Obsidian Second Brain Template: The 3-File System I Actually Use

TL;DR

Most "Obsidian second brain templates" you find online are designed for human note-taking: daily notes, MOCs, zettelkasten links, dashboards. They're beautiful and they don't help your AI at all. The template below is the opposite: three short files, written for an LLM to read, that turn Claude or ChatGPT from a generic chat bot into something that sounds like a coworker who remembers. Identity.md, projects.md, decisions.md. Total length under 50 lines each. Updated in 15 minutes a week. Fork it, fill in your own answers, and load it into any AI session. The compounding effect (by month two the AI starts citing your past decisions) is real. The mistake to avoid is treating this template like a normal Obsidian vault. It isn't. It's a context payload for an AI.

Why Most Obsidian Templates Fail for AI

Search "Obsidian second brain template" and you'll find vaults with daily notes, MOCs (maps of content), zettelkasten links, PARA folder hierarchies, and dashboards with 14 plugins. They are designed for a human to read, retrieve, and re-encounter ideas over time.

When you hand one of those vaults to Claude or ChatGPT, the AI does poorly. Not because the model is dumb, but because the vault is structured for the wrong reader. Daily notes are noisy. MOCs are recursive. Backlinks don't matter when the AI can read every linked file anyway. Half the content is meta-organization that adds tokens without adding signal.

A second brain template for AI throws all that out. What it keeps is what the AI actually uses to be useful: who you are, what you're working on, and what you've already decided. Everything else is optional.

The Three Files

Open Obsidian. Create a new vault called brain (or whatever you like). At the root, create three files:

1. identity.md

Who you are, how you work, what you refuse to do. The AI reads this first and stops giving generic advice.

# Identity

## Role
[Your job/role in one sentence. E.g. "Senior frontend engineer at a startup,
freelance on the side."]

## What I do
[Three bullets max: the actual work you spend time on.]

## Communication
- Direct, no fluff
- Push back when warranted
- [Anything else: language preferences, tone, jargon allowed]

## Languages
[Which languages you work in. When to switch. E.g. "English by default,
Arabic in casual messages."]

## What I refuse
- [Hard nos. E.g. "Not interested in crypto projects."]
- [E.g. "Won't suggest Docker for fewer than 20 containers."]

## What I'm optimizing for
[One sentence on the larger goal. E.g. "Shipping fast, low maintenance,
hand-off ready."]

That's about 300 - 400 words once filled in. Resist the urge to write more. Resist the urge to add subsections for hobbies, family, or hopes and dreams unless they shape your work.

2. projects.md

A one-paragraph summary per active project. Updated every Friday afternoon as part of your weekly review.

# Active Projects

## [Project A]
**Status:** [In progress / blocked / shipped]
**Stack:** [3 - 5 line stack summary]
**Recent decisions:** [What changed in the last 2 weeks?]
**Blockers:** [What's blocked?]
**Key people:** [Who else is involved?]

## [Project B]
...

About 600 - 1000 words total once you have 3 - 5 active projects. Anything that hasn't been touched in 30 days moves to archive/projects-archive.md.

3. decisions.md

The most underrated file in any AI workflow. Every meaningful decision and the reason for it. Append-only.

# Decisions

## Stack
- Use Vite, not Next.js, for SPAs: most clients don't need SSR. (2026-03)
- Host on Vercel, not Lovable: needed apex domain support. (2026-04)
- Use Supabase for backend: Postgres + auth + storage in one. (2025-12)

## Business
- Don't take projects under $3K: overhead doesn't justify rate. (2026-02)
- Quote in USD, invoice in TRY for Turkish clients. (2026-01)

## Tools
- Claude > ChatGPT for code. (Confirmed 2026-05)
- Obsidian > Notion for personal notes: local-first matters. (2025-09)

This file grows slowly, maybe 10 - 20 entries a month. Each entry is 1 - 2 lines. The format that works: decision · reason · date. Don't over-format.

