I noticed the bootstrap version used to compile the theme CSS file differs from the one produced when users use the theme customizer. The default.css compiled by mix is 5.3.1, which is fetched from /node_modules/ folder. However, the theme customizer uses the ‘concrete/bedrock’ folder in the core files.
I can include my own boostrap version inside the theme, and use that in the theme main.scss file. but I wonder if there is something the core team had in mind for such scenarios, as I followed the documentation to set up the theme foundation.
So there might be a few things going on here for you - The idea would be you want to keep your theme’s bootstrap and concrete bootstrap locked to the same version.
Bedrock specifies Concrete Bootstrap as 5.2.3
In November of 2023 bootstrap was locked at 5.2.3
You might have an older version of Bedrock with an outdated version constraint.
Before 1.4.11 or so. So that might be pulling in a higher version of Bootstrap there. Does that make sense?