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Updated 2d ago

by undefined-ui

second-brain-os

An AI second brain that maintains itself. Full guide, starter vault, agent skills and scripts for a self-organizing knowledge base in Claude Code and Obsidian.

  • Active — Updated in the last 14 days
Works with
  • Claude
View on GitHub (opens in a new tab)

1.1k GitHub stars (1,093)

+435 in 20 days

Stars gained per day · daily snapshots since Sep 26
Stars gained per day, Sep 26 to Oct 16: +435 in total; the busiest day was Sep 28 with +68 stars.Sep 27: +19 starsSep 28: +68 starsSep 29: +58 starsSep 30: +25 starsOct 1: +5 starsOct 2: +19 starsOct 3: +24 starsOct 4: +11 starsOct 5: +3 starsOct 6: +59 starsOct 7: +44 starsOct 8: +15 starsOct 9: +9 starsOct 10: +3 starsOct 11: +2 starsOct 12: +13 starsOct 13: +20 starsOct 14: +4 starsOct 15: +11 starsOct 16: +23 stars
Stars gained between daily snapshots
PeriodNew stars
Sep 27+19
Sep 28+68
Sep 29+58
Sep 30+25
Oct 1+5
Oct 2+19
Oct 3+24
Oct 4+11
Oct 5+3
Oct 6+59
Oct 7+44
Oct 8+15
Oct 9+9
Oct 10+3
Oct 11+2
Oct 12+13
Oct 13+20
Oct 14+4
Oct 15+11
Oct 16+23
  • 18 skills (18 skills found in its SKILL.md files)
  • 178 forks (178 forks)
  • 2d ago last update (Last updated 2d ago)

Install

Skills CLI

npx skills add undefined-ui/second-brain-os

Asks which skills and agents to install. Just one: npx skills add undefined-ui/second-brain-os --skill second-brain-backfill — add -g for every project.

Claude Code

git clone https://github.com/undefined-ui/second-brain-oscp -r "second-brain-os/skills/second-brain-backfill" ~/.claude/skills/

Copies the second-brain-backfill skill into ~/.claude/skills/ for every project (use .claude/skills/ for one project). Repeat for the other skills listed below.

Plugin

/plugin marketplace add undefined-ui/second-brain-os

Run inside Claude Code if the repository ships a plugin marketplace, then pick plugins from /plugin.

Skills can run code on your machine — read the SKILL.md first.

What it does

In the author's own words, from each skill's SKILL.md.

  • second-brain-backfill

    Import a large archive into the vault in controlled batches: triage what is worth ingesting, process oldest first, checkpoint after every batch, and keep cost visible. Use this skill whenever the user wants to import years of bookmarks, an export from another notes app, a downloads folder, a chat history dump, or says "backfill", "bulk import", "process my archive". Do NOT use for ingesting one o…

    skills/second-brain-backfill/SKILL.md on GitHub (opens in a new tab)

  • second-brain-changed-my-mind

    Trace where the user's recorded position on something has shifted: superseded claims, contradictions between sources of different dates, and what evidence moved them. Use this skill when the user asks what they have changed their mind about, how their thinking on a topic developed, what they used to believe, or wants a quarterly look back at their own positions. Do NOT use for finding contradicti…

    skills/second-brain-changed-my-mind/SKILL.md on GitHub (opens in a new tab)

  • second-brain-chat-import

    Triage an exported chat history into what to ingest, what to archive and what to delete, with a privacy pass first. Use this skill when the user has exported their Claude or ChatGPT history, asks to import old conversations, or asks what in their chat archive is worth keeping. Do NOT use for ingesting a single pasted conversation, or for any material the user has not explicitly asked to bring int…

    skills/second-brain-chat-import/SKILL.md on GitHub (opens in a new tab)

  • second-brain-graph

    Analyse the vault's link graph and report on its shape: orphan rate, average degree, components, hubs, bridges and clusters, with what each number means for retrieval. Use this skill when the user asks about the health or structure of their graph, wants metrics, asks which pages are most connected or most isolated, or asks whether the vault is fragmented. Do NOT use for fixing what it finds, whic…

    skills/second-brain-graph/SKILL.md on GitHub (opens in a new tab)

  • second-brain-ingest

    Turn raw source material in a second-brain vault into linked wiki pages: read the source, split it into concepts and entities, write or update pages, connect them to existing pages, and record the run in the log. Use this skill whenever the user drops a file into raw/, pastes an article, transcript or PDF and asks to add it to the vault, says "ingest this", "add this to my second brain", "process…

    skills/second-brain-ingest/SKILL.md on GitHub (opens in a new tab)

  • second-brain-lint

    Audit a second-brain vault for structural problems and repair them: broken wikilinks, orphan pages, empty stubs, frontmatter that violates the schema, near-duplicate pages, and stale index entries. Use this skill whenever the user asks to lint, clean, audit or check the health of their vault, says pages feel messy or links are broken, after a large bulk import, or when a scheduled maintenance run…

    skills/second-brain-lint/SKILL.md on GitHub (opens in a new tab)

