Genkit JS API reference
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    Class GenerateResponseChunk<T>

    Represents a single chunk of a streaming model response. Provides convenience accessors for extracting text, media, tool requests, and accumulated output from the chunk and all preceding chunks in the stream.

    Type Parameters

    • T = unknown

    Implements

    Index

    Constructors

    constructor

    Properties

    content custom? index parser? previousChunks? role

    Accessors

    accumulatedText data media output previousText reasoning text toolRequests

    Methods

    toJSON

    Constructors

    • Type Parameters

      • T = unknown

      Parameters

      • data: {
            aggregated?: boolean;
            content: (
                | {
                    custom?: Record<string, unknown>;
                    data?: unknown;
                    media?: undefined;
                    metadata?: Record<string, unknown>;
                    reasoning?: undefined;
                    resource?: undefined;
                    text: string;
                    toolRequest?: undefined;
                    toolResponse?: undefined;
                }
                | {
                    custom?: Record<string, unknown>;
                    data?: unknown;
                    media: { contentType?: string; url: string };
                    metadata?: Record<string, unknown>;
                    reasoning?: undefined;
                    resource?: undefined;
                    text?: undefined;
                    toolRequest?: undefined;
                    toolResponse?: undefined;
                }
                | {
                    custom?: Record<string, unknown>;
                    data?: unknown;
                    media?: undefined;
                    metadata?: Record<string, unknown>;
                    reasoning?: undefined;
                    resource?: undefined;
                    text?: undefined;
                    toolRequest: {
                        input?: unknown;
                        name: string;
                        partial?: boolean;
                        ref?: string;
                    };
                    toolResponse?: undefined;
                }
                | {
                    custom?: Record<string, unknown>;
                    data?: unknown;
                    media?: undefined;
                    metadata?: Record<string, unknown>;
                    reasoning?: undefined;
                    resource?: undefined;
                    text?: undefined;
                    toolRequest?: undefined;
                    toolResponse: { name: string; output?: unknown; ref?: string } & {
                        content?: (
                            | {
                                custom?: (...)
                                | (...);
                                data?: unknown;
                                media?: undefined;
                                metadata?: (...) | (...);
                                reasoning?: undefined;
                                resource?: undefined;
                                text: string;
                                toolRequest?: undefined;
                                toolResponse?: undefined;
                            }
                            | {
                                custom?: (...)
                                | (...);
                                data?: unknown;
                                media: { contentType?: ...; url: ... };
                                metadata?: (...) | (...);
                                reasoning?: undefined;
                                resource?: undefined;
                                text?: undefined;
                                toolRequest?: undefined;
                                toolResponse?: undefined;
                            }
                            | {
                                custom?: (...)
                                | (...);
                                data?: unknown;
                                media?: undefined;
                                metadata?: (...) | (...);
                                reasoning?: undefined;
                                resource?: undefined;
                                text?: undefined;
                                toolRequest: { input?: ...; name: ...; partial?: ...; ref?: ... };
                                toolResponse?: undefined;
                            }
                            | {
                                custom?: (...)
                                | (...);
                                data?: unknown;
                                media?: undefined;
                                metadata?: (...) | (...);
                                reasoning?: undefined;
                                resource?: undefined;
                                text?: undefined;
                                toolRequest?: undefined;
                                toolResponse: (...) & (...);
                            }
                            | {
                                custom?: (...)
                                | (...);
                                data?: unknown;
                                media?: undefined;
                                metadata?: (...) | (...);
                                reasoning?: undefined;
                                resource?: undefined;
                                text?: undefined;
                                toolRequest?: undefined;
                                toolResponse?: undefined;
                            }
                            | {
                                custom: Record<(...), (...)>;
                                data?: unknown;
                                media?: undefined;
                                metadata?: (...) | (...);
                                reasoning?: undefined;
                                resource?: undefined;
                                text?: undefined;
                                toolRequest?: undefined;
                                toolResponse?: undefined;
                            }
                            | {
                                custom?: (...)
                                | (...);
                                data?: unknown;
                                media?: undefined;
                                metadata?: (...) | (...);
                                reasoning: string;
                                resource?: undefined;
                                text?: undefined;
                                toolRequest?: undefined;
                                toolResponse?: undefined;
                            }
                            | {
                                custom?: (...)
                                | (...);
                                data?: unknown;
