diff --git a/.jules/sentinel.md b/.jules/sentinel.md
new file mode 100644
index 0000000..cb6d463
--- /dev/null
+++ b/.jules/sentinel.md
@@ -0,0 +1,4 @@
+## 2024-05-22 - Secure File Creation in Shell Scripts
+**Vulnerability:** TOCTOU race condition when creating sensitive files (like SSH keys) using redirection (`>`) followed by `chmod`.
+**Learning:** Files created via redirection inherit default permissions (usually 644/666) before `chmod` runs, leaving a window where they are world-readable.
+**Prevention:** Use `umask` inside a subshell to strictly control permissions at creation time: `(umask 077; command > file)`.
diff --git a/tools/setup-ssh-keys.sh b/tools/setup-ssh-keys.sh
index bde52fd..aef9fe0 100755
--- a/tools/setup-ssh-keys.sh
+++ b/tools/setup-ssh-keys.sh
@@ -153,12 +153,16 @@ cmd_restore() {
     chmod 700 "$SSH_DIR"
 
     # Read private key from 1Password and save locally
-    op read "op://$VAULT/$KEY_NAME/private_key" > "$PRIVATE_KEY_FILE"
-    chmod 600 "$PRIVATE_KEY_FILE"
+    (
+        umask 077
+        op read "op://$VAULT/$KEY_NAME/private_key" > "$PRIVATE_KEY_FILE"
+    )
 
     # Read public key from 1Password and save locally
-    op read "op://$VAULT/$KEY_NAME/public_key" > "$PUBLIC_KEY_FILE"
-    chmod 644 "$PUBLIC_KEY_FILE"
+    (
+        umask 022
+        op read "op://$VAULT/$KEY_NAME/public_key" > "$PUBLIC_KEY_FILE"
+    )
 
     say "SSH key restored to $SSH_DIR"
     echo ""