Build Your AI Second Brain with Obsidian and Claude

The idea of a "second brain" has been around for years. But in 2026, it finally works the way it was always supposed to — not just storing information, but actually thinking with you. The combination of Obsidian's local-first note system with Claude's reasoning capabilities creates something closer to a personal AI operating system than a simple knowledge base.

Here's how to build one that actually delivers value.

Why Obsidian + Claude?

Obsidian stores everything as plain Markdown files on your local machine. No vendor lock-in, no cloud dependency, no proprietary format trapping your data. With over 1.5 million users and 2,700+ community plugins, it has become the default choice for developers and knowledge workers who take ownership of their data seriously.

Claude, through Claude Code and the Model Context Protocol (MCP), can now read, search, and reason over your entire Obsidian vault. The result: an AI assistant that knows your projects, your meeting history, your research, and your ideas — without you repeating context every conversation.

Other tools like Notion offer built-in AI, but lock you into a single model and a proprietary ecosystem. Obsidian lets you bring any model — Claude, GPT, Gemini, or fully local models via Ollama — while keeping your files on your disk.

Setting Up in 30 Minutes

Step 1: Structure Your Vault

Create a folder hierarchy that mirrors how you think:

MyVault/
├── Projects/
├── Meetings/
├── Research/
├── Ideas/
├── Templates/
└── Daily/

Use descriptive filenames like 2026-02-24-meeting-product-roadmap.md and add YAML frontmatter for metadata:

---
tags: [meeting, product, Q1-2026]
project: website-redesign
status: actionable
---

Step 2: Install Key Plugins

In Obsidian, go to Settings → Community Plugins → Browse and install:

• Smart Connections — RAG-powered vault chat (ask questions about your notes)
• Templater — Automate note creation with templates
• Dataview — Query your vault like a database
• Calendar — Navigate daily notes visually

All free. You only pay for cloud API usage if you choose a cloud model.

Step 3: Connect Claude via MCP

This is where it gets powerful. Install the Obsidian MCP server:

npm install -g obsidian-mcp-server

Then configure Claude Code to use it in ~/.claude/settings.json:

{
  "mcpServers": {
    "obsidian": {
      "command": "obsidian-mcp-server",
      "args": ["--vault", "/path/to/your/vault"]
    }
  }
}

Once connected, Claude can search your meeting notes, create new documents within your project structure, find tagged content, and cross-reference information across hundreds of notes — all from the command line.

Workflows That Actually Work

Weekly Review

Ask Claude to summarize your weekly notes grouped by project. It scans daily logs, meeting notes, and task files, then generates a digest with completed items, open questions, and suggested priorities for next week.

Research Synthesis

After collecting 30-50 research notes on a topic, ask Claude to identify patterns, contradictions, and gaps. It produces a synthesis document with citations back to your original notes — something that would take hours manually.

Meeting Preparation

Before a meeting, query Claude about all decisions made and unresolved issues related to a specific project. It pulls from meeting notes, Slack summaries, and project documents to give you a comprehensive briefing.

Code Documentation

Store architecture decisions, debugging logs, and API notes in your vault. During development, reference them through MCP — Claude can find the relevant decision or pattern without you remembering which file it's in.

Context Engineering: Making AI Work Better

The quality of AI output depends directly on how well your vault is organized. A few principles make a significant difference:

Atomic notes: One concept per file. Instead of a monolithic "Project X Notes" file, create separate notes for each decision, meeting, and idea. This lets AI retrieve precisely what's relevant.

Consistent tagging: Use a small, fixed set of tags — #idea, #decision, #meeting, #research, #action. Claude uses these to filter and categorize when answering queries.

Explicit links: Obsidian's [[wikilinks]] create a knowledge graph. When Claude sees that a meeting note links to a project document that links to a research paper, it can traverse these connections to provide richer answers.

Regular maintenance: Review your tagging system monthly. Retire tags nobody uses. Archive completed projects. A clean vault produces better AI results.

Privacy and Control

Everything stays on your machine. Obsidian never sends your files anywhere. When you use Claude via API, only the specific notes relevant to your query get sent — not your entire vault. For maximum privacy, run a local model through Ollama and keep everything offline.

This is the fundamental advantage over cloud-based alternatives. Your knowledge base, your models, your rules.

The Practical Reality

This setup won't magically organize your life. The value comes from consistently capturing information in structured formats and asking good questions. Start small — daily notes and meeting summaries. Expand to research synthesis and project management as the system proves useful.

The developers and knowledge workers seeing the most benefit treat their vault as a living system: adding to it daily, pruning regularly, and using Claude to surface connections they would have missed.

In 2026, the best personal productivity system is not another app — it's a local folder of Markdown files with an AI that understands them.