From d947e8d6566bd7b58cdaeeab2f4558fbc16fd61c Mon Sep 17 00:00:00 2001
From: Brian Ward <bward@flatironinstitute.org>
Date: Fri, 28 Aug 2026 13:00:51 -0400
Subject: [PATCH] Flush JSON writer at end of records

---
 src/stan/callbacks/json_writer.hpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/stan/callbacks/json_writer.hpp b/src/stan/callbacks/json_writer.hpp
index d791b8a7371..efc572e30ff 100644
--- a/src/stan/callbacks/json_writer.hpp
+++ b/src/stan/callbacks/json_writer.hpp
@@ -228,6 +228,7 @@ class json_writer final : public structured_writer {
     } else {
       *output_ << "\n";
     }
+    output_->flush();
   }
 
   /**