stagehand-automation（舞台工作人员自动化）

Stagehand Automation

Overview

Stagehand v3 is the state-of-the-art AI browser automation framework that bridges brittle traditional automation with intelligent, self-healing capabilities. Built on Chrome DevTools Protocol (CDP), it's 44% faster than v2 and integrates seamlessly with Claude.

Key Innovation: When DOM changes, AI adapts instead of tests breaking.

Core APIs:

• act() - Perform actions using natural language
• extract() - Extract structured data from pages
• observe() - Identify elements and page state

Quick Start (10 Minutes)

1. Install Stagehand

npm install @browserbase/stagehand zod

2. Configure Claude API

# Add to .env
ANTHROPIC_API_KEY=your_api_key_here

3. Write First Automation

import { Stagehand } from "@browserbase/stagehand";
import { z } from "zod";

async function main() {
  const stagehand = new Stagehand({
    env: "LOCAL",
    modelName: "claude-sonnet-4-20250514",
    modelClientOptions: {
      apiKey: process.env.ANTHROPIC_API_KEY,
    },
  });

  await stagehand.init();
  await stagehand.page.goto("https://news.ycombinator.com");

  // AI-powered action - survives UI changes!
  await stagehand.act({ action: "click on the first story link" });

  // Extract structured data
  const data = await stagehand.extract({
    instruction: "extract the story title and author",
    schema: z.object({
      title: z.string(),
      author: z.string(),
    }),
  });

  console.log(data);
  await stagehand.close();
}

main();

4. Run

npx ts-node your-script.ts

Core APIs

act() - Perform Actions

Execute actions using natural language:

// Click elements
await stagehand.act({ action: "click the login button" });

// Fill forms
await stagehand.act({ action: "fill in the email field with 'test@example.com'" });
await stagehand.act({ action: "enter password 'securepass123'" });

// Navigate
await stagehand.act({ action: "scroll down to the pricing section" });
await stagehand.act({ action: "click the 'Sign Up' button in the header" });

// Complex actions
await stagehand.act({
  action: "select 'Premium' from the plan dropdown and click Continue"
});

Self-Healing: If the button ID changes from #login-btn to #auth-signin, Stagehand adapts automatically.

extract() - Get Structured Data

Extract data with schema validation:

import { z } from "zod";

// Simple extraction
const title = await stagehand.extract({
  instruction: "get the main page title",
  schema: z.object({
    title: z.string(),
  }),
});

// Complex extraction
const products = await stagehand.extract({
  instruction: "extract all products with name, price, and availability",
  schema: z.object({
    products: z.array(z.object({
      name: z.string(),
      price: z.number(),
      inStock: z.boolean(),
    })),
  }),
});

// Extract from specific area
const cartItems = await stagehand.extract({
  instruction: "get items in the shopping cart",
  schema: z.object({
    items: z.array(z.object({
      name: z.string(),
      quantity: z.number(),
      price: z.number(),
    })),
    total: z.number(),
  }),
});

observe() - Analyze Page State

Understand page elements and state:

// Find elements
const elements = await stagehand.observe({
  instruction: "find all clickable buttons on this page"
});

// Check state
const loginState = await stagehand.observe({
  instruction: "is the user logged in? Look for profile icons or logout buttons"
});

// Identify form fields
const formFields = await stagehand.observe({
  instruction: "identify all form input fields and their labels"
});

Self-Healing Patterns

Traditional vs Stagehand

// TRADITIONAL (Playwright) - Breaks when DOM changes
await page.click('#submit-btn-v2');  // Fails if ID changes
await page.click('.btn-primary:nth-child(2)');  // Fails if order changes

// STAGEHAND - Self-healing
await stagehand.act({ action: "click the submit button" });  // Always works
await stagehand.act({ action: "click the primary action button" });  // Adapts

When Self-Healing Activates

1. ID/Class Changes: Button ID changes from #old-id to #new-id
2. Structure Changes: Element moves in DOM tree
3. Text Changes: Button text changes from "Submit" to "Send"
4. Style Changes: CSS classes reorganized

Caching (Performance Optimization)

Stagehand v3 caches discovered elements:

// First call: AI analyzes page, finds element (slow)
await stagehand.act({ action: "click login" });

// Second call: Uses cached selector (fast)
await stagehand.act({ action: "click login" });

// Cache invalidated when page changes significantly

Hybrid Approach: Playwright + Stagehand

Combine traditional speed with AI resilience:

import { Stagehand } from "@browserbase/stagehand";
import { test, expect } from "@playwright/test";

test('hybrid test', async () => {
  const stagehand = new Stagehand({ env: "LOCAL" });
  await stagehand.init();

