fix(a2a): Checkpoint export + TaskState enum cleanup, pin release as 4.0.1

src/adcp/__init__.py

@@ -27,7 +27,7 @@
     build_synthetic_capabilities,
     validate_capabilities,
 )
-from adcp.client import ADCPClient, ADCPMultiAgentClient
+from adcp.client import ADCPClient, ADCPMultiAgentClient, Checkpoint
 from adcp.exceptions import (  # noqa: F401
     AdagentsNotFoundError,
     AdagentsTimeoutError,
@@ -566,6 +566,7 @@ def get_adcp_version() -> str:
     # Client classes
     "ADCPClient",
     "ADCPMultiAgentClient",
+    "Checkpoint",
     "RegistryClient",
     "PropertyRegistry",
     "RegistrySync",

src/adcp/protocols/a2a.py

@@ -523,7 +523,7 @@ def _process_task_response(self, task: Task, debug_info: DebugInfo | None) -> Ta
         """Process a Task response from A2A into our TaskResult format."""
         task_state = task.status.state
 
-        if task_state == "completed":
+        if task_state == TaskState.completed:
             # Extract the result from the artifacts array
             result_data = self._extract_result_from_task(task)
 
@@ -542,7 +542,7 @@ def _process_task_response(self, task: Task, debug_info: DebugInfo | None) -> Ta
                 },
                 debug_info=debug_info,
             )
-        elif task_state == "failed":
+        elif task_state == TaskState.failed:
             # Protocol-level failure - extract error message from TextPart
             error_msg = self._extract_text_from_task(task) or "Task failed"
             return TaskResult[Any](

tests/fixtures/public_api_snapshot.json

@@ -72,6 +72,7 @@
     "ChangeHandler",
     "CheckGovernanceRequest",
     "CheckGovernanceResponse",
+    "Checkpoint",
     "ComplyTestControllerRequest",
     "ComplyTestControllerResponse",
     "ConsentBasis",