CP shared KV current-only and partial-current paths were previously unsafe because owner-local current rows could be filled into dense page slots without synchronizing the current slots across CP ranks. This preserves the fast path and fixes the missing synchronization at the actual contract boundary: prefix slots remain materialized by the existing IPC/collective path, while freshly produced current slots are composed from current forward tensors and reduced only over the current slot ranges.\n\nThe change also keeps page-tail compute padding explicit, restores current-only index compose, fixes TAI index descriptor dtype consistency, and records the investigation ledger to avoid repeating discarded hypotheses.\n\nConstraint: CP shared KV must preserve current reuse and TAI materialize fast paths; blanket disable is not an acceptable fix.\nConstraint: Prefix slots must not be reduced twice after IPC/prefix materialization.\nRejected: Disable current-only MLA/index reuse | hides the owner-local composition bug and regresses the intended fast path.\nRejected: Disable TAI materialize globally | avoids symptoms without proving the byte/layout contract.\nConfidence: medium\nScope-risk: broad\nDirective: Do not remove current-slot range synchronization unless replacing it with an equivalent owner-aware P2P/IPC gather contract.\nTested: Local py_compile for touched files.\nTested: Remote g0034 py_compile for touched runtime/test files.\nTested: Remote test_cp_shared_kv_runtime.py: 111 passed, 5 warnings, 2 subtests passed.\nTested: Remote targeted current-slot compose tests and direct current-only index compose script.\nNot-tested: Full ETE output quality and decode accept len after restart.\nNot-tested: Full test_nsa_cp_utils.py collection on remote due incomplete installed sgl_kernel import/fake-op environment.
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