big-brain 🧠

A second brain for you and your AI assistants. Plain-markdown notes, projects, and tasks — Obsidian-compatible, owned by you, readable and writable by any LLM through the Model Context Protocol.

Your AI tools each keep their own memory of you, siloed and invisible. big-brain inverts that: one knowledge vault you own, that every assistant reads and writes. Claude Code, Claude Desktop, ChatGPT, Cursor — they all see the same projects, the same tasks, the same notes. Switch models freely; your context comes with you.

• Plain markdown files. No database, no lock-in. Open the vault in Obsidian, grep it, put it in git.

• MCP server with 22 tools: search, capture, daily logs, project and task management, link graph, related notes, vault health.

• CLI for humans: big-brain status, big-brain capture, big-brain tasks.

• Claude Code skills — /brain, /capture, /weekly — installed with one command.

• Projects as the unit of work — each is one file with a goal, checkbox tasks, and a running log.

• Deterministic retrieval first: full-text search (fuzzy, title-boosted), [[wikilink]] graph with backlinks, tags, frontmatter queries. No API keys, works offline.

• Optional local hybrid search: flip embeddings.enabled and a small on-device model (via @huggingface/transformers) adds semantic matching, fused with full-text by Reciprocal Rank Fusion — paraphrases match, exact identifiers still win, and nothing leaves your machine. Powers related_notes similarity too. See docs/vault-spec.md.

• Optional git auto-commit + push — flip a config flag and every write, from any tool, is committed and pushed automatically, so saves never sit uncommitted and your other machines stay in sync. Best-effort: a git failure never blocks a save.

Requires Node 20+.

Install

big-brain isn't on npm yet, so install from source (one-time):

git clone https://github.com/jzhao234/big-brain.git
cd big-brain
npm install
npm run build
npm link          # puts `big-brain` and `big-brain-mcp` on your PATH

npm link skips -g install quirks and lets you git pull && npm run build to update later. (Once published, this becomes npm i -g big-brain.)

Related MCP server: Obsidian MCP Server

Quickstart

big-brain init ~/brain --name "My Brain"   # scaffold a vault
cd ~/brain
big-brain status                           # look around
big-brain install-skills                   # add the /brain, /capture, /weekly skills

Then connect an AI tool (below) and, optionally, seed the vault from your existing AI history.

Connect your AI tools

The MCP server is the same everywhere: command big-brain-mcp, vault chosen by --vault <dir> or the BIG_BRAIN_VAULT env var.

Claude Code

claude mcp add --scope user big-brain -- big-brain-mcp --vault ~/brain
claude mcp list        # expect: big-brain ... ✔ Connected

Claude Desktop / Cursor / other MCP clients — add to the MCP config (e.g. claude_desktop_config.json). Use an absolute command path: GUI apps are launched without your shell's PATH, so a bare big-brain-mcp may not resolve (run which big-brain-mcp to get it).

{
  "mcpServers": {
    "big-brain": {
      "command": "/absolute/path/to/big-brain-mcp",
      "args": ["--vault", "/absolute/path/to/brain"]
    }
  }
}

ChatGPT and other MCP clients — any client that speaks MCP over stdio works the same way. For clients without MCP, the CLI's --json output makes the vault scriptable.

Browser (claude.ai / ChatGPT) — cloud AIs can't launch a local stdio server. The zero-infra option is to connect them to your vault's GitHub repo and let them read/write the markdown directly (you lose the computed overview/search/task tools — it's raw file access). See docs/browser-github-connector.md and paste prompts/browser-github-instructions.md.

Then teach the assistant how to use the vault: Claude Code reads the vault's CLAUDE.md automatically; for other tools, paste prompts/agent-instructions.md into their custom instructions.

Using it: load and save

The whole point is that you never re-feed context. The assistant loads a small, relevant slice on demand and saves small pieces as you work — you just talk to it.

Load — orient at the start, pull details as needed:

Save — as decisions, progress, and ideas happen (append-first; never destructive):

Review — /weekly runs a guided pass: triage the inbox, prune projects, reschedule overdue tasks, fix broken links, and consolidate — big-brain doctor flags bloated notes and near-duplicates, and the review proposes splits/merges/stale-fact pruning for your approval. Capture and search keep a brain useful; consolidation keeps it trustworthy.

Skills (Claude Code)

Three Claude Code skills wrap the tools into slash-commands:

• /brain — load the overview and switch into brain-aware mode for the session

• /capture — zero-friction capture to the inbox

• /weekly — a guided weekly review

big-brain install-skills          # add them to ~/.claude/skills (skips existing)
big-brain install-skills --force  # overwrite existing versions

They're path-agnostic — they call the big-brain CLI / MCP tools and resolve the vault from BIG_BRAIN_VAULT (or --vault), so the same skill works on every machine. Restart Claude Code to pick them up.

