Layers palette filter grabs focus when pressing Ctrl-C
Pressing Ctrl-C to copy something activates the focus on the filter field in the Layers palette. Using keyboard shortcuts becomes a landmine when this happens because you can inadvertently turn off layers or, in some cases, slow Illustrator way down by pasting SVG data into the field (Ctrl-V often follows pressing Ctrl-C). When the latter happens, Illustrator tries to filter by the text in the field, and it can take quite a while sometimes to regain focus enough to clear out the field. More often than not, however, I have to force quit and restart.
A potential side effect of this has been the lack of ability to copy color or width values from their respective. When attempting to do so, the ug is randomly triggered. Sometimes the text does still copy, other times it does not.
OS: MacOS Sequoia 15.3.1 (this has happened for a while across previous OS versions)
AI version: 29.3.1 (this has happened with previous versions of AI, going back to the introduction of the filter feature)

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Stuart McCoy commented
Not sure how I'd know if it stole focus or not but one of the "features" of this bug is the field I'm copying from sometimes loses focus when I press Ctrl-C. With the layers palette closed, I tried to copy from a field, and I only saw this happen once. After quite a few tries, I reopened the palette, and the field was populated with a character I had typed at one point, though. Not sure how to really test this one any further.
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What if you have Layers collapsed? hidden completely?