Software Engineer I

RunSybil•New York City, NY

20d•Hybrid

About The Position

About RunSybil Founded in 2023 by Ari Herbert-Voss and Vlad Ionescu, RunSybil is on a mission to automate hacker intuition. We’re building Sybil: an AI-driven pentester that discovers vulnerabilities before they’re exploited. As adversaries adopt AI to increase their attack surface, we’re putting cutting-edge offensive security into the hands of defenders. Backed by strong investor support and early customer traction, our team is composed of experts from OpenAI, Meta, Mandiant, Palantir, Cruise, Trail of Bits, and Aptiv. About the Role We are looking for a Software Engineer I who wants to do the best work of their first years anywhere. You will ship customer-facing features from your first weeks, build the agentic systems that power Sybil, and work directly alongside senior engineers and our founders every day. On a team this small, your code goes to production and customers use it. There is no shadow work here. This is a role for someone who builds because they want to. The strongest people we know at this stage have a trail of side projects, open source contributions, and things they taught themselves because a problem got under their skin. If that sounds like you, we will give you real ownership, fast feedback, and problems worth growing into.

Requirements

Strong Python fundamentals and real comfort with data structures; you write clean, working code and can explain every line of it
Evidence of shipping software in any setting: internships, team or class projects, research, or personal projects all count equally
A habit of initiative: times you took on more than the assignment asked, fixed the thing nobody owned, or taught yourself what the work needed
Hands-on experience coding with LLMs, and judgment about when to use them, how to validate their output, and when to just write the code yourself
Fast, honest communication; you say what you know, what you do not, and where you are stuck
Coachability: you take a hint, run with it, and carry the lesson forward

Nice To Haves

Familiarity with modern JavaScript and React is a plus

Responsibilities

Ship customer-facing features end to end, from first commit through production, with close review and support from senior engineers
Build and extend the agentic systems behind Sybil, working primarily in Python with TypeScript and React across the stack
Use LLMs as a core part of how you work: prompting, evaluating generated code, and building tooling that makes the whole team faster
Own small projects yourself, including scoping the problem, proposing the approach, and seeing it through to done
Debug real issues in a production system that customers rely on, and learn how long-running agentic workloads behave in the wild
Contribute to technical design discussions and code reviews, and speak up when you see a better way
Learn offensive security on the job from a team that includes some of the best in the field