Senior Software Engineer

Lightsprint (YC P26) is the collaborative product-development platform for the AI era. Think of the code-aware task board, the cloud coding agents, and the per-task preview environment as one system: every task on the board is a real agent session with its own environment, preview URL, and context.

AI made software engineering dramatically faster, and so the software design lifecycle, used in teams, is due an update. We believe human collaboration is here to stay: for taste, for ownership, for the simple fact that great products aren't made alone.

We're an early team, so this is a product engineer role. You'll talk to users, frame the problem, design the solution with us, and ship end-to-end, then watch the logs and usage data to see if it actually worked, and iterate. We dogfood relentlessly, and build Lightsprint with our own agents. We balance moving fast and reliability because the product is the infrastructure other teams ship on.

You'll employ the latest agentic tools to multiply your productivity. You'll build LLM brains, hillclimb multi-turn prompts, and turn non-deterministic agent behavior into interfaces people actually trust. We have hard technical problems, and genuinely novel product challenges: real-time multiplayer, an agent harness that orchestrates cloud coding agents, and a sandbox that spins up an isolated environment and live preview per task.

• 7+ years building and shipping production fullstack/web applications, at real scale or in fast 0-to-1 environments.
• Proven track record of driving complex, end-to-end features with visible product impact. You must have shipped something people actually use, and you must know your customer.
• Strong fundamentals in software engineering with experience across the stack: TypeScript, relational databases (e.g. Postgres), and real-time systems. Fluency in a modern frontend framework (Next.js, Svelte, or similar), and comfortable with modern DevOps (e.g. AWS, Vercel).
• Product sensibility and high ownership. You care about UX, performance, and polish; you push back when something doesn't feel right; you're comfortable shaping ambiguous problems without a roadmap handed to you.

• Experience in agent engineering: harnesses, tool-calling, evals, MCP, RAG, context management. Bonus if you actively build with coding agents and have opinions on how they should work.
• Experience designing real-time, multiplayer, or collaborative software: presence, live cursors/avatars, co-editing, contextual comments, shared state.
• Background in developer tools, work-management, or other complex B2B SaaS (Linear, Jira, Notion, Figma, Asana, Retool, and the like).
• Have owned product management or design, and shipped features where you held the PM hat, not just the engineering one.
• Track record of building platforms teams adopt: APIs, golden paths, migration playbooks, and guardrails that make systems easier to run.