LangGraph.js API Reference
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    Interface UseStreamOptions<StateType, Bag>

    interface UseStreamOptions<
        StateType extends Record<string, unknown> = Record<string, unknown>,
        Bag extends BagTemplate = BagTemplate,
    > {
        apiKey?: null | string;
        apiUrl?: string;
        assistantId: string;
        callerOptions?: AsyncCallerParams;
        client?: Client<DefaultValues, DefaultValues, unknown>;
        defaultHeaders?: Record<string, HeaderValue>;
        fetchStateHistory?: boolean | { limit: number };
        initialValues?: null | StateType;
        messagesKey?: string;
        onCheckpointEvent?: (
            data: {
                config: Config;
                metadata: Metadata;
                next: string[];
                tasks: ThreadTask[];
                values: StateType;
            },
            options: { namespace: undefined | string[] },
        ) => void;
        onCreated?: (run: RunCallbackMeta) => void;
        onCustomEvent?: (
            data: GetCustomEventType<Bag>,
            options: {
                mutate: (
                    update:
                        | Partial<StateType>
                        | ((prev: StateType) => Partial<StateType>),
                ) => void;
                namespace: undefined | string[];
            },
        ) => void;
        onError?: (error: unknown, run: undefined | RunCallbackMeta) => void;
        onFinish?: (
            state: ThreadState<StateType>,
            run: undefined | RunCallbackMeta,
        ) => void;
        onLangChainEvent?: (
            data: {
                data: unknown;
                event:
                    | string & {}
                    | "on_tool_start"
                    | "on_tool_stream"
                    | "on_tool_end"
                    | "on_chat_model_start"
                    | "on_chat_model_stream"
                    | "on_chat_model_end"
                    | "on_llm_start"
                    | "on_llm_stream"
                    | "on_llm_end"
                    | "on_chain_start"
                    | "on_chain_stream"
                    | "on_chain_end"
                    | "on_retriever_start"
                    | "on_retriever_stream"
                    | "on_retriever_end"
                    | "on_prompt_start"
                    | "on_prompt_stream"
                    | "on_prompt_end";
                metadata: Record<string, unknown>;
                name: string;
                parent_ids: string[];
                run_id: string;
                tags: string[];
            },
        ) => void;
        onMetadataEvent?: (data: { run_id: string; thread_id: string }) => void;
        onStop?: (
            options: {
                mutate: (
                    update:
                        | Partial<StateType>
                        | ((prev: StateType) => Partial<StateType>),
                ) => void;
            },
        ) => void;
        onTaskEvent?: (
            data:
                | {
                    error: string;
                    id: string;
                    interrupts: Interrupt<unknown>[];
                    name: string;
                }
                | {
                    id: string;
                    input: StateType;
                    interrupts: Interrupt<unknown>[];
                    name: string;
                    triggers: string[];
                }
                | {
                    id: string;
                    interrupts: Interrupt<unknown>[];
                    name: string;
                    result: [string, GetUpdateType<Bag, StateType>][];
                },
            options: { namespace: undefined | string[] },
        ) => void;
        onThreadId?: (threadId: string) => void;
        onUpdateEvent?: (
            data: { [node: string]: GetUpdateType<Bag, StateType> },
            options: {
                mutate: (
                    update:
                        | Partial<StateType>
                        | ((prev: StateType) => Partial<StateType>),
                ) => void;
                namespace: undefined | string[];
            },
        ) => void;
        reconnectOnMount?: boolean
        | (() => RunMetadataStorage);
        thread?: UseStreamThread<StateType>;
        threadId?: null | string;
        throttle?: number | boolean;
    }

    Type Parameters

    • StateType extends Record<string, unknown> = Record<string, unknown>
    • Bag extends BagTemplate = BagTemplate
    Index

    Properties

    apiKey? apiUrl? assistantId callerOptions? client? defaultHeaders? fetchStateHistory? initialValues? messagesKey? onCheckpointEvent? onCreated? onCustomEvent? onError? onFinish? onLangChainEvent? onMetadataEvent? onStop? onTaskEvent? onThreadId? onUpdateEvent? reconnectOnMount? thread? threadId? throttle?

    Properties

    apiKey?: null | string

    The API key to use.

    apiUrl?: string

    The URL of the API to use.

    assistantId: string

    The ID of the assistant to use.

    callerOptions?: AsyncCallerParams

    Custom call options, such as custom fetch implementation.

    client?: Client<DefaultValues, DefaultValues, unknown>

    Client used to send requests.

    defaultHeaders?: Record<string, HeaderValue>

    Default headers to send with requests.

    fetchStateHistory?: boolean | { limit: number }

    Whether to fetch the history of the thread. If true, the history will be fetched from the server. Defaults to 10 entries. If false, only the last state will be fetched from the server.

    true
    initialValues?: null | StateType

    Initial values to display immediately when loading a thread. Useful for displaying cached thread data while official history loads. These values will be replaced when official thread data is fetched.

