Reject empty HOME envvar

tests/integration.rs

@@ -284,6 +284,25 @@ fn relative_ro_path_works() {
     );
 }
 
+#[test]
+fn empty_home_rejected() {
+    let output = sandbox(&[])
+        .env("HOME", "")
+        .args(["--", "true"])
+        .output()
+        .expect("agent-sandbox binary failed to execute");
+
+    assert!(
+        !output.status.success(),
+        "expected failure with empty HOME, but got success"
+    );
+    let stderr = String::from_utf8_lossy(&output.stderr);
+    assert!(
+        stderr.to_lowercase().contains("home"),
+        "expected error mentioning HOME, got: {stderr}"
+    );
+}
+
 #[test]
 fn rw_missing_path_errors() {
     let output = sandbox(&["--rw", "/nonexistent/xyz"])