feat(sdk-py): emit id as part of stream events (#6581)

- **Description:** Provide the id of the event for routes that use SSE
streams. This will allow for more custom retry logic when streams
disconnect if needed.
  - **Issue:** N/A
  - **Dependencies:** N/A
  - **Twitter handle:** N/A

---------

Co-authored-by: William FH <13333726+hinthornw@users.noreply.github.com>

libs/langgraph/pyproject.toml

@@ -26,7 +26,7 @@ classifiers = [
 dependencies = [
     "langchain-core>=0.1",
     "langgraph-checkpoint>=2.1.0,<4.0.0",
-    "langgraph-sdk>=0.2.2,<0.3.0",
+    "langgraph-sdk>=0.3.0,<0.4.0",
     "langgraph-prebuilt>=1.0.2,<1.1.0",
     "xxhash>=3.5.0",
     "pydantic>=2.7.4",

libs/langgraph/tests/test_remote_graph.py

@@ -567,9 +567,9 @@ def test_stream():
         stream_parts.append(stream_part)
 
     assert stream_parts == [
-        ("updates", {"chunk": "data3"}),
-        ("updates", {"chunk": "data4"}),
-        ("updates", {"__interrupt__": ()}),
+        ("updates", {"chunk": "data3"}, None),
+        ("updates", {"chunk": "data4"}, None),
+        ("updates", {"__interrupt__": ()}, None),
     ]
 
     # subgraphs + list modes
@@ -739,9 +739,9 @@ async def test_astream():
         stream_parts.append(stream_part)
 
     assert stream_parts == [
-        ("updates", {"chunk": "data3"}),
-        ("updates", {"chunk": "data4"}),
-        ("updates", {"__interrupt__": ()}),
+        ("updates", {"chunk": "data3"}, None),
+        ("updates", {"chunk": "data4"}, None),
+        ("updates", {"__interrupt__": ()}, None),
     ]
 
     # subgraphs + list modes

libs/sdk-py/langgraph_sdk/__init__.py

@@ -3,6 +3,6 @@ from langgraph_sdk.client import get_client, get_sync_client
 from langgraph_sdk.encryption import Encryption
 from langgraph_sdk.encryption.types import EncryptionContext
 
-__version__ = "0.2.15"
+__version__ = "0.3.0"
 
 __all__ = ["Auth", "Encryption", "EncryptionContext", "get_client", "get_sync_client"]

libs/sdk-py/langgraph_sdk/schema.py

@@ -167,7 +167,7 @@ class Config(TypedDict, total=False):
     """
     Runtime values for attributes previously made configurable on this Runnable,
     or sub-Runnables, through .configurable_fields() or .configurable_alternatives().
-    Check .output_schema() for a description of the attributes that have been made 
+    Check .output_schema() for a description of the attributes that have been made
     configurable.
     """
 
@@ -301,7 +301,7 @@ class ThreadState(TypedDict):
     values: list[dict] | dict[str, Any]
     """The state values."""
     next: Sequence[str]
-    """The next nodes to execute. If empty, the thread is done until new input is 
+    """The next nodes to execute. If empty, the thread is done until new input is
     received."""
     checkpoint: Checkpoint
     """The ID of the checkpoint."""
@@ -476,7 +476,7 @@ class Item(TypedDict):
     """The namespace of the item. A namespace is analogous to a document's directory."""
     key: str
     """The unique identifier of the item within its namespace.
-    
+
     In general, keys needn't be globally unique.
     """
     value: dict[str, Any]
@@ -519,6 +519,8 @@ class StreamPart(NamedTuple):
     """The type of event for this stream part."""
     data: dict
     """The data payload associated with the event."""
+    id: str | None = None
+    """The ID of the event."""
 
 
 class Send(TypedDict):

libs/sdk-py/langgraph_sdk/sse.py

@@ -103,6 +103,7 @@ class SSEDecoder:
             sse = StreamPart(
                 event=self._event,
                 data=orjson.loads(self._data) if self._data else None,  # type: ignore[invalid-argument-type]
+                id=self.last_event_id,
             )
 
             # NOTE: as per the SSE spec, do not reset last_event_id.

libs/sdk-py/tests/test_client_stream.py

@@ -50,7 +50,7 @@ def iter_lines_raw(payload: list[bytes]) -> Iterator[BytesLike]:
     yield from decoder.flush()
 
 
-def test_stream_see():
+def test_stream_sse():
     for groups in (
         [RESPONSE_PAYLOAD],
         RESPONSE_PAYLOAD.splitlines(keepends=True),
@@ -150,9 +150,9 @@ def test_sync_http_client_stream_recovers_after_disconnect():
 
     assert call_count == 2
     assert parts == [
-        StreamPart(event="values", data={"step": 1}),
-        StreamPart(event="values", data={"step": 2}),
-        StreamPart(event="end", data=None),  # ty: ignore
+        StreamPart(event="values", data={"step": 1}, id="1"),
+        StreamPart(event="values", data={"step": 2}, id="2"),
+        StreamPart(event="end", data=None, id="2"),
     ]
 
 
@@ -222,9 +222,9 @@ async def test_http_client_stream_recovers_after_disconnect():
 
     assert call_count == 2
     assert parts == [
-        StreamPart(event="values", data={"step": 1}),
-        StreamPart(event="values", data={"step": 2}),
-        StreamPart(event="end", data=None),
+        StreamPart(event="values", data={"step": 1}, id="1"),
+        StreamPart(event="values", data={"step": 2}, id="2"),
+        StreamPart(event="end", data=None, id="2"),
     ]