Open Second Brain: memory tool for Hermes Agent

Local-first Hermes Agent memory in an Obsidian vault, with nightly dream passes that learn preferences

What Open Second Brain does

Open Second Brain keeps agent memory as plain Markdown files under a Brain/ folder in an Obsidian vault, so you can open, edit, grep and version it like any other note. Agents reach it through two MCP servers, lifecycle hooks and the o2b CLI. Learning follows a loop: an agent sends feedback as a signal in Brain/inbox/, a dream pass converts repeated signals into preference rules, rules are rendered into Brain/active.md, and that file is read at the start of the next session.

The dream pass is deterministic and runs no model, and applied or violated evidence confirms, quarantines or retires rules. A rebuildable SQLite index handles search, and your own notes are read but written only at a path the caller names. Hermes Agent is supported as a plugin and memory provider. Other clients include Claude Code, Codex, OpenClaw, opencode, Grok Build, Cursor, kiro, GitHub Copilot CLI and Gemini CLI, with an MCP server for anything else.

Key features

Markdown memory under Brain/ in an Obsidian vault
Two MCP servers, lifecycle hooks and the o2b CLI
A deterministic dream pass that turns repeated signals into rules and retires unused ones
Brain/active.md rendered for the next session
A rebuildable SQLite search index
Hermes plugin and memory provider, plus Claude Code, Codex, OpenClaw and more

When to use it

Stop repeating the same correction to an agent every session
Share one memory vault between Hermes Agent and another coding agent
Review and edit what the agent has learned as ordinary notes

Who it is for: Obsidian users who run Hermes Agent and want its memory stored in Markdown they can read and edit.

How it fits with Hermes Agent

The repository describes itself as memory for Hermes Agent and lists Hermes Agent as a client with a plugin and memory provider, with its own guide at install/hermes.md.

How to install Open Second Brain

These commands are copied from the project's README. Check the repository for the latest steps before you run them.

o2b init --vault /path/to/vault --name "My Second Brain"
o2b brain init --vault /path/to/vault
o2b doctor --vault /path/to/vault
o2b install --check

Requirements: Bun 1.1 or later and a vault folder

FAQ

What is Open Second Brain?

Open Second Brain is a local-first memory layer for AI agents that lives in an Obsidian vault. Everything the agent learns is a Markdown file under Brain/, and a nightly dream pass turns repeated corrections into confirmed preferences.

Does Open Second Brain work with Hermes Agent?

Yes. Hermes Agent is a supported client, integrated as a plugin and memory provider, and the README links a dedicated guide at install/hermes.md.

How do I install Open Second Brain?

Install Bun 1.1 or later, install the plugin for your client, then run o2b init and o2b brain init against your vault path. Check the result with o2b doctor and o2b install --check.