  // Use Playwright for stable, fast operations
  await stagehand.page.goto('https://app.example.com');
  await stagehand.page.fill('[data-testid="email"]', 'test@example.com');

  // Use Stagehand for dynamic/fragile elements
  await stagehand.act({ action: "click the login button" });

  // Use Playwright for assertions
  await expect(stagehand.page).toHaveURL(/dashboard/);

  // Use Stagehand for complex extraction
  const dashboardData = await stagehand.extract({
    instruction: "get user stats from dashboard",
    schema: z.object({
      totalOrders: z.number(),
      accountBalance: z.number(),
    }),
  });

  expect(dashboardData.totalOrders).toBeGreaterThan(0);
});

Claude Integration

Model Selection

// Claude Sonnet 4 (recommended - balance of speed/quality)
const stagehand = new Stagehand({
  modelName: "claude-sonnet-4-20250514",
  modelClientOptions: {
    apiKey: process.env.ANTHROPIC_API_KEY,
  },
});

// Claude Opus (highest quality, slower)
const stagehand = new Stagehand({
  modelName: "claude-opus-4-20250514",
});

// Claude Haiku (fastest, simpler tasks)
const stagehand = new Stagehand({
  modelName: "claude-3-5-haiku-20241022",
});

Cost Optimization

// Use Haiku for simple actions (cheaper)
const simpleStagehand = new Stagehand({
  modelName: "claude-3-5-haiku-20241022",
});
await simpleStagehand.act({ action: "click login" });

// Use Sonnet for complex extraction
const complexStagehand = new Stagehand({
  modelName: "claude-sonnet-4-20250514",
});
const data = await complexStagehand.extract({
  instruction: "extract all product details with nested specifications",
  schema: complexSchema,
});

Estimated Costs

MCP Integration

Use Stagehand with Claude Desktop via Model Context Protocol:

// Stagehand MCP server enables Claude to control browsers
// from Claude Desktop or any MCP-compatible client

import { StagehandMCPServer } from "@browserbase/stagehand/mcp";

const server = new StagehandMCPServer();
server.start();

// Now Claude can call:
// - stagehand.act({ action: "..." })
// - stagehand.extract({ instruction: "..." })
// - stagehand.observe({ instruction: "..." })

Error Handling

try {
  await stagehand.act({
    action: "click the non-existent button",
    timeout: 10000,  // 10 second timeout
  });
} catch (error) {
  if (error.message.includes('timeout')) {
    console.log('Element not found within timeout');
  } else if (error.message.includes('multiple')) {
    console.log('Multiple matching elements found - be more specific');
  } else {
    throw error;
  }
}

// Retry pattern
async function actWithRetry(stagehand, action, maxRetries = 3) {
  for (let i = 0; i < maxRetries; i++) {
    try {
      return await stagehand.act({ action });
    } catch (error) {
      if (i === maxRetries - 1) throw error;
      await new Promise(r => setTimeout(r, 1000));
    }
  }
}

Best Practices

1. Be Specific in Instructions

// BAD - ambiguous
await stagehand.act({ action: "click button" });

// GOOD - specific
await stagehand.act({ action: "click the blue 'Add to Cart' button below the product image" });

2. Use Context

// Provide context for better accuracy
await stagehand.act({
  action: "in the navigation menu, click on 'Settings'"
});

await stagehand.act({
  action: "in the user dropdown in the top right, click 'Logout'"
});

3. Combine with Playwright for Speed

// Fast: Use Playwright for data-testid elements
await stagehand.page.click('[data-testid="submit"]');

// Resilient: Use Stagehand for dynamic elements
await stagehand.act({ action: "dismiss the cookie banner" });

4. Schema Validation

// Always use Zod schemas for type safety
const schema = z.object({
  title: z.string().min(1),
  price: z.number().positive(),
  inStock: z.boolean(),
});

const data = await stagehand.extract({
  instruction: "get product details",
  schema,
});
// data is fully typed!

Use Cases

1. Self-Healing E2E Tests: Tests that survive UI redesigns
2. Web Scraping: Extract data from any website
3. Form Automation: Fill complex forms automatically
4. Testing AI Chatbots: Interact with conversational UIs
5. Cross-Site Workflows: Automate multi-site processes

References

• references/stagehand-v3-guide.md - Complete API reference
• references/claude-integration.md - API setup and model selection
• references/self-healing-patterns.md - Advanced patterns

Stagehand v3 brings AI-powered self-healing to browser automation - tests that adapt instead of break.