The CP draft shared-KV path only needs this rank's local draft tokens, but the previous compatibility path embedded the full prompt before CP-splitting. For long MTP/EAGLE prefill this recreates the large hidden activation that CP shared KV is trying to avoid.\n\nThis pads local draft input ids to the per-rank max token count recorded in NSA CP metadata, embeds the padded local tensor, then trims back to the true local length. That keeps rank shapes compatible while avoiding full-prompt embedding on every rank. Missing or stale metadata keeps the existing full-embedding fallback.\n\nConstraint: CP ranks can own uneven token counts, so the local embedding path needs a rank-uniform padded shape.\nRejected: Pad local ids to the full prompt length | this preserves compatibility but loses the intended memory reduction.\nConfidence: medium\nScope-risk: moderate\nDirective: Do not remove the full-embedding fallback unless all CP draft metadata producers guarantee max_rank_len for every prefill path.\nTested: g0034 container py_compile for utils.py and deepseek_nextn.py; g0034 container pytest -q test/registered/unit/layers/test_nsa_cp_utils.py => 25 passed, 5 warnings.\nNot-tested: Full distributed E2E with HiCache cache-hit MTP accept-length recovery.
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