diff --git a/AGENTS.md b/AGENTS.md
new file mode 100644
index 0000000..4b74347
--- /dev/null
+++ b/AGENTS.md
@@ -0,0 +1,10 @@
+# Codex attribution
+
+When Codex authors or substantially contributes to a commit in this repository,
+record that contribution in the commit metadata.
+
+- For Codex-authored work, use `Codex <codex@openai.com>` as the Git author and
+  preserve the human user's configured identity as the committer.
+- For mixed human and Codex work, preserve the human author and append
+  `Co-authored-by: Codex <codex@openai.com>` to the commit message.
+- Do not rewrite existing published history solely to add attribution.