import { BaseCallbackHandler, HandleLLMNewTokenCallbackFields, NewTokenIndices } from "@langchain/core/callbacks/base";
import { BaseMessage } from "@langchain/core/messages";
import { Serialized } from "@langchain/core/load/serializable";
import { LLMResult } from "@langchain/core/outputs";
import { ChainValues } from "@langchain/core/utils/types";
import { StreamChunk } from "./stream.js";
type Meta = [string[], Record<string, any>];
/**
 * A callback handler that implements stream_mode=messages.
 * Collects messages from (1) chat model stream events and (2) node outputs.
 */
export declare class StreamMessagesHandler extends BaseCallbackHandler {
    name: string;
    streamFn: (streamChunk: StreamChunk) => void;
    metadatas: Record<string, Meta>;
    seen: Record<string, BaseMessage>;
    emittedChatModelRunIds: Record<string, boolean>;
    stableMessageIdMap: Record<string, string>;
    lc_prefer_streaming: boolean;
    constructor(streamFn: (streamChunk: StreamChunk) => void);
    _emit(meta: Meta, message: BaseMessage, runId: string | undefined, dedupe?: boolean): void;
    handleChatModelStart(_llm: Serialized, _messages: BaseMessage[][], runId: string, _parentRunId?: string, _extraParams?: Record<string, unknown>, tags?: string[], metadata?: Record<string, unknown>, name?: string): void;
    handleLLMNewToken(token: string, _idx: NewTokenIndices, runId: string, _parentRunId?: string, _tags?: string[], fields?: HandleLLMNewTokenCallbackFields): void;
    handleLLMEnd(output: LLMResult, runId: string): void;
    handleLLMError(_err: any, runId: string): void;
    handleChainStart(_chain: Serialized, inputs: ChainValues, runId: string, _parentRunId?: string, tags?: string[], metadata?: Record<string, unknown>, _runType?: string, name?: string): void;
    handleChainEnd(outputs: ChainValues, runId: string): void;
    handleChainError(_err: any, runId: string): void;
}
export {};