The metatag module is modifying the page title when applying htmlentities_decode to the meta values.
See https://git.drupalcode.org/project/metatag/-/blob/2.0.x/src/MetatagManag...
On a vanilla install of D10 with metatag module enabled, create a page with a less than symbol and some text with no space, ie "this is my
Save the page and view
With metatag module enabled, the title is truncated from the less than (becomes "this is my")
Leave the node unchanged and disable the metatag module.
The title is now correct.
I'm not sure if we need metatag to modify the page title at all. Maybe it could be excluded from the loop processing the values.
Note that this code exists also in 2.1.x; https://git.drupalcode.org/project/metatag/-/blob/2.1.x/src/MetatagManag...
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It couldn't be completely excluded as that's where some of the token processing is done.
Maybe we should start with updating the test coverage to track what the output should look like, and work from there?