diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 00000000..bcae2ac2
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,3 @@
+[submodule "vendor/codex"]
+	path = vendor/codex
+	url = https://github.com/openai/codex.git
diff --git a/README.md b/README.md
index 477d806c..20e7c340 100644
--- a/README.md
+++ b/README.md
@@ -18,6 +18,14 @@ flutter test
 flutter run -d macos
 ```
 
+## Vendor Repositories
+
+`vendor/codex` is tracked as a git submodule for future built-in code agent integration.
+
+```bash
+git submodule update --init --recursive
+```
+
 ## macOS Packaging
 
 ```bash
diff --git a/vendor/codex b/vendor/codex
new file mode 160000
index 00000000..78280f87
--- /dev/null
+++ b/vendor/codex
@@ -0,0 +1 @@
+Subproject commit 78280f872a58dfbb51d2883791d036db00cbfe0f