Founding Product Engineer (Accel/Index)

About the Company

Day One Partners is a search firm that partners with venture capital firms to help build high-growth startups. We lead confidential searches for leadership and critical roles across a range of company stages, industries, and functions.

About the Role

We’re hiring a Founding Product Engineer to join a recently emerged-from-stealth company rethinking workplace communication for the AI-agent era. Founded by a 2x founder and Thiel Fellow, the company has raised a $20M seed round led by Accel and Index.

You’ll join a small engineering team and have meaningful ownership over what gets built, how it gets built, and how the product reaches users. This is a role for someone who wants to make consequential product and architecture decisions, ship quickly, and help set the bar for an engineering organization from its earliest days.

You will work closely with the founder and early team, own major areas end to end, and help shape the company’s product direction, technical foundations, recruiting, and culture.

What We’re Building

We’re building a new messaging platform designed for humans and AI agents to work together.

Rather than bolting AI onto Slack or email, we’re designing communication around persistent context, durable memory, proactive agents, and the ability for agents to take action across tools and workflows.

That means solving hard problems across real-time messaging, persistent memory and retrieval, proactive agent orchestration, tool use, sandboxed execution, and developer infrastructure. The goal is software that feels fast, dependable, and genuinely useful enough to become part of how teams work every day.

Responsibilities

• Architect and ship core messaging infrastructure that is fast, reliable, and delightful to use.
• Build state-of-the-art memory and retrieval systems for persistent human–agent collaboration.
• Design and develop a proactive agent orchestration layer.
• Build the MCP/API, agent developer platform, and sandbox infrastructure used by outside developers.
• Experiment with tool use and new interaction patterns for humans and AI agents working together.
• Make foundational product and architecture decisions as an early member of the engineering team.
• Raise the bar for engineering craft, contribute to recruiting, and help shape the engineering culture.
• Dogfood the product every day and turn firsthand insights into product improvements.

Qualifications

• 3+ years of professional software engineering experience, with at least 1 year in a senior IC role.
• Proven experience building or scaling AI-powered applications.
• Ability to move fast without compromising quality.
• Strong product sense and attention to the small details that make great software exceptional.

Preferred Skills

• Love the messy beauty of early stage building and want those late nights with a small team you’ll remember years later.
• Crave the dopamine of shipping product that reaches hundreds of thousands of users — not slow-moving enterprise deployments.
• Want to do the best work of your life alongside people who push you to be better — and help build that team, too.
• We deeply care about how AI shapes our work.

Compensation and Work Policy

Competitive salary and meaningful founding-stage equity, flexible medical benefits, and health/wellness perks. This is a high-ownership environment with ambitious standards, but not a 996 culture.

About the Hiring Process

• 30 min intro call
• Technical conversation - walk us through an app you've shipped
• Paid take-home or IRL work trial

Equal Opportunity Statement

Day One Partners is committed to fostering a diverse and inclusive environment. All qualified applicants will receive consideration for opportunities without regard to race, color, religion, gender, gender identity or expression, sexual orientation, national origin, genetics, disability, age, or veteran status.