YC Root Access

Sim: The Visual, End-to-End Agent Builder

Sim is building the visual, end-to-end agent builder — a platform where developers can design, test, and deploy real AI agents that work in production. Founded by Emir Karabeg and Waleed Latif, Sim grew from a small San Francisco apartment to a community of 60,000 developers and 18,000 GitHub stars, recently raising a $7M Series A. In this interview with YC’s Aaron Epstein, Emir shares how they’re building the infrastructure for the agent era, and what it takes to create AI systems that reason, retrieve, and act safely at scale. Learn more about Sim at https://www.sim.ai. Chapters: 00:00 – Building the Visual Agent Builder 00:36 – What Sim Does and Why It Matters 02:05 – From a SF Apartment to 60,000 Developers 04:20 – Finding Early Users and Product-Market Fit 07:05 – Designing an End-to-End Platform for Agents 10:30 – Powering the Open Source Agent Ecosystem 13:25 – Raising a $7M Series A 16:20 – Building Agents That Actually Work 20:10 – The Infrastructure for the Agent Era 23:40 – Advice for Builders in AI

AEAaron EpsteinhostEKEmir Karabegguest

Nov 12, 2025·25m·Watch on YouTube ↗

📖 CHAPTERS

1. 1

   Sim.ai in one sentence: a Figma-like canvas to build AI agents

   Amir explains Sim as a visual, end-to-end agent builder: a canvas where you can drag-and-drop or use natural language prompts to assemble agentic workflows. The goal is to make building agents feel as intuitive as designing in Figma, while still being powerful enough for real automation.

2. 2

   Early traction: 60,000 cloud developers and rapid open-source growth

   The conversation opens with Sim’s current traction metrics and positioning. Amir highlights both cloud adoption and open-source momentum as core indicators of progress.

3. 3

   Founders’ origin story: meeting at Berkeley and the leap to SF

   Amir shares how he met co-founder Waleed through a Berkeley roommate connection and how their friendship became the foundation for the company. The turning point was a decisive call where Waleed quit his job and moved to San Francisco to build together.

4. 4

   The first startup idea (and YC reality check): personalized landing pages

   Before Sim, they pursued a dynamic landing page product tailored to individual visitors using browsing/CRM data. They struggled because they didn’t understand the sales/marketing customer deeply, and a YC interview exposed how unclear the product was.

5. 5

   The spark for Sim: internal pain building hundreds of agents

   While building the prior product, they ended up assembling many “agents” chained together—research, copy generation, image prompting, image generation, and page assembly. The complexity revealed that orchestration, reusability, and collaboration around agents was the real problem they cared about.

6. 6

   January prototype and conviction: combining Figma + notebooks for workflows

   Amir describes the early decision to prototype a Figma-like agent canvas, despite skepticism from Waleed. A five-day experiment turned into full commitment once Waleed joined, and they began building continuously without looking back.

7. 7

   Differentiation: making workflows truly AI-native (not old automation tools)

   Amir contrasts Sim with legacy workflow automation: Sim is designed for AI-first orchestration, including repeated agent runs, synthesis, and natural-language workflow creation. He argues workflows are a new programming paradigm as abstraction continues to rise (like Cursor for code generation).

8. 8

   Open-source strategy: philosophy, distribution, and community trust

   Sim’s open-source approach is both ideological and strategic: code is less defensible in an era of powerful models, and adoption/network effects matter more. Amir emphasizes developers value authenticity—being truly open source and engaging actively earns trust and contributions.

9. 9

   Getting to GitHub Trending: coordinated launches as a growth lever

   Amir explains that GitHub Trending was a major driver of star growth, and the team learned to plan launches around it. Coordinated bursts of attention across multiple platforms can push a repo onto Trending, triggering large daily star influxes.

10. 10

    Monetization path: converting open-source users into cloud customers

    Sim ties open-source interest to its hosted cloud product: the GitHub repo funnels users to Sim.ai for easier setup and managed execution. Growth in GitHub stars correlated strongly with new cloud users, and revenue comes from paid inference/convenience.

11. 11

    Operating cadence and product culture: shipping every two weeks

    The team maintains urgency by adhering to a launch calendar with a strict two-week release rhythm. Amir adopts the mindset that shipping is a schedule commitment, not a perfection milestone, extending the YC habit of frequent public launches post-batch.

12. 12

    Hiring profile and the ‘agent era’ infrastructure thesis

    Amir frames the future as an engineering challenge—bringing agent-building capability to more people, not just specialists. Sim looks for highly curious builders excited by AI’s trajectory, with strong drive and willingness to ship over narrow stack-specific expertise.

13. 13

    Founder lessons: long time horizons, sustainable intensity, and honest self-awareness

    Amir reflects on the shift from scrappy early days to building for a 10–15 year journey. He stresses compounding through consistent effort, maintaining health to sustain pace, and choosing work you’d still do in the hardest moments years later.