Memory

pub trait BaseMemory: Send + Sync {
    fn messages(&self) -> Vec<Message>;
    fn add_message(&mut self, message: Message);
    fn add_user_message(&mut self, message: impl Into<String>);  // convenience
    fn add_ai_message(&mut self, message: impl Into<String>);    // convenience
    fn clear(&mut self);
}

use langchainx::memory::{SimpleMemory, WindowBufferMemory, DummyMemory};

// Unbounded history
let mem = SimpleMemory::new();

// Sliding window — keeps last N exchanges
let mem = WindowBufferMemory::new(5);

// No-op — for chains that require memory param but don't need it
let mem = DummyMemory::new();

All memory types implement Into<Arc<Mutex<dyn BaseMemory>>>. Use .into():

use std::sync::Arc;
use tokio::sync::Mutex;
use langchainx::{
    memory::SimpleMemory,
    schemas::memory::BaseMemory,
};

// Preferred — .into() calls Arc::new(Mutex::new(self))
let mem: Arc<Mutex<dyn BaseMemory>> = SimpleMemory::new().into();

// Equivalent explicit form
let mem = Arc::new(Mutex::new(SimpleMemory::new())) as Arc<Mutex<dyn BaseMemory>>;

Pass to chain/agent builders:

ConversationalChainBuilder::new()
    .memory(SimpleMemory::new().into())
    ...

let mem: Arc<Mutex<dyn BaseMemory>> = SimpleMemory::new().into();

// Lock to read
let guard = mem.lock().await;
let messages = guard.messages();
drop(guard);  // release lock before any await

// Lock to write
let mut guard = mem.lock().await;
guard.add_user_message("Hello");
guard.add_ai_message("Hi there!");

Never hold the lock across an .await — use a separate scope or drop before await points.