CoT-RVS: Zero-Shot Chain-of-Thought Reasoning Segmentation for Videos

ICLR 2026 Conference SubmissionAnonymous Authors
Multimodal Large Language ModelReasoning Video Object Segmentation
Abstract:

Reasoning Video Object Segmentation is a challenging task, aiming at generating a mask sequence from an input video given a complex and implicit text query. While existing works finetune Multimodal Large Language Models (MLLM) for the task, they still fail in video inputs given complex temporally-sensitive queries, indicating their lack of temporal and spatial integration in complex scenarios. In this paper, we propose CoT-RVS, a novel framework employing the zero-shot Chain-of-Thought (CoT) capability of MLLM to address these complex challenges by temporal-semantic reasoning: CoT-RVS analyzes the visible objects within a given frame that possibly match the language query (semantic), and chooses a corresponding keyframe for each object that can be observed effortlessly among all frames (temporal). Notably, the CoT-RVS framework is training-free and compatible with closed-source MLLMs, which can be applied to Reasoning Video Instance Segmentation. Our framework's training-free feature further allows its extension to process online video streams, where the CoT is used at test time to update the object of interest when a better target starts to emerge and becomes visible. We conduct extensive experiments on video object segmentation with explicit and implicit queries. The results show that CoT-RVS significantly outperforms previous works in both cases, qualitatively and quantitatively.

Disclaimer
This report is AI-GENERATED using Large Language Models and WisPaper (A scholar search engine). It analyzes academic papers' tasks and contributions against retrieved prior work. While this system identifies POTENTIAL overlaps and novel directions, ITS COVERAGE IS NOT EXHAUSTIVE AND JUDGMENTS ARE APPROXIMATE. These results are intended to assist human reviewers and SHOULD NOT be relied upon as a definitive verdict on novelty.
NOTE that some papers exist in multiple, slightly different versions (e.g., with different titles or URLs). The system may retrieve several versions of the same underlying work. The current automated pipeline does not reliably align or distinguish these cases, so human reviewers will need to disambiguate them manually.
If you have any questions, please contact: mingzhang23@m.fudan.edu.cn

Overview

Overall Novelty Assessment

The paper proposes CoT-RVS, a training-free framework that applies chain-of-thought reasoning from multimodal large language models to reasoning video object segmentation. It resides in the 'Chain-of-Thought and Explicit Reasoning' leaf, which contains five papers total including the original work. This leaf sits within the broader 'Temporal Reasoning and Query Understanding' branch, indicating a moderately populated research direction focused on interpretable temporal logic rather than end-to-end learned fusion. The taxonomy shows this is an active but not overcrowded area, with sibling works exploring similar explicit reasoning paradigms.

The taxonomy reveals neighboring leaves addressing temporal constraints through event-based reasoning and LLM-driven world knowledge integration, both under the same parent branch. Adjacent branches include 'Multimodal Fusion and Alignment' emphasizing learned cross-modal attention without explicit reasoning steps, and 'Temporal Consistency and Propagation' focusing on memory-based tracking mechanisms. The paper's scope note explicitly excludes implicit latent embedding methods, positioning it closer to structured decomposition approaches like Think Before Segment rather than unified transformer architectures. This placement suggests the work diverges from purely data-driven fusion toward interpretable temporal analysis.

Among twenty-eight candidates examined, the first contribution on zero-shot CoT-based segmentation shows one refutable candidate from ten examined, indicating some prior overlap in training-free reasoning approaches. The keyframe selection pipeline examined ten candidates with none refutable, suggesting relative novelty in this specific temporal reasoning mechanism. The online reasoning extension examined eight candidates with no refutations, pointing to less explored territory in adaptive keyframe re-selection. The limited search scope means these statistics reflect top semantic matches rather than exhaustive coverage, so unexamined work may exist in related areas.

Given the constrained literature search of twenty-eight candidates, the framework appears to occupy a moderately novel position within explicit reasoning methods for video segmentation. The training-free aspect and keyframe selection mechanisms show fewer direct precedents among examined papers, though the broader zero-shot reasoning paradigm has some prior exploration. The analysis captures top semantic neighbors but does not claim comprehensive field coverage, leaving open the possibility of additional related work in adjacent research directions.

