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<img src="web/public/brainmdlogo.png" alt="brain.md" width="120" />

brain.md

A local-first second brain for you — and for your AI agents.

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What you get

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📝   Obsidian-compatible markdown	Wikilinks, embeds, callouts, math, mermaid, tasks, frontmatter, aliases. Open your existing Obsidian vault — it just works.
⚡   Live editor + preview	CodeMirror 6 with cursor-anchored scroll sync, autosave, instant tooltips, command palette, quick switcher.
🔍   Semantic search built in	Per-vault embedded vector store (pure JS, no external DB). Notes are chunked, embedded and indexed on every save.
🤖   Pluggable embedders	Default: bge-small-en-v1.5 running locally via bundled WASM ONNX — works in the prebuilt single binary, zero native deps. Or point at Ollama, LM Studio, OpenAI — anything with /v1/embeddings.
🛰️   MCP server (streamable HTTP)	16 tools + 2 resources mounted on the same port. Claude Desktop, Claude Code, Cursor and any MCP-compliant agent can read, search, query and write your notes.
🔒   Per-folder agent permissions	Right-click a folder → set {read, write} for the MCP surface. Keep Journal/Private/ out of agent reach without locking down the vault.
🔑   Optional password auth	argon2id, bearer tokens, 24-hour TTL — gates both HTTP API and MCP. Off by default, on with one click.
📜   Git autocommit	Every save lands in git. Full history, diff, restore, manual checkpoints. The vault is a real git repo on disk.
🌍   No vendor lock-in	Your vault is a folder of .md files. Open it in VSCode, Obsidian, cat, anything. brain.md is just one more way to view and query it.
💸   Zero API keys required	Out of the box it runs fully offline. Cloud embedders are an opt-in, not a default.

---

Why brain.md

LLMs are only as smart as the context you give them. brain.md turns your notes into that context — without dragging them into someone else's cloud, without locking them inside a proprietary format, and without asking you to plumb a vector database yourself.

You write markdown. brain.md gives you:

• a polished editor + live preview with the full Obsidian-flavor dialect (wikilinks, embeds, callouts, math, mermaid, highlights, tasks, frontmatter, aliases),
• a per-vault embedded vector store (pure JS, ships in the single binary) with a local bge-small-en-v1.5 embedder by default running via bundled WASM ONNX — switch to Ollama, LM Studio, OpenAI, or anything else with a /v1/embeddings endpoint with one toggle,
• an MCP server (streamable HTTP) mounted on the same port, so Claude Desktop (or any MCP client) can read, search and write your notes safely — with per-folder read/write permissions for the agent surface,
• optional password auth and git autocommit / restore for the whole vault.

Everything runs on your machine. The vault is a plain folder of .md files you can open in any editor at any time.

How it compares

	Obsidian	Logseq	Notion	brain.md
License	Proprietary	AGPL-3.0	Proprietary	AGPL-3.0
Local-first vault on disk	✓	✓	✗ (cloud)	✓
Plain .md files (no proprietary db)	✓	✓ (block model)	✗	✓
Built-in MCP server	✗ (3rd-party plugin)	✗	✗	✓ — 16 tools
Vector RAG built-in	✗ (paid plugin)	✗	✓ (cloud only)	✓ — embedded, local
Per-folder agent permissions	n/a	n/a	n/a	✓
Single binary, no Electron	✗ (Electron)	✗ (Electron)	n/a	✓ — bun --compile
Works fully offline (incl. embeddings)	✓ (no AI)	✓ (no AI)	✗	✓ — bundled WASM ONNX

brain.md is not trying to replace Obsidian's plugin ecosystem or Notion's databases. It's narrower on purpose: a markdown vault designed from day one as a memory layer for AI agents over the Model Context Protocol.

