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Personality & Voice Definition

Headmaster lets you define the agent’s personality, tone, and voice through a personality file — a Markdown document that sits at the top of the system prompt and shapes every response.

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What it is

The personality file (called SOUL.md in the runtime) is a Markdown document that defines:
  • Basic identity — who the agent is, what it does.
  • How to talk — tone, style, vocabulary, sentence structure.
  • Rules — what to never do, what to always do.
  • Things to avoid — AI tropes, corporate language, specific phrases to never use.
  • The point — the core philosophy of how the agent should behave.
The personality file is injected as slot #1 in the system prompt — it’s the first thing the agent sees, before memory, before skills, before your message. It shapes every response.

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Editing the personality file

1

Open Personality settings

Go to Settings → My Headmaster → Profile → Personality.
2

Edit the Markdown

Write your personality definition. Save.
The change applies to the next conversation. Existing conversations keep their original personality.

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What to put in it

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Basic identity

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How to talk

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Rules

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Things to never do

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The point

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The system prompt stack

The personality file is the broadest layer — it applies to everything. Specialist rules narrow it for a specific role.

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Multiple personalities with profiles

If you have multiple profiles, each can have its own personality file:
  • Work profile — professional, concise personality.
  • Personal profile — casual, friendly personality.
  • Research profile — academic, thorough personality.
Switch profiles to switch personalities. See Profiles.

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Context files

In addition to the personality file, Headmaster supports project-level context files that the agent reads at the start of every conversation in that project:
If your project folder has an AGENTS.md file, the agent reads it at the start of every conversation.
If your project folder has a CLAUDE.md file, the agent also reads it. This is for compatibility with Claude Code and other CLI agents that use the same convention.
The agent also recognizes:
  • .cursorrules — Cursor AI rules.
  • Any file specified in the runtime config under context_files.
These are injected into the system prompt alongside the personality file and memory.

Specialists

Configure specialist-level rules that narrow the global personality.

Profiles

Give each profile its own personality.