CP shared-KV marks all forwards with uses_cp_shared_kv, but TARGET_VERIFY/decode style forwards may legitimately carry no extend prefix page-plan. The CP split helper previously ran the hard page-plan validator before checking context-parallel extend eligibility, so non-extend spec paths could fail before the later no-split decision.
Hoist the eligibility check and only validate page-plan metadata for real context-parallel EXTEND or shared-KV draft extend forwards. Add a regression that TARGET_VERIFY with no prefix metadata returns no-split instead of failing.
Constraint: Absorb syh 7fea88278 only; MQA logits chunk and per-forward budget changes are intentionally excluded.
Rejected: Relax the validator globally | real prefill page-plan violations must remain fail-fast.
Confidence: high
Scope-risk: narrow
Directive: Do not run CP shared-KV page-plan validation for non-context-parallel forward modes without proving those modes own extend_prefix_lens_cpu.
Tested: Remote g0034 container py_compile for utils/test file.
Tested: Remote g0034 container pytest test_nsa_cp_utils.py -k can_cp_split: 8 passed, 92 deselected.
Not-tested: Full ETE speculative non-deepep MoE path.
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