W4-1 needs target index/top-k sync correctness before current/partial-current reuse can be restored. Batch-size>1 in-seq CP produces local q/weights in request-segment order, so top-k must consume req0_prev, req0_next, req1_prev, req1_next rather than treating the flattened batch as one scalar prev/next pair.
The implementation adds a batch dispatch for _get_topk_in_seq_cp_pair, reuses one synchronous shared-index materialization per layer, and calls _get_topk_ragged_with_cp per request segment with an explicit batch_idx. The scalar bs=1 path remains unchanged.
Constraint: This is W4-1 target index/top-k sync correctness; original W4 current/partial-current reuse remains a separate follow-up.
Constraint: Phase W4-1 must not enable bs>1 index prefetch, current reuse, partial-current reuse, or the cp_index multi-batch branch.
Rejected: Use cp_index branch for multi-batch | source marks that path as having accuracy issues.
Rejected: Pad batch requests to max length | wastes compute and violates packed/ragged batch contract.
Confidence: high
Scope-risk: moderate
Directive: Keep bs>1 target top-k ordered by request segment unless a later fused descriptor proves identical ordering and correctness.
Tested: Remote g0034 py_compile for nsa_indexer.py
Tested: Remote g0034 PYTHONPATH=python pytest test/registered/unit/layers/test_nsa_cp_utils.py -> 45 passed
Tested: Remote g0034 PYTHONPATH=python pytest test_nsa_cp_utils.py test_cp_shared_kv_layout.py test_cp_shared_kv_runtime.py -> 172 passed, 2 subtests passed
Not-tested: Full ETE bs>1 serving run with live traffic
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