Module allocation 

Pressure-driven tool row allocation ladder.

The ladder is the automatic layer that the live region uses to fit ever-taller blocks (tool calls with diffs, file reads with full previews, command outputs) into a finite viewport. It is pure: given a list of per-block natural heights and a row budget, it returns the rendered row count for each block. The renderer decides how to draw the quantized shapes (glyph / folded / full); this module decides how many rows each block gets.

Allocation levels

• 0 — block is hidden entirely (emergency truncation; the caller reserves a single banner row instead).
• 1 — glyph row (▸ tool · activity), animated wall-clock pulse on a shared period so the live region breathes.
• 2 — folded card (╭─ tool · activity / ╰─ …), the static “something is here” affordance.
• natural — full block at its natural height.

Allocations are quantized to those four shapes: a block never receives 3..natural-1 rows, because the live-region renderer maps any allocation of 3 or more rows to the FULL natural render — a “3 of 5” allocation would paint 5 rows and overflow the budget.

User-set BlockDisplayMode overrides happen at the call site (see render_transcript); the ladder applies only to blocks without a manual override.

Structs

BlockAlloc

Row budget assigned to a single block by allocate_rows.

Functions

allocate_rows

Allocate a row budget across the given per-block natural heights. Pure function: same (block_heights, budget) always yields the same Vec<BlockAlloc>. See module docs for the algorithm.