Second Brain
NicholasSpisak/second-brain
Set up a new Obsidian knowledge base with the LLM Wiki pattern.
Merge two pages that describe the same thing, preserving every distinct claim, redirecting inbound links, and recording the merge.
Install Second Brain Merge
$ npx skills add undefined-ui/second-brain-os --skill second-brain-merge -a claude-codeProject install by default; add -g for ~/.claude/skills/.
$ gh skill install undefined-ui/second-brain-os second-brain-merge --agent claude-codeProject scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).
$ git clone --depth 1 https://github.com/undefined-ui/second-brain-os.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/second-brain-merge .claude/skills/second-brain-merge && rm -rf skills-srcUse ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.
Claude Code skills documentation · loads skills from .claude/skills/
Install the "second-brain-merge" agent skill from https://github.com/undefined-ui/second-brain-os/tree/main/skills/second-brain-merge into .claude/skills/second-brain-merge/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "second-brain-merge", then confirm the skill loads.Claude Code copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$skill-installer install https://github.com/undefined-ui/second-brain-os/tree/main/skills/second-brain-mergeType this inside Codex. $skill-installer <name> installs a curated skill from openai/skills. The installer writes to $CODEX_HOME/skills (default ~/.codex/skills). Restart Codex if the skill does not show up.
$ npx skills add undefined-ui/second-brain-os --skill second-brain-merge -a codexProject install goes to .agents/skills/; add -g for ~/.codex/skills/.
$ gh skill install undefined-ui/second-brain-os second-brain-merge --agent codexProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/undefined-ui/second-brain-os.git skills-src && mkdir -p .agents/skills && cp -r skills-src/skills/second-brain-merge .agents/skills/second-brain-merge && rm -rf skills-srcUse ~/.agents/skills/ instead of .agents/skills for a personal install.
Codex skills documentation · loads skills from .agents/skills/
Install the "second-brain-merge" agent skill from https://github.com/undefined-ui/second-brain-os/tree/main/skills/second-brain-merge into .agents/skills/second-brain-merge/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "second-brain-merge", then confirm the skill loads.Codex copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add undefined-ui/second-brain-os --skill second-brain-merge -a cursorProject install goes to .agents/skills/; add -g for ~/.cursor/skills/.
$ gh skill install undefined-ui/second-brain-os second-brain-merge --agent cursorProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/undefined-ui/second-brain-os.git skills-src && mkdir -p .cursor/skills && cp -r skills-src/skills/second-brain-merge .cursor/skills/second-brain-merge && rm -rf skills-srcUse ~/.cursor/skills/ instead of .cursor/skills for a personal install.
Cursor skills documentation · loads skills from .cursor/skills/, .agents/skills/, .claude/skills/, .codex/skills/
Install the "second-brain-merge" agent skill from https://github.com/undefined-ui/second-brain-os/tree/main/skills/second-brain-merge into .cursor/skills/second-brain-merge/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "second-brain-merge", then confirm the skill loads.Cursor copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gemini skills install https://github.com/undefined-ui/second-brain-os.git --path skills/second-brain-merge--scope user (default) or --scope workspace; --path is the subfolder of the repo that holds the skill; --consent skips the security confirmation prompt.
$ npx skills add undefined-ui/second-brain-os --skill second-brain-merge -a gemini-cliProject install goes to .agents/skills/; add -g for ~/.gemini/skills/.
$ gh skill install undefined-ui/second-brain-os second-brain-merge --agent gemini-cliProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/undefined-ui/second-brain-os.git skills-src && mkdir -p .gemini/skills && cp -r skills-src/skills/second-brain-merge .gemini/skills/second-brain-merge && rm -rf skills-srcUse ~/.gemini/skills/ instead of .gemini/skills for a personal install, then run /skills reload.
