Scripty: An External Script Supervisor for Continuity in Story-Level Video Generation

Story-level video generation runs a model clip by clip inside a harness that writes prompts and picks reference images, yet a detail set in one clip, such as a cut braid, often reverts in the next: retaining event history does not specify the current state, and correct text can still conflict with an outdated reference image. The harness must know which states still apply, and both the prompt and the reference images must show them. We present Scripty, a continuity module that works like a film set's script supervisor, attached via host-specific adapters without modifying host code or models. From frozen storyboards, asset lists, and reference images it builds a state record, each change citing its storyboard line, and it keeps each state until the storyboard changes it, injecting states into prompts and guiding reference-variant generation. Generated prompts and clips never serve as state evidence. We introduce StateHold, a benchmark that asks whether a later clip depicts the state the storyboard specified at that point. On a fixed host across 42 stories, Scripty reaches 48.8% cross-unit fact pass rate versus 26.0% for native recap (+22.8 pp); adding reference-image variants improves this further, with some within-unit losses. These results support improved storyboard-state conformance but do not establish better viewer-perceived continuity or reliable state expiry.