>>>>> Unfortunately, I discovered that it causes treesit-node-outdated errors.
>>>>> 
>>>>> This is because overlays are updated by 'pre-redisplay-functions'
>>>>> later than outline-minor-mode uses them by 'after-change-functions',
>>>>> since 'after-change-functions' runs before 'pre-redisplay-functions'.
>>>> 
>>>> This fixes the problem:
>>>> 
>>>>  (defun outline--fix-buttons-after-change (beg end _len)
>>>> +  (when (fboundp 'treesit-update-ranges)
>>>> +    (treesit-update-ranges beg end))
>>>>    ;; Handle whole lines
>>>>    (save-excursion (goto-char beg) (setq beg (pos-bol)))
>>>>    (save-excursion (goto-char end) (setq end (pos-eol)))
>>> 
>>> Using treesit-update-ranges is the right approach.  But is there no
>>> better place to put it?  I assume there should be a function that
>>> involves tree-sitter, in front of which you can put this call.
>> 
>> 'treesit-outline-search' has no information about the positions of
>> the beginning and end of the range of changed text.  Only
>> 'after-change-functions' has access to this information.
>> 
>> So what we could do is this, and I've tested that this approach works:
>> 
>> #+begin_src diff
>> diff --git a/lisp/treesit.el b/lisp/treesit.el
>> index 07861603244..c77b28c4647 100644
>> --- a/lisp/treesit.el
>> +++ b/lisp/treesit.el
>> @@ -4044,6 +4112,10 @@ treesit-outline-level
>> 
>>     level))
>> 
>> +(defun treesit--after-change (beg end _len)
>> +  "Force updating the ranges after each text change."
>> +  (treesit-update-ranges beg end))
>> +
>> ;;; Hideshow mode
>> 
>> (defun treesit-hs-block-end ()
>> @@ -4338,7 +4410,16 @@ treesit-major-mode-setup
>>       (setq treesit-outline-predicate
>>             #'treesit-outline-predicate--from-imenu))
>>     (setq-local outline-search-function #'treesit-outline-search
>> -                outline-level #'treesit-outline-level))
>> +                outline-level #'treesit-outline-level)
>> +    (add-hook 'outline-minor-mode-hook
>> +              (lambda ()
>> +                (if (bound-and-true-p outline-minor-mode)
>> +                    (add-hook 'after-change-functions
>> +                              #'treesit--after-change
>> +                              0 t)
>> +                  (remove-hook 'after-change-functions
>> +                               #'treesit--after-change t)))
>> +              nil t))
>> 
>>   ;; Remove existing local parsers.
>>   (dolist (ov (overlays-in (point-min) (point-max)))
>> #+end_src
>
> This seems a bit convoluted to me.  What do you think about adding
> some hook or generic function to outline-minor-mode?

Is this better?