Gemini CLI skills documentation · loads skills from .gemini/skills/, .agents/skills/
Install the "second-brain-merge" agent skill from https://github.com/undefined-ui/second-brain-os/tree/main/skills/second-brain-merge into .gemini/skills/second-brain-merge/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "second-brain-merge", then confirm the skill loads.Gemini CLI copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ gh skill install undefined-ui/second-brain-os second-brain-mergeInstalls for Copilot at project scope by default; add --scope user for a personal install. Preview a skill first with gh skill preview. Needs GitHub CLI 2.90.0 or later (public preview).
$ npx skills add undefined-ui/second-brain-os --skill second-brain-merge -a github-copilotProject install goes to .agents/skills/; add -g for ~/.copilot/skills/.
$ git clone --depth 1 https://github.com/undefined-ui/second-brain-os.git skills-src && mkdir -p .github/skills && cp -r skills-src/skills/second-brain-merge .github/skills/second-brain-merge && rm -rf skills-srcUse ~/.copilot/skills/ instead of .github/skills for a personal install. Commit .github/skills so cloud agent and code review can use it.
GitHub Copilot skills documentation · loads skills from .github/skills/, .claude/skills/, .agents/skills/
Install the "second-brain-merge" agent skill from https://github.com/undefined-ui/second-brain-os/tree/main/skills/second-brain-merge into .github/skills/second-brain-merge/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "second-brain-merge", then confirm the skill loads.GitHub Copilot copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
$ npx skills add undefined-ui/second-brain-os --skill second-brain-merge -a opencodeOpenCode documents no install command of its own. Project install goes to .agents/skills/; add -g for ~/.config/opencode/skills/.
$ gh skill install undefined-ui/second-brain-os second-brain-merge --agent opencodeProject scope by default (.agents/skills/); add --scope user for a personal install.
$ git clone --depth 1 https://github.com/undefined-ui/second-brain-os.git skills-src && mkdir -p .opencode/skills && cp -r skills-src/skills/second-brain-merge .opencode/skills/second-brain-merge && rm -rf skills-srcUse ~/.config/opencode/skills/ instead of .opencode/skills for a personal install.
OpenCode skills documentation · loads skills from .opencode/skills/, .claude/skills/, .agents/skills/
Install the "second-brain-merge" agent skill from https://github.com/undefined-ui/second-brain-os/tree/main/skills/second-brain-merge into .opencode/skills/second-brain-merge/ in this project. Copy the whole folder (SKILL.md and every file beside it), keep the folder name "second-brain-merge", then confirm the skill loads.OpenCode copies the folder itself, the same result as the manual copy. Check what it changed before you commit it.
Facts
- Skill name
second-brain-merge- GitHub stars
- 1k
- Token cost
- ~470 tokens
- SKILL.md length
- 193 words
- Files
- 1
- Skills in repo
- 23
- Repo updated
- First seen
- Licence
- MIT
At a glance
Merge two pages that describe the same thing, preserving every distinct claim, redirecting inbound links, and recording the merge.
- Works in 6 steps: Pick the survivor by canonical name, not… → Merge content. Every distinct claim… → Merge aliases, including the dead page's… → …
- The user approves a duplicate merge
- SKILL.md covers Core rule, Workflow, Output format and Calibration
- Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md
What it does
Second Brain Merge is an agent skill from undefined-ui/second-brain-os. 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 into several.
Its SKILL.md is about 470 tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.
It sits in Knowledge Management, covering Second brain. The repository describes itself as: 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. The licence is MIT.
When your agent uses it
- The user approves a duplicate merge
- Says these are the same page
- Asks to clean up near-duplicates that a lint run proposed
- Merge pages on your own judgement
Example prompts
- “these are the same page”
- “merge X into Y”
- “/second-brain-merge”
Workflow steps
6 steps, taken from the first numbered list in SKILL.md.
- Pick the survivor by canonical name, not by which page is longer.
- Merge content. Every distinct claim survives with its source. Overlapping
- Merge aliases, including the dead page's title as an alias on the
- Redirect inbound links to the survivor. Check every backlink.
- Delete the old page, or leave a stub only if it was linked from outside
- Record in log.md: both names, the date, and why.
