Python: Add Cosmos DB NoSQL Checkpoint Storage for Python Workflows

python/packages/azure-cosmos/README.md

@@ -35,4 +35,93 @@ Container naming behavior:
 - Container name is configured on the provider (`container_name` or `AZURE_COSMOS_CONTAINER_NAME`)
 - `session_id` is used as the Cosmos partition key for reads/writes
 
-See `samples/cosmos_history_provider.py` for a runnable package-local example.
+See `samples/history_provider/cosmos_history_basic.py` for a runnable package-local example.
+
+## Cosmos DB Workflow Checkpoint Storage
+
+`CosmosCheckpointStorage` implements the `CheckpointStorage` protocol, enabling
+durable workflow checkpointing backed by Azure Cosmos DB NoSQL. Workflows can be
+paused and resumed across process restarts by persisting checkpoint state in Cosmos DB.
+
+### Basic Usage
+
+#### Managed Identity / RBAC (recommended for production)
+
+```python
+from azure.identity.aio import DefaultAzureCredential
+from agent_framework import WorkflowBuilder
+from agent_framework_azure_cosmos import CosmosCheckpointStorage
+
+checkpoint_storage = CosmosCheckpointStorage(
+    endpoint="https://<account>.documents.azure.com:443/",
+    credential=DefaultAzureCredential(),
+    database_name="agent-framework",
+    container_name="workflow-checkpoints",
+)
+```
+
+#### Account Key
+
+```python
+from agent_framework_azure_cosmos import CosmosCheckpointStorage
+
+checkpoint_storage = CosmosCheckpointStorage(
+    endpoint="https://<account>.documents.azure.com:443/",
+    credential="<your-account-key>",
+    database_name="agent-framework",
+    container_name="workflow-checkpoints",
+)
+```
+
+#### Then use with a workflow
+
+```python
+from agent_framework import WorkflowBuilder
+
+# Build a workflow with checkpointing enabled
+workflow = WorkflowBuilder(
+    start_executor=start,
+    checkpoint_storage=checkpoint_storage,
+).build()
+
+# Run the workflow — checkpoints are automatically saved after each superstep
+result = await workflow.run(message="input data")
+
+# Resume from a checkpoint
+latest = await checkpoint_storage.get_latest(workflow_name=workflow.name)
+if latest:
+    resumed = await workflow.run(checkpoint_id=latest.checkpoint_id)
+```
+
+### Authentication Options
+
+`CosmosCheckpointStorage` supports the same authentication modes as `CosmosHistoryProvider`:
+
+- **Managed identity / RBAC** (recommended): Pass `DefaultAzureCredential()`,
+  `ManagedIdentityCredential()`, or any Azure `TokenCredential`
+- **Account key**: Pass a key string via `credential` parameter
+- **Environment variables**: Set `AZURE_COSMOS_ENDPOINT`, `AZURE_COSMOS_DATABASE_NAME`,
+  `AZURE_COSMOS_CONTAINER_NAME`, and `AZURE_COSMOS_KEY` (key not required when using
+  Azure credentials)
+- **Pre-created client**: Pass an existing `CosmosClient` or `ContainerProxy`
+
+### Database and Container Setup
+
+The database and container are created automatically on first use (via
+`create_database_if_not_exists` and `create_container_if_not_exists`). The container
+uses `/workflow_name` as the partition key. You can also pre-create them in the Azure
+portal with this partition key configuration.
+
+### Environment Variables
+
+| Variable | Description |
+|---|---|
+| `AZURE_COSMOS_ENDPOINT` | Cosmos DB account endpoint |
+| `AZURE_COSMOS_DATABASE_NAME` | Database name |
+| `AZURE_COSMOS_CONTAINER_NAME` | Container name |
+| `AZURE_COSMOS_KEY` | Account key (optional if using Azure credentials) |
+
+See `samples/checkpoint_storage/cosmos_checkpoint_workflow.py` for a standalone example,
+`samples/checkpoint_storage/cosmos_checkpoint_foundry.py` for an end-to-end example
+with Azure AI Foundry agents, or `samples/cosmos_e2e_foundry.py` for both
+history and checkpointing together.

python/packages/azure-cosmos/agent_framework_azure_cosmos/__init__.py

@@ -2,6 +2,7 @@
 
 import importlib.metadata
 
+from ._checkpoint_storage import CosmosCheckpointStorage
 from ._history_provider import CosmosHistoryProvider
 
 try:
@@ -10,6 +11,7 @@
     __version__ = "0.0.0"  # Fallback for development mode
 
 __all__ = [
+    "CosmosCheckpointStorage",
     "CosmosHistoryProvider",
     "__version__",
 ]