How to provide default values for individual fields in Angular 21 Signal Forms (without UI flicker) when implementing a FormValueControl?

We're starting to look at Angular 21's new signal-based forms, but I can't find a clean way to define default values for each form field, especially when building forms for objects where multiple keys may be undefined.

Ideally, I'd like to set a default value either:

• On the whole form, so that missing properties in the model are patched with defaults (like with a schema or options parameter); or

• Directly on fields, so that if a field's value is undefined, the form provides a fallback until the user provides input.

Here's what I'd like to do, but I think this isn't supported in Angular 21:

@Component({ selector: 'signal-form-default-value-example-1', template: `<input type="number" [field]="valueForm" />`, imports: [Field] }) export class SignalFormDefaultValueExample1 implements FormValueControl<number | undefined> { public readonly value = model<number>(); protected readonly valueForm = form(this.value, { defaultValue: 42 }); // << would be ideal! } 

I know that I can set the default up-front in the model (works for flat values):

public readonly value = model<number>(42); protected readonly valueForm = form(this.value); 

But for complex objects where fields may be missing, this doesn't scale:

interface Value { a?: number; b?: number } @Component({ selector: 'signal-form-default-value-example-3', template: `<input type="number" [field]="valueForm.a" /> <input type="number" [field]="valueForm.b" />`, imports: [Field] }) export class SignalFormDefaultValueExample3 implements FormValueControl<Value | undefined> { public readonly value = model<Value>(); protected readonly valueForm = form(this.value, { defaultValue: { a: 17, b: 42 } }); // not supported } 

or per-field default:

<input type="number" [field]="valueForm.a" [fieldDefault]="17" /> 

I've tried:

• Using effects to patch missing values, but the UI briefly shows no/default state, causing flicker. Or I get type errors when I want to pass a field to an edit component that requires a value

• Separating the value input and valueChange output and a linkedSignal in between to patch the default there - but the FormValueControl expects a value model, so I can't split input and output.

Is there any "official" or ergonomic way to provide default values for individual fields in Angular 21 signal forms, so that fields always start with a meaningful value even when the data is missing or partially undefined? If not, what are recommended patterns to work around this cleanly (without UI flicker)?

My main requirements:

• Defaults are applied before the UI renders.
• I can specify defaults at field level and/or globally.
• No extraneous UI flicker from patching values after initialization.