---

Table of contents

• Quick start
• Install
• The interface
  • Editor + preview
  • Markdown that actually does things
  • Command palette + quick switcher
  • Tasks across the vault
• AI for agents
  • Semantic search (RAG)
  • MCP server
  • Per-folder permissions
  • Optional password auth
• CLI
• Defaults & paths
• Architecture
• Roadmap
• Contributing
• License

---

⚡ Quick start

One line. No clone, no Bun, no Node — the installer detects your OS + arch, downloads the matching prebuilt binary from the latest GitHub release, drops it in ~/.local/bin (or %USERPROFILE%\.brain.md\bin on Windows), and verifies it runs.

macOS / Linux

curl -fsSL https://raw.githubusercontent.com/mi4uu/brain.md/main/install.sh | bash

Windows (PowerShell)

powershell -c "irm https://raw.githubusercontent.com/mi4uu/brain.md/main/install.ps1 | iex"

Then:

brainmd                  # serve on :3000, vault at $HOME/.local/share/brain.md/vault
open http://localhost:3000

Open http://localhost:3000. First run creates your vault at the XDG default ($HOME/.local/share/brain.md/vault on macOS / Linux, the equivalent on Windows).

To enable semantic search and the MCP similar_notes tool, open Settings → AI / RAG and flip the switch. Default embedder is bge-small-en-v1.5 running locally via bundled WASM ONNX (one-time ~34 MB quantized model download, then fully offline — no Ollama, no Python, no native deps).

Want a tour? Point brain.md at the demo vault that ships with the repo:

brainmd --vault-dir ./example/vault

Every screenshot below was taken against example/vault/.

---

📦 Install

Option A — install script (recommended, see Quick start)

# macOS / Linux
curl -fsSL https://raw.githubusercontent.com/mi4uu/brain.md/main/install.sh | bash

# Windows
powershell -c "irm https://raw.githubusercontent.com/mi4uu/brain.md/main/install.ps1 | iex"

The script picks the right asset for your OS and CPU, writes it to ~/.local/bin/brain (or %USERPROFILE%\.brain.md\bin\brain.exe), chmod's it, and verifies it boots. Pin a version with BRAIN_VERSION=v0.1.0, change the install dir with BRAIN_INSTALL=….

Option B — download the binary manually

Every release ships a single-file executable per platform with the web UI embedded inside it. No Bun runtime, no Node.js, no git clone, no bun install — just download, mark executable, run.

Grab the file for your machine from the latest release: 👉 github.com/mi4uu/brain.md/releases/latest

Platform	Architecture	Asset
🍎   macOS — Apple Silicon	arm64	brain-md-darwin-arm64
🍎   macOS — Intel	x64	brain-md-darwin-x64
🐧   Linux	x64	brain-md-linux-x64
🐧   Linux	arm64	brain-md-linux-arm64
🪟   Windows	x64	brain-md-windows-x64.exe

One-liner — macOS / Linux

# macOS Apple Silicon — swap the URL suffix for your platform from the table above
curl -L -o brainmd \
  https://github.com/mi4uu/brain.md/releases/latest/download/brain-md-darwin-arm64
chmod +x brainmd
./brainmd                                # → serves on http://localhost:3000

# Optional: drop it on your $PATH so you can run `brainmd` anywhere
sudo mv brainmd /usr/local/bin/brainmd
brainmd --help                           # see all flags
brainmd --port 4000                      # custom port
brainmd --vault-dir ~/notes/my-vault     # custom vault location

One-liner — Windows (PowerShell)

iwr https://github.com/mi4uu/brain.md/releases/latest/download/brain-md-windows-x64.exe `
    -OutFile brainmd.exe
.\brainmd.exe                            # → serves on http://localhost:3000
.\brainmd.exe --help                     # all flags

First run: brain.md creates an empty vault at the XDG default ($HOME/.local/share/brain.md/vault on macOS/Linux, the equivalent on Windows) and serves the editor at http://localhost:3000. Want to try the demo vault first? Download example/vault/ and pass it with brain --vault-dir ./vault.

Untagged commits also produce binaries — they live as build artifacts on the Actions page with 30-day retention.

Option C — from source

git clone https://github.com/mi4uu/brain.md.git
cd brain.md
bun install
bun run start            # runs the production server on :3000

For development:

bun run dev:server       # backend on :3000
bun run dev:web          # vite on :5173 (with /api proxy)

If you run bun run start from a fresh source checkout (no compiled binary, no web/dist), the server downloads the matching web bundle from the GitHub release into $XDG_CACHE_HOME/brain.md/web/<version>/ on first request and serves from there. To always work offline, run bun --cwd web run build once.

