diff --git a/src/langsmith/agent-server-changelog.mdx b/src/langsmith/agent-server-changelog.mdx
index f9e6315530..8579171346 100644
--- a/src/langsmith/agent-server-changelog.mdx
+++ b/src/langsmith/agent-server-changelog.mdx
@@ -5,6 +5,14 @@ sidebarTitle: Agent Server changelog
 
 [Agent Server](/langsmith/agent-server) is an API platform for creating and managing agent-based applications. It provides built-in persistence, a task queue, and supports deploying, configuring, and running assistants (agentic workflows) at scale. This changelog documents all notable updates, features, and fixes to Agent Server releases.
 
+<a id="2025-11-20"></a>
+## v0.5.20
+- Resolved an error in the executor service that occurred when handling large messages.
+
+<a id="2025-11-19"></a>
+## v0.5.19
+- Upgraded built-in langchain-core to version 1.0.7 to address a prompt formatting vulnerability.
+
 <a id="2025-11-19"></a>
 ## v0.5.18
 - Introduced persistent cron threads with `on_run_completed: {keep,delete}` for enhanced cron management and retrieval options.