Open Source · Apache 2.0 · Local-first

Your Second Brain,
powered by Claude.

Drop in any document — PDF, DOCX, HTML, plain text — and watch it turn into a structured, linked Markdown wiki. A desktop app that thinks with you, stores everything on your disk, and versions every change with Git (OPTIONAL).

Runs on macOS, Linux & Windows No telemetry Your data never leaves your machine
Features

Everything you need to think in public, privately.

A complete knowledge workflow — from raw dump to structured wiki to AI-powered reasoning — in one desktop app.

📥

Drag & drop ingestion

PDFs, DOCX, HTML, TXT, CSV, JSON — all converted to Markdown on upload. Duplicate detection built in.

🧠

AI-powered structuring

Claude reads each new source and proposes entities, concepts, and syntheses as wiki pages with wikilinks.

💬

Takeaway discussions

Every extracted insight gets a sparring chat. Talk it out, then optionally save as a synthesis page.

🕸️

Knowledge graph

Interactive force-directed visualization of every page and every wikilink. See your thinking take shape.

🔍

Ask your wiki

BM25-ranked retrieval with a persistent index, Claude streaming, and full source citations on every answer.

🩺

Health check & lint

Mechanical repair plus AI-generated questions, gap analysis, and synthesis candidates to keep your wiki alive.

Review workflow

Dedicated queue for unreviewed, seed, and stale pages. Inline preview, frontmatter editor, and compound-loop protection — AI output never feeds back unchecked.

🔎

Wiki inspector

Side panel showing backlinks, frontmatter details, and quick actions for every wiki page. Understand connections at a glance.

📄

Output generation

Custom syntheses from your wiki with source readiness checks. Marp presentations render directly in the app as live slide decks.

🎨

Brand foundation

Define voice, style, and positioning once — injected into every AI call so all output sounds like you.

⚙️

Built-in skills

Curated prompt modules (like marp-presentation) installable in one click. Extend with your own.

⌨️

Command palette

Hit Cmd+K to jump to any page, action, or setting. Keyboard-first navigation for power users.

🔄

Git-native sync

Every upload, ingest, and output is committed automatically. Push, pull, and collaborate like with code. Browse change history in-app.

📁

Multi-project

Keep work, research, and personal knowledge in separate vaults — all under one roof, one repo.

🔐

Encrypted secrets

API keys and Git tokens stored via the OS keychain (Electron safeStorage). Never in plaintext.

Workflow

From raw dump to reasoned wiki in four steps.

No prompt engineering. No folder structure decisions. Just drop, review, build.

STEP 01

Drop in anything

Drag a PDF, paste a URL, upload a folder of DOCX files. The converter handles format, the deduper handles duplicates.

STEP 02

Let Claude ingest

The AI reads each source, extracts takeaways, and proposes wiki operations: create, update, or merge pages with proper wikilinks.

STEP 03

Review & refine

Walk through AI-generated pages in the review queue. Confirm, edit, or flag them. Only reviewed pages flow into outputs — compound-loop protection built in.

STEP 04

Query & output

Ask questions with full source citations. Run the linter to spot gaps. Generate presentations, essays, or reports from your reviewed knowledge.

Privacy

Your data stays where it belongs — on your disk.

SecondBrain is local-first by design. Every page, every raw input, every generated output lives in a plain Markdown folder you control. The only network calls go to the Claude API, only when you trigger them.

  • No cloud storage. Your vault is a regular folder. Back it up, sync it with Git, or zip it up.
  • No telemetry. Zero usage tracking, zero analytics, zero phone-home.
  • Encrypted secrets. API keys and Git tokens go through the OS keychain via Electron safeStorage.
  • Auditable. Every change is, if you want, a Git commit. You can see exactly what the AI did, and roll it back.
# Your vault structure ~/Library/Application Support/ Zettelkasten/repos/ └── MyVault/ ├── brand/ │ ├── voice.md │ ├── style.md │ └── positioning.md ├── raw/ # original uploads ├── wiki/ # linked markdown │ ├── concepts/ │ ├── entities/ │ └── synth/ ├── output/ # generated docs └── .git/ # full history
Under the hood

Built on a stack you can trust and extend.

Open source, typed end-to-end, and structured so every contribution is straightforward.

Desktop
Electron 41
Frontend
React 19
State
Zustand
AI
Anthropic SDK
Git
isomorphic-git
Bundler
Vite
Language
TypeScript
Graph
react-force-graph
Testing
Vitest
Markdown
markdown-it
Ranking
BM25
License
Apache 2.0

Start building your second brain today.

Clone the repo, add your Claude API key, drop in your first document. Under five minutes to a running wiki.