                                media?: undefined;
                                metadata?: (...) | (...);
                                reasoning?: undefined;
                                resource: { uri: ... };
                                text?: undefined;
                                toolRequest?: undefined;
                                toolResponse?: undefined;
                            }
                        )[];
                    };
                }
                | {
                    custom?: Record<string, unknown>;
                    data?: unknown;
                    media?: undefined;
                    metadata?: Record<string, unknown>;
                    reasoning?: undefined;
                    resource?: undefined;
                    text?: undefined;
                    toolRequest?: undefined;
                    toolResponse?: undefined;
                }
                | {
                    custom: Record<string, any>;
                    data?: unknown;
                    media?: undefined;
                    metadata?: Record<string, unknown>;
                    reasoning?: undefined;
                    resource?: undefined;
                    text?: undefined;
                    toolRequest?: undefined;
                    toolResponse?: undefined;
                }
                | {
                    custom?: Record<string, unknown>;
                    data?: unknown;
                    media?: undefined;
                    metadata?: Record<string, unknown>;
                    reasoning: string;
                    resource?: undefined;
                    text?: undefined;
                    toolRequest?: undefined;
                    toolResponse?: undefined;
                }
                | {
                    custom?: Record<string, unknown>;
                    data?: unknown;
                    media?: undefined;
                    metadata?: Record<string, unknown>;
                    reasoning?: undefined;
                    resource: { uri: string };
                    text?: undefined;
                    toolRequest?: undefined;
                    toolResponse?: undefined;
                }
            )[];
            custom?: unknown;
            index?: number;
            role?: "user"
            | "model"
            | "tool"
            | "system";
        }
      • options: {
            index: number;
            parser?: ChunkParser<T>;
            previousChunks?: {
                aggregated?: boolean;
                content: (
                    | {
                        custom?: Record<string, unknown>;
                        data?: unknown;
                        media?: undefined;
                        metadata?: Record<string, unknown>;
                        reasoning?: undefined;
                        resource?: undefined;
                        text: string;
                        toolRequest?: undefined;
                        toolResponse?: undefined;
                    }
                    | {
                        custom?: Record<string, unknown>;
                        data?: unknown;
                        media: { contentType?: string; url: string };
                        metadata?: Record<string, unknown>;
                        reasoning?: undefined;
                        resource?: undefined;
                        text?: undefined;
                        toolRequest?: undefined;
                        toolResponse?: undefined;
                    }
                    | {
                        custom?: Record<string, unknown>;
                        data?: unknown;
                        media?: undefined;
                        metadata?: Record<string, unknown>;
                        reasoning?: undefined;
                        resource?: undefined;
                        text?: undefined;
                        toolRequest: {
                            input?: unknown;
                            name: string;
                            partial?: boolean;
                            ref?: string;
                        };
                        toolResponse?: undefined;
                    }
                    | {
                        custom?: Record<string, unknown>;
                        data?: unknown;
                        media?: undefined;
                        metadata?: Record<string, unknown>;
                        reasoning?: undefined;
                        resource?: undefined;
                        text?: undefined;
                        toolRequest?: undefined;
                        toolResponse: { name: string; output?: unknown; ref?: string } & {
                            content?: (...)[];
                        };
                    }
                    | {
                        custom?: Record<string, unknown>;
                        data?: unknown;
                        media?: undefined;
                        metadata?: Record<string, unknown>;
                        reasoning?: undefined;
                        resource?: undefined;
                        text?: undefined;
                        toolRequest?: undefined;
                        toolResponse?: undefined;
                    }
                    | {
                        custom: Record<string, any>;
                        data?: unknown;
                        media?: undefined;
                        metadata?: Record<string, unknown>;
                        reasoning?: undefined;
                        resource?: undefined;
                        text?: undefined;
                        toolRequest?: undefined;
                        toolResponse?: undefined;
                    }
                    | {
                        custom?: Record<string, unknown>;
                        data?: unknown;
                        media?: undefined;
                        metadata?: Record<string, unknown>;
                        reasoning: string;
                        resource?: undefined;
                        text?: undefined;
                        toolRequest?: undefined;
                        toolResponse?: undefined;
                    }
                    | {
                        custom?: Record<string, unknown>;
                        data?: unknown;
                        media?: undefined;
                        metadata?: Record<string, unknown>;
                        reasoning?: undefined;
                        resource: { uri: string };
                        text?: undefined;
                        toolRequest?: undefined;
                        toolResponse?: undefined;
                    }
                )[];
                custom?: unknown;
                index?: number;
                role?: "user"
                | "model"
                | "tool"
                | "system";
            }[];
            role: "user"
            | "model"
            | "tool"
            | "system";
        }

