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Designer → Sandbox

This page connects Design your first system and Try the Sandbox into a single walkthrough. By the end you’ll have a real EvidentSource component (that you designed) running in the Sandbox and reachable from a client.

1. Model it in Designer

Section titled “1. Model it in Designer”

Open designer.evidentsource.com. Create a project. Sketch:

  • Events: what your system records
  • Commands: what users send in
  • State views: what the app reads back

Full walkthrough: Design your first system.

2. Generate the code

Section titled “2. Generate the code”

Hit Generate in Designer. Pick your language. Download the archive or clone the generated repo.

You’ll get decide function stubs for each command and evolve stubs for each state view. Fill in the business logic — the types, commands, and view shapes are already in place.

3. Build the WASM components

Section titled “3. Build the WASM components”

Each SDK has a single build command that produces WebAssembly components from your decide and evolve functions. The generated repo has a README with the exact command for your language.

4. Deploy to the Sandbox

Section titled “4. Deploy to the Sandbox”

From Designer, click Deploy to Sandbox. Your components are uploaded and registered against a database in the Sandbox namespace. The page gives you the database name to point your clients at.

Alternatively, deploy from the CLI — see Deploying to Sandbox.

5. Issue a command from an SDK

Section titled “5. Issue a command from an SDK”

Point any SDK at https://sandbox.evidentsource.com and send one of the commands you just modeled. See Connecting with an SDK for the exact client setup per language.

6. Read a state view

Section titled “6. Read a state view”

Query one of your state views. The evolve function you wrote has been folding the events into it since step 5.

7. Trace what happened

Section titled “7. Trace what happened”

Query the event stream for your subject. You’ll see the event your decide function emitted, with full metadata — the command that produced it, when it landed, and the component version that handled it.

That’s an EvidentSource decision trace. Read Decision Traces & AI-Readiness for why this matters.

What’s next

Section titled “What’s next”