Dear Maintainer,
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I initially discovered this in a build of emacs 30 that I made myself with the --with-pgtk option.
To remedy it, I tried to install the debian version of emacs-pgtk and discovered it there.
Reproduction:
0. Install 'emacs-pgtk'.
1. Open emacs-pgtk in GUI mode with no config using 'emacs -q'.
2. Run 'M-x fido-mode'.
3. Run another commmand by typing 'M-x open'. Notice that the completions after point do not change to show matches.
4. Type backspace so the command is 'M-x ope' and see that the completions now update for some reason.
5. Close Emacs.
6. Start emacs with 'emacs -q -nw'.
7. Repeat step 3 and it will demonstrate the correct behavior, with completions updating as you type.
I tried to reproduce with 'emacs-gtk' and that seems to work properly, so for now a workaround is to use that package.
Initially I discovered this using the 'consult' package, but I don't think the problem is there since it is reproducible with fido-mode.
I was running emacs-pgtk in kwin on KDE with Wayland.
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