Senior Staff AI Engineer

SonicJobs; San Francisco (CA); On-site; USD 150,000 - 200,000; Full time

Job summary

SonicJobs is searching for a Senior Staff AI Engineer to lead architecture and training for web-native AI agents. This impactful role involves fine-tuning LLMs, mentoring colleagues, and shaping the future of job application technology. Join a focused, ambitious team committed to redefining job platforms.

Benefits

Onsite work in a focused team

Ownership in a frontier space

Smart, ambitious tech team

Qualifications

• Strong ML background — PhD or equivalent.
• Experience fine-tuning LLMs.
• Deep understanding of applied Reinforcement Learning.

Responsibilities

• Fine-tune foundation models for web-use.
• Design and run reinforcement learning systems.
• Own the full agent stack from policy models to frameworks.

Skills

Reinforcement Learning

Machine Learning

Python

Education

PhD in AI, ML, Computer Science or equivalent experience

Job description

At SonicJobs, we’re building the next generation of autonomous web agents based on computer-use technologies. Our agents operate on job application flows, similar to how candidates do. If you’ve ever dreamed of building AI that actually uses a website, this is your moment.

We’re a small, tight-knit team with big ambitions, leveraging cutting-edge tools to build agents that understand and control web environments end-to-end.

We move fast, avoid unnecessary hierarchy, and aim high. We’re not automating job applications — we’re redefining how job applications work to help candidates find the opportunities they deserve.

We are backed by top VC firms and serve over a hundred corporate clients, including several Fortune 500 companies.

About the role

We’re looking for an AI expert to own the architecture, training, and evolution of our AI agent stack. As a Senior Staff AI Engineer, you’ll be responsible for fine-tuning LLMs that support web-native agents capable of learning, adapting, and thriving in complex job application flows.

This is a demanding, high-impact role. You’ll be shipping code, training models, designing experiments, and shaping our strategy. You’ll report to the CTO. If you’re excited about coding, reviewing training runs, and designing new RL environments, you’ll thrive here. You’ll also mentor colleagues to elevate their agentic skills.

What you'll do

• Fine-tune foundation models for web-use using techniques like LoRA, PEFT, DPO, RLHF, and others based on your judgment.
• Design and run reinforcement learning systems to enhance agent reasoning and performance.
• Own the full agent stack: from policy models to interface planning and simulation frameworks.
• Prototype quickly, test aggressively, and push the limits of what agents can do.
• Collaborate directly with the founding team on product direction and research priorities.
• Help grow a team of dedicated engineers and researchers.
• Create multi-agent flows with clear trajectories, role assignments, and memory management.

What you'll bring

• Strong ML background — PhD or equivalent experience in AI, ML, Computer Science, or industry experience.
• Experience fine-tuning LLMs.
• Deep understanding of applied Reinforcement Learning.
• Hands-on: enjoy coding, running experiments, and seeing tangible results.
• Ownership mentality: focused on building, not just managing.
• Experience in managing and growing teams.
• High-impact research or open-source contributions.
• Comfort working in a fast-paced startup environment.

What we offer

• Salary depends on experience.
• Onsite work with a focused, no-nonsense team.
• Ownership and shaping a frontier space.
• Smart, ambitious tech team without corporate nonsense.

Sounds like you?

Let’s talk. This isn’t just a job — it’s a chance to lead the future of job platform technology.

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Senior Engineer AI • San Francisco, CA, United States