs 31.1 automates tree-sitter grammars and retires unexec

GNU Emacs 31.1 was released on 24 August 2026, and the change most likely to alter a working day is small: tree-sitter grammars can now install themselves. The release announcement, posted to the info-gnu-emacs mailing list by Sean Whitton, points to etc/NEWS for the details rather than listing them, so the shape of the release comes from the rundowns published alongside it - a rewritten completion system, a set of window-layout commands, and the removal of the unexec dumper that has been deprecated since Emacs 27.

Tree-sitter grammars stop being a manual chore

Emacs 31.1 adds a treesit-auto-install-grammar option that installs tree-sitter grammars automatically, according to Mastering Emacs's rundown of the release. Until now, using a tree-sitter major mode meant sourcing the grammar yourself and keeping its version aligned with what the mode expected - a mismatch produced errors that looked like editor bugs rather than a dependency problem. Mastering Emacs describes the new option as eliminating that manual version management.

Tree-sitter navigation also gets more complete. The same rundown lists treesit-forward-sexp-list and treesit-forward-list for movement across structural nodes, plus a treesit-explore command for inspecting the parse tree - the practical way to work out why a mode is highlighting or indenting something unexpectedly.

The completion system was rewritten

The Completions buffer can now appear eagerly rather than waiting to be asked for, and the flex matching algorithm has been rewritten, per both Mastering Emacs and Linux Compatible's coverage of the release candidate. Completion categories can inherit from one another, and RET now selects the candidate chosen with M-UP or M-DOWN.

Linux Compatible also documents minibuffer-visible-completions gaining an up-down value: "You can also use minibuffer-visible-completions with a new 'up-down' value to navigate completions independently of the minibuffer." For anyone who has assembled this behaviour out of third-party packages, the question worth asking after upgrading is which of those packages are now redundant.

Window layouts get first-class commands

Rearranging a window layout has meant deleting and re-splitting windows by hand. Emacs 31.1 adds commands that operate on the layout as a whole, listed by Mastering Emacs:

Command	What it does
window-layout-rotate-clockwise	Rotates the layout clockwise
window-layout-counterclockwise	Rotates it the other way
window-layout-flip-topdown	Flips the layout vertically
window-layout-flip-leftright	Flips it horizontally
window-layout-transpose	Transposes rows and columns
other-window-backward (C-x O)	Moves to the previous window

split-window can also resurrect a window that was deleted, per the same source. Two terminal-facing changes land alongside these: xterm-mouse-mode is enabled by default in terminals that support it, and child frames now work on TTY frames.

What was removed, and one fix that did not land

The unexec dumper is gone. It had been deprecated since Emacs 27, and Mastering Emacs marks its removal as "the end of an era" - relevant mainly to anyone building Emacs themselves or maintaining packaging for it. The built-in ctags program was also removed, with Universal Ctags the expected replacement.

Two items did not make this release. The garbage collector work has been postponed to Emacs 32, according to Mastering Emacs. And Linux Compatible reports that a vulnerability in Emacs Lisp symbol shorthands has a mitigation in this release line but that the full resolution is deferred to version 32 - worth knowing if you open Elisp files from sources you do not control.

Unicode support moves to version 17.0, with new input methods for polytonic Greek, Tifinagh, Northern Iroquoian languages including Mohawk and Oneida, Burmese variants, and Syriac.

What this means for developers

The tree-sitter change is the one to act on first. If your config carries hand-rolled grammar-installation code or a pinned grammar commit, try treesit-auto-install-grammar on a scratch config before deleting anything - then remove whatever it makes redundant. The same applies to completion: the eager Completions buffer and the rewritten flex matcher overlap with what several popular packages exist to provide, and running 31.1 with a deliberately minimal config for an afternoon is the fastest way to find out what you no longer need to carry.

If you build Emacs from source or maintain a package for a distribution, read the unexec removal as a build-system change and check your recipe before upgrading users. The ctags removal deserves the same treatment: anything shelling out to the bundled binary needs Universal Ctags installed instead.

Two things argue for patience rather than haste. The announcement itself delegates the detail to etc/NEWS, so C-h n inside a freshly built 31.1 is the authoritative list - not any summary, including this one. And the symbol shorthand fix landing only in Emacs 32 means the security story here is incomplete; if you routinely open untrusted Elisp, that is a reason to keep watching rather than to consider the matter closed.