diff --git a/README.md b/README.md
index 28ed1a7..9cd58a9 100644
--- a/README.md
+++ b/README.md
@@ -57,6 +57,17 @@ And one thing at the end that is meant to be *withheld*: **"done"** has a defini
 clean log is not one of them. Anything short of all six is a checkpoint, and should be reported as a
 checkpoint with what remains.
 
+**What the split costs is not measured, and the claim should not be overstated.** `SKILL.md` loads in
+full; a reference loads when the symptom index or `references/routing.md` sends you to one. That is
+usually described as "cheaper context", and only half of it has been measured here: the always-loaded
+body has a measured size and a gate that fails when it grows (`check_budget.py`). The other half has
+not — how many references a real question pulls in, and whether fetching them one at a time ends up
+costing more than the alternative would have. A question that needs four references is not obviously
+cheaper than one longer file would have been, and every reference also carries its own entry in the
+index that has to be read to find it. Treat the split's economy as `unknown` -- nothing here has
+measured it -- and treat the body budget as `observed`. The second is the one that compounds on every
+task, which is why it is the one gated.
+
 If you are an agent reading this: the cheapest possible first command is
 `python skills/apk-reverse/scripts/doctor.py`. It tells you which of these tools exist here, which
 scripts can actually run, and whether something in the environment is already poisoning your
diff --git a/README.zh-CN.md b/README.zh-CN.md
index e0ed8ad..e9291f7 100644
--- a/README.zh-CN.md
+++ b/README.zh-CN.md
@@ -41,6 +41,8 @@
 
 另外还有一样在结尾、应当被**扣住**的东西：**「done」**有定义（六项）。一份干净的日志不在其中。少于六项全部达成，就只是一个检查点，应当作为检查点汇报，并说明还剩什么。
 
+**这套切分的成本没有被测量过，所以不要把它说大了。** `SKILL.md` 全文加载；某个 reference 则是在症状索引或 `references/routing.md` 把你送过去时才加载。这通常被描述为「更省上下文」，但这里只测了其中一半：常驻加载的那部分有实测体积，也有门禁在它膨胀时失败（`check_budget.py`）。另一半没有测 —— 一个真实问题会牵出几个 reference，以及一次取一个是否反而比另一种做法更贵。一个要读四个 reference 才能回答的问题，并不显然比一个更长的文件更便宜，而且每个 reference 还要连带为找到它所读的索引行。把切分带来的经济性当作 `unknown`（这里没有任何东西测量过它），把主体预算当作 `observed`。后者才是每个任务都会累积的那一半，也正是被门禁管住的那一半。
+
 如果你是正在读这段的 agent：成本最低的第一条命令是 `python skills/apk-reverse/scripts/doctor.py`。它会告诉你这里存在哪些工具、哪些脚本真的能跑，以及环境里是否已经有什么东西在污染你的测量结果。
 
 ## 它擅长什么