Phase 8 needs a narrow boundary because previous shared-KV phases already changed persistent layout and materialize behavior. The plan records an MLA-only, one-layer-ahead prefix prefetch path that targets chunked-prefill/radix-hit sync materialize overhead without adding index prefetch or bandwidth scheduling yet.
Constraint: Phase 8 must not introduce SGLANG_CP_SHARED_KV_LAYER_PREFETCH_KIND
Constraint: Current request is documentation only; do not modify runtime code
Rejected: Add index K/scale prefetch to the same phase | widens topk correctness and collective-order risk before MLA overlap is validated
Rejected: Persist dense KV across chunks | reintroduces large full-context memory pressure
Confidence: high
Scope-risk: narrow
Directive: Keep Phase 8 v1 MLA-only unless profiling proves index materialize is the next blocker
Tested: git diff --check -- docs/advanced_features/nsa_prefill_cp_phase8_mla_prefix_prefetch_plan.md
Not-tested: Runtime/server execution; documentation-only commit
2317952a01