      Returns GenerateResponseChunk<T>

    Properties

    content

    content: (
        | {
            custom?: Record<string, unknown>;
            data?: unknown;
            media?: undefined;
            metadata?: Record<string, unknown>;
            reasoning?: undefined;
            resource?: undefined;
            text: string;
            toolRequest?: undefined;
            toolResponse?: undefined;
        }
        | {
            custom?: Record<string, unknown>;
            data?: unknown;
            media: { contentType?: string; url: string };
            metadata?: Record<string, unknown>;
            reasoning?: undefined;
            resource?: undefined;
            text?: undefined;
            toolRequest?: undefined;
            toolResponse?: undefined;
        }
        | {
            custom?: Record<string, unknown>;
            data?: unknown;
            media?: undefined;
            metadata?: Record<string, unknown>;
            reasoning?: undefined;
            resource?: undefined;
            text?: undefined;
            toolRequest: {
                input?: unknown;
                name: string;
                partial?: boolean;
                ref?: string;
            };
            toolResponse?: undefined;
        }
        | {
            custom?: Record<string, unknown>;
            data?: unknown;
            media?: undefined;
            metadata?: Record<string, unknown>;
            reasoning?: undefined;
            resource?: undefined;
            text?: undefined;
            toolRequest?: undefined;
            toolResponse: { name: string; output?: unknown; ref?: string } & {
                content?: ({ text: string; custom?: Record<string, unknown> | undefined; metadata?: Record<string, unknown> | undefined; media?: undefined; toolRequest?: undefined; toolResponse?: undefined; data?: unknown; reasoning?: undefined; resource?: undefined; } | ... 6 more ... | { ...; })[];
            };
        }
        | {
            custom?: Record<string, unknown>;
            data?: unknown;
            media?: undefined;
            metadata?: Record<string, unknown>;
            reasoning?: undefined;
            resource?: undefined;
            text?: undefined;
            toolRequest?: undefined;
            toolResponse?: undefined;
        }
        | {
            custom: Record<string, any>;
            data?: unknown;
            media?: undefined;
            metadata?: Record<string, unknown>;
            reasoning?: undefined;
            resource?: undefined;
            text?: undefined;
            toolRequest?: undefined;
            toolResponse?: undefined;
        }
        | {
            custom?: Record<string, unknown>;
            data?: unknown;
            media?: undefined;
            metadata?: Record<string, unknown>;
            reasoning: string;
            resource?: undefined;
            text?: undefined;
            toolRequest?: undefined;
            toolResponse?: undefined;
        }
        | {
            custom?: Record<string, unknown>;
            data?: unknown;
            media?: undefined;
            metadata?: Record<string, unknown>;
            reasoning?: undefined;
            resource: { uri: string };
            text?: undefined;
            toolRequest?: undefined;
            toolResponse?: undefined;
        }
    )[]

    The content generated in this chunk.

    custom?: unknown

    Custom model-specific data for this chunk.

    index: number

    The index of the message this chunk corresponds to, starting with 0 for the first model response of the generation.

    parser?: ChunkParser<T>

    The parser to be used to parse output from this chunk.

