add cosmos db sample for checkpointer

src/oss/langchain/short-term-memory.mdx

@@ -107,6 +107,9 @@ const checkpointer = PostgresSaver.fromConnString(DB_URI);
 ```
 :::
 
+<Note>
+For more checkpointer options including SQLite, Postgres, and Azure Cosmos DB, see the [list of checkpointer libraries](/oss/langgraph/persistence#checkpointer-libraries) in the Persistence documentation.
+</Note>
 
 ## Customizing agent memory
 
@@ -679,7 +682,7 @@ def update_user_info(
     runtime: ToolRuntime[CustomContext, CustomState],
 ) -> Command:
     """Look up and update user info."""
-    user_id = runtime.context.user_id 
+    user_id = runtime.context.user_id
     name = "John Smith" if user_id == "user_123" else "Unknown user"
     return Command(update={  # [!code highlight]
         "user_name": name,
@@ -704,7 +707,7 @@ agent = create_agent(
     model="gpt-5-nano",
     tools=[update_user_info, greet],
     state_schema=CustomState, # [!code highlight]
-    context_schema=CustomContext,  
+    context_schema=CustomContext,
 )
 
 agent.invoke(

src/oss/langgraph/persistence.mdx

@@ -1069,6 +1069,7 @@ Under the hood, checkpointing is powered by checkpointer objects that conform to
 * `langgraph-checkpoint`: The base interface for checkpointer savers (@[`BaseCheckpointSaver`]) and serialization/deserialization interface (@[`SerializerProtocol`]). Includes in-memory checkpointer implementation (@[`InMemorySaver`]) for experimentation. LangGraph comes with `langgraph-checkpoint` included.
 * `langgraph-checkpoint-sqlite`: An implementation of LangGraph checkpointer that uses SQLite database (@[`SqliteSaver`] / @[`AsyncSqliteSaver`]). Ideal for experimentation and local workflows. Needs to be installed separately.
 * `langgraph-checkpoint-postgres`: An advanced checkpointer that uses Postgres database (@[`PostgresSaver`] / @[`AsyncPostgresSaver`]), used in LangSmith. Ideal for using in production. Needs to be installed separately.
+* `langgraph-checkpoint-cosmosdb`: An implementation of LangGraph checkpointer that uses Azure Cosmos DB (@[`CosmosDBSaver`] / @[`AsyncCosmosDBSaver`]). Ideal for using in production with Azure. Supports both sync and async operations. Needs to be installed separately.
 :::
 
 :::js