For longer-term persistence across chat sessions, you can swap out the default in-memory chatHistory that backs chat memory classes like BufferMemory for Convex.

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Setup

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Create project

Get a working Convex project set up, for example by using: 
npm create convex@latest

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Add database accessors

Add query and mutation helpers to convex/langchain/db.ts:
convex/langchain/db.ts
export * from "@langchain/community/utils/convex";

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Configure your schema

Set up your schema (for indexing):
convex/schema.ts
import { defineSchema, defineTable } from "convex/server";
import { v } from "convex/values";

export default defineSchema({
  messages: defineTable({
    sessionId: v.string(),
    message: v.object({
      type: v.string(),
      data: v.object({
        content: v.string(),
        role: v.optional(v.string()),
        name: v.optional(v.string()),
        additional_kwargs: v.optional(v.any()),
      }),
    }),
  }).index("bySessionId", ["sessionId"]),
});

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Usage

Each chat history session stored in Convex must have a unique session id.
See this section for general instructions on installing LangChain packages.
npm
npm install @langchain/openai @langchain/community @langchain/core