Mooncake is the only disaggregation transfer backend in this branch with CP shared-KV owner filtering plus logical-page-position destination selection. NIXL still slices destination pages by the original chunk slice, so allowing CP shared-KV prefill on NIXL can silently pair filtered prefill pages with the wrong decode pages.
This keeps the supported path narrow while preserving the page-aligned transfer contract: non-page-aligned valid tails transfer their physical tail page, but do not get padded to CP-size pages.
Constraint: CP shared-KV transfer remaps prefill logical pages to per-rank physical pages while decode metadata remains request-position based.
Rejected: Let NIXL continue through the generic slice path | it lacks logical-page-position selection and can silently corrupt CP shared-KV transfers.
Confidence: high
Scope-risk: narrow
Directive: Do not enable CP shared-KV on another PD transfer backend until its sender filters owner pages and selects decode pages by logical request-page position.
Tested: Local py_compile for server_args and touched tests.
Tested: Remote g0034 pytest test_cp_shared_kv_transfer_mapping.py test_req_to_token_pool.py TestHiCacheArgs: 22 passed, 8 subtests passed.
Not-tested: End-to-end PD transfer with a live non-page-aligned prompt.
Co-authored-by: OmX <omx@oh-my-codex.dev>
CP HiCache now treats draft KV as a strict target-owned payload through pending write visibility, host eviction, and state-buffer registration. Host metadata created before async D2H ack is no longer request-visible, so match_prefix cannot select an in-flight host node. Draft host eviction now fails before target cleanup when draft metadata is missing, and prefill/decode share one helper for draft NSA state buffers so shared-KV mode cannot silently skip mismatched draft state.
Constraint: CP shared KV + HiCache + EAGLE/MTP must not expose target-only host hits or skipped draft state as valid cache hits
Rejected: Rely on event-loop ordering and lock_ref to hide in-flight writes | match_prefix does not consult lock_ref and can observe host_len/cp_hicache directly
Rejected: Keep draft state mismatch as debug-only skip | it can poison speculative acceptance while looking like a successful cache hit
Confidence: high
Scope-risk: moderate
Directive: Do not reintroduce silent draft/target fallback in CP shared-KV HiCache paths; malformed strong-sync metadata should fail fast
Tested: python -m py_compile targeted modified files
Tested: remote g0034 container pytest test/registered/unit/mem_cache/test_cp_hicache_metadata.py test/registered/unit/managers/test_hicache_controller_cp.py test/registered/unit/disaggregation/test_cp_shared_kv_transfer_mapping.py -q (91 passed)
Not-tested: Full CP shared KV + HiCache + EAGLE/MTP ETE server run after this commit
Prefill CP previously replicated NSA/MLA persistent KV on every CP rank, so CP8 consumed eight copies of KV memory while exposing only one rank of logical cache capacity. This change splits logical KV locs from per-rank physical storage, shards MLA latent KV and NSA index K/scale by deterministic page ownership, and keeps existing NSA attention kernels working through a full-view runtime materialization layer.
Mooncake PD transfer now sends each prefill CP rank's owned physical pages with explicit logical page positions so non-CP decode can reconstruct full-layout KV. The implementation is guarded by an explicit server flag and startup checks, and the design documentation records the implemented scope, debug environment, and Phase 3 boundary.
Constraint: Phase 2 must preserve existing NSA attention/index kernels via runtime full-view materialization
Constraint: Decode side remains non-CP and receives full KV through Mooncake
Rejected: Shard-aware NSA attention in this change | belongs to Phase 3 because it requires distributed topk/softmax/output contracts
Rejected: Request-contiguous CP ownership | unstable under chunked prefill and tied to attention split mode
Confidence: medium
Scope-risk: broad
Directive: Do not enable round-robin CP shared KV without wiring runtime materialization/PD transfer contracts for that split mode
Directive: Keep SGLANG_DEBUG_CP_SHARED_KV disabled for perf measurements; it intentionally enables CUDA-syncing diagnostics
Tested: Remote py_compile for shared-KV touched Python files in g0034 container
Tested: Remote pytest selected cp_shared/shared_kv/nsa suite: 37 passed, 34 deselected
Not-tested: Full GLM5 multi-node throughput/regression run after final doc update
Not-tested: Phase 3 shard-aware runtime, round-robin CP mode, and non-Mooncake PD backends
