((_, config) => {
return `You are a helpful assistant. Address the user as ${config.context?.userName}.`;
}),
],
});
const result = await agent.invoke(
{
messages: [{ role: "user", content: "What is the weather in SF?" }],
},
{
context: {
userName: "John Smith",
},
}
);
for (const message of result.messages) {
console.log(message);
}
/**
* HumanMessage {
* "content": "What is the weather in SF?",
* // ...
* }
* AIMessage {
* // ...
* "tool_calls": [
* {
* "name": "get_weather",
* "args": {
* "city": "San Francisco"
* },
* "type": "tool_call",
* "id": "call_tCidbv0apTpQpEWb3O2zQ4Yx"
* }
* ],
* // ...
* }
* ToolMessage {
* "content": "The weather in San Francisco is always sunny!",
* "tool_call_id": "call_tCidbv0apTpQpEWb3O2zQ4Yx"
* // ...
* }
* AIMessage {
* "content": "John Smith, here's the latest: The weather in San Francisco is always sunny!\n\nIf you'd like more details (temperature, wind, humidity) or a forecast for the next few days, I can pull that up. What would you like?",
* // ...
* }
*/
```
### 模型之前
```mermaid theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
%%{
init: {
"fontFamily": "monospace",
"flowchart": {
"curve": "basis"
}
}
}%%
graph TD
S(["\_\_start\_\_"])
PRE(before_model)
MODEL(model)
TOOLS(tools)
END(["\_\_end\_\_"])
S --> PRE
PRE --> MODEL
MODEL -.-> TOOLS
MODEL -.-> END
TOOLS --> PRE
classDef blueHighlight fill:#E5F4FF,stroke:#006DDD,color:#030710;
classDef neutral fill:#F2FAFF,stroke:#40668D,stroke-width:2px,color:#2F4B68;
class S blueHighlight;
class END blueHighlight;
class PRE,MODEL,TOOLS neutral;
```
```typescript theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
import { RemoveMessage } from "@langchain/core/messages";
import { createAgent, createMiddleware, trimMessages } from "langchain";
import { MemorySaver } from "@langchain/langgraph";
import { REMOVE_ALL_MESSAGES } from "@langchain/langgraph";
const trimMessageHistory = createMiddleware({
name: "TrimMessages",
beforeModel: async (state) => {
const trimmed = await trimMessages(state.messages, {
maxTokens: 384,
strategy: "last",
startOn: "human",
endOn: ["human", "tool"],
tokenCounter: (msgs) => msgs.length,
});
return {
messages: [new RemoveMessage({ id: REMOVE_ALL_MESSAGES }), ...trimmed],
};
},
});
const checkpointer = new MemorySaver();
const agent = createAgent({
model: "gpt-5-nano",
tools: [],
middleware: [trimMessageHistory],
checkpointer,
});
```
### 模型之后
```mermaid theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
%%{
init: {
"fontFamily": "monospace",
"flowchart": {
"curve": "basis"
}
}
}%%
graph TD
S(["\_\_start\_\_"])
MODEL(model)
POST(after_model)
TOOLS(tools)
END(["\_\_end\_\_"])
S --> MODEL
MODEL --> POST
POST -.-> END
POST -.-> TOOLS
TOOLS --> MODEL
classDef blueHighlight fill:#E5F4FF,stroke:#006DDD,color:#030710;
classDef greenHighlight fill:#F6FFDB,stroke:#6E8900,color:#2E3900;
classDef neutral fill:#F2FAFF,stroke:#40668D,stroke-width:2px,color:#2F4B68;
class S blueHighlight;
class END blueHighlight;
class POST greenHighlight;
class MODEL,TOOLS neutral;
```
```typescript theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
import { RemoveMessage } from "@langchain/core/messages";
import { createAgent, createMiddleware } from "langchain";
import { REMOVE_ALL_MESSAGES } from "@langchain/langgraph";
const validateResponse = createMiddleware({
name: "ValidateResponse",
afterModel: (state) => {
const lastMessage = state.messages.at(-1)?.content;
if (
typeof lastMessage === "string" &&
lastMessage.toLowerCase().includes("confidential")
) {
return {
messages: [
new RemoveMessage({ id: REMOVE_ALL_MESSAGES }),
],
};
}
return;
},
});
const agent = createAgent({
model: "gpt-5-nano",
tools: [],
middleware: [validateResponse],
});
```
***
[将这些文档连接](/use-these-docs)到Claude、VSCode等，通过MCP获取实时答案。
[在GitHub上编辑此页面](https://github.com/langchain-ai/docs/edit/main/src/oss/langchain/short-term-memory.mdx)或[提交问题](https://github.com/langchain-ai/docs/issues/new/choose)。
要在代理中总结消息历史记录，请使用内置的[`summarizationMiddleware`](/oss/javascript/langchain/middleware#summarization)：
```typescript theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
import { createAgent, summarizationMiddleware } from "langchain";
import { MemorySaver } from "@langchain/langgraph";
const checkpointer = new MemorySaver();
const agent = createAgent({
model: "gpt-5.4",
tools: [],
middleware: [
summarizationMiddleware({
model: "gpt-5.4-mini",
trigger: { tokens: 4000 },
keep: { messages: 20 },
}),
],
checkpointer,
});
const config = { configurable: { thread_id: "1" } };
await agent.invoke({ messages: "hi, my name is bob" }, config);
await agent.invoke({ messages: "write a short poem about cats" }, config);
await agent.invoke({ messages: "now do the same but for dogs" }, config);
const finalResponse = await agent.invoke({ messages: "what's my name?" }, config);
console.log(finalResponse.messages.at(-1)?.content);
// Your name is Bob!
```
有关更多配置选项，请参阅[`summarizationMiddleware`](/oss/javascript/langchain/middleware#summarization)。
## 访问记忆
你可以通过多种方式访问和修改代理的短期记忆（状态）：
### 工具
#### 在工具中读取短期记忆
使用`runtime`参数（类型为`ToolRuntime`）在工具中访问短期记忆（状态）。
`runtime`参数在工具签名中是隐藏的（因此模型看不到它），但工具可以通过它访问状态。
```typescript theme={"theme":{"light":"catppuccin-latte","dark":"catppuccin-mocha"}}
import { createAgent, tool, type ToolRuntime } from "langchain";
import { StateSchema } from "@langchain/langgraph";
import * as z from "zod";
const CustomState = new StateSchema({
userId: z.string(),
});
const getUserInfo = tool(
async (_, config: ToolRuntime