Backend Contract

Transports receive model values keyed by resolved mappedTo targets:

{
  "modelValues": {
    "feature_key": "serialized value"
  }
}

Return explicit report envelopes:

{
  "reports": [
    {
      "backend": "default",
      "mappedTo": "report_key",
      "status": "ready",
      "payload": { "value": "model output" }
    }
  ],
  "meta": {
    "model": "version"
  }
}

Use request.displayValues for review/export data keyed by displayKey; fields without displayKey are omitted. Use request.modelValues for backend/model data keyed by mappedTo. Field id remains a runtime handle for UI state.

These identities must be unambiguous. Schema normalization rejects duplicate displayKey values and overlapping submission paths produced by mappedTo, valuePath, or custom definition hooks. Both exact duplicates (profile.name twice) and parent/child overlaps (profile with profile.name) fail before the runtime is created. Targets used only by separate backend routes must still be unique because a snapshot without a backend includes every applicable target.

Use createSubmissionSnapshot(form, options) when an app needs the same records for review, persistence, or export before submit. Snapshot records and their plain object and array containers are frozen. Opaque values such as dates, maps, sets, binary views, and blobs are cloned for isolation but retain their platform mutation APIs; clone a snapshot before adapting it to a mutable application format.

Use createMultiBackendSubmissionSnapshot(form, { backends }) when one visible form feeds several models with different mappedTo keys. Use executeMultiBackendPipeline({ form, backends }) when one user action should submit each backend and keep per-backend results, report fetch outputs, errors, skipped reports, and report contexts. Backend names must be non-empty and unique. Ordinary failures follow continueOnError; cancellation always stops the remaining runs.

ready requires payload. pending carries optional report-specific context into client fetch. skipped records non-applicability as terminal state. Each envelope is addressed by its exact (backend, mappedTo) pair; malformed and legacy shapes fail submission.