Butter YC Application

Winter 2025Active

Butter went through Y Combinator in the Winter 2025 batch as a B2B company. Below: what the company does, who founded it, and its application to YC, reconstructed question by question in the real YC form.

YC batch: Winter 2025
Industry: B2BInfrastructure
Team size: 2
Status: Active
Launched: 2025

Founders

Erik DuntemanFounder

What Butter does

Butter is building bVisor, an incredibly lightweight sandbox runtime for AI agents. It embeds directly into your local process, providing a safe bash environment without the overhead of VMs or remote infra.

Butter's YC application, reconstructed

Y Combinator application

Butter, Winter 2025 batch. The real form questions, answered from public data.

Founders2
Company7
Progress7
Idea4
Equity3
Curious2
Batch Preference1

Company

Company name

Butter

Describe what your company does in 50 characters or less.

Embedded Sandboxes for Agents

What is your company going to make? Please describe your product and what it does or will do.

We are building bVisor, a lightweight sandbox runtime for AI agents that runs embedded directly inside a local process. It provides a safe bash environment without the overhead of virtual machines or remote infrastructure, making it fast, efficient, and secure for developers building AI tools.

Where do you live now, and where would the company be based after YC?

We live in San Francisco, and the company will remain based here after YC.

Explain your decision regarding location.

San Francisco is where we live and have access to the ecosystem we need for building and scaling Butter. Being here helps with hiring and connections critical for a B2B infrastructure company focused on AI tooling.

21 more answers in the full application

Founders, Progress, Idea, Equity, Curious, Batch Preference are in the full version. Create a free account to open it in YC Insights, next to every other YC batch.

See full application

Frequently Asked Questions

Is this the real Butter YC application?

No. Y Combinator keeps submitted applications private. This is a reconstruction: the real YC form questions, answered from Butter's public data (launch notes, founder backgrounds, product description). It shows how a company like Butter would present itself to YC, not the text they submitted.