Requires Bun ≥ 1.3. brain.md uses Bun.password (built-in argon2id) so you don't need a native crypto build.

---

🖥️ The interface

Editor + preview

Two synchronised panes powered by CodeMirror 6 and a unified / remark / rehype rendering pipeline. The active block in the preview stays anchored to the cursor in the editor; a thin SVG connector marks the link between them.

The right rail collects Bookmarks · Vault · Tags · Outline · Backlinks · Related. Each section is collapsible and remembers its state per device (localStorage). The Tags panel splits into In this note and Other tags the moment you open a note. The Related panel powers itself from the RAG index — same engine the agents use — and after every save brain.md quietly suggests up to three tags borrowed from your closest semantic neighbours.

Markdown that actually does things

Callouts

Math (KaTeX)

Mermaid diagrams

Syntax-highlighted code

Command palette + quick switcher

• ⌘P / Ctrl+P — search across titles and bodies
• ⌘O / Ctrl+O — fuzzy quick switcher

Both are powered by cmdk inside a Radix Dialog.

Tasks across the vault

Every - [ ] and - [x] in your notes is collected into a single view, with filters for open / done / all and a click-through to the source line.

📜 Auto versioning & history

Every save is auto-committed to git in the background (debounced, ~15 s). Open any note's History panel to see every prior revision, side-by-side unified diffs, and a one-click Restore this version. Filter by the current note or by the whole vault. No "save as", no daily snapshots cron — the vault is a real git repo on disk, so git log, git blame, git diff all work from the terminal too.

📱 Mobile

brain.md is not a desktop-only tool. The same vault, the same self-hosted instance, the same editor — usable from your phone over LAN, Tailscale, or a Cloudflare Tunnel (Zero Trust, no public port, no DDNS). The server itself is tiny — a single Bun binary that runs comfortably on the free tier of Oracle Cloud or AWS (ARM micro instances, ≤1 vCPU / ≤1 GB RAM). Drop the binary on a $0/month VPS, route a hostname to it through Cloudflare, and you have a private second brain reachable from any device, anywhere.

The mobile layout adapts: editor and preview swap in place via a bottom tab, the topbar scrolls horizontally with a sticky brand + hamburger, the sidebar slides in as a drawer.

<p align="center"> <img src="docs/img/mobile1.jpeg" alt="brain.md mobile — preview" width="30%" /> <img src="docs/img/mobile2.jpeg" alt="brain.md mobile — editor" width="30%" /> <img src="docs/img/mobile3.jpeg" alt="brain.md mobile — sidebar drawer" width="30%" /> </p>

Real phone, not a Chrome DevTools emulator. Captures notes on the move; the same RAG, tags, backlinks, and tasks you have on desktop.

---

🤖 AI for agents

This is what makes brain.md more than another markdown editor.

🔍 Semantic search (RAG)

When a note is saved, brain.md chunks it (≤ 512 tokens, ~64-token overlap, paragraph-aligned, frontmatter excluded), embeds each chunk, and upserts the vectors into a per-vault embedded store at <VAULT>/.brain/vectors.json (pure JS, brute-force cosine — well under 10ms for typical vaults).

Provider	Model	dim	Local?	API key
Local (default)	bge-small-en-v1.5 (WASM)	384	✓	—
Ollama	e.g. nomic-embed-text	768	✓	—
LM Studio	any served GGUF embedder	varies	✓	—
OpenAI	text-embedding-3-small	1536	—	✓

Out of the box, in the prebuilt binary. The local embedder ships as bundled WASM ONNX with a hand-rolled BERT tokenizer — no onnxruntime-node, no sharp, no platform-specific .node bindings. Toggle Enable RAG in Settings → AI / RAG, brain.md fetches the ~34 MB quantized model once and works fully offline after that, on macOS / Linux / Windows alike. Want to keep your existing Ollama or hosted endpoint? Switch to OpenAI-compatible in the same panel.

