Run Your First Slice

This walkthrough shows a slice going from Planned on your Eventmodelers board to a tested, working Cratis vertical slice in your .NET / C# project — with no manual coding in between.

Prerequisites

Install the kit and connect it to a board first. The loop needs a running agent (node .build-kit/ralph-claude.js) and valid credentials in .eventmodelers/config.json.

Look at the example slice first

Every install ships a working example under SomeModule/SomeFeature/ — a Registration slice (a command and its event) and a Listing slice (a projection and read model). Open them before you build your own; they show every convention the kit’s build skills reproduce:

• One file per slice, with the command/event/reactor together
• @Command/@EventType-style artifacts with a handle()-shaped method that returns the event
• The React screen and command wiring in .tsx/.ts files beside them

Start the loop

node .build-kit/ralph-claude.js

The loop polls for two independent triggers — see Understanding the Loop — and idles quietly until one fires.

1. Mark a slice Planned on your board

On app.eventmodelers.ai, create or open a slice and set its status to Planned. For example, a “Register Author” slice might look like:

{
  "id": "slice-123",
  "title": "Register Author",
  "status": "Planned",
  "contextName": "Authors",
  "sliceType": "StateChange",
  "commands": ["RegisterAuthor"],
  "events": ["AuthorRegistered"],
  "description": "Register a new author with name and email"
}

2. The kit fetches and persists the slice

The real-time subscription picks up the status change and saves the definition to .build-kit/.slices/Authors/register-author/slice.json.

3. The kit generates the vertical slice

Because the slice only carries commands/events (no processors, no projections/queries), the loop routes to the build-state-change skill, which generates Authors/Registration/RegisterAuthor.cs:

[Command]
public record RegisterAuthor(AuthorId Id, AuthorName Name) : ICanProvideEventSourceId
{
    public EventSourceId GetEventSourceId() => Id;

    public AuthorRegistered Handle() => new(Id, Name);
}

[EventType]
public record AuthorRegistered(AuthorId Id, AuthorName Name);

4. The kit builds and tests the slice

dotnet build Authors.Registration
dotnet test Authors.Registration.Specs

5. The kit updates the board to Done

Once the build and tests pass, the kit calls back to the platform and marks the slice Done — closing the loop without you touching an editor.

What’s next

• Try a slice with projections/readModel set — it routes to build-state-view instead
• Try a slice with processors set — it routes to build-automation
• If a slice gets stuck in InProgress, check the loop’s terminal output, confirm dotnet build succeeds locally, then re-run the loop