Senior Frontend Engineer

You’ll own the interface where clients work with their AI assistant, from onboarding through daily workflow. Today the product is built with a server-rendered HTMX + Flask approach; the team is splitting its internal and external portals, and the external experience is being rebuilt in React. A key part of this role is spearheading that migration - and the shift from a traditional software interface toward a human-plus-AI co-working workspace where users come in and actually finish the task, not just view data. This is an engineering role, not a design role: there is already a designer, and this person owns the frontend build.

What you’ll be doing

• Own the end-to-end experience users rely on, from onboarding through daily workflow
• Design interaction patterns that surface what the AI is doing and keep expert users in control
• Build responsive, performant interfaces on HTMX, Flask templates, and modern CSS/JS, and spearhead the external move to React
• Partner closely with the designer and backend engineers to turn complex workflows into something that feels simple
• Own performance, accessibility, and polish - details close deals

Tech stack: HTMX, Flask (Python), modern CSS/JS; external product migrating to React

• 5+ years product-facing frontend
• Strong HTML / CSS / JS fundamentals
• React (can lead HTMX to React migration)
• AI-native builder
• Hybrid: Philadelphia, New York, or DC
• Portfolio

Green Flags

• Coded pre-AI, so fundamentals are deep enough to pick up HTMX quickly, and now genuinely AI-native in how they build
• Early-stage team experience: collaborative, comfortable owning a piece end to end
• Understands the backend (Python) well enough to be effective, and translates design intent into polished frontend
• Simplifies complex workflows for users in a B2B setting, and can manage stakeholders (designer, backend, founder)
• Strong portfolio or side project, and real interest and opinions on human-AI co-working interfaces

Red Flags

• Purely B2C background with no complex-workflow or B2B experience
• Five years but purely IC at a large company, no 0-to-1 ownership, no compelling side project or portfolio
• Not genuinely AI-native in their building
• A product designer looking for a design role rather than an engineer who owns the build
• Cannot be based in or commute from Philadelphia, New York, or DC (remote-only is not a fit)

• Meaningful equity on the generous side, as an early hire
• Hybrid schedule with a real HQ for in-person collaboration
• Visa sponsorship (H-1B transfer / F-1 OPT)
• Spearhead a greenfield React rebuild and shape genuinely novel human-AI co-working interfaces

A seed-stage, AI-native startup building vertical AI for a high-stakes corner of the construction industry. The product pairs every client with an AI-powered assistant that compresses days of expert work into minutes - pulling scope from complex documents, managing back-and-forth, and generating polished output at a speed no individual could match. VC-backed, growing fast, with an aggressive plan to scale over the next year.

Founded 2023 · 11-50 people · Industry: Vertical AI / Construction Tech