Constant DEFAULT_MAX_DELTA_BYTES 

pub const DEFAULT_MAX_DELTA_BYTES: usize = _; // 268_435_456usize

D4’s default derivation memory budget: 256 MiB of accounted delta (see DeltaBudget), shared by every table a transaction touches. High enough that no OLTP transaction or existing test fires it; a bulk load that does trips [RindleError::DeltaOverflow] — the load-shed signal (the host commits the data and re-hydrates the affected queries) — instead of an OOM. The spill (design §7 / plan S6) lifts it later.

Sized to land near the row cap it replaced (1M rows) for a small row: at ~100 byte rows with a couple of secondary sorts this trips around 1M rows. The point of the change is the other end — a 1 KiB row now sheds at ~230k rows instead of holding ~1.1 GiB, which the row cap permitted.