FCoT

FCoT (Chain‑of‑Thought Segmentation) is replicate the step-by-step reasoning process a human annotator follows when using SAM2 to generate masks. Each example pairs an image with:

• A bounding box locating the target object,

• A sequence of foreground/background point prompts for refining the mask,

• Natural language explanations (chain‑of‑thought) generated by Gemini‑2.5‑Pro summarizing the annotation process.