REST surface:

Method	Path	What
GET	/api/similar?q=…&k=…	Top-k semantic hits with snippet + line range
GET	/api/related/*path?k=…	Notes semantically close to a given path
POST	/api/context	Pack top chunks into a token-budgeted markdown block
GET	/api/orphans?limit=…	Notes with no backlinks AND low semantic neighbours
GET	/api/digest?since=7d	Topic clusters across recently modified notes
GET	/api/rag/status	Provider, model, dim, chunks, needsReindex
POST	/api/rag/reindex	Walks the vault and rebuilds the index
POST	/api/rag/test	Dry-run an embedder config without saving

Related notes, in the sidebar

The same engine the agents use also powers a Related panel in the sidebar. Open any note → the panel lists semantically close neighbours with score, line range and a snippet preview. Click jumps you there.

Tag suggestions on save

After every save, brain.md quietly looks at the closest neighbours' frontmatter tags and suggests up to three you haven't used yet. One click drops the tag into your frontmatter.

🛰️ MCP server

brain.md mounts a Model Context Protocol server on the same Elysia app at POST /mcp. Transport is the 2024-11-05 streamable HTTP variant in stateless JSON-response mode — one POST returns the full JSON-RPC response in a single round trip, no SSE stream, a fresh McpServer + transport per request. Sounds wasteful, but it's the only mode that survives clients that open and close a transport per tool call (Claude Desktop and LM Studio both do this).

Tools (16):

Tool	Folder perm	What it does
search_notes	none	Full-text vault search
similar_notes	none	Semantic RAG (top-k chunks)
read_note	read	Note body + mtime
list_notes	read	Filtered vault tree
get_backlinks	read	Inbound wikilinks
list_tags	none	Tag → count map
get_tasks	none	Aggregate tasks (filter: open/done/all)
write_note	write	Create or overwrite a note
append_note	write	Append a paragraph (blank-line separator)
find_related	read	Notes semantically close to a given path (excludes self)
find_similar_tasks	read	Semantic search across task lines (filter: open/done/all)
semantic_outline	read	Cluster a note's chunks into topical groups (cosine ≥ threshold)
context_for_query	read	Pack top-relevant chunks into a markdown context block (token cap)
find_orphans	read	Notes with 0 backlinks AND low semantic neighbour density
weekly_digest	read	Topic clusters across notes modified in a recent window (e.g. 7d)
compare_notes	read	Cosine sim + unified diff + shared headings between two notes

Resources (2):

• vault://tree — JSON {folders, notes} filtered by read perms
• vault://note/<path> — markdown body

Drop this into the MCP config of any client that speaks streamable HTTP natively — Claude Code, Cursor, Continue, Cline, Zed, the official @modelcontextprotocol/inspector, etc.:

{
  "mcpServers": {
    "brain.md": {
      "type": "streamable-http",
      "url": "http://localhost:3000/mcp"
    }
  }
}

Restart the client; the tools appear.

Claude Desktop — stdio bridge required

The Claude Desktop app (macOS / Windows) only speaks stdio — streamable HTTP and SSE are not supported as of writing. Bridge it through mcp-remote, which runs as a stdio child of Claude Desktop and forwards every JSON-RPC call over HTTP to your brain.md server:

{
  "mcpServers": {
    "brain.md": {
      "command": "npx",
      "args": [
        "mcp-remote",
        "http://localhost:3000/mcp"
      ]
    }
  }
}

Drop that into ~/Library/Application Support/Claude/claude_desktop_config.json (macOS) or the equivalent on your OS, then restart Claude Desktop.

Note: mcp-remote upstream warns that Cursor and Claude Desktop (Windows) have a bug where spaces inside args aren't escaped. Keep URL and header values quote-clean, no embedded spaces.

Full reference: docs/mcp.md.

🔒 Per-folder permissions

Right-click any folder → MCP permissions… to set explicit {read, write} flags. Resolution walks the parent chain to root; nearest explicit override wins; default is read + write.

This is how you keep Journal/Private/ out of agent reach without locking down the whole vault.