    previousChunks?: {
        aggregated?: boolean;
        content: (
            | {
                custom?: Record<string, unknown>;
                data?: unknown;
                media?: undefined;
                metadata?: Record<string, unknown>;
                reasoning?: undefined;
                resource?: undefined;
                text: string;
                toolRequest?: undefined;
                toolResponse?: undefined;
            }
            | {
                custom?: Record<string, unknown>;
                data?: unknown;
                media: { contentType?: string; url: string };
                metadata?: Record<string, unknown>;
                reasoning?: undefined;
                resource?: undefined;
                text?: undefined;
                toolRequest?: undefined;
                toolResponse?: undefined;
            }
            | {
                custom?: Record<string, unknown>;
                data?: unknown;
                media?: undefined;
                metadata?: Record<string, unknown>;
                reasoning?: undefined;
                resource?: undefined;
                text?: undefined;
                toolRequest: {
                    input?: unknown;
                    name: string;
                    partial?: boolean;
                    ref?: string;
                };
                toolResponse?: undefined;
            }
            | {
                custom?: Record<string, unknown>;
                data?: unknown;
                media?: undefined;
                metadata?: Record<string, unknown>;
                reasoning?: undefined;
                resource?: undefined;
                text?: undefined;
                toolRequest?: undefined;
                toolResponse: { name: string; output?: unknown; ref?: string } & {
                    content?: (
                        (...)
                        | (...)
                        | (...)
                        | (...)
                        | (...)
                        | (...)
                        | (...)
                        | (...)
                    )[];
                };
            }
            | {
                custom?: Record<string, unknown>;
                data?: unknown;
                media?: undefined;
                metadata?: Record<string, unknown>;
                reasoning?: undefined;
                resource?: undefined;
                text?: undefined;
                toolRequest?: undefined;
                toolResponse?: undefined;
            }
            | {
                custom: Record<string, any>;
                data?: unknown;
                media?: undefined;
                metadata?: Record<string, unknown>;
                reasoning?: undefined;
                resource?: undefined;
                text?: undefined;
                toolRequest?: undefined;
                toolResponse?: undefined;
            }
            | {
                custom?: Record<string, unknown>;
                data?: unknown;
                media?: undefined;
                metadata?: Record<string, unknown>;
                reasoning: string;
                resource?: undefined;
                text?: undefined;
                toolRequest?: undefined;
                toolResponse?: undefined;
            }
            | {
                custom?: Record<string, unknown>;
                data?: unknown;
                media?: undefined;
                metadata?: Record<string, unknown>;
                reasoning?: undefined;
                resource: { uri: string };
                text?: undefined;
                toolRequest?: undefined;
                toolResponse?: undefined;
            }
        )[];
        custom?: unknown;
        index?: number;
        role?: "user"
        | "model"
        | "tool"
        | "system";
    }[]

    Accumulated chunks for partial output extraction.

    role: "user" | "model" | "tool" | "system"

    The role of the message this chunk corresponds to. Will always be model or tool.

    Accessors

    • get accumulatedText(): string

      Concatenates all text parts of all chunks from the response thus far.

      Returns string

      A string of all concatenated chunk text content.

    • get data(): T | null

      Returns the first detected data part of a chunk.

      Returns T | null

      The first data part detected in the chunk (if any).

    • get media(): { contentType?: string; url: string } | null

      Returns the first media part detected in the chunk. Useful for extracting (for example) an image from a generation expected to create one.

      Returns { contentType?: string; url: string } | null

      The first detected media part in the chunk.

    • get output(): T | null

      Parses the chunk into the desired output format using the parser associated with the generate request, or falls back to naive JSON parsing otherwise.

      Returns T | null

    • get previousText(): string

      Concatenates all text parts of all preceding chunks.

      Returns string

    • get reasoning(): string

      Concatenates all reasoning parts present in the chunk with no delimiter.

      Returns string

      A string of all concatenated reasoning parts.

    text

    • get text(): string

      Concatenates all text parts present in the chunk with no delimiter.

      Returns string

      A string of all concatenated text parts.

    • get toolRequests(): {
          custom?: Record<string, unknown>;
          data?: unknown;
          media?: undefined;
          metadata?: Record<string, unknown>;
          reasoning?: undefined;
          resource?: undefined;
          text?: undefined;
          toolRequest: {
              input?: unknown;
              name: string;
              partial?: boolean;
              ref?: string;
          };
          toolResponse?: undefined;
      }[]

      Returns all tool request found in this chunk.

      Returns {
          custom?: Record<string, unknown>;
          data?: unknown;
          media?: undefined;
          metadata?: Record<string, unknown>;
          reasoning?: undefined;
          resource?: undefined;
          text?: undefined;
          toolRequest: {
              input?: unknown;
              name: string;
              partial?: boolean;
              ref?: string;
          };
          toolResponse?: undefined;
      }[]

      Array of all tool request found in this chunk.