What it can do on your machine
Read from SKILL.md and the folder at commit c7fa35b. It shows what the files ask for, not the result of running them.
Tool permissions
Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.
From allowed-tools in the SKILL.md frontmatter.
Runs code
No scripts in the folder and no shell commands in SKILL.md.
From the folder's file list and the shell code blocks in SKILL.md.
Network
No URLs in SKILL.md.
From URLs in SKILL.md, links to its own repository left out.
Credentials
Names no API keys, tokens, secrets or passwords.
From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.
Context cost
Second Brain Merge loads about 470 tokens when it runs. Until then it costs about 107 tokens; SKILL.md has 193 words of instructions outside code blocks.
Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.
Safety
Auto-check passed
The automated check found no risky patterns in SKILL.md.
Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.
SKILL.md
The full file from undefined-ui/second-brain-os at commit c7fa35b, republished under its MIT licence (© undefined-ui). 193 words, ~470 tokens.
Download SKILL.mdSave it as
.claude/skills/second-brain-merge/SKILL.md (or your agent's skills folder).- name
- second-brain-merge
- description
- 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 into several.
Merge duplicate pages
A merge is irreversible in the way that matters: afterwards you cannot tell which claim came from which page. Two ideas that look identical from their summaries are often a general case and a specific one.
Core rule
Never merge unprompted. Propose, wait for approval, then follow the procedure exactly.
Workflow
- Pick the survivor by canonical name, not by which page is longer.
- Merge content. Every distinct claim survives with its source. Overlapping claims collapse; differing ones both stay, following the contradiction rules.
- Merge aliases, including the dead page's title as an alias on the survivor. This is what keeps old links and the user's memory working.
- Redirect inbound links to the survivor. Check every backlink.
- Delete the old page, or leave a stub only if it was linked from outside the vault.
- Record in
log.md: both names, the date, and why.
Output format
Merged: [[old]] -> [[survivor]]
Claims kept from old page: <n>
Aliases added: <list>
Inbound links redirected: <n>
Conflicts recorded: <none | description>Calibration
If the two pages disagree about anything factual, that is a signal they may not be duplicates. Surface the disagreement and ask before proceeding.
Never merge a page marked maintained_by: human into another without explicit
confirmation naming that page.
© undefined-ui, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file
Files
Just SKILL.md in skills/second-brain-merge of undefined-ui/second-brain-os.
Open the folder on GitHubat commit c7fa35b
Compare with similar skills
Second Brain Merge next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.
| Skill | Stars | Used in | Tokens | Auto-check | Licence | Repo updated |
|---|---|---|---|---|---|---|
| Second Brain Merge this skillundefined-ui/second-brain-os | 1k | — | ~470 | Automated safety check: Pass | MIT | |
| Second BrainNicholasSpisak/second-brain | 736 | 1 repos | ~1.5k | Automated safety check: Notes | None | |
| 3D Brainnateherkai/AIS-OS | 1.6k | — | ~2.1k | Automated safety check: Pass | Custom licence | |
| Obsidian Canvas BoardsAgriciDaniel/claude-obsidian | 15k | — | ~1.4k | Automated safety check: Pass | MIT | |
| Icm ArchitectRinDig/icm-architect | 1.8k | — | ~3.2k | Automated safety check: Pass | MIT | |
| Obsidian CLI Read TransportAgriciDaniel/claude-obsidian | 15k | 1 repos | ~762 | Automated safety check: Pass | MIT |
Similar skills
3D Brain
nateherkai/AIS-OS
A skill your agent uses when someone asks to build a 3D brain, visualize their AIOS or second brain, turn their knowledge into an interactive graph, or run /3d-brain or /3D brain.
Obsidian Canvas Boards
AgriciDaniel/claude-obsidian
Creates, inspects and updates Obsidian JSON Canvas boards in a vault, with text, file, link, group and edge nodes, using safe recoverable edits.