🔑 Optional password auth

Default: no auth. Set a password in Settings → Security to switch on bearer-token authentication for both the HTTP API and the MCP endpoints. Password is hashed with argon2id (Bun's built-in Bun.password, no native crypto build needed); tokens live in memory with a 24-hour TTL.

MCP config when auth is enabled

The plain-text MCP example earlier in the README assumes no auth. When you turn auth on, every request to /mcp needs an Authorization: Bearer <token> header. Most MCP clients have a field for it:

Claude Code / Cursor / Continue / any streamable-HTTP client:

{
  "mcpServers": {
    "brain.md": {
      "type": "streamable-http",
      "url": "https://brainmd.example.com/mcp",
      "headers": {
        "Authorization": "Bearer YOUR_TOKEN_HERE"
      }
    }
  }
}

Claude Desktop (stdio-only — needs mcp-remote bridge):

{
  "mcpServers": {
    "brain.md": {
      "command": "npx",
      "args": [
        "mcp-remote",
        "https://brainmd.example.com/mcp",
        "--header",
        "Authorization: Bearer YOUR_TOKEN_HERE"
      ]
    }
  }
}

How to get a token. brain.md issues tokens through POST /api/auth/login. You can do it from anywhere — most useful is a quick curl:

curl -X POST https://brainmd.example.com/api/auth/login \
  -H 'content-type: application/json' \
  -d '{"password":"YOUR_PASSWORD"}' | jq -r .token

Paste the returned token into the headers.Authorization field above, restart the MCP client, done.

Heads-up. Tokens have a 24-hour TTL and are stored in memory only — a server restart invalidates every token. If your agent suddenly starts seeing 401 Unauthorized, get a fresh token. Long-term: pin the token on the client and let your agent re-login on 401 (most MCP clients don't do this yet — patches welcome).

If you're embedding the URL itself anywhere persistent, prefer a secret-manager / .env over hard-coding the bearer string.

---

⌨️ CLI

brainmd [options]            # or: bun run start
brainmd --help               # -h
brainmd --version
brainmd --vault-dir <path>   # -v <path>
brainmd --port <n>           # -p <n>
brainmd --mcp-disabled       # skip mounting MCP at /mcp/*

Precedence: CLI flag > env var > XDG default. Unknown flag → stderr error + exit 2.

---

🗂️ Defaults & paths

Purpose	Env var	Default
Vault	XDG_DATA_HOME	$HOME/.local/share/brain.md/vault
Settings	XDG_CONFIG_HOME	$HOME/.config/brain.md/

Same logic on macOS, Linux, Windows — no OS branching. The vault dir is mkdir -p-ed on first run.

Per-vault state lives under <VAULT>/.brain/:

<VAULT>/
├── Welcome.md
├── Folder/
│   ├── Note.md
│   └── .media/
│       └── img.png
└── .brain/
    ├── index.json          # mtime-based search index
    ├── settings.json       # bookmarks, dailyDir, git autocommit, rag config
    ├── folder-meta.json    # icons, colors, per-folder MCP perms
    ├── auth.json           # argon2id hash — absent when auth is off
    ├── vectors.json        # embedded RAG store (vectors + metadata), git-ignored
    └── trash/<ts>/...      # recoverable deletes

Every env knob:

Var	Default	Notes
VAULT_DIR	XDG	Overridden by --vault-dir.
PORT	3000	Overridden by --port.
XDG_DATA_HOME	—	Base for default vault location.
XDG_CONFIG_HOME	—	Base for default settings location.
GIT_AUTOCOMMIT	1	1 / 0. Bootstrap default only.
GIT_AUTOCOMMIT_DEBOUNCE_MS	15000	Bootstrap default only.

