Senior Software Engineer

About the role

As Founding Software Engineer, you will sit at the intersection of product, infrastructure, and AI. You will take part in building Arcline's agentic legal platform, which automates 80% of legal work and manages communication between lawyers and clients.

This is a high-impact role for someone energized by building from zero to one, owning hard technical problems end-to-end, and shipping reliable, scalable systems that power complex AI-driven workflows. You will work in a team of highly talented designers, software engineers and AI engineers, reporting directly to the CTO.

What You'll Do

Product Engineering

• Build and ship full-stack features end-to-end, from data model to UI, with a high bar for reliability and code quality
• Work directly with founders and customers to turn ambiguous problems into shipped product
• Own features through the full lifecycle: scoping, implementation, testing, and iteration based on user feedback

Platform and Infrastructure

• Design and maintain the backend systems and APIs powering our agentic workflows
• Build document processing pipelines that ingest, parse, and structure legal documents at scale
• Own search infrastructure that makes an entire case history instantly queryable
• Own infrastructure and observability for the systems you build, on AWS

AI Engineering

• Build the intake agent that gathers and structures client information before a lawyer ever gets involved
• Build document generation pipelines that draft legal documents from firm playbooks
• Build the systems that generate those playbooks — learning from historical documents to codify how elite lawyers approach recurring work
• Integrate LLM capabilities into product surfaces: streaming responses, inline editing, human-in-the-loop review flows

What We're Looking For

• 3+ years of experience in software engineering, with a track record of shipping production systems
• Strong full-stack proficiency — we use Next.js, TypeScript, and Python on the backend
• Solid fundamentals in system design, data modeling, and API development
• Comfortable owning ambiguous problems and making pragmatic technical decisions
• Experience building and operating cloud infrastructure (AWS or equivalent)
• Strong product instincts — you care about what you're building and why, not just how
• Fluent with AI-assisted development: you use Codex, Claude, or similar tools daily and have strong opinions on how to get the most out of them — not as a crutch, but as a force multiplier
• Excellent communication skills — you can articulate technical tradeoffs clearly to non-engineers
• Genuine curiosity about the legal domain — you don't need a law degree, but you should be excited to understand how legal work actually functions and let that inform your technical decisions

Bonus Points

• Experience as an early engineer at a startup (ideally pre-Series A)
• Familiarity with agentic AI patterns: tool use, orchestration, retrieval, structured generation
• Background from legaltech, fintech, or other regulated B2B SaaS
• Familiarity with the mechanics of legal workflows — contracts, entity formation, employment, IP — even if only from the client side
• Experience with SOC 2 / ISO 27001 compliance or enterprise-readiness work
• Contributions to or opinions about developer tooling, CI/CD, or platform engineering

Why Arcline

• Direct access to both founders from day one — shape the technical foundation from scratch
• Define the engineering culture of an AI-native company
• High degree of trust and autonomy
• Hot market: we're building the defining AI-native firm in a $1T+ industry
• Accelerated growth path: evolve into a Staff Engineer or Engineering Lead role
• Backed by Y Combinator — be part of the best startup network in the world, with regular opportunities to visit and work with the team in San Francisco

Apply using YC's job portal. We review every application and respond only to relevant applicants within 1–2 week(s).

About the interview

• Intro call with a founder
• Take home assignment or work trial
• Final conversation with both founders