diff --git a/codex/cli.py b/codex/cli.py
index b111c88..7d005dd 100644
--- a/codex/cli.py
+++ b/codex/cli.py
@@ -1,3 +1,8 @@
 import typer
 
 app = typer.Typer(help="codex — personal knowledge base for scientific papers.")
+
+
+@app.callback()
+def _main() -> None:
+    """codex CLI — commands land here in F-07."""