---

🏗️ Architecture

+----------------+        /api/*        +-------------------+
|  React + CM6   | <------------------> |                   |
|  web client    |                      |                   |
+----------------+                      |   Elysia (Bun)    |  +-------------+
                                        |                   |  | Vault FS    |
+----------------+   /mcp HTTP+SSE      |   - Vault         |  | .brain/     |
| Claude Desktop | <------------------> |   - VaultIndex    |--|   index     |
| (or any MCP    |                      |   - GitRepo       |  |   trash     |
|  client)       |                      |   - SettingsStore |  |   vectors   |
+----------------+                      |   - AuthStore     |  |   auth.json |
                                        |   - MCP server    |  +-------------+
                                        |   - RAG pipeline  |
                                        +-------------------+
                                                  |
                                                  v
                                        +---------------------+
                                        | Embedded RAG store  |
                                        | (pure-JS, JSON)     |
                                        | WASM ONNX / OAI emb.|
                                        +---------------------+

• Runtime: Bun
• Backend: Elysia + native FS + GitRepo (libgit-free shell wrapper with an async write mutex)
• Frontend: React 18 + CodeMirror 6 + unified/remark/rehype + highlight.js + KaTeX + mermaid (lazy) + Radix UI primitives + Tailwind tokens (CSS vars under the hood)
• Vector store: embedded pure-JS store (JSON-on-disk, brute-force cosine) — no native binding, ships in the single binary
• Embedder: bundled onnxruntime-web (WASM) + hand-rolled BERT WordPiece tokenizer — no onnxruntime-node, no sharp, no Python
• MCP transport: @modelcontextprotocol/sdk WebStandardStreamableHTTPServerTransport
• Auth: Bun.password (argon2id, no native build)

Per-component documentation lives next to the code; see docs/ for the MCP reference.

---

🛣️ Roadmap

• Daily-note templates with variable interpolation
• Snippet expansion in the editor (/ trigger)
• Hybrid search (BM25 + dense), fused via RRF
• Multi-vault support behind a single server
• Encrypted vaults (age key per vault)
• Docker image (multi-arch, < 200 MB compressed)
• Notarised macOS .app wrapping the binary
• Hosted read-only demo

Want to nudge one of these up the list? Open an issue or PR.

---

💖 Sponsor

brain.md is a solo open-source effort. If it's useful to you and you can chip in, sponsorship pays for the time that goes into new features, docs and review.

<p align="center"> <a href="https://github.com/sponsors/mi4uu"> <img src="https://img.shields.io/badge/Sponsor-mi4uu-ec4899?logo=github-sponsors&logoColor=white&style=for-the-badge" alt="Sponsor mi4uu on GitHub" /> </a> </p>

The Sponsor ❤ button at the top of this repo and the small heart in the brain.md topbar (next to About) both lead here.

---

🤝 Contributing

Contributions welcome.

1. Open an issue first for anything non-trivial — a quick design sketch saves a long PR rewrite.
2. Write the test before the implementation. Server tests run with bun test; the suite is currently 187 green.
3. Open a PR. CI runs typecheck (server + web) + bun test.

---

⭐ Star history

Found brain.md useful? A ⭐ helps other people running local-first agent workflows discover it. No newsletter, no tracking, no follow-up email — just a signal that this exists.

---

📄 License

GNU Affero General Public License v3.0 or later — see LICENSE.

brain.md is, and will stay, free / libre / open-source. The AGPL was picked over weaker permissive licenses for two specific reasons:

1. It closes the SaaS loophole. If you modify brain.md and run it as a network service for others — hosted, multi-tenant, rebranded, whatever — you must publish your modified source under the same AGPL. Strong copyleft for a server-side tool means the community always gets the improvements back.
2. It can't be relicensed under a permissive license downstream. Forks stay open forever. Nobody can scoop the project, slap a new logo on it, and ship a proprietary "Pro" cut.

You're free to:

• run brain.md, personally or commercially, without limits;
• fork, modify, redistribute, even rebrand — provided your fork stays under the AGPL and you publish the source you're running.

You're not free to:

• ship a closed-source product based on brain.md;
• host a modified brain.md as a public service without publishing your modifications under the AGPL.

Trademarks

The name brain.md and the brain.md logo are not covered by the AGPL. If you fork the project, you're welcome to do almost anything with the code — but please use your own name and your own mark for your fork so users aren't confused about which project they're running.

---

<div align="center">

brain.md — your notes, your machine, your agents.

Built by Michał Lipiński  ·  github.com/mi4uu/brain.md  ·  report a bug

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