building-with-typesafe-jev

Building with TypeSafe Jev Typed decisions with calibrated confidence, for your coding agent. Links to 150+ community projects, sorted by shape, with a code sketch for each.

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[!NOTE] This is an unofficial, community skill. It is not made, reviewed, or endorsed by TypeSafe AI. TypeSafe publishes its own skill at typesafe-ai/skills. See How this differs from the official skill.

Coding agents treat Jev like one more chat model. This skill teaches them to design for it: typed questions, calibrated confidence, and links to 150+ community projects, sorted by how they work, with a code sketch for each pattern. It installs in Claude Code, Codex, Antigravity CLI, Muse, and Muse Code.

Jev is a System One model. It does not write text. You send it content and a set of typed questions, and it answers each one with a value and a calibrated probability, usually in 100 to 200 ms:

• Choice picks one option from a list. Example: route a ticket to billing, shipping, or support.
• Score places the content on a scale you describe. Example: grade a pull request from "ignores the spec" to "meets the spec".
• Noul gives the probability that a yes/no statement is true. Example: "this shell command deletes files outside the project."

Install

Claude Code

claude plugin marketplace add aaddrick/building-with-typesafe-jev

claude plugin install building-with-typesafe-jev@building-with-typesafe-jev

The skill loads on its own when you work on Jev code. To load it by hand, type:

/building-with-typesafe-jev:building-with-typesafe-jev

Claude Desktop, Cowork, and claude.ai

Step 1. Open Customize > Plugins, select Add, then Add marketplace.

Step 2. Choose Add from a repository.

Step 3. Enter aaddrick/building-with-typesafe-jev. Leave Sync automatically on so the plugin updates when this repository does. Then select Sync.

Step 4. Select Add next to Building with typesafe jev.

Step 5. Claude confirms the plugin is installed. It also appears in the desktop app and Cowork on the same account.

Codex

codex plugin marketplace add aaddrick/building-with-typesafe-jev

codex plugin add building-with-typesafe-jev@building-with-typesafe-jev

Start a new thread. Codex loads the skill when the task matches. To load it by hand, type:

$building-with-typesafe-jev:building-with-typesafe-jev

Antigravity CLI

agy plugin install https://github.com/aaddrick/building-with-typesafe-jev

Check that it installed:

agy plugin list

Start a new session. Antigravity CLI loads the skill when the task matches. To load it by hand, type:

/building-with-typesafe-jev:building-with-typesafe-jev

Coming from Gemini CLI? If agy plugin import gemini brought this extension over, run the install command above anyway so the current copy replaces the imported one.

Muse (muse.ai)

Muse loads skills from ~/workspace/skills/ on its own computer. Paste this command into a Muse chat and ask Muse to run it:

curl -fsSL https://raw.githubusercontent.com/aaddrick/building-with-typesafe-jev/main/scripts/install_muse.sh | bash

The script copies the skill folder there and rewrites the SKILL.md header into the shape Muse reads. Start a new chat. Muse loads the skill when the task matches. To update, run the command again.

Muse Code

Clone the repository:

git clone https://github.com/aaddrick/building-with-typesafe-jev.git

Install the skill for every project:

muse skills install building-with-typesafe-jev/skills/building-with-typesafe-jev --scope user

Check that it installed:

muse skills list

Start a new session. Muse Code loads the skill when the task matches. To load it by hand, type:

/building-with-typesafe-jev

Any other agent that reads SKILL.md

Copy the skills/building-with-typesafe-jev/ folder into your agent's skills folder. Keep the whole folder. SKILL.md links to the files beside it.

Set up an API key (optional, recommended)

The skill works without a key. With TYPESAFE_API_KEY set in the agent's shell, the agent can check its design against the live API before the code reaches your project. That catches wrong field names, and questions Jev reads differently than you meant. Each call costs a fraction of a cent.

Create, store, and troubleshoot a key

Create a key (four steps in the TypeSafe console)

Step 1. Sign in at console.typesafe.ai and open API Keys in the sidebar.

Step 2. Click Create key at the top right.

Step 3. Name the key after where it will live, such as the machine or the agent. Then click Create key.

Step 4. Copy the key now. The console shows it once. If you lose it, create a new one and revoke the old one.

Store the key (macOS, Linux, Windows)

Keep the key in its own file, readable only by you, and export it as TYPESAFE_API_KEY. Agents often start shells without a terminal, so each section puts the key where those shells can see it. Pick your system.

macOS (zsh, the default shell)

Save the key to a private file:

mkdir -p ~/.config/typesafe && umask 077 && printf 'export TYPESAFE_API_KEY=%s\n' 'YOUR_KEY' > ~/.config/typesafe/env

Load it from ~/.zshenv. Every zsh reads that file, including shells that agents start without a terminal. ~/.zshrc is read only by interactive shells.