Threadrunner 丝行者 is a Spider‑Man‑style parkour traversal video generation app built on Seedance 2.5. Upload any subject—person, animal, doll, robot—and the app has that subject fire webs, swing high across New York’s skyline, do a three‑step wall run, push off taxi roofs, then charge up a red‑brick facade onto the rooftop and stick the landing. Realistic gravity and inertia, 16:9 cinematic framing; movements are cool and restrained, like an urban climber who’s done it a hundred times.