[Bug]: example/browser.ts fails due to accessing a property of undefined

[betterhyq]

Link to minimal reproduction

https://stackblitz.com/~/github.com/betterhyq/agent-browser-sdk

Steps to reproduce

1. pnpm install
2. cd packages/browser
3. npx tsx example/browser.ts

What is expected?

Run successfully

What is actually happening?

~/JDProjects/osc/agent-browser-sdk/packages/browser (bugfix_115_test_20260130) » npx tsx example/browser.ts                                         1 ↵ heyongqi10@ZBMAC-ce39a67f0
npm warn Unknown user config "home". This will stop working in the next major version of npm.
npm warn Unknown user config "always-auth" (//registry.m.jd.com/:always-auth). This will stop working in the next major version of npm.
/Users/heyongqi10/JDProjects/osc/agent-browser-sdk/packages/browser/src/browser/browser.ts:149
      options.defaultViewport,
              ^


TypeError: Cannot read properties of undefined (reading 'defaultViewport')
    at Browser.#processOptions (/Users/heyongqi10/JDProjects/osc/agent-browser-sdk/packages/browser/src/browser/browser.ts:149:15)
    at Browser.#init (/Users/heyongqi10/JDProjects/osc/agent-browser-sdk/packages/browser/src/browser/browser.ts:75:35)
    at Browser.create (/Users/heyongqi10/JDProjects/osc/agent-browser-sdk/packages/browser/src/browser/browser.ts:27:19)
    at main (/Users/heyongqi10/JDProjects/osc/agent-browser-sdk/packages/browser/example/browser.ts:8:33)
    at <anonymous> (/Users/heyongqi10/JDProjects/osc/agent-browser-sdk/packages/browser/example/browser.ts:30:1)
    at Object.<anonymous> (/Users/heyongqi10/JDProjects/osc/agent-browser-sdk/packages/browser/example/browser.ts:30:6)
    at Module._compile (node:internal/modules/cjs/loader:1734:14)
    at Object.transformer (/Users/heyongqi10/JDProjects/osc/agent-browser-sdk/node_modules/.pnpm/tsx@4.20.6/node_modules/tsx/dist/register-D46fvsV_.cjs:3:1104)
    at Module.load (node:internal/modules/cjs/loader:1469:32)
    at Module._load (node:internal/modules/cjs/loader:1286:12)

Node.js v24.0.2

System Info

  System:
    OS: macOS 15.7.3
    CPU: (12) arm64 Apple M2 Pro
    Memory: 109.31 MB / 16.00 GB
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 24.0.2 - /Users/heyongqi10/.nvm/versions/node/v24.0.2/bin/node
    Yarn: 1.22.22 - /Users/heyongqi10/.nvm/versions/node/v24.0.2/bin/yarn
    npm: 11.3.0 - /Users/heyongqi10/.nvm/versions/node/v24.0.2/bin/npm
    pnpm: 10.28.0 - /Users/heyongqi10/.nvm/versions/node/v24.0.2/bin/pnpm
    bun: 1.3.6 - /Users/heyongqi10/.nvm/versions/node/v24.0.2/bin/bun
    Watchman: 2024.10.07.00 - /opt/homebrew/bin/watchman
  Browsers:
    Chrome: 144.0.7559.110
    Firefox: 147.0.2
    Safari: 26.2