FLUX.1 Fill [pro] is a specialized model within Black Forest Labs's FLUX.1 lineup, available through AI Gateway since October 1, 2024 as part of the image-only model expansion. Unlike the Kontext models that focus on instruction-based editing, Fill Pro is specifically engineered for inpainting: generating content for a defined masked area within an existing image.
Inpainting requires a model that simultaneously understands the unmasked context (colors, textures, lighting direction, perspective, stylistic character) and generates new content for the masked region that blends seamlessly. FLUX.1 Fill [pro] treats this as its primary function, making it more appropriate for mask-based fill workflows than general-purpose editing models.
Practical applications include object removal and replacement, background extension (outpainting), e-commerce product photo cleanup, and generative content insertion (placing a new element by masking its target region and describing it in a text prompt).