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Guide · Agent skill

How to use the LifeOS Development skill: install and run it

Updated · written with AI from the project's own documentation and checked against our catalogue data

The LifeOS Development skill is an agent skill that makes your coding agent build, test, modify and audit software against an ISA, a written set of acceptance criteria kept alongside the code. It is for developers who already use the LifeOS ISA system, or who want a written spec and test evidence before shipping. After this guide you will know how to install the skill, how to phrase requests so it triggers, what it needs to run, and what it will and will not do.

LifeOS Development Skilldanielmiessler/LifeOS · MIT

Quick start

  1. 1Confirm prerequisites. Make sure Bun is installed and that you have a LifeOS installation with the paths and tools the skill references.
  2. 2Download and unzip. Download the Development ZIP from this page and unzip it so the Development folder is intact.
  3. 3Place the folder. Put it in ~/.claude/skills/ for personal use, or in a project's .claude/skills/ folder for one project.
  4. 4Or upload in the Claude apps. Open Settings → Capabilities → Skills in the Claude apps and upload the skill.
  5. 5Make a natural request. Describe the work in plain words, such as building a feature or asking for a health check.
  6. 6Review the ISA and results. Check the criteria the agent wrote and the acceptance verdict it records before accepting the work as done.

What an agent skill is and what this one makes the agent do

An agent skill is a folder of instructions and optional tools that an AI agent loads when a request matches the skill's description. This one, Development, covers software work: it turns what you want into ISA criteria, makes them pass, and checks later whether the code still agrees with them.

It routes each request to one of four workflows. Build turns intent into ISA criteria and makes them pass. Test proves the ISA is well formed, matches the code, and that each criterion's Assay eval passes. Modify changes criteria first, then code. Checkup joins the ISA with production, Vigil, Errata and Achilles, explains why each red criterion is red, and repairs the ISA. Small work is handled inline; wide work runs as a workflow.

  • Build: new app, site, game, tool, CLI or pipeline, or a feature in an existing repo with no ISA
  • Test: run the app evals and check the code is in sync with the ISA
  • Modify: change, fix or remove behavior in an app that already has an ISA
  • Checkup: health check, audit the ISA, or explain why criteria are red

Install the Development skill from a ZIP

Download the ZIP for the Development skill from this page and unzip it. For a personal install, place the unzipped Development folder inside ~/.claude/skills/. For a single project, place it inside that project's .claude/skills/ folder. The agent loads skills from these locations.

If you use the Claude apps instead, upload the skill under Settings → Capabilities → Skills.

  • Personal: ~/.claude/skills/Development
  • Per project: .claude/skills/Development inside the project folder
  • Claude apps: Settings → Capabilities → Skills, then upload

Check the requirements before you rely on it

The skill is not standalone. It needs the Bun runtime, because its bundled tools are TypeScript run with bun. It also needs a LifeOS installation that provides the paths and tools it references: Paths.ts, IsaTestStrategy, Assay and the ISA templates.

Vigil, Errata and Achilles are optional sources read by Checkup. If any is missing, Checkup reports it as unavailable rather than clean. The skill runs scripts but does not use the network.

  • Bun runtime (the bundled tools are TypeScript run with bun)
  • A LifeOS installation with Paths.ts, IsaTestStrategy, Assay and ISA templates
  • Optional: Vigil, Errata and Achilles for Checkup; missing ones show as unavailable
  • Runs scripts: yes. Uses network: no.

Trigger the skill with natural requests

You do not need a special command. Describe the work in plain words and the agent matches it against the skill's trigger phrases. Phrases the skill lists include build an app, start a new project, implement or change a feature, fix a bug in an app, test the app, is the code in sync with the ISA, run the app evals, health check, why are these ISCs red and audit the ISA.

The skill is not for every request. It excludes editing an ISA's wording alone, eval or judge design, creating new skills, workflow definitions, slides, images, and deploying. For deployment, use the project's own deploy command.

  • Good: "Build a small inventory app and get its ISA written first."
  • Good: "Is the code in sync with the ISA? Run the app evals."
  • Good: "Health check this app and tell me why these ISCs are red."
  • Not for: "Deploy this to production" (use the project's deploy command).

Know what it will and will not do

Before code changes, the agent records acceptance criteria in an ISA. For user-facing work it expects a reference to compare against and a recorded acceptance verdict before calling anything done. Trivial changes such as a typo can skip the ISA, but in a project that has an ISA the skill says even small changes still touch it.

The skill does not deploy and does not write production data. Build and Modify end with an independent code review on the committed code the run touched. A run cannot clear its own review with the override flags; those are reserved for the principal.

  • Criteria are written before the code that satisfies them
  • User-facing work needs an approved reference and a recorded acceptance verdict
  • No deployment and no production data writes

What people use it for

  • Start a new small app with a written ISA and passing evals before the first deploy
  • Add a feature to an existing app that already has an ISA, with criteria written first
  • Fix a bug and leave behind a criterion whose eval would have caught it
  • Run a health check that explains why specific ISA criteria are failing
  • Bring an old repo with no ISA into a criteria document, then keep it in sync

Frequently asked questions

How do I install the LifeOS Development skill?

Download the Development ZIP from this page and unzip it. Place the folder in ~/.claude/skills/ for personal use or in a project's .claude/skills/ folder for one project. In the Claude apps, you can instead upload it under Settings → Capabilities → Skills.

What does the Development skill require?

It requires the Bun runtime because its tools are TypeScript run with bun, and a LifeOS installation providing Paths.ts, IsaTestStrategy, Assay and the ISA templates. Vigil, Errata and Achilles are optional for Checkup and are reported as unavailable if missing.

Is the LifeOS Development skill free?

The skill is published under the MIT licence, as stated on this page. Check the repository's licence file for the full terms.

Does the Development skill use the network or run scripts?

It runs scripts, since its bundled tools are TypeScript run with bun. It does not use the network, according to this page's listing.

Will it deploy my app?

No. The skill states it does not deploy or write production data. Deployment is handled by the project's own gated deploy command.

Can I use it without the LifeOS ISA system?

Not as described. The skill assumes LifeOS folder structure and tools such as Assay, Vigil and Errata, so without them it will not work as described. For quick one-off scripts, the criteria overhead is not worth it.

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Our verdict

Use the Development skill if you already work with LifeOS ISA files, want your agent to keep code and acceptance criteria in agreement, or want written criteria and test evidence before shipping a feature. Skip it if you do not use LifeOS, need a quick one-off script, or want an agent that deploys for you.

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