Software Engineer, Platform

About this role

About Sim
Sim is the open-source platform to build, deploy, and orchestrate AI agents. Over 70,000 developers — from early-stage startups to the U.S. Department of Defense — use Sim to turn ideas into production-grade agentic workflows on a visual, Figma-like canvas. We connect to 1,000+ apps and LLMs, and our Copilot is the state of the art for building workflows with natural language.


We're a team of 5, YC X25, and backed by a $7M Series A led by Standard Capital with participation from Paul Graham, Perplexity, SV Angel, and Y Combinator. We're based in San Francisco and build in person every day.


Our mission is simple: agents will run the world, and Sim is the primary means by which that happens.


About The Role
You'll lead the Sim platform: the visual, end-to-end agent builder that tens of thousands of developers use every day. You'll own the front-end architecture, the real-time canvas, and the systems that turn visual flows into reliable, production agents.


Sim has been called the "Figma for AI agents" — an intuitive drag-and-drop canvas where developers connect LLMs, tools, APIs, and logic blocks into complex agentic workflows. Your job is to make this experience fast, delightful, and powerful enough that developers never want to go back to writing agents in code.


This is a foundational role. You'll define the front-end architecture, set performance standards, and shape the developer ergonomics of a product used by 70,000+ builders. On a team of 5, you own the entire surface area that developers interact with.


What You'll Do

• Own the Sim visual canvas — the real-time, drag-and-drop workflow editor at the heart of the product
• Architect and build the front-end systems that render, connect, and manage complex agent workflows
• Design the interaction model for how developers create, test, debug, and deploy agents visually
• Build the bridge between visual flows and the underlying execution engine — ensuring wha...