add cosmos db sample for checkpointer

[TheovanKraay]

Overview

added cosmos db sample for checkpointer in short term memory section

Type of change

Update existing documentation

Related issues/PRs

N/A

Checklist

• I have read the contributing guidelines
• I have tested my changes locally using docs dev
• All code examples have been tested and work correctly
• I have used root relative paths for internal links
• I have updated navigation in src/docs.json if needed
• I have gotten approval from the relevant reviewers
• (Internal team members only / optional) I have created a preview deployment using the Create Preview Branch workflow

Additional notes

There are actually many checkpointer store implementations now: https://pypi.org/search/?q=langgraph-checkpoint. Perhaps this doc could further be revised to make that clear. However, I cannot comment authoritatively on those (I am PM in Cosmos DB engineering team). so just adding the Cosmos DB sample in addition to the existing Postgres sample.

[Copilot]

Pull Request Overview

This PR adds documentation for using Azure Cosmos DB as a checkpoint saver for LangChain agents, providing an alternative to the existing PostgreSQL example.

Key changes:

• Added installation instructions and Python code example for the langgraph-checkpoint-cosmosdb package
• Included configuration details for authentication and database/container setup
• Added a note about sync/async support and RBAC credentials

[Copilot]

The Cosmos DB example should follow the same pattern as the PostgreSQL example above (lines 92-98) by using a context manager. Consider wrapping the CosmosDBSaver initialization in a with statement to ensure proper resource cleanup, unless the CosmosDBSaver doesn't support context managers.

Suggested change

	checkpointer = CosmosDBSaver( # [!code highlight]
	database_name="your_database", # [!code highlight]
	container_name="your_container" # [!code highlight]
	) # [!code highlight]
	agent = create_agent(
	"gpt-5",
	[get_user_info],
	checkpointer=checkpointer, # [!code highlight]
	)
	with CosmosDBSaver( # [!code highlight]
	database_name="your_database", # [!code highlight]
	container_name="your_container" # [!code highlight]
	) as checkpointer: # [!code highlight]
	agent = create_agent(
	"gpt-5",
	[get_user_info],
	checkpointer=checkpointer, # [!code highlight]
	)

[Copilot]

The note is placed inside the :::python block, which means it will only appear in the Python-specific documentation. Since this is general information about Azure Cosmos DB (not Python-specific), consider placing it outside the :::python block to ensure it appears in all documentation versions.

Suggested change

	<Note>
	Azure Cosmos DB checkpointer supports both sync and async operations. If the database and container already exist, you can use default RBAC credentials (e.g., `az login`) instead of setting the endpoint and key.
	</Note>
	:::
	:::
	<Note>
	Azure Cosmos DB checkpointer supports both sync and async operations. If the database and container already exist, you can use default RBAC credentials (e.g., `az login`) instead of setting the endpoint and key.
	</Note>