InternVideo3: Multimodal Context Reasoning Empowers Video Agents

This article introduces InternVideo3 developed by Shanghai AI Laboratory/OpenGVLab. It extends open-source multimodal models into visual agents supporting long-term video understanding and iterative interaction through Multimodal Context Reasoning (MCR) and Multimodal Multi-Head Latent Attention (M²LA) technologies. The model addresses challenges in video understanding such as long-term dependencies and temporal dynamics. The open-source project is available at https://github.com/OpenGVLab/InternVideo, and the original paper was published on arXiv (2026-06-10, link: http://arxiv.org/abs/2606.12195v1).

Large Language Models (LLMs) are evolving into agents that can autonomously perform multi-step tasks, but open-source agent research is mainly focused on text scenarios, with exploration of visual multimodal capabilities lagging behind. Video understanding faces unique challenges: long-term dependencies (needing to maintain memory of early content), temporal dynamics (understanding event sequence and causality), multimodal fusion (heterogeneous information like vision/audio/subtitles), and iterative interaction (repeated viewing for verification). Existing solutions use a "single-pass" architecture, which has limitations such as context length constraints, lack of iterative ability, static representations losing temporal information, and inability to use tools.

Core Innovations: 1. Multimodal Context Reasoning (MCR): Defines video understanding as closed-loop reasoning, maintaining dynamic context (observation, instruction, reasoning, tool actions, memory), and processes long videos through a cyclic mechanism of evidence collection → reasoning verification → conclusion formation; 2. Multimodal Multi-Head Latent Attention (M²LA): Uses token retention reparameterization technology to compress KV cache into a low-dimensional latent space, balancing efficiency and accuracy, reducing memory usage by 60-80%.

Training Strategy: Four stages: 1. Continuous pre-training (building basic capabilities with large-scale video-text data); 2. Short-to-long supervised fine-tuning (transitioning from 1-minute to over 1-hour long videos); 3. Rule-based reinforcement learning (optimizing tool usage and evidence collection strategies); 4. Online policy distillation (transferring strategies to efficient models).

It performs excellently on multiple authoritative benchmarks: 1. Video-MME (Video Multimodal Understanding): Achieves state-of-the-art results in multiple subtasks, with obvious advantages in long video tasks; 2. MLVU (Long Video Understanding): Significantly outperforms single-pass baselines, and the evidence collection strategy improves accuracy; 3. EgoSchema (First-person Perspective): Excels in fine-grained action recognition, and context reasoning helps understand complex activities.

In addition, video agent demos show that it can integrate retrieval tools (semantic search, result integration) and has evidence-oriented behaviors (systematic collection, conflict identification, conclusions based on evidence).

Technical Contributions: 1. MCR framework: Converts video understanding into a closed-loop evidence accumulation process; 2. M²LA mechanism: Efficient attention technology reduces memory and computational overhead; 3. Phased training: Progressive strategy builds long video processing capabilities; 4. Open-source implementation: Promotes community research.

Application Prospects: Video content moderation (violation clip identification and interpretable reports), educational video analysis (knowledge point extraction and summary generation), surveillance video understanding (abnormal event identification and timeline generation), film and television production assistance (material tagging and scene retrieval).

Current Limitations: Still significant computational resource requirements, real-time video stream processing needs optimization, insufficient multilingual support.

Future Directions: Develop real-time video agents (for live broadcast monitoring), multi-agent collaboration to process ultra-long videos/video libraries, combine embodied intelligence to support visual autonomous decision-making, integrate world models to enhance reasoning capabilities.