Port upstream IndexCache for DeepSeek-V3.2 / GLM-5 (#21405 + #27114 gate fix) to
our diverged tree, matching upstream HEAD's merged form. The NSA indexer topk is
computed every `index_topk_freq` layers; `skip_topk` layers reuse the previous
layer's topk via prev_topk_indices threaded through the model forward. Default
index_topk_freq=1 => no sharing => zero behavior change until the model config opts in.
- forward_mla.py: gate the two indexer call sites
(`if not skip_topk or (is_nextn and prev_topk_indices is None)`), else reuse
prev_topk_indices; forward_absorb_core returns (output, topk_indices) when
next_skip_topk is set (topk_indices already threaded prepare->core via inner_state).
- deepseek_v2.py: AttentionMLA.__init__ skip_topk/next_skip_topk setup
(freq/pattern/offset; is_nextn=True/True); thread prev_topk_indices through
forward/forward_prepare/op_core; DecoderLayer returns a 3-tuple (tuple-unpack
placed AFTER the CP shared-KV finally); Model.forward loop threads topk_indices.
- deepseek_nextn.py: 3-tuple decoder unpack.
- server_args.py: port the #27114 guard - raise on --enable-two-batch-overlap with
index-topk sharing (the TBO op path does not propagate topk across layers, so
shared layers would run sparse attention with no indices).
All DecoderLayer.forward callers covered (Model loop, nextn, glm4_moe_lite /
mistral_large_3_eagle inherit, TBO op-path discards via op_core). Did NOT port
#24392 (orthogonal indexer-topk capture/output infra). Import-validated on the
B300 / torch-2.11 image. Enabling it requires setting `index_topk_freq` in the
model config (Zhipu-confirmed for GLM-5.1).
Refs: WI-2026-06-07-001
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
(cherry picked from commit af2a41b8d396033e378b6bdd5f6baebf2a98c301)
leavelet
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