Grain
AI agents either skip grain entirely or link to a PNG tile. Real film grain uses an inline SVG feTurbulence noise applied through an oversized pseudo-element that jumps between positions using steps() — not smooth tweening. The grain must use mix-blend-mode: soft-light and pointer-events: none, or it either blocks content or looks like a white sheet pasted on top. Agents miss the animation, miss the blend mode, and miss the data URI technique.