Struct SpecBoundaryCapture 

pub struct SpecBoundaryCapture {
    pub snap: CacheSnapshot,
    pub pos: usize,
    pub logits: Vec<f32>,
}

PREFIX-CACHE BOUNDARY CAPTURE (lane/spec-prefix-cache, 2026-08-14): the state a spec session records at its cold-prime split so the WORKER can publish a cross-request prefix entry — the commit-gated-publication port (research/cache-spec-design-20260814/PORT-PLAN.md item 1). Only the pieces that are DESTROYED by continuing the prime need copies here: the in-place GDN conv/ssm states (via Cache::snapshot, same mechanism as [SpecCheckpoint]) and the boundary logits. Full-attn KV rows [0..pos) and draft-scratch rows [0..pos) are append-only for the session’s lifetime (rollbacks never truncate below the prime boundary), so the worker slices those from the live caches post-burst instead of copying at prime time.

Fields

snap: CacheSnapshot

pos: usize

Token boundary (== cache.pos at capture; == the worker’s miss-LCP split).

logits: Vec<f32>

Full-vocab logits after the prefix prime — the entry’s boundary logits.