docs(bench): the first three-engine table, including where mcpp loses

15 ok / 0 failed / 零告警 —— 三条臂第一次同时产出可运行二进制,所以这是第一份
真实的三方数据。此前 cmake 与 xmake 两列一直是 `failed`,表只能是 mcpp 对 mcpp。

| 场景 | mcpp | cmake | xmake |
|---|---|---|---|
| cold | 92.49s · 1.29x | 119.46s | 105.02s · 1.14x |
| noop | 0.74s · **0.49x** | 0.36s | 0.40s · 0.90x |
| touch-hub | **1.79s · 54.96x** | 98.16s | 98.16s |
| edit-body | 88.38s · 1.11x | 98.43s | 98.00s |
| edit-comment | 93.81s · 1.04x | 97.98s | 97.97s |

**两处是 mcpp 输,都写进了正文而不是脚注:**

* `noop` 0.49x —— 什么都不做时 mcpp 是三者里最慢的(0.74s vs cmake 0.36s)。
  这是每次调用的固定开销,也是用户在「改一行、构建一次」循环里唯一每次都感受
  得到的数字。
* `edit-comment` 只有 1.04x,不是 mcpp 自身负载上的 200x。注释插进了 xlings 保留
  在接口单元里的内联函数体,BMI 真的变了,**级联是欠的**。格子的 note 记录当次
  是哪种形态,不要读成优化失效。

`touch-hub` 54.96x 才是真结果,而且 cmake 与 xmake 相差 **0.00s** —— 两个时间戳
驱动的引擎本就该长这样。

原始报告存进 bench/results/xlings-3way-20260814/;中英文两版同步。旧的
old→new 两风格对照表保留,并标明它两列都是 mcpp、不受外部臂当时未完成的影响。

Author: speak-agent

bench/README.md

@@ -194,14 +194,43 @@ Four things this says, and the fixture can say none of them:
 are the same project either side of one refactor. Ratios against the released
 mcpp.
 
-> **These numbers predate the foreign arms working.** For a long time this said
-> the cmake and xmake arms "stop at the link", and that was recorded as a known
-> gap — it was not a gap, it was unfinished work, and calling it a gap let it
-> sit. The cmake and bazel arms now build both trees into a running binary
-> (`xlings --version` reports the tree's own version on each); xmake is in
-> progress. The table below is still mcpp-against-mcpp because it has not been
-> re-measured since. Until it is, do not read the absence of cmake and xmake
-> columns here as a statement about those engines.
+#### The three engines, on the combined tree
+
+First measurement in which all three arms produce a running binary — the cmake
+and xmake columns below were `failed` cells until the arms were finished, and the
+table that stood here was mcpp-against-mcpp for that reason.
+
+| scenario | **mcpp** | cmake | xmake |
+|---|---|---|---|
+| `cold` | **92.49s** · 1.29x | 119.46s · 1.00x | 105.02s · 1.14x |
+| `noop` | **0.74s** · 0.49x | 0.36s · 1.00x | 0.40s · 0.90x |
+| `touch-hub` | **1.79s** · 54.96x | 98.16s · 1.00x | 98.16s · 1.00x |
+| `edit-body` | **88.38s** · 1.11x | 98.43s · 1.00x | 98.00s · 1.00x |
+| `edit-comment` | **93.81s** · 1.04x | 97.98s · 1.00x | 97.97s · 1.00x |
+
+<sub>xlings `2026.8.11.2`, gcc 16.1.0 payload, Linux x86_64 · i9-13900K · n=1 ·
+`--baseline cmake`. Raw report: `bench/results/xlings-3way-20260814/`.</sub>
+
+Three things in that table are worth reading carefully, because two of them are
+mcpp LOSING:
+
+* **`noop` is 0.49x — mcpp is the slowest of the three at doing nothing.** 0.74s
+  against cmake's 0.36s. It is a fixed cost on every invocation, and it is the
+  one number here that a user feels on every keystroke-to-build cycle.
+* **`edit-comment` is 1.04x, not the 200x the mcpp workload shows.** The comment
+  lands INSIDE an inline function body that xlings keeps in its interface unit,
+  so the BMI genuinely changes and the cascade is owed. The cell's note records
+  which form ran; see §3, and do not read this as the optimisation failing.
+* **`touch-hub` is the real result: 54.96x.** Content unchanged, so mcpp compares
+  the BMI it just produced against the previous one and skips 45 importers.
+  cmake and xmake decide by timestamp and rebuild all of them — to within 0.00s
+  of each other, which is what two timestamp-driven engines should look like.
+
+#### The two code styles, mcpp against mcpp
+
+Older run, kept because it is the only side-by-side of the two pinned
+styles. Both columns are mcpp, so the foreign arms being unfinished at the
+time does not affect it.
 
