docs: [LangGraph Server Changelog Bot] Changelog updates for new version(s) (#1527)

Automated changelog update created by the LangGraph Server Changelog
Bot.

Feel free to merge anytime.

Author: samecrowder

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="2025-11-19"></a>
+## v0.5.18
+- Introduced persistent cron threads with `on_run_completed: {keep,delete}` for enhanced cron management and retrieval options.
+
+<a id="2025-11-19"></a>
+## v0.5.17
+- Enhanced task handling to support multiple interrupts, aligning with open-source functionality.
+
 <a id="2025-11-18"></a>
 ## v0.5.15
 - Added custom JSON unmarshalling for `Resume` and `Goto` commands to fix map-style null resume interpretation issues.