Taxonomy

Core-task Taxonomy Papers
50
3
Claimed Contributions
28
Contribution Candidate Papers Compared
1
Refutable Paper

Research Landscape Overview

Core task: Reasoning video object segmentation with complex temporal queries. The field addresses the challenge of identifying and segmenting objects in videos based on natural language expressions that involve temporal reasoning, such as 'the person who enters the room after the dog leaves.' The taxonomy reveals five main branches that capture complementary aspects of this problem. Temporal Reasoning and Query Understanding focuses on parsing and interpreting complex temporal expressions, with works like Chain-of-Thought RVOS[23] and Think Before Segment[6] emphasizing explicit reasoning steps. Multimodal Fusion and Alignment explores how to effectively combine visual and linguistic modalities, as seen in Multimodal Transformers RVOS[1] and Vision-Language RVOS[7]. Temporal Consistency and Propagation addresses maintaining coherent segmentations across frames through memory mechanisms like Hybrid Memory RVOS[4] and RMem[42]. Training Paradigms and Efficiency investigates learning strategies and computational trade-offs, while Specialized Applications and Extensions covers domain-specific adaptations such as surgical videos and audio-visual reasoning. Recent work has increasingly emphasized the role of structured reasoning to handle intricate temporal dependencies. A particularly active line explores chain-of-thought approaches that decompose queries into interpretable steps before segmentation, exemplified by CoT-RVS[0], which sits within the explicit reasoning cluster alongside Think Before Segment[6] and ReVSeg[33]. These methods contrast with end-to-end fusion approaches like VISA[3] and Villa[5], which rely more heavily on learned cross-modal attention without explicit intermediate reasoning. Another emerging theme involves leveraging large language models for hierarchical decomposition, as in Hierarchical Reasoning LLM[49] and ThinkVideo[39], raising questions about the trade-off between interpretability and computational overhead. CoT-RVS[0] distinguishes itself by integrating chain-of-thought prompting directly into the segmentation pipeline, positioning it closer to works that prioritize transparent temporal logic over purely data-driven alignment, though it shares the broader goal of robust temporal query understanding with the entire branch.

Claimed Contributions

CoT-RVS framework for zero-shot reasoning video segmentation

The authors introduce CoT-RVS, a training-free framework that uses Chain-of-Thought prompting with multimodal large language models to perform reasoning video segmentation. The framework analyzes visible objects matching language queries (semantic) and selects keyframes where objects are most observable (temporal), without requiring fine-tuning.

10 retrieved papers
Can Refute
Keyframe selection pipeline based on CoT prompting for temporal reasoning

The authors develop a keyframe selection method that uses Chain-of-Thought prompting to enable MLLMs to perform temporal reasoning by localizing and describing scene-relevant frames, going beyond simple object retrieval to handle temporally-sensitive queries.

10 retrieved papers
Online reasoning extension for adaptive keyframe re-selection

The authors propose an online variant of CoT-RVS that adaptively updates keyframe selection during inference when processing video streams, allowing the system to re-select target objects when better-matching objects emerge mid-video.

8 retrieved papers

Core Task Comparisons

Comparisons with papers in the same taxonomy category

Contribution Analysis

Detailed comparisons for each claimed contribution

Contribution

CoT-RVS framework for zero-shot reasoning video segmentation

The authors introduce CoT-RVS, a training-free framework that uses Chain-of-Thought prompting with multimodal large language models to perform reasoning video segmentation. The framework analyzes visible objects matching language queries (semantic) and selects keyframes where objects are most observable (temporal), without requiring fine-tuning.

Contribution

Keyframe selection pipeline based on CoT prompting for temporal reasoning

The authors develop a keyframe selection method that uses Chain-of-Thought prompting to enable MLLMs to perform temporal reasoning by localizing and describing scene-relevant frames, going beyond simple object retrieval to handle temporally-sensitive queries.

Contribution

Online reasoning extension for adaptive keyframe re-selection

The authors propose an online variant of CoT-RVS that adaptively updates keyframe selection during inference when processing video streams, allowing the system to re-select target objects when better-matching objects emerge mid-video.