BufferWindowMemory

A sliding-window message buffer. Keeps the last k messages and discards older ones. The simplest and most commonly used memory implementation.

Usage

import { BufferWindowMemory } from "flowneer/plugins/memory";

const memory = new BufferWindowMemory({ maxMessages: 20 });

memory.add({ role: "user", content: "Hello!" });
memory.add({ role: "assistant", content: "Hi there!" });

const context = memory.toContext();
// "user: Hello!\nassistant: Hi there!"

const messages = memory.get();
// [{ role: "user", content: "Hello!" }, ...]

Constructor Options

Option	Type	Default	Description
maxMessages	number	20	Maximum number of messages to retain

Methods

Method	Signature	Description
add	(msg: MemoryMessage) => void	Append a message; prunes when over limit
get	() => MemoryMessage[]	Return a copy of current messages
clear	() => void	Remove all messages
toContext	() => string	Format as "role: content\n..." string

With withMemory

import { FlowBuilder } from "flowneer";
import { withMemory, BufferWindowMemory } from "flowneer/plugins/memory";

const AppFlow = FlowBuilder.extend([withMemory]);

const memory = new BufferWindowMemory({ maxMessages: 10 });
const flow = new AppFlow<ChatState>()
  .withMemory(memory)
  .startWith(async (s) => {
    s.__memory!.add({ role: "user", content: s.input });
    const ctx = s.__memory!.toContext();
    s.response = await callLlm(ctx);
    s.__memory!.add({ role: "assistant", content: s.response });
  });

Pruning Behaviour

When messages.length > maxMessages, the oldest messages are dropped so only the most recent maxMessages remain:

[msg1, msg2, ..., msg20, msg21]  →  [msg2, msg3, ..., msg21]

This preserves the most recent context without unbounded growth.