Senior Browser Automation Engineer — Scale & Autonomy

Horizon3; United States; Hybrid; USD 169,000 - 208,000; Full time

Benefits offered by this job

Inclusive culture

Career growth

Innovative culture

Hybrid/Remote work

Competitive compensation

Job summary

Horizon3.ai is building an autonomous, black-box web app pentester. You’ll own the browser-driven crawler, tackle SPA timing and auth flows, and push a scalable, deterministic automation stack that maps to production customer environments.

Join a remote-friendly, innovative team with opportunities to work across large enterprise and government environments, emphasizing reliability and deep security expertise.

Qualifications

• Production software experience with browser automation against real web apps.
• Strong TypeScript / Node.js skills inside headless-browser stacks.
• Proven ability to tame flaky, JS-heavy apps and SPA timing issues.
• Experience with distributed, concurrent systems and scalable browser sessions.
• Bias toward determinism, debuggability, and selective use of LLMs.

Responsibilities

• Own and harden the browser automation and crawling engine used in autonomous pentests.
• Advance crawling with Playwright and Stagehand in complex web apps.
• Handle modern web app challenges: SPA routing, auth, file uploads, WebSocket traffic.
• Extend login/auth capabilities for unattended, production-safe runs.
• Improve crawl coverage, dedupe, queueing, and state management.
• Collaborate with attackers-engineers to map output into the app graph.

Skills

Browser automation

TypeScript / Node.js

SPA timing handling

Distributed systems

Determinism & debugging

Ownership mindset

Tools

Playwright

Puppeteer

Selenium

Job description

Horizon3.ai is building an autonomous, black-box web app pentester. You’ll own the browser-driven crawler, tackle SPA timing and auth flows, and push a scalable, deterministic automation stack that maps to production customer environments.

Join a remote-friendly, innovative team with opportunities to work across large enterprise and government environments, emphasizing reliability and deep security expertise.