    Methods

    • Returns {
          aggregated?: boolean;
          content: (
              | {
                  custom?: Record<string, unknown>;
                  data?: unknown;
                  media?: undefined;
                  metadata?: Record<string, unknown>;
                  reasoning?: undefined;
                  resource?: undefined;
                  text: string;
                  toolRequest?: undefined;
                  toolResponse?: undefined;
              }
              | {
                  custom?: Record<string, unknown>;
                  data?: unknown;
                  media: { contentType?: string; url: string };
                  metadata?: Record<string, unknown>;
                  reasoning?: undefined;
                  resource?: undefined;
                  text?: undefined;
                  toolRequest?: undefined;
                  toolResponse?: undefined;
              }
              | {
                  custom?: Record<string, unknown>;
                  data?: unknown;
                  media?: undefined;
                  metadata?: Record<string, unknown>;
                  reasoning?: undefined;
                  resource?: undefined;
                  text?: undefined;
                  toolRequest: {
                      input?: unknown;
                      name: string;
                      partial?: boolean;
                      ref?: string;
                  };
                  toolResponse?: undefined;
              }
              | {
                  custom?: Record<string, unknown>;
                  data?: unknown;
                  media?: undefined;
                  metadata?: Record<string, unknown>;
                  reasoning?: undefined;
                  resource?: undefined;
                  text?: undefined;
                  toolRequest?: undefined;
                  toolResponse: { name: string; output?: unknown; ref?: string } & {
                      content?: (
                          | {
                              custom?: (...)
                              | (...);
                              data?: unknown;
                              media?: undefined;
                              metadata?: (...) | (...);
                              reasoning?: undefined;
                              resource?: undefined;
                              text: string;
                              toolRequest?: undefined;
                              toolResponse?: undefined;
                          }
                          | {
                              custom?: (...)
                              | (...);
                              data?: unknown;
                              media: { contentType?: ...; url: ... };
                              metadata?: (...) | (...);
                              reasoning?: undefined;
                              resource?: undefined;
                              text?: undefined;
                              toolRequest?: undefined;
                              toolResponse?: undefined;
                          }
                          | {
                              custom?: (...)
                              | (...);
                              data?: unknown;
                              media?: undefined;
                              metadata?: (...) | (...);
                              reasoning?: undefined;
                              resource?: undefined;
                              text?: undefined;
                              toolRequest: { input?: ...; name: ...; partial?: ...; ref?: ... };
                              toolResponse?: undefined;
                          }
                          | {
                              custom?: (...)
                              | (...);
                              data?: unknown;
                              media?: undefined;
                              metadata?: (...) | (...);
                              reasoning?: undefined;
                              resource?: undefined;
                              text?: undefined;
                              toolRequest?: undefined;
                              toolResponse: (...) & (...);
                          }
                          | {
                              custom?: (...)
                              | (...);
                              data?: unknown;
                              media?: undefined;
                              metadata?: (...) | (...);
                              reasoning?: undefined;
                              resource?: undefined;
                              text?: undefined;
                              toolRequest?: undefined;
                              toolResponse?: undefined;
                          }
                          | {
                              custom: Record<(...), (...)>;
                              data?: unknown;
                              media?: undefined;
                              metadata?: (...) | (...);
                              reasoning?: undefined;
                              resource?: undefined;
                              text?: undefined;
                              toolRequest?: undefined;
                              toolResponse?: undefined;
                          }
                          | {
                              custom?: (...)
                              | (...);
                              data?: unknown;
                              media?: undefined;
                              metadata?: (...) | (...);
                              reasoning: string;
                              resource?: undefined;
                              text?: undefined;
                              toolRequest?: undefined;
                              toolResponse?: undefined;
                          }
                          | {
                              custom?: (...)
                              | (...);
                              data?: unknown;
                              media?: undefined;
                              metadata?: (...) | (...);
                              reasoning?: undefined;
                              resource: { uri: ... };
                              text?: undefined;
                              toolRequest?: undefined;
                              toolResponse?: undefined;
                          }
                      )[];
                  };
              }
              | {
                  custom?: Record<string, unknown>;
                  data?: unknown;
                  media?: undefined;
                  metadata?: Record<string, unknown>;
                  reasoning?: undefined;
                  resource?: undefined;
                  text?: undefined;
                  toolRequest?: undefined;
                  toolResponse?: undefined;
              }
              | {
                  custom: Record<string, any>;
                  data?: unknown;
                  media?: undefined;
                  metadata?: Record<string, unknown>;
                  reasoning?: undefined;
                  resource?: undefined;
                  text?: undefined;
                  toolRequest?: undefined;
                  toolResponse?: undefined;
              }
              | {
                  custom?: Record<string, unknown>;
                  data?: unknown;
                  media?: undefined;
                  metadata?: Record<string, unknown>;
                  reasoning: string;
                  resource?: undefined;
                  text?: undefined;
                  toolRequest?: undefined;
                  toolResponse?: undefined;
              }
              | {
                  custom?: Record<string, unknown>;
                  data?: unknown;
                  media?: undefined;
                  metadata?: Record<string, unknown>;
                  reasoning?: undefined;
                  resource: { uri: string };
                  text?: undefined;
                  toolRequest?: undefined;
                  toolResponse?: undefined;
              }
          )[];
          custom?: unknown;
          index?: number;
          role?: "user"
          | "model"
          | "tool"
          | "system";
      }

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