Icm Architect
RinDig/icm-architect
Design any process, idea, problem, or body of knowledge into an ICM (Interpretable Context Methodology) workspace — folder structure as agent architecture — or restructure an existing folder, repo…
Obsidian CLI Read Transport
AgriciDaniel/claude-obsidian
Detects and uses the official Obsidian command-line interface for read-only vault access, falling back to direct file reads, while all mutations stay on a separate transaction core.
Cascading Goal Tracker
ballred/obsidian-claude-pkm
Tracks three-year, yearly, monthly, and weekly goals in linked Markdown files, calculating completion percentages and flagging stalled goals.
More from undefined-ui/second-brain-os
All 23 skills in this repoGoal Test
undefined-ui/second-brain-os
Turn a vague task into a testable definition of done and generate an executable goal-test script for it, optionally with a bounded retry loop around a headless agent.
Context Audit
undefined-ui/second-brain-os
Audit an agent's context layout against the four places: system prompt, tools, history, tail.
Evals Bootstrap
undefined-ui/second-brain-os
Scaffold a first eval suite for an agent: mine real failures into cases, write behavioural checks over traces, and generate the runner.
Gate Check
undefined-ui/second-brain-os
Find the decisions in a pipeline that do not need the expensive model and propose the gate for each: a rule, a classic classifier, or a small model, with fail-closed routing.
Harness Audit
undefined-ui/second-brain-os
Audit an agent's harness against the four rings: containment, guides, sensors, permissions.
Second Brain Chat Import
undefined-ui/second-brain-os
Triage an exported chat history into what to ingest, what to archive and what to delete, with a privacy pass first.
Related
Categories
Questions about Second Brain Merge
What does Second Brain Merge do?
Merge two pages that describe the same thing, preserving every distinct claim, redirecting inbound links, and recording the merge. Second Brain Merge is an agent skill from undefined-ui/second-brain-os. Merge two pages that describe the same thing, preserving every distinct claim, redirecting inbound links, and recording the merge.
When should I use Second Brain Merge?
Second Brain Merge fits situations like: the user approves a duplicate merge; says these are the same page; asks to clean up near-duplicates that a lint run proposed; merge pages on your own judgement.
How do I install Second Brain Merge in Claude Code?
Run `npx skills add undefined-ui/second-brain-os --skill second-brain-merge -a claude-code`. Or copy the skill folder (skills/second-brain-merge in undefined-ui/second-brain-os) into .claude/skills/second-brain-merge in your project. Claude Code loads it when a task matches its description.
How do I install Second Brain Merge in Codex?
Run `npx skills add undefined-ui/second-brain-os --skill second-brain-merge -a codex`. Or copy the skill folder (skills/second-brain-merge in undefined-ui/second-brain-os) into .agents/skills/second-brain-merge in your project. Codex loads it when a task matches its description.
Can I use Second Brain Merge in Cursor, Gemini CLI or GitHub Copilot?
Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add undefined-ui/second-brain-os --skill second-brain-merge -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/second-brain-merge, .gemini/skills/second-brain-merge, .github/skills/second-brain-merge and .opencode/skills/second-brain-merge in your project.
What does Second Brain Merge need to run?
SKILL.md names no scripts, command-line tools or credentials: Second Brain Merge is instructions for the agent only.
Does Second Brain Merge access the network?
SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.
Is Second Brain Merge safe to install?
Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.
What licence does Second Brain Merge use?
Second Brain Merge is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.
How many tokens does Second Brain Merge use?
About 470 tokens (SKILL.md is roughly 1.9k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.
What are the alternatives to Second Brain Merge?
Skills that share tags, products or a category with Second Brain Merge: Second Brain (NicholasSpisak/second-brain, 736 stars), 3D Brain (nateherkai/AIS-OS, 1.6k stars), Obsidian Canvas Boards (AgriciDaniel/claude-obsidian, 15k stars) and Icm Architect (RinDig/icm-architect, 1.8k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.
Who maintains Second Brain Merge?
undefined-ui (a GitHub user) maintains it in undefined-ui/second-brain-os, which has 1,009 GitHub stars. The repository holds 23 skills in this directory. The repository was last updated on October 7, 2026.
Source: undefined-ui/second-brain-os on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.