StreamPart

A discriminated union of all v2 stream part types.

Use part["type"] to narrow the type:

async for part in graph.astream(input, version="v2"):
    if part["type"] == "values":
        part["data"]  # OutputT — full state (pydantic/dataclass/dict)
    elif part["type"] == "messages":
        part["data"]  # tuple[BaseMessage, dict] — (message, metadata)
    elif part["type"] == "custom":
        part["data"]  # Any — user-defined