Vertex AI Search adds search-as-you-type for custom search apps in Preview

Agent Search: Search-as-you-type for custom search apps (Preview)

You can configure schema fields to support search-as-you-type in custom search apps. Search-as-you-type returns a refreshed set of ranked documents on every keystroke before a user finishes typing a full query. Unlike autocomplete, which suggests query strings, search-as-you-type returns matching documents so that users can browse an updating result list and find the right result mid-query.

This feature is in Public Preview. For more information, see Configure field settings.