Personality & SOUL.md: Give Your AI a Real Identity

In our last post, we talked about how Hermes Agent never forgets a conversation. But here’s a question: who exactly is Hermes when you talk to it? A generic assistant? A robot with no personality?

The answer is: that’s entirely up to you now.

Hermes Agent’s personality is fully customizable, and it all starts with a single file called SOUL.md. Think of it as your AI’s DNA — the core identity that shapes everything it says and does.

What Is SOUL.md?

SOUL.md is the primary identity of your Hermes Agent. It’s the very first thing loaded into the system prompt, sitting in slot #1 — the most important position. This file defines who the agent is before anything else happens.

By default, Hermes creates a starter SOUL.md for you automatically at:

~/.hermes/SOUL.md

If you run Hermes with a custom home directory, it uses that instead:

$HERMES_HOME/SOUL.md

Why This Design Matters

Here’s the clever part: Hermes only loads SOUL.md from your HERMES_HOME directory — never from your current working folder. Why does that matter?

Imagine you’re working on three different projects. If Hermes loaded personality from whatever folder you happened to be in, your AI’s personality could shift wildly between projects. One minute it’s a serious engineer, the next it’s a pirate captain — just because you changed directories.

By loading only from HERMES_HOME, your personality stays consistent. It belongs to the Hermes instance itself, not to any particular project.

What Should Go in SOUL.md?

Use SOUL.md for durable voice and personality guidance:

Tone and communication style
Level of directness
Default interaction style
What to avoid stylistically
How to handle uncertainty or disagreement

Don’t put project-specific stuff in there — no file paths, repo conventions, or temporary workflow details. Those belong in AGENTS.md (more on that in a moment).

Here’s a simple example of what a good SOUL.md looks like:

# Personality

You are a pragmatic senior engineer with strong taste.
You optimize for truth, clarity, and usefulness over politeness theater.

## Style
- Be direct without being cold
- Prefer substance over filler
- Push back when something is a bad idea
- Admit uncertainty plainly
- Keep explanations compact unless depth is useful

## What to avoid
- Sycophancy
- Hype language
- Repeating the user's framing if it's wrong
- Overexplaining obvious things

SOUL.md vs. AGENTS.md — The Golden Rule

This is the most important distinction to remember:

SOUL.md = identity, tone, style, communication defaults (follows you everywhere)
AGENTS.md = project architecture, coding conventions, repo workflows (belongs to a specific project)

A useful rule of thumb: if it should follow you everywhere, it belongs in SOUL.md. If it belongs to a project, it belongs in AGENTS.md.

SOUL.md vs. /personality

SOUL.md is your durable default personality. The /personality command is a session-level overlay — a temporary mode switch.

Think of it this way:

SOUL.md = your baseline voice
/personality = a temporary costume change

For example, you might keep a pragmatic default SOUL, then use /personality teacher when tutoring someone, or /personality creative for a brainstorming session.

Built-in Personalities

Hermes ships with several fun built-in personalities you can switch to anytime:

Name	Description
helpful	Friendly, general-purpose assistant
concise	Brief, to-the-point responses
technical	Detailed, accurate technical expert
creative	Innovative, outside-the-box thinking
teacher	Patient educator with clear examples
kawaii	Cute expressions, sparkles, and enthusiasm ★
pirate	Captain Hermes, tech-savvy buccaneer
noir	Hard-boiled detective narration
surfer	Totally chill bro vibes

Security First

One important note: SOUL.md goes through prompt-injection scanning before it’s used, just like other context files. So keep it focused on persona and voice — don’t try to sneak in strange meta-instructions. If the file is empty or can’t be loaded, Hermes gracefully falls back to its built-in default identity.

Ready to Give Your AI a Soul?

Editing SOUL.md is the simplest way to make Hermes truly yours. Open the file, write a personality you’d enjoy talking to, and save it. Your AI will remember who it is — every single conversation.

Next up: We’ll dive into how AGENTS.md helps your AI understand your projects. Stay tuned!