evictfaithful

the question

Which configurable eviction policies can a subtree-closed radix prefix cache actually deliver in the same order they would produce without the tree constraint?

what came out

A policy is faithful if and only if its priority key is path-monotone, key(parent) >= key(child) on every edge. LRU, LFU, SLRU, and priority qualify and are exactly the four CLI-exposed policies; FIFO, FILO, and MRU invert on some edge and are unfaithful. Verified against real SGLang with 0 inversions over 8.4M.

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