diff --git a/.jules/sentinel.md b/.jules/sentinel.md
new file mode 100644
index 0000000..7877f7f
--- /dev/null
+++ b/.jules/sentinel.md
@@ -0,0 +1,4 @@
+## 2025-02-03 - File Creation Race Conditions
+**Vulnerability:** SSH private keys were created with default umask permissions (world-readable) before being restricted with `chmod`.
+**Learning:** Shell redirection (`>`) creates files with default umask permissions immediately. `chmod` after creation leaves a window of exposure (race condition).
+**Prevention:** Use `umask 077` in a subshell or block before creating sensitive files to ensure they are born secure.
diff --git a/tools/setup-ssh-keys.sh b/tools/setup-ssh-keys.sh
index bde52fd..ad32583 100755
--- a/tools/setup-ssh-keys.sh
+++ b/tools/setup-ssh-keys.sh
@@ -149,11 +149,17 @@ cmd_restore() {
     say "Restoring SSH key from 1Password..."
 
     # Create SSH directory
-    mkdir -p "$SSH_DIR"
+    (
+        umask 077
+        mkdir -p "$SSH_DIR"
+    )
     chmod 700 "$SSH_DIR"
 
     # Read private key from 1Password and save locally
-    op read "op://$VAULT/$KEY_NAME/private_key" > "$PRIVATE_KEY_FILE"
+    (
+        umask 077
+        op read "op://$VAULT/$KEY_NAME/private_key" > "$PRIVATE_KEY_FILE"
+    )
     chmod 600 "$PRIVATE_KEY_FILE"
 
     # Read public key from 1Password and save locally