Senior UI/UX Designer - Prototyping

Obsidian; San Francisco (CA); On-site; USD 180,000 - 230,000; Full time

Job summary

Cincinnatus LLC is seeking a senior product designer with exceptional taste to shape how AI models design for the web and games. You’ll build high-quality prototypes and work closely with researchers to define great UI/UX patterns.

The role requires 7+ years of experience, strong prototyping skills in code or AI tools, and the ability to dedicate 40 hours per week. This is a full-time W-2 engagement with potential placement at a leading AI lab.

Qualifications

• 7+ years of experience as a product designer or design lead.
• Hands-on prototyping in code (HTML, CSS, JavaScript, React, Tailwind) or AI tools.
• Strong grounding in user-centered design and rapid prototyping.
• Senior-level design judgment and ability to set direction.
• Ability to engage reliably for 40 hours/week.
• Clear written communication and constructive feedback.

Responsibilities

• Partner with AI researchers to define UI/UX principles and rubrics.
• Build polished, interactive web prototypes in code or with AI-native tools.
• Provide actionable feedback on layout, hierarchy, interactions, and polish.
• Explore varied visual styles and animation approaches for different products.
• Collaborate with designers and researchers to raise quality standards.

Skills

UI/UX design

Prototyping

React

Tailwind

HTML/CSS/JS

AI-native prototyping tools

Tools

Cursor

v0

Lovable

Bolt

Framer

Job description

Help a leading AI lab define what great design looks like, and build the prototypes that prove it.

1. Overview

A leading AI lab is looking for senior product designers and design-minded engineers with exceptional taste to help shape how its AI models design and build for the web and for games. You'll work directly with the lab's researchers to define what "great" looks like in UI and UX, and you'll build high-quality prototypes that show it. If you care deeply about great interfaces, like to prototype in code or with AI tools, and can explain why one design works better than another, this role is for you. This is a full-time commitment of 40 hours per week.

This is a W-2 employment position with Cincinnatus LLC, with the opportunity to be placed at a leading AI lab as part of their extended workforce.

2. Key Responsibilities

• Partner with AI researchers to identify best-in-class UI and UX patterns, and turn them into clear principles and rubrics that define what great design looks like.

• Build polished, interactive web prototypes, in code or with AI-native tools such as Cursor, v0, Lovable or Bolt, that showcase strong and diverse design patterns across many product categories.

• Review AI-generated interfaces and prototypes, and give specific, actionable written feedback on layout, hierarchy, interaction, motion and visual polish.

• Explore a wide range of visual styles, frameworks and animation approaches, from focused productivity tools to playful consumer apps and games.

• Collaborate with other designers and researchers to keep standards consistent and keep raising the quality bar.

3. Core Qualifications

• 7+ years of experience as a product designer, design lead, design engineer, or creative front-end engineer at a product- or design-led company (for example Apple, Airbnb, Stripe, Figma, Linear, Spotify or Notion) or a top design agency.

• Hands-on prototyping skills: you build working web prototypes yourself, in code (HTML, CSS, JavaScript, React, Tailwind) or with AI-native tools (Cursor, v0, Lovable, Bolt, Framer).

• A strong grounding in user-centered design, interaction design and rapid prototyping.

• Senior-level design judgment, and the confidence to set direction and explain clearly why a design works.

• Ability to engage reliably for 40 hours/week during weekdays.

• Clear written communication and the ability to give precise, constructive design feedback.

Nice to have: Fluency with motion and animation (Framer Motion, GSAP, Rive, Lottie, After Effects) or 3D and WebGL, and game design experience in 2D or 3D. You don't need all of these to apply.

About Cincinnatus LLC:Cincinnatus LLC is an enterprise staffing company that partners with leading technology companies to source and employ highly skilled professionals for contingent and contract-based opportunities. Cincinnatus serves as the employer of record for these engagements, providing W-2 employment, payroll, benefits, and compliance, while placing employees directly within client teams to work on high-impact initiatives.

Equal Employment Opportunity:Cincinnatus is proud to be an Equal Employment Opportunity employer. We do not discriminate based upon race, religion, color, national origin, sex (including pregnancy, childbirth, reproductive health decisions, or related medical conditions), sexual orientation, gender identity, gender expression, age, status as a protected veteran, status as an individual with a disability, genetic information, political views or activity, or any other legally protected characteristic.