Spill is decoupled from eviction (approach D, user-confirmed): a rank-synced background maintainer at
check_hicache_events COPIES the coldest resident committed objects (replicated SLRU order, not-yet-in-L3,
unpinned) to L3 off the critical path. The object stays L2-resident; protect_host pins the LIVE node during
the async bg gather (no freed-range hazard). owned_pages owner = object-local i%cp_size (verified vs
_shared_l2_current_page_owners); per-payload base_page from object_ranges; logical pages only. Bounded +
backpressured (cp_l3_spill_max_inflight). Replicated selection -> lockstep object-granular acks. Spill-ack
(in _drain_l3_control_queues): release_host + node.l3_durable=True (O(1) skip; memoized from exists_prefix
for reloaded nodes). Eviction unchanged (drops L2; L3 copy survives -> reload in 3.2; not-yet-spilled =
recompute, fail-soft). Compiles; default-off. Live validation via flag-on smoke (branch sync).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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