 | scenario | combined `2026.8.11.2` old → new | split `2026.8.13.1` old → new | what the split buys |
 |---|---|---|---|

bench/README.zh-CN.md

@@ -159,6 +159,34 @@ job 一个测量都没有，这个状态持续了好几周。
 
 ---
 
+## 4b. 三个引擎在 combined 树上的实测
+
+**第一次三条臂都能产出可运行二进制的测量** —— 在此之前 cmake 与 xmake 两列一直是
+`failed`,所以这里原本只有 mcpp 对 mcpp。
+
+| 场景 | **mcpp** | cmake | xmake |
+|---|---|---|---|
+| `cold` | **92.49s** · 1.29x | 119.46s · 1.00x | 105.02s · 1.14x |
+| `noop` | **0.74s** · 0.49x | 0.36s · 1.00x | 0.40s · 0.90x |
+| `touch-hub` | **1.79s** · 54.96x | 98.16s · 1.00x | 98.16s · 1.00x |
+| `edit-body` | **88.38s** · 1.11x | 98.43s · 1.00x | 98.00s · 1.00x |
+| `edit-comment` | **93.81s** · 1.04x | 97.98s · 1.00x | 97.97s · 1.00x |
+
+<sub>xlings `2026.8.11.2`,gcc 16.1.0 载荷,Linux x86_64 · i9-13900K · n=1 ·
+`--baseline cmake`。原始报告:`bench/results/xlings-3way-20260814/`。</sub>
+
+这张表里有三处值得细读,其中**两处是 mcpp 输**:
+
+* **`noop` 是 0.49x —— 什么都不做时 mcpp 是三者中最慢的。** 0.74s 对 cmake 的
+  0.36s。这是每次调用的固定开销,也是用户在「改一行、构建一次」的循环里唯一
+  每次都感受得到的数字。
+* **`edit-comment` 是 1.04x,不是 mcpp 自身工作负载上的 200x。** 注释插进了
+  xlings 保留在接口单元里的内联函数体,BMI 真的变了,级联是**欠的**。格子的
+  note 会记录当次是哪种形态(见 §3),不要把它读成优化失效。
+* **`touch-hub` 才是真结果:54.96x。** 内容没变,mcpp 拿编译器刚产出的 BMI 和
+  上一份比,跳过 45 个导入者;cmake 与 xmake 按时间戳判断,把它们全部重建 ——
+  两者相差 0.00s,这正是两个时间戳驱动的引擎该有的样子。
+
 ## 5. 可观测性：跑的时候看得见
 