Loading the Template

Two ways to use it depending on the tool:

Claude Code: Save the three files at the root of your project directory. Rename identity.md to CLAUDE.md and the project picks it up automatically on every session. For per-project context, add a project-specific CLAUDE.md inside the project folder, it stacks on top of the root one.

Claude.ai or ChatGPT web: Keep a "starter pack" prompt saved as a snippet. Paste the contents of all three files at the start of any meaningful session. Clunky compared to Claude Code but covers the chat use case.

Both routes give you the same outcome: the AI never starts cold for anything that matters.

The Mistake to Avoid

The biggest mistake people make with this template is treating it like a normal Obsidian vault: adding daily notes, building MOCs, linking everything to everything else.

Don't. The vault is a context payload, not a knowledge base. Every file you add competes for the AI's attention. Every backlink the AI doesn't understand is noise. Every "meta" file (templates, dashboards, indexes) is tokens spent on infrastructure instead of substance.

If you want a traditional Obsidian PKM setup and an AI second brain, keep them in separate vaults. They have incompatible design goals.

The Maintenance Habit

The discipline that separates a useful second brain from a stale one: update projects.md every Friday afternoon. Non-negotiable.

It takes ten minutes. Open the file, walk through each project, ask:

Friday afternoon is intentional. Mondays are reactive; you don't have perspective. Fridays you do. Put it on your calendar. If you skip three Fridays in a row, your vault is stale, and a stale vault makes the AI worse, not better.

What the Compounding Looks Like

Week 1 feels like overhead. You wrote files for an AI and the answers don't feel different.

Week 4, you notice the AI stops re-suggesting Docker. It starts asking about your existing stack before recommending changes. It stops adding "depending on your use case" qualifiers because it knows your use case.

Week 8, it sounds like you. References past decisions. Matches your tone. Refuses approaches you've already ruled out. You stop writing "remember that the stack is X" at the top of every message because you no longer have to.

That's the shift. It is felt, not measured. Once you've felt it, you don't go back.

What's Not in This Template

Things people ask about that aren't here, and why:

Start with three files. Add only when you've felt the absence in a real session.

Forking the Template

The template is intentionally simple enough that you don't need to download anything: three files, copy the markdown above, fill in your own answers. No plugins, no Templater syntax, no Dataview queries.

If you want a starting point, the pillar second-brain article walks through the philosophy in more depth, and the Steph Ango skills setup covers how to layer reusable AI workflows on top of this base.

The whole point is that a second brain isn't a tool problem. It's a curation problem. The template is just the cheapest possible scaffold to get out of your way.

# الهويّة

## الدور
[دورك/مهنتك في جملة واحدة.]

## ما أعمل عليه
[ثلاث نقاط كحدّ أقصى: العمل الذي تقضي فيه وقتك فعلاً.]

## التواصل
- مباشر، بلا حشو
- اعترض إن لزم
- [أيّ تفضيلات أخرى]

## اللغات
[اللغات التي تعمل بها. متى تبدّل.]

## ما أرفض
- [خطوط حمراء واضحة]

## ما أحسّنه
[الهدف الأكبر في جملة واحدة.]

# المشاريع النشطة

## [مشروع A]
**الحالة:** [قيد العمل / متوقّف / مُسلَّم]
**الستاك:** [3-5 أسطر ملخّص]
**قرارات حديثة:** [ما تغيّر في آخر أسبوعين؟]
**معوّقات:** [ما المعطَّل؟]
**الأشخاص:** [من غيرك معنيّ؟]

# القرارات

## الستاك
- استخدم Vite، لا Next.js، لتطبيقات SPA: أغلب العملاء لا يحتاجون SSR. (2026-03)
- الاستضافة على Vercel، لا Lovable: لاحتجنا apex domain. (2026-04)
- Supabase للـ backend: Postgres + auth + storage في خدمة واحدة. (2025-12)

## الأعمال
- لا مشاريع تحت 3000$: التكلفة الإداريّة لا تبرّر السعر. (2026-02)
- التسعير بالدولار، الفواتير بالليرة للعملاء الأتراك. (2026-01)