soul.md

A soul.md file is a project-specific context document populated with raw meeting transcripts and other source material, intended to serve as an exhaustive source of truth about a project's goals, language, and decisions — functioning as an alternative to mood boards or high-level notes summaries.

Concept and Purpose

Eve Bouffard (YC's Head of Design) describes creating a soul.md by recording all project meetings and dumping the full transcripts into a single file, rather than distilling them into curated notes or takeaways. The key design decision is to preserve raw fidelity: "I wanted to treat that soul.md file as the source of truth and exhaustive glossary of this project." This makes it an explicit alternative to a mood board — prioritizing verbal, contextual, and conceptual richness over visual or summary-level references.

Role in Agent-Driven Development

Bouffard positions soul.md within a broader philosophy of context maximalism for agents: "capturing as much information as possible and sharing that information with your agent is the best way to build software moving forward." The file is fed directly to an AI agent so it can operate with deep project knowledge rather than relying on sparse, high-level prompts.

A key claimed benefit is emergent quality: when an agent is given this level of rich context, it produces outputs that go beyond what the designer explicitly specified — "when you unlock so much information for your agent, your agent knows so much that when you're going to give it full reign it's going to surprise you." The implication is that designers who invest in thorough context documents get back unexpected, valuable design details and ideas they would not have generated themselves.

Summary of Advocated Practice

Step	Practice
Input	Record all project meetings
Processing	Dump full transcripts (not summaries) into soul.md
Usage	Treat file as authoritative project glossary; share with agent
Expected output	Agent surprises designer with contextually grounded details