RMT Playground

The RMT Playground compiles RMT-vNext source inside the Developer Center. It uses x-surface-manager for the workspace, x-textarea for the first editor version, diagnostics and JSON output panels, and a safe preview target that never renders raw compiler HTML.

Try It

The interactive playground is rendered below this article. Change the source and the compiler runs after a short debounce. Diagnostics show line and column ranges when the compiler can provide them.

template learn.rmt.playground {
  state preview.message type object preserve {
    initial {
      id "hello"
      text "Hello from the playground"
      tone "success"
    }
  }

  selector preview.message from state preview.message {
    output PreviewMessage
  }

  surface preview.card kind card component x-status {
    source selector preview.message
    key message.id

    lane visible weight 80 {
      hydrate preview-card from selector preview.message
    }
  }
}

Safety Model

The compile endpoint accepts POST requests only, limits source size and returns JSON diagnostics plus core output. The preview surface renders a structured summary with DOM APIs, not innerHTML.

Maraca Runtime Preview

Successful sources are also sent with playgroundMode: "maraca-preview" to docs/index.php?xtend-rmt-playground=compile. The response still contains coreJson and preview, and adds maraca.schema = "xtend.docs.rmt-playground.maraca-preview.v1" with feature status for orchestration, kernel, hydration, validation and transitions.

Choose the Customer Service Kernel preset to run the app from tools/rmt-language/fixtures/kernel-orchestration-contract.rmt in the browser. The preview loads only the whitelisted runtime modules from DOCS_RMT_PLAYGROUND_MARACA_RUNTIME_MODULES, materializes surfaces in an isolated root, routes DOM events to RMT actions, patches validation gates such as product.service.nextContact and records transition events such as xtend-maraca:surface-transition-start.

Browser smokes can read window.xtendDocsRmtPlaygroundLastMaraca. A successful snapshot includes kernel, validation and transition counters; the local gate is node scripts/run_xtend_tests.js rmt-playground-docs rmt-playground-security --json.

From Playground To Bundle

Use the playground for quick syntax and model tests, but rely on Maraca for production app orchestration. Copy a working example into a .rmt file, add real portals, validation and transitions, then build it with xt maraca build. That checks the same RMT expression against the bundle report, kernel plan and browser bridge instead of only the preview output.

Next Step

Finish the guided path with Next Steps.

Current source and compiler backend

The Playground keeps at most one compile/diagnostics request active and retains only the latest pending source per operation. Automatic compile waits 300 ms and diagnostics 160 ms; Run flushes the latest source without further debounce. Stale responses, preset loads and preview boots cannot replace newer state. Leaving releases fetch, scheduler and preview-runtime resources. A new preview still performs a full boot; there is no live DOM patch.

The default backend is legacy. Hosts may explicitly enable Hydrangea JIT to combine compile, safe preview and Maraca preparation in one Node process and reuse verified framework artifacts. Request coordination and generation guards apply independently of that backend switch.

XTend Developer Center