If I change my blog's URL path, what happens to the posts already published?

What I changed

I opened the blog's own settings and changed its URL path, then saved it. Then I checked every kind of address from outside the dashboard, before and after, with a fresh request each time so a cached copy could not fake the result: the blog's own front page, a post, and a category page.

What happened immediately

Everything moved at once. The blog's front page, every post on it, and every category page switched to the new path in the same moment. The old front page, the old post address and the old category address all returned a 404, with no redirect of any kind. The new addresses, built the same way with the new path in place of the old one, answered normally.

Nothing is offered in place of the old addresses

The old addresses do not fade out gradually and nothing steps in for them. A 404 is what a visitor gets from the old front page, the old post link and the old category link, all at the same moment the new path takes effect. Anyone who bookmarked a post, shared a link, or has one saved in an old email is sent nowhere.

No article anywhere in systeme.io's help centre documents a redirect feature, for a page or for a blog. Changing a single page's URL path inside a funnel produces the identical result: an immediate 404 with nothing put in its place.

Changing it back undoes all of it

I set the path back to what it was before. Every original address returned to normal immediately, and every address using the temporary path started returning a 404 in its place. It runs the same way in both directions, and running it a second time restores the site exactly as it was.

What I have not checked

Whether systeme.io offers a redirect setting anywhere for this: I did not go looking for one. And what a search engine does with the 404s if the change is left in place for a while. Both are genuinely open.