 harness 会把进度实时打到 **stderr**（逐行 flush），stdout 留给报告：

bench/results/xlings-3way-20260814/xlings-combined-3way.json

@@ -0,0 +1,241 @@
+{
+  "protocol_version": 1,
+  "started_at": "2026-08-13T17:43:09Z",
+  "host": {
+    "os": "linux",
+    "arch": "x86_64",
+    "cpu_model": "13th Gen Intel(R) Core(TM) i9-13900K",
+    "logical_cores": 32,
+    "physical_cores": 24,
+    "heterogeneous": true,
+    "ram_bytes": 67147722752,
+    "toolchain": "/home/speak/.mcpp/registry/data/xpkgs/xim-x-gcc/16.1.0/bin/g++"
+  },
+  "cells": [
+    {
+      "engine": "mcpp@2026.8.13.1",
+      "compiler": "gcc",
+      "profile": "release",
+      "scenario": "cold",
+      "fixture": "xlings-2026.8.11.2",
+      "variant": "modules",
+      "status": "ok",
+      "note": "mcpp 2026.8.13.1",
+      "runs": 1,
+      "median_s": 92.493,
+      "min_s": 92.493,
+      "max_s": 92.493,
+      "samples": [92.493]
+    },
+    {
+      "engine": "mcpp@2026.8.13.1",
+      "compiler": "gcc",
+      "profile": "release",
+      "scenario": "noop",
+      "fixture": "xlings-2026.8.11.2",
+      "variant": "modules",
+      "status": "ok",
+      "note": "mcpp 2026.8.13.1",
+      "runs": 1,
+      "median_s": 0.744,
+      "min_s": 0.744,
+      "max_s": 0.744,
+      "samples": [0.744]
+    },
+    {
+      "engine": "mcpp@2026.8.13.1",
+      "compiler": "gcc",
+      "profile": "release",
+      "scenario": "touch-hub",
+      "fixture": "xlings-2026.8.11.2",
+      "variant": "modules",
+      "status": "ok",
+      "note": "mcpp 2026.8.13.1",
+      "runs": 1,
+      "median_s": 1.786,
+      "min_s": 1.786,
+      "max_s": 1.786,
+      "samples": [1.786]
+    },
+    {
+      "engine": "mcpp@2026.8.13.1",
+      "compiler": "gcc",
+      "profile": "release",
+      "scenario": "edit-body",
+      "fixture": "xlings-2026.8.11.2",
+      "variant": "modules",
+      "status": "ok",
+      "note": "mcpp 2026.8.13.1 · perturbation: in-body",
+      "runs": 1,
+      "median_s": 88.379,
+      "min_s": 88.379,
+      "max_s": 88.379,
+      "samples": [88.379]
+    },
+    {
+      "engine": "mcpp@2026.8.13.1",
+      "compiler": "gcc",
+      "profile": "release",
+      "scenario": "edit-comment",
+      "fixture": "xlings-2026.8.11.2",
+      "variant": "modules",
+      "status": "ok",
+      "note": "mcpp 2026.8.13.1 · perturbation: in-body",
+      "runs": 1,
+      "median_s": 93.813,
+      "min_s": 93.813,
+      "max_s": 93.813,
+      "samples": [93.813]
+    },
+    {
+      "engine": "cmake",
+      "compiler": "gcc",
+      "profile": "release",
+      "scenario": "cold",
+      "fixture": "xlings-2026.8.11.2",
+      "variant": "modules",
+      "status": "ok",
+      "note": "cmake version 4.0.2 + ninja",
+      "runs": 1,
+      "median_s": 119.458,
+      "min_s": 119.458,
+      "max_s": 119.458,
+      "samples": [119.458]
+    },
+    {
+      "engine": "cmake",
+      "compiler": "gcc",
+      "profile": "release",
+      "scenario": "noop",
+      "fixture": "xlings-2026.8.11.2",
+      "variant": "modules",
+      "status": "ok",
+      "note": "cmake version 4.0.2 + ninja",
+      "runs": 1,
+      "median_s": 0.361,
+      "min_s": 0.361,
+      "max_s": 0.361,
+      "samples": [0.361]
+    },
+    {
+      "engine": "cmake",
+      "compiler": "gcc",
