# Build a source-linked second brain with Obsidian and Codex

Organise originals and summaries, trace answers back to notes, and resume work in a fresh Codex task.

[HTML](https://lukejbyrne.com/library/guides/hixuiuranl0/)
Content language: en
Author: Luke Byrne
Video published: 2026-10-26
Guide published: 2026-10-31

[Watch the video](https://www.youtube.com/watch?v=hiXuiuRANL0)
Video language: English

## Keep originals separate from summaries

Obsidian provides a vault of local notes; Codex works with the same folder. The demonstration uses a fictional workshop, so you can follow the process without copying private business data into a test.

The folder structure separates raw material from derived pages. A project summary should make it easier to find the original evidence, rather than silently replace it.

## Set up the shared workspace

No separate Obsidian plugin is required for the route in the video. Only use information you are comfortable sharing with your AI service.

1. Install Obsidian and create a vault.
2. Set up Codex and open that same vault folder.
3. Ask Codex to read a specific note and check it found the right source.
4. Organise raw notes, wiki summaries and AGENTS.md instructions.
5. Add the fictional workshop notes and build a project page linking to them.

## Use and maintain the project page

Ask a question across the notes, then follow the answer’s links back to the originals. If a decision is missing, keep it visibly missing: a suggestion is not an agreed decision.

The demonstration updates the plan when a decision changes, then starts a fresh task to pick up the work. Check that the new task reads the maintained files, rather than relying on a previous conversation’s memory.

1. Ask a project question and check the cited notes.
2. Record a missing decision separately from proposed answers.
3. Update the plan when a real decision changes.
4. Start a fresh task and verify the current project state.

## The takeaway

Maintain a small source-linked project page, keep the raw notes intact, and check important answers against the originals.

## Workflow resources

- [obsidian.md](https://obsidian.md)

## Chapters

- [0:00 What we're building](https://www.youtube.com/watch?v=hiXuiuRANL0&t=0s)
- [0:50 What Obsidian does](https://www.youtube.com/watch?v=hiXuiuRANL0&t=50s)
- [1:22 Install Obsidian and create a vault](https://www.youtube.com/watch?v=hiXuiuRANL0&t=82s)
- [2:47 Set up Codex](https://www.youtube.com/watch?v=hiXuiuRANL0&t=167s)
- [3:52 Open the same vault in Codex](https://www.youtube.com/watch?v=hiXuiuRANL0&t=232s)
- [5:09 Check that Codex can read a note](https://www.youtube.com/watch?v=hiXuiuRANL0&t=309s)
- [6:18 Organise raw, wiki and AGENTS.md](https://www.youtube.com/watch?v=hiXuiuRANL0&t=378s)
- [8:03 Add the fictional workshop notes](https://www.youtube.com/watch?v=hiXuiuRANL0&t=483s)
- [9:25 Turn your notes into a project page](https://www.youtube.com/watch?v=hiXuiuRANL0&t=565s)
- [11:01 Ask questions and check the sources](https://www.youtube.com/watch?v=hiXuiuRANL0&t=661s)
- [12:09 Find a missing decision](https://www.youtube.com/watch?v=hiXuiuRANL0&t=729s)
- [12:44 Update the plan when a decision changes](https://www.youtube.com/watch?v=hiXuiuRANL0&t=764s)
- [14:00 Pick up in a fresh task](https://www.youtube.com/watch?v=hiXuiuRANL0&t=840s)
- [14:39 Keep your second brain useful](https://www.youtube.com/watch?v=hiXuiuRANL0&t=879s)

## Sources and limitations

Companion prepared 31 October 2026 from the exact published YouTube description and chapter markers, with original resource links. The final video was not independently watched or transcribed for this article, and the current product was not retested. Statements about demonstrated results are attributed to the published video. Current prices, interface details and availability can change.

[Original video](https://www.youtube.com/watch?v=hiXuiuRANL0)