Skills

Agent skills for software engineering with Claude Code, Codex, and other coding agents.

Each skill is a folder with a SKILL.md that follows the open Agent Skills standard. Install them all as one plugin that stays up to date, or pick individual skills.

Skills

Skill	What it does
learnings	Turns your coding agent's work history into ranked, evidence-backed lessons.

learnings

Learn from the work your coding agent did. The learnings skill reviews your accessible coding-agent work history and turns useful discoveries into ranked lessons, such as debugging insights, consequential decisions, and ways to direct or verify the agent. Each lesson explains when it applies, the concept behind it, and how strongly the evidence supports it. Explanations adapt to your experience level.

By default, it reviews the current agent's work today, in your timezone, for the current project or directory. You can choose a period, a project, a topic, or all accessible projects. It reads other agents' local logs only when you ask. The review is read-only, reports gaps in the available history, and leaves its findings in chat.

Use the learnings skill to review today's work.
Use learnings for this week's infrastructure work. Explain the concepts as you go.
Use learnings for last week across all projects. Focus on advanced debugging lessons.
Use learnings for this week's work, including both Codex and Claude Code logs.

How far back learnings can look depends on the agent's history tools and local logs. If those are unavailable, it reviews what it can from the current conversation and says what it could not see.

Installation

There are two ways to install:

Plugin (recommended). Installs every skill in this repo as the sebnilsson-skills plugin. Your agent updates it from the marketplace, and new skills arrive with it.
Individual skills. Copies only the skills you choose into your agent's skills folder. You update them yourself.

In the individual-skill commands below, replace <skill> with a name from the skills table.

Choose one method per agent. If you install both, every skill shows up twice.

Claude Code

Plugin

claude plugin marketplace add sebnilsson/skills
claude plugin install sebnilsson-skills@sebnilsson

Or, inside a Claude Code session:

/plugin marketplace add sebnilsson/skills
/plugin install sebnilsson-skills@sebnilsson

Update with claude plugin update sebnilsson-skills@sebnilsson. To get updates automatically, enable auto-update for the sebnilsson marketplace in /plugin.

Individual skills

Use the skills CLI (requires Node.js 22.20 or later):

npx skills@latest add sebnilsson/skills --skill <skill> -a claude-code -g

Leave out -g to install into the current project instead of your user profile. Leave out --skill to choose from a list. Update with npx skills@latest update.

To install by hand, copy the skills/<skill> folder to ~/.claude/skills/<skill> for all projects, or to .claude/skills/<skill> for one project.

Codex

Plugin

codex plugin marketplace add sebnilsson/skills
codex plugin add sebnilsson-skills@sebnilsson

You can also run /plugins inside Codex and install sebnilsson-skills from the Sebastian Nilsson Skills marketplace. Start a new Codex session after installing.

Update with codex plugin marketplace upgrade sebnilsson.

Individual skills

Ask Codex's built-in skill installer:

$skill-installer install https://github.com/sebnilsson/skills/tree/main/skills/<skill>

Or use the skills CLI:

npx skills@latest add sebnilsson/skills --skill <skill> -a codex -g

To install by hand, copy the skills/<skill> folder to ~/.agents/skills/<skill> for all projects, or to .agents/skills/<skill> in a repository.

Restart Codex after installing. To update, run npx skills@latest update, or remove the skill folder and install it again.

Other agents

The skills CLI installs these skills into Cursor, GitHub Copilot, OpenCode, Gemini CLI, and many other agents:

npx skills@latest add sebnilsson/skills

Using the skills

Agents load a skill automatically when your request matches its description, so you can describe the task and mention the skill by name:

Use the <skill> skill to ...

You can also invoke a skill directly:

Agent	Plugin install	Individual install
Claude Code	`/sebnilsson-skills:<skill>`	`/<skill>`
Codex	`$<skill>`, or pick it from `/skills`	`$<skill>`, or pick it from `/skills`

Each skill's section under Skills has example prompts.

Repository layout

skills/<name>/SKILL.md            The skill itself, plus any files it references
skills/<name>/agents/openai.yaml  Codex display metadata for the skill
.agents/plugins/marketplace.json  Codex marketplace manifest
.claude-plugin/                   Claude Code plugin and marketplace manifests
plugin.json                       Agent Plugins manifest, read by Codex
scripts/validate.mjs              Checks skills and manifests; runs in CI

Contributing

See CONTRIBUTING.md. Coding agents working in this repo follow AGENTS.md.

License

MIT