Software Engineer, Agent Harness

About Cartesia Our mission is to architect AI that learns from and interacts with the world like humans do. We're pioneering the model architectures that will make this possible. Our founding team met as PhDs at the Stanford AI Lab, where we invented State Space Models or SSMs, a new primitive for training efficient, large-scale foundation models. Our team combines deep expertise in model innovation and systems engineering paired with a design-minded product engineering team to build and ship cutting edge models and experiences. We're funded by leading investors at Index Ventures and Lightspeed Venture Partners, along with Factory, Conviction, A Star, General Catalyst, SV Angel, Databricks and others. We're fortunate to have the support of many amazing advisors, and 90+ angels across many industries, including the world's foremost experts in AI.

About

the Role Cartesia is hiring a Software Engineer, Agents to build the backend platform behind Line, our voice agents product. The Agents stack — a Go API with Python workers — is what customers rely on to run real-time, production-grade voice agents. You'll own backend work end-to-end and directly shape the latency, reliability, and developer experience of every agent built on Cartesia. Your Impact Build and operate the distributed systems behind Cartesia's voice agents: load balancing servers, workers, and the realtime media pipelines that tie them together. Take projects from spec to production: design, build, ship, monitor, iterate. Make the architectural calls that compound over time — latency budgets, reliability targets, scaling primitives — and clearly articulate the tradeoffs. Define the developer experience for engineers building on Cartesia: APIs, observability, and applied evaluations. What You Bring 3+ years building distributed backend systems in production, ideally at a high-growth startup. We care more about what you've shipped than strict YOE. Strong product instincts for platform work - you think in customer-facing latency, reliability, and developer experience, and you have opinions on what to build and why. Second-order thinking about backend architecture - you can explain why a design choice was made and what it trades off. Fluent, day-to-day use of AI coding tools, and a habit of keeping pace with the frontier. A strong communicator with both technical and non-technical audiences; comfortable writing clear specs and contributing actively in design reviews. Nice-To-Haves Experience with Go and/or Python in a backend platform context. Realtime media systems in production (WebRTC, SIP, RTP, low-latency audio) Deep experience with cloud and infra primitives (Kubernetes, Docker, NATS, gRPC, OpenTelemetry and modern observability stacks). Distributed systems at scale dealing with non-trivial throughput, autoscaling, multi-region architectures. Voice agents or agent framework experience (Pipecat, LiveKit, OpenAI Agents SDK, Claude SDK, Vercel AI SDK). Note: Cartesia participates in E-Verify and will provide the federal government with Form I-9 information to confirm employment eligibility after hire. More Details 🏢 In-office policy: We’re an in-person team based out of offices in 🇺🇸 San Francisco, 🇬🇧 London and 🇮🇳 Bangalore. We love being in the office, hanging out together, and learning from each other every day. 🌎 Visa sponsorship: We provide visa sponsorship support and assess each circumstance on a case-by-case basis. However, visa sponsorship is dependent on many factors, including

the role you are applying for, and the location you are going to be based, and so we can't always guarantee success. Your Recruiter will work with you to understand your visa sponsorship needs from the first call. 🚢 We ship fast. All of our work is novel and cutting edge, and execution speed is paramount. We have a high bar, and we don’t sacrifice quality or design along the way. 🤝 We support each other. We have an open & inclusive culture that’s focused on giving everyone the resources they need to succeed. Our

Benefits (US Employees Only) 💰

Compensation Competitive base salary alongside attractive equity package. 🩺 Health Insurance Fully covered medical insurance along with dental and vision for you and your family. 🧑‍🧑‍🧒‍🧒 Parental Leave 9 weeks paternity & 12 weeks maternity leave 🏦 401(k) 🚆 Commuter Allowance A monthly stipend to help you get to and from the office. 🏖️ Flexible PTO Take as much time as you need to recharge your batteries. 🍲 Meals & Snacks Lunch, dinner and plenty of snacks, provided daily. 🦖 Your own personal Yoshi Our Commitment to Equal Opportunity Cartesia is an equal opportunity employer. We consider qualified applicants without regard to race, color, religion, sex, national origin, age, disability, veteran status, genetic information, or any other legally protected status.