Function default_dflash_gamma 

pub const fn default_dflash_gamma(trained_block_size: usize) -> usize

The served DFlash gamma for a drafter of this trained block size, when no --dflash-gamma was given.

THE SSOT, and it must stay that way: the drafter head resolves its gamma through this, and so does every preflight that sizes a pool or a reserve from a peeked dflash_config.block_size. Two spellings of this rule is how the SSM MTP intermediates came to be reserved for K=9 while verify asked for K=10, a hard error at the first verify step, mid-graph-capture.

block + 2, because these drafters chain PAST their trained block: measured on Qwen3.8-27B DFlash2 (block 8), gamma 8 runs 7 drafts, one short, while gamma 10 holds full-block 9/9 accepts and is the fastest measured serve (63.0 vs 56.2 tok/s on GB10, 2026-08-29).

Clamped to MAX_F16_TWIN_DFLASH_GAMMA so a block-16-class drafter lands on 15, the widest verify width with kernel coverage under both h-state dtypes, instead of gamma 18 / K=19, which no wyN kernel serves.