  • second-brain-merge

    Merge two pages that describe the same thing, preserving every distinct claim, redirecting inbound links, and recording the merge. Use this skill when the user approves a duplicate merge, says "these are the same page", "merge X into Y", or asks to clean up near-duplicates that a lint run proposed. Do NOT use to merge pages on your own judgement, to delete a page outright, or to split one page in…

    skills/second-brain-merge/SKILL.md on GitHub (opens in a new tab)

  • second-brain-metrics

    Record a dated snapshot of the vault's health numbers and compare against previous snapshots so trends are visible. Use this skill for a monthly or quarterly check, when the user asks whether the vault is improving, or asks to track its numbers over time. Do NOT use for a one-off graph analysis, which is second-brain-graph, or for structural repairs.

    skills/second-brain-metrics/SKILL.md on GitHub (opens in a new tab)

  • second-brain-privacy

    Audit the vault for material that should not be in it: credentials, other people's private information, confidential work, and anything the user would not want synced or backed up. Use this skill when the user asks about privacy, is about to share or sync the vault, has just imported chat history or meeting notes, or asks what is sensitive in their notes. Do NOT use to delete anything on your own…

    skills/second-brain-privacy/SKILL.md on GitHub (opens in a new tab)

  • second-brain-project

    Set up or update a project in the vault: the four-stage folder pipeline, a project-scoped CLAUDE.md with one goal, and links to the concept pages it depends on. Use this skill when the user starts something new they will work on over time, says "create a project", "set up a folder for X", or asks to define the goal and structure of ongoing work. Do NOT use for one-off tasks, for wiki pages about…

    skills/second-brain-project/SKILL.md on GitHub (opens in a new tab)

  • second-brain-publish

    Prepare a subset of the vault for publishing: check opt-in flags, find private material, and report what would leak through links before anything is exported. Use this skill when the user wants to publish notes as a site or digital garden, asks what is safe to make public, or is setting up an export. Do NOT use for exporting a single document, or for running the publishing tool itself.

    skills/second-brain-publish/SKILL.md on GitHub (opens in a new tab)

  • second-brain-query

    Answer a question from a second-brain vault by reading its own pages, citing the pages used, and saying plainly when the vault does not contain the answer. Use this skill whenever the user asks what they know about a topic, what they have read on something, what connects two ideas, what they have changed their mind about, or asks any question that should be answered from their own notes rather th…

    skills/second-brain-query/SKILL.md on GitHub (opens in a new tab)

  • second-brain-quiz

    Generate questions from the user's own concept pages so they can find out what they saved but never learned, and compare their answers against what the pages say. Use this skill when the user wants to test themselves, revise, make flashcards from their notes, or asks what they have forgotten. Do NOT use for generic quizzing on a topic the vault does not cover, or for answering a question from the…

    skills/second-brain-quiz/SKILL.md on GitHub (opens in a new tab)

  • second-brain-rename

    Rename a page safely: update the file, fix every inbound wikilink, add the old name as an alias, and log it. Use this skill whenever a page needs a different canonical title, the user says "rename X to Y", asks to fix an inconsistent title, or after a lint run flags naming problems. Do NOT use for merging two pages, for moving a page between folders without a name change, or for renaming files ou…

    skills/second-brain-rename/SKILL.md on GitHub (opens in a new tab)

  • second-brain-report

    Produce a research report from the vault: scope the question against existing pages, name the gaps, and write findings with citations, disagreements and limits. Use this skill when the user asks for a research report, a deep write-up on a topic, or wants to understand a subject thoroughly using what they have collected. Do NOT use for a quick answer from the vault, for drafting an article in the…

    skills/second-brain-report/SKILL.md on GitHub (opens in a new tab)

  • second-brain-review

    Produce a periodic review of a second-brain vault: what was added, which topics are growing, what contradicts what, which questions are still open, and what is worth reading next. Use this skill whenever the user asks for a weekly or monthly review, asks what changed in their vault, what they have been learning about lately, or what they should look at next, and when a scheduled review task fires…

    skills/second-brain-review/SKILL.md on GitHub (opens in a new tab)

  • second-brain-transcript

    Clean a raw transcript before ingestion: punctuate, paragraph, label speakers, fix mistranscribed technical terms, and split long recordings by topic. Use this skill when the user drops an auto-generated transcript, subtitle file, podcast or lecture transcript, meeting recording text, or asks to process a video or audio source. Do NOT use for text that is already prose, for summarising a transcri…

    skills/second-brain-transcript/SKILL.md on GitHub (opens in a new tab)

  • second-brain-write

    Draft from the vault: outline from concept pages, keep citations to the user's own sources, and surface where their material disagrees. Use this skill when the user wants to write an article, post, essay or newsletter based on what they have collected, or asks what they could write about a topic. Do NOT use for research reports, for writing with no grounding in the vault, or for editing text the…

    skills/second-brain-write/SKILL.md on GitHub (opens in a new tab)

Review before you install

A skill is a set of instructions and scripts your agent will follow, and it can run code on your machine. Read the SKILL.md and any scripts first — this listing is not a security review.