Load-back owner-lane eviction can need to evict a device-resident node whose radix value is a valid tail shorter than the physical tail page. The eviction planner now pads that value only to the page boundary before deriving owner counts, matching the existing write/load capacity contract without exposing padding to radix or scheduler lengths.
Constraint: CP HiCache capacity remains page-owner based while radix node values remain valid-token based.
Constraint: Avoid collectives; owner-lane capacity must be deterministic from local metadata and logical page ids.
Rejected: Require device-resident victim values to be page-aligned | valid-tail cache nodes are now an intentional supported state.
Rejected: Pad to cp_size pages | this would waste KV and violate the page-boundary-only contract.
Confidence: medium
Scope-risk: narrow
Directive: If split-inside-tail support is added later, preserve page ownership/refcount semantics before sharing one padded physical page across radix nodes.
Tested: local py_compile for hiradix_cache.py and touched CP HiCache tests.
Tested: remote g0034 new C8 exact tests: 3 passed, 3 warnings.
Tested: remote g0034 CP HiCache impacted suites: 146 passed, 5 warnings.
Tested: remote g0034 CP shared KV C1-C5 suite: 122 passed, 5 warnings.
Not-tested: full local pytest, blocked by missing runtime dependencies such as starlette.
Not-tested: CUDA E2E runtime for this commit.
Co-authored-by: OmX <omx@oh-my-codex.dev>
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