    Note: UI components from initialValues will render immediately if they're predefined in LoadExternalComponent's components prop, providing instant cached UI display without server fetches.

    messagesKey?: string

    Specify the key within the state that contains messages. Defaults to "messages".

    "messages"
    onCheckpointEvent?: (
        data: {
            config: Config;
            metadata: Metadata;
            next: string[];
            tasks: ThreadTask[];
            values: StateType;
        },
        options: { namespace: undefined | string[] },
    ) => void

    Callback that is called when a checkpoints event is received.

    onCreated?: (run: RunCallbackMeta) => void

    Callback that is called when a new stream is created.

    onCustomEvent?: (
        data: GetCustomEventType<Bag>,
        options: {
            mutate: (
                update: Partial<StateType> | ((prev: StateType) => Partial<StateType>),
            ) => void;
            namespace: undefined | string[];
        },
    ) => void

    Callback that is called when a custom event is received.

    onError?: (error: unknown, run: undefined | RunCallbackMeta) => void

    Callback that is called when an error occurs.

    onFinish?: (
        state: ThreadState<StateType>,
        run: undefined | RunCallbackMeta,
    ) => void

    Callback that is called when the stream is finished.

    onLangChainEvent?: (
        data: {
            data: unknown;
            event:
                | string & {}
                | "on_tool_start"
                | "on_tool_stream"
                | "on_tool_end"
                | "on_chat_model_start"
                | "on_chat_model_stream"
                | "on_chat_model_end"
                | "on_llm_start"
                | "on_llm_stream"
                | "on_llm_end"
                | "on_chain_start"
                | "on_chain_stream"
                | "on_chain_end"
                | "on_retriever_start"
                | "on_retriever_stream"
                | "on_retriever_end"
                | "on_prompt_start"
                | "on_prompt_stream"
                | "on_prompt_end";
            metadata: Record<string, unknown>;
            name: string;
            parent_ids: string[];
            run_id: string;
            tags: string[];
        },
    ) => void

    Callback that is called when a LangChain event is received.

    https://langchain-ai.github.io/langgraph/cloud/how-tos/stream_events/#stream-graph-in-events-mode for more details.

    onMetadataEvent?: (data: { run_id: string; thread_id: string }) => void

    Callback that is called when a metadata event is received.

    onStop?: (
        options: {
            mutate: (
                update: Partial<StateType> | ((prev: StateType) => Partial<StateType>),
            ) => void;
        },
    ) => void

    Callback that is called when the stream is stopped by the user. Provides a mutate function to update the stream state immediately without requiring a server roundtrip.

    onStop: ({ mutate }) => {
      mutate((prev) => ({
        ...prev,
        ui: prev.ui?.map(component =>
          component.props.isLoading
            ? { ...component, props: { ...component.props, stopped: true, isLoading: false }}
            : component
        )
      }));
    }
    onTaskEvent?: (
        data:
            | {
                error: string;
                id: string;
                interrupts: Interrupt<unknown>[];
                name: string;
            }
            | {
                id: string;
                input: StateType;
                interrupts: Interrupt<unknown>[];
                name: string;
                triggers: string[];
            }
            | {
                id: string;
                interrupts: Interrupt<unknown>[];
                name: string;
                result: [string, GetUpdateType<Bag, StateType>][];
            },
        options: { namespace: undefined | string[] },
    ) => void

    Callback that is called when a tasks event is received.

    onThreadId?: (threadId: string) => void

    Callback that is called when the thread ID is updated (ie when a new thread is created).

    onUpdateEvent?: (
        data: { [node: string]: GetUpdateType<Bag, StateType> },
        options: {
            mutate: (
                update: Partial<StateType> | ((prev: StateType) => Partial<StateType>),
            ) => void;
            namespace: undefined | string[];
        },
    ) => void

    Callback that is called when an update event is received.

    reconnectOnMount?: boolean | (() => RunMetadataStorage)

    Will reconnect the stream on mount

    thread?: UseStreamThread<StateType>

    Manage the thread state externally.

    threadId?: null | string

    The ID of the thread to fetch history and current values from.

    throttle?: number | boolean

    Throttle the stream. If a number is provided, the stream will be throttled to the given number of milliseconds. If true, updates are batched in a single macrotask. If false, updates are not throttled or batched.

    true

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