Reserve the safety text

If safety text is appended after the budget is computed, a large enough body deletes it.

A handoff delivered into another agent's context is now wrapped in a frame saying it is historical evidence rather than instructions. The frame only works if it is actually there, and the tempting implementation — compose the body, then wrap it — puts it exactly where it can be squeezed out.

This project had already learned the lesson in a duller form. An earlier release appended the delivery pointer and closing notice after the size calculation, so both pushed the payload over its own limit. The fix then was to reserve their bytes up front. The frame now shares that reservation.

The general form: anything added after a limit is applied is optional, whatever you intended. And it disappears under load — meaning the safety wrapper vanishes precisely when there is the most content to be careful about, which is the worst possible correlation.

Reserve first, then fill what is left.