High cache-hit CP shared-KV batches can have small extend tokens while still carrying substantial prefix/load-back work. Add a CP-specific cached-token admission limit so operators can bound that pressure independently from extend-token batching.
Constraint: The limit must not deadlock a single high-cache-hit request; it only stops adding additional requests to a non-empty batch.
Constraint: Cached tokens are counted after L2 load-back planning via prefix_len, so L1 hits and successful L2 hits share one scheduler budget.
Rejected: Reuse max_prefill_tokens | it limits generic input budget and does not represent cached-token work.
Rejected: Count only L1 prefix before load-back | would miss L2 hit pressure, which is one of the target cases.
Confidence: high
Scope-risk: moderate
Directive: Keep cached-token and extend-token limits separate; they bound different scheduler costs.
Tested: Remote pytest targeted cached-token PrefillAdder cases: 2 passed.
Tested: Remote pytest test/registered/unit/managers/test_prefill_adder.py: 18 passed.
Tested: Remote ServerArgs CP validation smoke: SERVER_ARGS_CACHED_LIMIT_OK.
Not-tested: Full ETE replay with a production cached-token limit value.
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