Senior Product Engineer, AI Startup, San Francisco (On-Site)

Urgent hire. Senior frontend-primary engineer owning the full product surface of an autonomous AI assistant that integrates with Slack, Gmail, and Linear. Early-stage team of 20, working directly with the founding team. 5 days a week on-site in San Francisco. Full-time.

What you’ll own

• Frontend architecture across the product: React, Next.js, TypeScript, TanStack Query. You set the patterns, not inherit them.

• Complex, high-performance UI: multiplayer surfaces, large-data views, streaming and real-time interfaces under production load.

• Full-stack feature ownership end to end: API routes, database migrations, UI, and analytics, without waiting for a backend engineer to unblock you.

• State management and rendering optimization at scale. You can explain your caching, invalidation, and optimistic-update strategy unprompted.

• Product decisions on rough ideas: you take a direction with no PRD and ship a working first version, then iterate.

Required

• Deep production expertise in React, Next.js, and TypeScript. Frontend is your strongest craft, not a secondary skill. Can describe specific rendering optimization decisions made in a real shipped product.

• Background at an AI-native company (core product is AI, not AI features bolted on) or an elite startup of Notion or Linear calibre. Can name what you personally owned there.

• Shipped and owned a complex web product in production: multiplayer, large-data, streaming, or real-time UI, with specific scaling decisions you made and can describe.

• Owns full-stack features end to end: API routes, database migrations, UI, and analytics. Not blocked by the absence of a dedicated backend engineer.

• Publicly inspectable evidence of shipped work before submission: a personal site, a shipped product with real users, a substantial public repository, or a named contribution to a real design system. No portfolio means no submission.

• Based in San Francisco or genuinely open to relocating before the start date for 5-days-a-week on-site work.

• Open to a one-week paid in-person trial assessment as part of the process. Roughly 70% of trial candidates convert to full-time.

Visa and relocation (screened before any technical step)

European candidates are welcome if genuinely open to relocating to San Francisco. Work authorization and sponsorship need are reported per candidate and assessed individually. Visa risk, travel constraints, and San Francisco cost of living are discussed explicitly before technical interviews. Relocation cases include an additional interview with the Europe-based CTO. Accommodation and flights are covered for the trial if relocating.

Disqualifiers:

• Unwilling to work on-site 5 days a week in San Francisco.

• Unwilling to complete the one-week trial assessment.

• No senior frontend architecture depth: a hybrid design/UI profile without strict senior engineering capability.

• No startup experience anywhere in the career: entire career in big tech, enterprise, or consultancy.

• Needs structured PRDs or Figma files before starting development.

• Has not tried the product before interviewing. On the sister search, not having tried it was an instant rejection.

Strong plus

• Founded a company, or was a founding or first-five engineer at an AI agent or AI tooling startup.

• Daily use of Claude Code, Cursor, or Windsurf. Has built AI side projects or worked with Vercel AI SDK, agent runtimes, or MCP servers.

• Experience building local-first clients with TanStack Query and IndexedDB.

• Europe-based and open to relocating. Both founders are European and the only candidate to reach the paid trial on the sister search came from this pool.