#Host-managed data sources

The next runtime loads dynamic options through the embedding host. A form document stores only an approved registry key and bounded scheduling settings, never endpoint addresses or credentials.

const hostAdapter = {
  async resolveDataSource(request, signal) {
    return modelCatalog.list({
      provider: request.value.provider,
      query: request.query,
      cursor: request.cursor,
      limit: request.limit,
      signal,
    });
  },
};

A data source can declare field dependencies, a mount or focus trigger, TTL caching, search debounce, and cursor pagination. The Renderer coalesces identical in-flight requests, cancels work replaced by a newer request, and scopes caches to the current host adapter. Unrelated field changes do not reload options.

#Option sources in Designer

After a document declares dataSources, the property panel for select, radio, and multi-select displays an Option source setting. Selecting a host data source exposes the registry key, load trigger, and search capability while hiding the static option editor. Switching back to a static source restores the option editor.

A dynamic source stores only its data-source ID. It does not store endpoints, credentials, or loaded results. Field Schema still owns value types and business constraints; an enum can remain as an allowlist when dynamic results must be restricted.

Loading, unmet dependencies, empty results, failure and retry, and load-more behavior are accessible runtime states. Legacy option arrays and paginated { options, nextCursor } responses are both accepted and structurally checked before rendering.

Repeaters can declare dependencies such as routes.*.provider. The Renderer sends the concrete row location to the host:

request.scope = {
  nodeId: 'route-model',
  valuePath: 'routes.2.model',
  rowIndices: [2],
  dependencies: [
    { template: 'routes.*.provider', path: 'routes.2.provider' },
  ],
};

The host reads request.value at the supplied concrete paths. Request keys, cancellation, caches, and pagination remain isolated per row. Form-level fields can still reuse an identical data-source request.

See the complete data-source protocol for compiler limits, request keys, custom components, and tenant isolation.