Compared with Angular Reactive Forms

An honest comparison — Reactive Forms is a good, official API. This library exists because Signals allow a different trade-off, not because Reactive Forms is “wrong”.

The side-by-side snippet below is not pseudocode: it’s mirrored verbatim in comparison-reactive-forms.spec.ts, which builds both forms and asserts they agree on the same invalid → valid transition for the same inputs.

Side by side

The same form in both APIs:

// Reactive Forms
readonly form = new FormGroup({
  email: new FormControl("", { nonNullable: true, validators: [Validators.required, Validators.email] }),
  address: new FormGroup({ city: new FormControl("Rome", { nonNullable: true }) }),
});
// template: <input formControlName="email" />  — "email" is a string, typos are runtime bugs
// value: Partial<…> with disabled-field caveats; state via valueChanges (RxJS)

// @modyra/angular
readonly form = mdyForm({
  email: field("", [mdyRequired(), mdyEmail()]),
  address: group({ city: field("Rome") }),
});
// template: <mdy-control-text [field]="form.f.email" />  — typos do not compile
// value: fully typed; state via signals (form.f.email.valid(), form.state.canSubmit())

Concrete differences

Aspect	Reactive Forms	@modyra/angular
State model	FormControl/FormGroup classes, RxJS streams	Signals: value(), valid(), pending() are computed
Field binding	formControlName="email" (string)	[field]="form.f.email" (compile-checked)
RxJS	Required (valueChanges, async validators)	Not used: no runtime dependency, no Observables in the public API, none internally
Async validation	AsyncValidatorFn (Observable/Promise)	Promise-based, debounce + cancellation + last-wins + timeout + cross-field built in
UI controls	Bring your own / Material	Optional built-in renderer catalog, or headless /adapter
Change detection	Works everywhere	Signals-first; zoneless-friendly
Stability & ecosystem	Official, mature, huge ecosystem	Young, one maintainer, smaller surface tested
Migration cost	—	Incremental via mdyCva (CVA interop)

serverValidator() also differs from the newer Angular signal forms validateHttp: there’s no inline URL to couple to a service — you call your own service method and get ctx.signal/ctx.form for cancellation and cross-field reads, so the library handles the plumbing without owning the HTTP layer.

Choose this library if…

• You want field bindings checked by the compiler, not by runtime errors.
• Your app is signals-first (or zoneless) and you don’t want RxJS in forms.
• You want async/cross-field validation, drafts, undo/redo and devtools without assembling them yourself.
• You can accept a young library (pin versions, read the changelog).

Stay with Reactive Forms if…

• You need the stability and support guarantees of an official Angular API.
• Your team already has deep Reactive Forms expertise and tooling.
• You rely on ecosystem packages built around AbstractControl.
• You target Angular versions older than 21.

Performance

No published benchmarks yet — we make no performance claims until reproducible measurements exist. Architecturally, per-field signals mean a keystroke recomputes that field’s computeds rather than re-validating the whole tree, but verify with your own workload.