StreamConverter

Close partial output and emit an Agent Server checkpoint event.

Handle a payload from stream_mode="messages".

The payload carries either one token chunk of a streaming chat model response or a whole :class:AIMessage (non-streaming LLM call, or a node that built the message itself). Payloads sharing a message id accumulate into a single message output item; a different id closes the open item and starts a new one.

Handle a payload from stream_mode="updates".

payload is {node_name: state_update}; state_update is the partial state returned by the node, which for MessagesState graphs contains a messages channel with the messages that node appended.

Close any in-flight builders. Called after the graph stream ends.