EAGLE draft shared-KV is supposed to mirror the target CP layout, so bs>1 must not fall back to legacy full-input or padded-hidden behavior when required batch metadata is missing or inconsistent. This change keeps the existing bs=1 compatibility path but makes batched CP draft fail fast on missing/mismatched spec hidden states, embedding pad metadata, or input embed shapes. The docs record the current W7 boundary: draft prefill follows target metadata, while scheduler admission and ETE remain gated.
Constraint: CP draft KV must mirror target layout and must not silently diverge under bs>1 shared-KV.
Rejected: Allow bs>1 to use the old full-input fallback | it can hide wrong owner/page metadata and corrupt accept length.
Confidence: medium
Scope-risk: moderate
Directive: Do not open the scheduler bs>1 CP gate until EAGLE accept length/output length are verified with this fail-fast path enabled.
Tested: Remote g0034 targeted EAGLE fail-fast unit test passed; remote full test/registered/unit/layers/test_nsa_cp_utils.py passed 70 tests.
Not-tested: EAGLE bs>1 ETE, because scheduler CP bs>1 admission gate remains closed.
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