Browser-owned input

Drafts stay in the renderer

Declare ui.local("form", initialValue) inside the surface and select the field that an editable control should change. For a form with a numeric temperature:

• TypeScript: use form.field("temperature").bind() for a control and form.field("temperature").value() in an action payload.
• Python: use a typed initial value, such as a RunInput dataclass, and pass form.temperature as the control’s bind=. Pass input=form to send the whole form or input={"temperature": form.temperature} to compose the payload. Explicit typed projection uses form.field("temperature", float) followed by .bind() or .value().
• Rust: derive ActionInput for RunInput, then use form.field(RunInput::field_temperature()).bind()? for a control and form.field(RunInput::field_temperature()).value() in the generated RunInputInput.

bind() and value() take no pointer argument. Without a field projection, they refer to the whole Local value. See the SDK reference for action registration and SDK examples for complete forms.

When the user invokes the action, the renderer resolves expressions into concrete JSON. The application runtime never stores the unfinished draft.

Rerenders and resets

A Local’s initial value is applied once. Server rerenders preserve an existing draft. Use resetKey (TypeScript), reset_key (Python), or local_with (Rust) when you explicitly need to reset it. Updating application state alone is not a request to overwrite a draft.

Use stable component keys for controls that appear conditionally. See the SDK examples for a complete form.