Applied AI Engineer, Video Agent

We Love AI Jobs; San Francisco (CA); On-site; USD 180,000 - 240,000; Full time

Job summary

HeyGen is hiring for a Video Agent role in San Francisco, on-site. You will design the agent's tools and prompts, improve planning and recovery from mistakes, and ship user-facing features in React with backend services in Python and Go.

You will work closely with product managers, researchers, and rendering teams to deliver end-to-end video agent capabilities. The role emphasizes building evals, running experiments, and owning features from ideation through launch and follow-up, with a focus on

Qualifications

• You have built and shipped an AI agent that real people use.
• You have built evals or test sets for model behavior and can distinguish real improvement from noise.

Responsibilities

• Build the agent. Design tools, prompts, and context to improve planning and recovery from mistakes.
• Measure quality. Build evals and offline replays of real sessions; run experiments behind feature flags.

Skills

AI agents

AI evaluation

TypeScript

React

Python

Go

AB testing

Feature flags

Tools

TypeScript

React

Python

Go

Job description

The Video Agent team builds a product that turns prompts, documents, and assets into finished videos. You’ll improve its agent behavior and quality measures, then ship features across the product’s React frontend and Python or Go backend.* Permanent* On-site* 2+ years* Degree not required### Skills and expertiseAI agentsAI evaluationTypeScriptReactPythonGoA/B testingfeature flags### Key responsibilities* Design the agent’s tools, prompts, and context to improve planning and recovery from mistakes.* Build evaluations, replay real sessions, and run experiments to measure agent quality.* Ship user-facing React features and backend services or workflows in Python and Go.## How this job comparesCompared with 329 open mid-level machine learning jobs on October 10, 2026.Pay: This job pays $180K to $240K a year. The 119 open mid-level machine learning jobs that publish US pay start at $180K on average, so this job starts in line with them.Similar open jobs: We Love AI Jobs lists 329 open mid-level machine learning jobs at 145 companies.Remote work: This job is on site. 66 of the 329 mid-level machine learning jobs (20%) are remote.AI in this role: High. AI is the core of the work: building, training or deploying AI systems. The core product is a multi-step AI agent, and the role directly improves its planning, tools, and behavior. The posting also says engineers work directly with HeyGen’s in-house models and build evaluations of agent performance.## Full descriptionAbout HeyGenAt HeyGen, our mission is to make visual storytelling accessible to all. Over the last decade, visual content has become the preferred method of information creation, consumption, and retention. But the ability to create such content, in particular videos, continues to be costly and challenging to scale. Our ambition is to build technology that equips more people with the power to reach, captivate, and inspire audiences.Learn more at www.heygen.com. Visit our Mission and Culture doc here.About the Video Agent teamVideo Agent turns a prompt, a document, or a handful of assets into a finished video. Behind a simple chat box sits a multi-step AI agent. It plans a storyboard, writes the script, chooses avatars, voices, and visuals, calls many tools along the way, and hands the result to our rendering pipeline. Customers use it every day to make training videos, product explainers, marketing content, and more.We are a small team that owns the agent end to end. That covers the prompts and tools the agent uses, the backend services that run it, and the product screens where people chat with it and edit what it makes.This is not a role where you only call someone else’s model through an API. HeyGen trains its own models in house, and the agent is built on top of them. You will work directly with those models and with the researchers who build them, which is an experience few applied AI roles offer.About the roleYou will make Video Agent better at doing what the user actually asked for, and you will prove it with data. Some weeks that means redesigning a tool the agent calls. Other weeks it means building an eval, running an A/B test, or shipping a new editing experience in React. You will own features from the first idea through launch and follow-up, and you will decide which problems belong to the model and which belong to plain, deterministic code.What you’ll do• Build the agent. Design the tools, prompts, and context the agent works with. Improve how it plans, how it recovers from mistakes, and how it handles long, multi-turn conversations.• Measure quality. Build evals and offline replays of real sessions. Run experiments behind feature flags and read the results honestly. Watch real user sessions and agent traces to find where things go wrong.• Ship across the stack. Build user-facing features in TypeScript and React. Build backend services and long-running workflows in Python and Go.• Work closely with others. Partner with product managers, designers, and the research and rendering teams that the agent depends on.What we’re looking for• You have built and shipped an AI agent that real people use. We mean a system where a model calls tools, plans across several steps, and acts on the results. A chat wrapper or a prompt demo is not enough on its own. We want to hear what broke in production and how you fixed it.• You know how to tell whether an AI system got better. You have built evals or test sets for model behavior. You can tell a real improvement from noise, and you are skeptical of results that look too good.• You are a strong full-stack engineer. You have 2 or more years of professional experience. You are fluent in TypeScript and React on the frontend and Python on the backend.• You have strong product sense. You use what you build, you care how it feels, and you look at how customers actually use it.• You take ownership. You do not wait for a spec. You find the most important problem, fix it, and tell people what changed.A degree in computer science or a related field is welcome but not required. Equivalent experience counts.Nice to have• You have fine-tuned models before.• You have worked on code-to-video models, which generate video by writing code such as HTML or animation scripts.• You have worked on video agent models in general.Show us an agent you’ve builtWith your application, please include a short note (a few sentences is fine) about an agent you have built. Tell us what it does, how you measured whether it worked, and one failure you found and fixed. A link to code, a demo, or a write-up is a bonus.