type MediaInputRole =
| "reference"
| "mask"
| "control"
| "start_frame"
| "end_frame"
| "character";Defined in: packages/ai/src/types.ts:1715
Optional role hint on a media input part (image / video / audio). Adapters read metadata.role to route the part to the provider-specific request field — e.g. 'mask' → OpenAI mask / fal mask_url, 'end_frame' → fal end_image_url, 'reference' → fal reference_image_urls. When omitted the adapter falls back to positional routing.