Use it on multiple machines

The vault is a git repo, so this is just git: clone it on each machine, and each machine runs its own big-brain-mcp against its own clone. Git keeps them in sync.

• Write side — automatic. Set git.autoCommit (and git.autoPush) in brain.config.json and every write — from any tool, any machine — is committed and pushed. See docs/vault-spec.md.

• Read side — pull before you start. Add a SessionStart hook so a session always opens on the latest:

  // ~/.claude/settings.json
  "hooks": { "SessionStart": [ { "hooks": [ { "type": "command",
    "command": "git -C \"$HOME/brain\" pull --ff-only --quiet 2>/dev/null || true" } ] } ] }

  --ff-only means a pull never clobbers local work. (Or just git -C ~/brain pull by hand.)

On a fresh machine: install big-brain (above), git clone your vault, big-brain install-skills, register the MCP server. Four commands and you're identical to your other machines.

Seed it from your existing AI history

An empty brain is useless; the fastest way to a useful one is extracting what your LLMs already know about you. Every assistant you've used heavily — ChatGPT, Claude, Gemini — has months of context about your projects, preferences, and goals sitting in its memory and chat history. Seeding pulls that out, once, into files you own.

1. Run the seed interview in each LLM you use. Copy the prompt from prompts/seed-interview.md into each assistant — ideally the account with the most history, with memory/personalization enabled. It's a structured export interview: profile, current projects, stack, how you like to work with AI, goals, people, routines, standing constraints, open loops, and blind spots. It instructs the model to be concrete, mark inferences (inferred), and write "No data" instead of inventing — so the output is honest enough to build on.

2. Save each output into the vault's inbox/ as one file per model (inbox/seed-chatgpt.md, inbox/seed-claude.md, …). Don't organize anything yet — capture first is the whole inbox philosophy.

3. Triage. Ask a vault-connected assistant to run the process-inbox MCP prompt (or just say "triage my inbox" / run /weekly in Claude Code). It merges duplicates across models — different LLMs know different slices of you, and they mostly complement rather than conflict — then turns the material into real structure: projects with tasks for everything in flight, people/ notes, a preferences note your agent instructions can point at, reference notes for your stack/setup, and open loops as tasks. You confirm per item; raw exports can be kept in archive/ for provenance.

4. Repeat occasionally. Models keep accumulating context about you — re-running the interview every few months and triaging the diff keeps the vault ahead of any one provider's memory.

Two more seeding paths worth knowing: if you already keep an Obsidian vault, big-brain can adopt it in place (add a brain.config.json, map your folder names via the folders config — see docs/vault-spec.md); and a work session with a vault-connected agent seeds as a side effect — the agent instructions tell it to create projects and capture facts as you work, so the brain fills in from real activity even if you skip the interview.

The vault

brain/
├── BRAIN.md          # index & ground rules
├── CLAUDE.md         # agent instructions (picked up by Claude Code)
├── brain.config.json
├── inbox/            # capture now, organize later
├── daily/            # one note per day: focus, log, tasks
├── projects/         # one file per project: goal, tasks, log
├── areas/            # ongoing responsibilities
├── notes/            # evergreen knowledge, densely [[linked]]
├── people/           # one note per person
├── reference/        # external facts, docs, how-tos
├── archive/          # nothing is deleted, only archived
└── templates/        # daily/project/note/person templates

Notes are markdown + YAML frontmatter (type, tags, status, due…). Tasks are - [ ] checkboxes with Obsidian Tasks-style metadata: 📅 2026-03-01 due, ⏫ priority, ✅ done-date. Full details in docs/vault-spec.md.

MCP tools

Plus three MCP prompts: orient, weekly-review, process-inbox.

CLI

big-brain init [dir]            scaffold a vault        big-brain tasks [--project X]
big-brain status                overview                big-brain task add|done ...
big-brain search <query>        search (hybrid if on)   big-brain projects [--status active]
big-brain show <note>           print a note            big-brain project new|status ...
big-brain new <title>           create a note           big-brain links <note>
big-brain related <note>        related notes + why     big-brain tags
big-brain capture <text>        quick capture           big-brain doctor
big-brain daily [--log "..."]   daily note / journal    big-brain index [--status|--rebuild]
big-brain install-skills        add Claude Code skills  big-brain mcp   run the MCP server

Every list command takes --json for scripting.

Design principles

1. Files over databases. Markdown you can read in 30 years beats any app.

2. The human owns the vault; agents are guests. Agents append and capture freely, but rewriting and archiving are deliberate acts.

3. Deterministic beats clever. Search + links + tags retrieves reliably and works offline; the semantic layer is opt-in, fully local, and fused with — never a replacement for — exact search.

4. Model-agnostic by construction. Everything goes through MCP or the filesystem — nothing assumes a particular AI vendor.

Development

npm install
npm run typecheck && npm run lint && npm test
npm run build

MIT © Junhao Zhao