Altering Details block styles doubling .wp-block-details class in the output

[randewoo]

By defaut Details block styles outputs styles for inner paragraph like:

.wp-block-details>:not(summary) {
    margin-block-end: 0;
    margin-block-start: var(--wp--style--block-gap);

---

If I want to change margin-block-start on the block level styles I use:

.wp-block-details>:not(summary) {
    margin-block-start: 0;}

BUT it outputs:

.wp-block-details.wp-block-details>:not(summary) {
    margin-block-start: 0;}

---

HOWEVER,
If I use the same in the Additional CSS section of Styles Editor it produce expected:

.wp-block-details>:not(summary) {
    margin-block-start: 0;}

[wildworks]

In per block additional CSS via global styles, selectors for block names are automatically added. The following nested selectors will give you the expected results.

& >:not(summary) {
    margin-block-start: 0;
}

For more information, please see the "Per Block Custom CSS" section of this dev note: ​https://make.wordpress.org/core/2023/03/06/custom-css-for-global-styles-and-per-block/