Found my issue.
In my theme, a really old piece of code adds the circle like the Air theme.
.published-page {
&::before {
background: linear-gradient(
90deg,
var(--tertiary-hover) 0%,
var(--tertiary) 100%
);
clip-path: ellipse(148% 70% at 91% -14%);
content: "";
width: 100%;
height: 100%;
display: block;
position: fixed;
z-index: 0;
}
.background-container {
display: none;
}
}
I’ll remove it.