diff --git a/.jules/sentinel.md b/.jules/sentinel.md
index 8cfef1b..0880885 100644
--- a/.jules/sentinel.md
+++ b/.jules/sentinel.md
@@ -1,3 +1,18 @@
+# Sentinel Journal
+
+## 2026-04-15 - Prevent TOCTOU in SSH Key Restoration
+
+**Vulnerability:** A Time-of-Check to Time-of-Use (TOCTOU) vulnerability where an
+SSH private key is briefly world-readable upon creation before `chmod 600` is
+applied.
+
+**Learning:** Redirecting output to a file creates the file with default
+permissions (often `644`), which exposes sensitive data for a fraction of a
+second.
+
+**Prevention:** Wrap commands that create sensitive files in a subshell using
+`umask 077` to ensure the file is created with secure permissions (`600`)
+natively.
 # Sentinel Security Journal
 
 ## 2026-04-16 - Prevent TOCTOU and Symlink Attacks via Insecure Temporary Directories
diff --git a/tools/setup-ssh-keys.sh b/tools/setup-ssh-keys.sh
index bde52fd..6ecd8db 100755
--- a/tools/setup-ssh-keys.sh
+++ b/tools/setup-ssh-keys.sh
@@ -153,7 +153,7 @@ cmd_restore() {
     chmod 700 "$SSH_DIR"
 
     # Read private key from 1Password and save locally
-    op read "op://$VAULT/$KEY_NAME/private_key" > "$PRIVATE_KEY_FILE"
+    (umask 077 && op read "op://$VAULT/$KEY_NAME/private_key" > "$PRIVATE_KEY_FILE")
     chmod 600 "$PRIVATE_KEY_FILE"
 
     # Read public key from 1Password and save locally