Eventmodelers Build Kit - Java

Real-time Claude agent that connects to the Eventmodelers Platform and implements board slices as Cratis (Arc + Chronicle) vertical slices in a Java project.

What This Kit Does

When a slice is marked Planned on your Eventmodelers board, this kit automatically:

1. Connects to the Eventmodelers Platform in real-time
2. Fetches the slice definition and board context
3. Generates a complete Cratis vertical slice (commands, events, projections, read models, React components)
4. Builds the slice with ./gradlew build and runs tests with ./gradlew test
5. Updates the board status to Done when complete

The entire process happens automatically, with your Claude agent implementing the slice according to Cratis best practices.

Where to Start

• Install the Kit — Get up and running in five minutes
• Run Your First Slice — Watch a slice go from Planned to Done
• Connect a Board — Wire the kit up to your Eventmodelers board

How It Works

The kit implements the Eventmodelers Build Kits platform contract:

1. Real-time board subscription — The kit subscribes to your board’s slice status changes
2. Status-based triggers — Two independent loops:
   • tasks.json non-empty → run prompt.md (reacts to status changes)
   • Slice is Planned in .slices/*/index.json → run backend-prompt.md (builds one slice)
3. Slice-type routing — Automatically routes to the correct build skill:
   • TRANSLATION or processors[] → build-automation (reactors/automation)
   • projections/queries/readModel → build-state-view (read models)
   • Otherwise (commands/events) → build-state-change (commands/events)
4. Cratis conformance — Generated slices follow Cratis best practices:
   • One public type per file (one slice folder per slice) — command, event, and reactor sit together
   • @Command records carry a handle() method — no separate handler class
   • @EventType records use past-tense, self-describing names
   • ConceptAs<T> wraps identities and values in events and read models instead of raw primitives
   • Read models are exposed as Arc queries annotated with @Path
   • Package mirrors the folder structure

See Understanding the Loop for the full mechanics.

Place in the Cratis Ecosystem

This kit sits between the Eventmodelers Platform and Cratis:

• Upstream: Eventmodelers Build Kits — The platform that manages board slices
• This Repository: Eventmodelers-Build-Kit-Java — The Java implementation
• Downstream: Cratis Chronicle + Cratis Arc — The frameworks the generated slices build on

See the sibling kits for other language implementations: C# and Kotlin.

Installation

Install from git (this package is private, so use the git install path):

npx github:Cratis/Eventmodelers-Build-Kit-Java install

Or use the upstream CLI with this repository as a git stack:

npx @eventmodelers/cli init --stack cratis-java --git https://github.com/Cratis/Eventmodelers-Build-Kit-Java

After installation, run:

node .build-kit/ralph-claude.js

Next Steps

1. Install the kit
2. Connect your Eventmodelers board
3. Mark a slice as Planned on your board
4. Watch the kit automatically implement it as a Cratis vertical slice — see Run Your First Slice

See Also

• Understanding the Loop — How the two triggers work independently
• CLI Commands — install, uninstall, and status
• Cratis Conventions — The conventions the kit enforces, generated from the Cratis AI corpus
• Eventmodelers Build Kits platform contract — The platform skills the kit uses