diff --git a/documents/.pages b/documents/.pages
index 87c059d32..afbdb5f99 100644
--- a/documents/.pages
+++ b/documents/.pages
@@ -12,6 +12,7 @@ nav:
     - 卷七 · 工程实践: vol7-engineering/
   - 领域实战:
     - 卷八 · 领域应用: vol8-domains/
+    - 卷九 · 开源项目学习: vol9-open-source-project-learn/
     - 编译与链接: compilation/
     - 实战项目: projects/
   - 参考:
diff --git a/documents/index.md b/documents/index.md
index 544611e95..d530b1597 100644
--- a/documents/index.md
+++ b/documents/index.md
@@ -84,6 +84,14 @@ CMake、包管理、测试、静态分析、DevOps。
 
 ---
 
+### 卷九：开源项目学习
+
+通过分析真实开源项目源码（如 Chromium），学习工业级 C++ 代码的设计与实现。
+
+- [开始阅读](vol9-open-source-project-learn/index.md)
+
+---
+
 ### 编译与链接深入
 
 深入探讨 C/C++ 的编译、链接、静态库、动态库、符号可见性等核心概念。共 10 篇文章。
diff --git a/documents/vol9-open-source-project-learn/.pages b/documents/vol9-open-source-project-learn/.pages
new file mode 100644
index 000000000..50fd7d60e
--- /dev/null
+++ b/documents/vol9-open-source-project-learn/.pages
@@ -0,0 +1,3 @@
+title: 卷九 · 开源项目学习
+nav:
+  - chrome
diff --git a/documents/vol9-open-source-project-learn/chrome/.pages b/documents/vol9-open-source-project-learn/chrome/.pages
new file mode 100644
index 000000000..bf837ee6e
--- /dev/null
+++ b/documents/vol9-open-source-project-learn/chrome/.pages
@@ -0,0 +1,3 @@
+title: Chromium
+nav:
+  - 01_once_callback
diff --git a/documents/vol9-open-source-project-learn/index.md b/documents/vol9-open-source-project-learn/index.md
new file mode 100644
index 000000000..e12fa910f
--- /dev/null
+++ b/documents/vol9-open-source-project-learn/index.md
@@ -0,0 +1,9 @@
+# 卷九 · 开源项目学习
+
+通过分析真实开源项目源码，学习工业级 C++ 代码的设计与实现。
+
+## 项目列表
+
+### Chromium
+
+- [OnceCallback：从 Chromium 学到的回调设计](chrome/01_once_callback/)