Why I Did Not Make NotebookLM My Second Brain: What Comparing It with Codex and Obsidian Showed

February 12, 2026Updated: July 25, 2026Articles

If you are building a second brain, is Google’s NotebookLM the right home, or locally stored Obsidian? In February 2026 I chose Obsidian, on the grounds that Codex could reach it easily.

This article reworks a comparison note published on 11 February 2026, presented as a record dated 12 February 2026. NotebookLM was renamed Gemini Notebook on 16 July 2026, so the current name and what changed are noted below.

The deciding question was which AI I wanted to reach it from

NotebookLM is good at answering questions about material you give it and pulling out the key points. Obsidian, by contrast, is a note app that stores Markdown files on your own computer.

What I wanted was less a dedicated service for reading information than notes that AI agents such as Codex and Claude Code could reach from the same place as my daily work. With local files you can ask for search, rewriting, categorizing, and conversion to another format as one continuous task.

Why NotebookLM did not fit

In February 2026, what bothered me was how hard it was to reach information inside NotebookLM from my main working environment. Even as material accumulated, it was unclear how I would use the same asset after switching to a different AI.

Obsidian’s files, on the other hand, are ordinary Markdown. Easy to read out after changing apps, easy to back up, easy to keep under Git — that was the reassuring part.

This is not to say NotebookLM is worse

They are for different things. When you want to read several documents against each other and check sources as you go, NotebookLM is often the clearer option. It suits situations where the material in question is well defined: course material, research reports, meeting documents.

Obsidian suits being a long-term home for information whose purpose is not yet decided — diaries, work logs, passing thoughts, URLs. The freedom to organize it comes with having to think about storage and backups yourself.

Choose by what you are going to put in it

Read a defined set of documents deeply: Gemini Notebook
Grow daily notes over a long period: Obsidian
Work mainly in Gemini and Google services: Gemini Notebook
Operate on local files from Codex or Claude Code: Obsidian

You do not have to standardize on one. Keeping the originals in Obsidian and using Gemini Notebook for research on a specific topic works too.

A note as of 20 July 2026

Google renamed NotebookLM to Gemini Notebook on 16 July 2026. It remains a standalone research service, while integration with the Gemini app and Google Search has widened, and Google says a secure cloud computer per notebook and code execution are rolling out in stages.

The impression I had in February 2026 — a document store closed inside Google — is therefore starting to change. Choosing Obsidian because you want your own files reachable from any AI remains a valid position, though.

The details of the rename are covered in what changed when NotebookLM became Gemini Notebook.