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The TypeScript SDK gives you full programmatic control over BAP servers. Use it to build agent backends, custom automation tools, or integrate browser control into your application.

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Installation

npm install @browseragentprotocol/client

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Quick Start

import { BAPClient, role, label, text } from "@browseragentprotocol/client";

const client = new BAPClient("ws://localhost:9222");
await client.connect();

// Launch browser and navigate
await client.launch({ browser: "chromium", headless: false });
await client.createPage({ url: "https://example.com" });

// Interact with semantic selectors
await client.click(role("button", "Submit"));
await client.fill(label("Email"), "user@example.com");

// Get page state for AI reasoning
const { tree } = await client.accessibility();

await client.close();
Use createClient() as a shorthand that creates and connects in one call:
import { createClient } from "@browseragentprotocol/client";
const client = await createClient("ws://localhost:9222");

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Semantic Selector Helpers

The SDK exports factory functions for all selector types: 
import { role, text, label, testId } from "@browseragentprotocol/client";

// By ARIA role and accessible name
await client.click(role("button", "Submit"));
await client.fill(role("textbox", "Search"), "query");

// By visible text
await client.click(text("Sign in"));

// By form label
await client.fill(label("Email address"), "user@example.com");

// By data-testid
await client.click(testId("submit-button"));

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API Reference

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Connection

const client = new BAPClient(url, options?);
await client.connect();
await client.close();

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Browser Lifecycle

await client.launch({ browser: "chromium", headless: true });
await client.closeBrowser();

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Page Management

const page = await client.createPage({ url: "https://example.com" });
await client.navigate("https://another.com");
await client.reload();
await client.goBack();
await client.goForward();
await client.closePage();

// Multi-tab
const pages = await client.listPages();
await client.activatePage(pages[1].id);

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Actions

await client.click(selector);
await client.dblclick(selector);
await client.fill(selector, "text");
await client.type(selector, "text");
await client.clear(selector);
await client.press("Enter");
await client.hover(selector);
await client.scroll({ direction: "down", amount: 500 });
await client.select(selector, "option-value");
await client.check(selector);
await client.uncheck(selector);

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Observations

// Screenshot (returns base64 data)
const { data } = await client.screenshot();

// Full accessibility tree
const { tree } = await client.accessibility();

// Token-efficient YAML snapshot
const { snapshot } = await client.ariaSnapshot();

// Page content as text or markdown
const { content } = await client.content("text");

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AI Agent Methods

// Observe: AI-optimized page snapshot
const observation = await client.observe();

// Act: execute multiple steps atomically
const result = await client.act([
  BAPClient.step("action/fill", {
    selector: label("Email"),
    value: "user@example.com",
  }),
  BAPClient.step("action/click", {
    selector: role("button", "Submit"),
  }),
]);

// Extract: structured data extraction
const data = await client.extract({
  instruction: "Extract product names and prices",
  schema: {
    type: "array",
    items: {
      type: "object",
      properties: {
        name: { type: "string" },
        price: { type: "number" },
      },
    },
  },
});

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Events

client.on("page", (event) => console.log("Page:", event));
client.on("console", (event) => console.log("Console:", event));
client.on("network", (event) => console.log("Network:", event));
client.on("dialog", (event) => console.log("Dialog:", event));
client.on("download", (event) => console.log("Download:", event));

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WebMCP Discovery

// Discover tools exposed by the current page
const tools = await client.discoverTools();

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Connection Options

The BAPClient constructor accepts an options object: 
const client = new BAPClient("ws://localhost:9222", {
  timeout: 30000, // Request timeout (ms)
  token: "my-auth-token", // Authentication token
  maxReconnectAttempts: 5, // Auto-reconnect attempts
  reconnectDelay: 1000, // Base delay between reconnects (ms)
});
The transport uses exponential backoff for reconnection: delay * 2^attempt.

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Starting the Server

The TypeScript SDK requires a running BAP server. Start one with: 
npm i -g @browseragentprotocol/cli
bap open
# Server starts automatically on port 9222

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Requirements

  • Node.js >= 20.0.0
  • A running BAP Playwright server