horizon3ai - Senior Software Engineer, Browser Automation
Requirements
• Experience building production software, with deep, hands-on experience in browser automation (Playwright, Puppeteer, or Selenium) against real, non-trivial web applications. • Strong TypeScript / Node.js skills and comfort living inside the headless-browser stack, including Chromium internals, the Chrome DevTools Protocol, network interception, the DOM, and JS execution contexts. • A track record of taming flaky, stateful, JavaScript-heavy apps. You've fought SPA timing, authentication, and anti-automation defenses and won. • Solid instincts for distributed/concurrent systems: queues, backpressure, retries, idempotency, and running many browser sessions reliably at scale. • A bias toward determinism and debuggability, and the judgment to reach for an LLM only when a deterministic approach genuinely can't do the job. • Ownership mentality: you are comfortable taking a critical subsystem from "works" to "works unattended, at scale, against someone else's production environment." • Experience with agentic browser frameworks (Stagehand, Browser Use, or similar) or building LLM-in-the-loop automation. • Background in web application security or offensive tooling — familiarity with broken access control, IDOR/BOLA, SQLi, XSS, SSRF, or SSTI in the wild. • Familiarity with graph data models (e.g., Neo4j) for representing application structure. • Experience with large-scale crawling, endpoint discovery (e.g., parsing/analyzing client-side JS), or session/credential management for automated access. • Comfort working in an environment where correctness against a live customer system is a hard, non-negotiable constraint. • What makes you stand out: • You’ve gone beyond using tools like Playwright or Puppeteer to actually hacking on their internals or contributing to the core. • You’ve built browser automation at extreme scale, handling thousands of sessions against hostile, heavily-defended targets. You know exactly how systems break under pressure and have the war stories to prove it. • You’ve successfully outmaneuvered sophisticated WAFs, anti-bot defenses, and fingerprinting mechanisms in production environments. • You have an offensive security mindset: you don’t just navigate a web app; you actively map its attack surface and hunt for unreachable paths. • You have battle-tested experience with LLMs in production. You understand the engineering trade-offs: knowing when AI is an asset and when it introduces unacceptable latency or nondeterminism compared to a deterministic script.
Responsibilities
• Please note this job description is not designed to cover or contain a comprehensive listing of activities, duties or responsibilities that are required of the employee. Duties, responsibilities, and activities may change at any time with or without notice. • Application Note • Application Note • In any materials you submit, you may redact or remove age-identifying information such as age, date of birth, or dates of school attendance or graduation. You will not be penalized for redacting or removing this information.
Benefits
• Inclusive Team: We value diversity and promote an inclusive culture where everyone can thrive. • Growth Opportunities: Be part of a dynamic and growing team with numerous career development opportunities. • Innovative Culture: Work in a collaborative environment that encourages creativity and out-of-the-box thinking. • Hybrid & Remote Work: We embrace a mix of remote and hybrid work models depending on role and location, including our Chicago office, where some roles require regular in-office presence. • Competitive Compensation: We offer competitive salary, equity and benefits. Our benefits include health, vision & dental insurance for you and your family, a flexible vacation policy, and generous parental leave. • At Horizon3, we believe that our people are our greatest asset, and our compensation philosophy reflects this core value. We are committed to fostering an environment where all employees feel valued, respected, and rewarded for their contributions. Our compensation structure is designed to be fair, competitive, and transparent, ensuring that every team member is recognized and compensated equitably across roles, levels, and locations. • In accordance with various State’s transparency regulations, we provide the following salary range information for this position: • Base salary range: $169,000 - $208,000 annually. The exact salary will be determined based on the selected candidate’s location, qualifications, experience, and relevant skills. • Additional compensation: All full-time roles are eligible for an equity package in the form of stock options. • You Belong Here
Apply in one click
Upload My Resume
Drop here or click to browse · Tap to choose · PDF, DOCX, DOC, RTF, TXT