diff --git a/public/userportal/api/_debug.php b/public/userportal/api/_debug.php
new file mode 100644
index 0000000..cd4764d
--- /dev/null
+++ b/public/userportal/api/_debug.php
@@ -0,0 +1,18 @@
+<?php
+// TEMPORARY
+/** Appends one timestamped line. Silent if the file cannot be written. */
+function debug_log(string $message): void
+{
+    $path = dirname(__DIR__, 3) . '/storage/logs/casadoc-api.log';
+
+    $dir = dirname($path);
+    if (!is_dir($dir) && !@mkdir($dir, 0775, true) && !is_dir($dir)) {
+        return;
+    }
+
+    @file_put_contents(
+        $path,
+        '[' . date('Y-m-d H:i:s') . '] ' . rtrim($message) . "\n",
+        FILE_APPEND | LOCK_EX
+    );
+}