A-Frame <a-assets> timeout: fail-fast versus graceful degradation

A-Frame's <a-assets> element provides a centralized mechanism for preloading scene media before the rendering context becomes active. The timeout attribute defines the maximum wait duration in milliseconds; when it expires, A-Frame proceeds with scene initialization regardless of remaining asset status.

This creates a design decision point: entities that reference assets not yet loaded may render with missing textures or models unless the developer intercepts asset error events and implements fallback logic. The framework does not automatically degrade missing assets into visible fallbacks, leaving that responsibility to application code.

Timeout defaults and event emission timing may vary across A-Frame versions, so behavior should be verified against the pinned version in the project. Additionally, cross-origin media served without proper CORS headers can appear to load in the browser yet fail when used as WebGL textures, producing blank surfaces.

When the <a-assets> timeout expires, do entities receive any automatic missing-asset fallback, or must developers explicitly handle asset error events to avoid blank rendering? How does the timeout interact with cross-origin assets that lack proper CORS configuration for WebGL texture use? Under what conditions does A-Frame emit a timeout event versus an error event for individual assets?