RENDER a timeline the way an export would and report what does not work — call it before you call any timeline done. inspect_timeline shows a few frames through the preview path, which quietly substitutes a nearby picture where a frame cannot be rendered; this renders every motion segment the timeline reads (through every nested timeline) exactly, then composites every frame with every layer (footage decoded), and fails where an export would. Returns {jobId}; poll get_job_status every ~5 s. When done, result is {verdict: ok | problems | incomplete, checked, notChecked, segments, chunks, problems: [...same shape as get_problems, with related warnings that often name the cause...], stale?, note}. incomplete is NOT a pass: something could not be checked. stale: true means the timeline was edited while it ran — verify again. Sound is not checked. Needs the project open in the editor tab you are paired with (error PROJECT_NOT_OPEN otherwise).