Studio opens with your job already set up — the trim, the bleed, the safe area, and the number of printed sides, taken from the format you configured. You design inside the lines the press actually cuts to.

Size, stock, finish, quantity, and speed are set on the product page. Studio is handed the result.
A short-lived, single-use token. Your configuration is held here, not carried in the address bar.
Studio sets the canvas from the manufacturing spec, so what you draw fits what will be cut.
The design is refused if the configuration changed while you were away. Artwork built for one stock cannot print on another.
If you cancel, if the handoff expires, or if you close the tab, your configuration stays in the cart exactly as you set it. The only thing a failed handoff loses is the handoff.