CP shared KV cannot treat capacity as a scalar token count: cache-hit load-back and fresh extend allocation both have to preserve the logical page owner pattern or later direct writes, HiCache reload, and prefix materialization can read the wrong lane. This change moves the critical paths to owner-lane plans, makes owner-lane exhaustion recoverable during prefill scheduling, and routes shared-KV prefix prefetch through prefetch-stream-safe KV getters so HiCache layer-load waits do not attach to the forward stream.
Constraint: CP shared KV correctness depends on page owner lane preservation across allocation, backup, load, eviction, and prefix materialization.
Constraint: Avoid adding CP/global collectives for capacity agreement; derive capacity from deterministic local owner-lane state.
Rejected: Keep SGLANG_DISABLE_TAI_OWNER_SELECT fallback | legacy allocation can silently break owner-lane invariants.
Rejected: Scalar total-token eviction for CP HiCache load-back | total capacity can be sufficient while the required owner lane is exhausted.
Confidence: medium
Scope-risk: broad
Directive: Do not reintroduce silent legacy fallback in owner-lane paths; unexpected owner-lane failure must be warning-level fail-closed or recoverable capacity wait.
Tested: Remote g0034 container PYTHONPATH=python python -m pytest test/registered/unit/mem_cache/test_alloc_pages_with_owners.py test/registered/unit/mem_cache/test_cp_shared_kv_layout.py test/registered/unit/mem_cache/test_cp_hicache_load_back_owner_lanes.py test/registered/unit/mem_cache/test_cp_shared_kv_runtime.py -q -> 95 passed.
Tested: Local py_compile for modified runtime/cache/scheduler modules.
Not-tested: Full CUDA ETE performance trace for cache-hit overlap and MTP accept-rate impact.
Co-authored-by: OmX <omx@oh-my-codex.dev>
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