fix: Gemini text chat - prevent sending broken messageContent and history

.changeset/sharp-knives-ring.md

@@ -0,0 +1,5 @@
+---
+"llamaindex": patch
+---
+
+Improve Gemini message and context preparation

packages/core/src/Prompt.ts

@@ -371,6 +371,7 @@ export function messagesToHistoryStr(messages: ChatMessage[]) {
 }
 
 export const defaultContextSystemPrompt = ({ context = "" }) => {
+ if (!context) return "";
  return `Context information is below.
 ---------------------
 ${context}

packages/core/src/llm/gemini.ts

@@ -139,7 +139,7 @@ class GeminiHelper {
  > = {
  user: "user",
  system: "user",
- assistant: "user",
+ assistant: "model",
  memory: "user",
  };
 
@@ -152,38 +152,26 @@ class GeminiHelper {
  };
 
  public static mergeNeighboringSameRoleMessages(
- messages: ChatMessage[],
- ): ChatMessage[] {
- // Gemini does not support multiple messages of the same role in a row, so we merge them
- const mergedMessages: ChatMessage[] = [];
- let i: number = 0;
-
- while (i < messages.length) {
- const currentMessage: ChatMessage = messages[i];
- // Initialize merged content with current message content
- const mergedContent: MessageContent[] = [currentMessage.content];
-
- // Check if the next message exists and has the same role
- while (
- i + 1 < messages.length &&
- this.ROLES_TO_GEMINI[messages[i + 1].role] ===
- this.ROLES_TO_GEMINI[currentMessage.role]
- ) {
- i++;
- const nextMessage: ChatMessage = messages[i];
- mergedContent.push(nextMessage.content);
- }
-
- // Create a new ChatMessage object with merged content
- const mergedMessage: ChatMessage = {
- role: currentMessage.role,
- content: mergedContent.join("\n"),
- };
- mergedMessages.push(mergedMessage);
- i++;
- }
-
- return mergedMessages;
+ messages: GeminiMessageContent[],
+ ): GeminiMessageContent[] {
+ return messages.reduce(
+ (
+ result: GeminiMessageContent[],
+ current: GeminiMessageContent,
+ index: number,
+ ) => {
+ if (index > 0 && messages[index - 1].role === current.role) {
+ result[result.length - 1].parts = [
+ ...result[result.length - 1].parts,
+ ...current.parts,
+ ];
+ } else {
+ result.push(current);
+ }
+ return result;
+ },
+ [],
+ );
  }
 
  public static messageContentToGeminiParts(content: MessageContent): Part[] {
@@ -214,8 +202,8 @@ class GeminiHelper {
  message: ChatMessage,
  ): GeminiMessageContent {
  return {
- role: this.ROLES_TO_GEMINI[message.role],
- parts: this.messageContentToGeminiParts(message.content),
+ role: GeminiHelper.ROLES_TO_GEMINI[message.role],
+ parts: GeminiHelper.messageContentToGeminiParts(message.content),
  };
  }
 }
@@ -260,22 +248,20 @@ export class Gemini extends ToolCallLLM<GeminiAdditionalChatOptions> {
  chat: ChatSession;
  messageContent: Part[];
  } {
- const { messages } = params;
- const mergedMessages =
- GeminiHelper.mergeNeighboringSameRoleMessages(messages);
- const history = mergedMessages.slice(0, -1);
- const nextMessage = mergedMessages[mergedMessages.length - 1];
- const messageContent = GeminiHelper.chatMessageToGemini(nextMessage).parts;
+ const messages = GeminiHelper.mergeNeighboringSameRoleMessages(
+ params.messages.map(GeminiHelper.chatMessageToGemini),
+ );
+
+ const history = messages.slice(0, -1);
 
  const client = this.session.gemini.getGenerativeModel(this.metadata);
 
  const chat = client.startChat({
- history: history.map(GeminiHelper.chatMessageToGemini),
+ history,
  });
-
  return {
  chat,
- messageContent,
+ messageContent: messages[messages.length - 1].parts,
  };
  }
 

packages/core/src/llm/index.ts

@@ -5,7 +5,7 @@ export {
  Anthropic,
 } from "./anthropic.js";
 export { FireworksLLM } from "./fireworks.js";
-export { GEMINI_MODEL, Gemini } from "./gemini.js";
+export { GEMINI_MODEL, Gemini, GeminiSession } from "./gemini.js";
 export { Groq } from "./groq.js";
 export { HuggingFaceInferenceAPI } from "./huggingface.js";
 export {