+      "profile": "release",
+      "scenario": "touch-hub",
+      "fixture": "xlings-2026.8.11.2",
+      "variant": "modules",
+      "status": "ok",
+      "note": "cmake version 4.0.2 + ninja",
+      "runs": 1,
+      "median_s": 98.161,
+      "min_s": 98.161,
+      "max_s": 98.161,
+      "samples": [98.161]
+    },
+    {
+      "engine": "cmake",
+      "compiler": "gcc",
+      "profile": "release",
+      "scenario": "edit-body",
+      "fixture": "xlings-2026.8.11.2",
+      "variant": "modules",
+      "status": "ok",
+      "note": "cmake version 4.0.2 + ninja · perturbation: in-body",
+      "runs": 1,
+      "median_s": 98.434,
+      "min_s": 98.434,
+      "max_s": 98.434,
+      "samples": [98.434]
+    },
+    {
+      "engine": "cmake",
+      "compiler": "gcc",
+      "profile": "release",
+      "scenario": "edit-comment",
+      "fixture": "xlings-2026.8.11.2",
+      "variant": "modules",
+      "status": "ok",
+      "note": "cmake version 4.0.2 + ninja · perturbation: in-body",
+      "runs": 1,
+      "median_s": 97.979,
+      "min_s": 97.979,
+      "max_s": 97.979,
+      "samples": [97.979]
+    },
+    {
+      "engine": "xmake",
+      "compiler": "gcc",
+      "profile": "release",
+      "scenario": "cold",
+      "fixture": "xlings-2026.8.11.2",
+      "variant": "modules",
+      "status": "ok",
+      "note": "xmake v3.1.0+HEAD.96ad28e, A cross-platform build utility based on Lua",
+      "runs": 1,
+      "median_s": 105.024,
+      "min_s": 105.024,
+      "max_s": 105.024,
+      "samples": [105.024]
+    },
+    {
+      "engine": "xmake",
+      "compiler": "gcc",
+      "profile": "release",
+      "scenario": "noop",
+      "fixture": "xlings-2026.8.11.2",
+      "variant": "modules",
+      "status": "ok",
+      "note": "xmake v3.1.0+HEAD.96ad28e, A cross-platform build utility based on Lua",
+      "runs": 1,
+      "median_s": 0.401,
+      "min_s": 0.401,
+      "max_s": 0.401,
+      "samples": [0.401]
+    },
+    {
+      "engine": "xmake",
+      "compiler": "gcc",
+      "profile": "release",
+      "scenario": "touch-hub",
+      "fixture": "xlings-2026.8.11.2",
+      "variant": "modules",
+      "status": "ok",
+      "note": "xmake v3.1.0+HEAD.96ad28e, A cross-platform build utility based on Lua",
+      "runs": 1,
+      "median_s": 98.157,
+      "min_s": 98.157,
+      "max_s": 98.157,
+      "samples": [98.157]
+    },
+    {
+      "engine": "xmake",
+      "compiler": "gcc",
+      "profile": "release",
+      "scenario": "edit-body",
+      "fixture": "xlings-2026.8.11.2",
+      "variant": "modules",
+      "status": "ok",
+      "note": "xmake v3.1.0+HEAD.96ad28e, A cross-platform build utility based on Lua · perturbation: in-body",
+      "runs": 1,
+      "median_s": 97.999,
+      "min_s": 97.999,
+      "max_s": 97.999,
+      "samples": [97.999]
+    },
+    {
+      "engine": "xmake",
+      "compiler": "gcc",
+      "profile": "release",
+      "scenario": "edit-comment",
+      "fixture": "xlings-2026.8.11.2",
+      "variant": "modules",
+      "status": "ok",
+      "note": "xmake v3.1.0+HEAD.96ad28e, A cross-platform build utility based on Lua · perturbation: in-body",
+      "runs": 1,
+      "median_s": 97.974,
+      "min_s": 97.974,
+      "max_s": 97.974,
+      "samples": [97.974]
+    }
+  ]
+}