Brains

A brain is a named snapshot of soul + persona + rules. Instead of switching three things separately, save your setup once and activate it in one command.

Saving a brain

Set up the configuration you want, then snapshot it:

brainjar soul use craftsman
brainjar persona use reviewer
brainjar rules add boundaries
brainjar rules add security
brainjar brain save review

Activating a brain

brainjar brain use review

This activates the soul, persona, and all rules from the snapshot in one shot.

Managing brains

brainjar brain list          # See available brains
brainjar brain show review   # Inspect a brain's config
brainjar brain drop review   # Deactivate a brain (clears soul, persona, rules)
brainjar brain delete review # Permanently delete a brain

Brain vs. individual layers

Approach	When to use
Brain	Repeatable workflow you do often (code review, design, debugging)
Individual layers	Exploratory work, one-off overrides, or changing one thing

Brains and compose

Brains are the primary input to compose, which assembles a full prompt for subagent dispatch:

mcp__brainjar__compose(brain="review", task="Review the changes in src/sync.ts")

This returns the complete prompt (soul + persona + rules + task) ready to pass to Claude Code’s Agent tool. See Subagent Orchestration for compose basics and Orchestration Patterns for multi-agent workflow patterns.