toolCallLimitMiddleware

import { toolCallLimitMiddleware } from "@langchain/langchain/agents/middleware";
import { createAgent } from "@langchain/langchain/agents";

// Block exceeded tools but let other tools and model continue
const limiter = toolCallLimitMiddleware({
  threadLimit: 20,
  runLimit: 10,
  exitBehavior: "continue", // default
});

const agent = createAgent({
  model: "openai:gpt-4o",
  middleware: [limiter]
});

// End execution immediately with an AI message
const limiter = toolCallLimitMiddleware({
  runLimit: 5,
  exitBehavior: "end"
});

const agent = createAgent({
  model: "openai:gpt-4o",
  middleware: [limiter]
});

// Strict limit with exception handling
const limiter = toolCallLimitMiddleware({
  toolName: "search",
  threadLimit: 5,
  exitBehavior: "error"
});

const agent = createAgent({
  model: "openai:gpt-4o",
  middleware: [limiter]
});

try {
  const result = await agent.invoke({ messages: [new HumanMessage("Task")] });
} catch (error) {
  if (error instanceof ToolCallLimitExceededError) {
    console.log(`Search limit exceeded: ${error}`);
  }
}