The compose box used to sit at a fixed height no matter how much you wrote, stretching the full width of the card regardless of where the post was headed. Now it behaves like a sheet of the destination feed: it starts at one card height and grows with your draft — every new line and every soft-wrapped one — up to about a screenful before it scrolls internally. And the column now defaults to how the post will actually read on the platform you picked: X composes at its feed width, Substack at its reading column, with the tightest selected platform winning so you always write against the most constraining canvas. The corner-resize handle still works as a manual override that sticks until reload.