The advancement of multimodal large language models (MLLMs) has enabled impressive perception capabilities. However, their reasoning process often remains a "fast thinking" paradigm, reliant on end-to-end generation or explicit, language-centric chains of thought (CoT), which can be inefficient, verbose, and prone to hallucination. This work posits that robust reasoning should evolve within a latent space, integrating multimodal signals seamlessly. We propose multimodal latent reasoning via HIerarchical Visual cuEs injection (HIVE), a novel framework that instills deliberate, "slow thinking" without depending on superficial textual rationales. Our method recursively extends transformer blocks, creating an internal loop for iterative reasoning refinement. Crucially, it injectively grounds this process with hierarchical visual cues from global scene context to fine-grained regional details directly into the model's latent representations. This enables the model to perform grounded, multi-step inference entirely in the aligned latent space. Extensive evaluations demonstrate that test-time scaling is effective when incorporating vision knowledge, and that integrating hierarchical information significantly enhances the model's understanding of complex scenes.
Figures & tables
Figure 1: Visualization of traditional MLLMs, visual features extracted from a vision tower are projected into the language space and directly concatenated with text tokens. This combined sequence is then fed into a stack of transformer decoder blocks. HIVE is built upon Huginn, a recursive architecture that iteratively processes token representations through a unified set of layers to enhance feature depth. We have extended this by incorporating the visual modality and, for the first time, introducing hierarchical visual information into latent space reasoning.
Figure 2: Our framework incorporates a pre-trained vision encoder, with a group of lightweight patch merger that maps visual features into the LLM embedding space. During multimodal alignment, the [CLS] token is removed. represents Embedding , Recurrent , Head blocks respectively.
Method
Visual
Text
Hierarchical
CoT Data Requirement
Training-induced Recurrence
Coconut
✗
✓
-
High
Heima
✓
✓
✗
High
Loop Transformer Recurrence
Huginn
✗
✓
-
Low
HIVE (Ours)
✓
✓
✓
Low
Table 1: Comparison of Latent Space Reasoning Approaches. Coconut/Heima progressively abstract CoT text into learnable tokens without altering model architecture; Heima is the first to include multimodal input. Huginn/ HIVE utilize a Loop Transformer architecture to reason via iterations, reducing dependency on CoT tokens. HIVE further introduces hierarchical visual features.
Gemma3
LLaMA2
Phi-3-mini
Huginn
Param
4B
7B
3.8B
3.5B
Train Tokens
4T
2.0T
3.3T
0.8T
GSM8K
38.4
-
-
28.20
GSM8K-CoT (8-shot)
-
-
82.5
34.57
HumanEval
36.0
29.9
58.5
23.17
Table 2: Comparison of Various Backbone LMMs, including Gemma3 ( Team, 2025 ) , LLaMA2 ( Touvron et al., 2023 ) , Phi-3-mini ( Abdin et al., 2024 ) and Huginn ( Geiping et al., 2025 ) . We detail model sizes, training token counts, and benchmark performances. The results indicate that the inherent language capabilities of our backbone LLM are constrained, which may, in turn, impact the overall performance of the resulting MLLMs. The missing entries are unavailable results.
Parameters
Stage 1
Stage 2
Stage 3
Learning Rate
1×10−3
1×10−5
1×10−6
Max Dynamic Patches (#)
4
2
2
Max Tokens
1536
2048
2048
Table 3: Training configurations across different stages.
Gemma3-4B-PT
MobileVLM V2 7B
Bunny-v1.1-4B
Imp-4B
Emu3
HIVE
Backbone
Gemma3
Vicuna-7B-v1.5
Phi-3-3.8B
Phi-3-3.8B
-
Huginn
Param.
4B
7B
4B
4B
8B
4B
Train Data
4T*
3.6M
2.7M
1.6M
-
6.5M
General VQA
MMB
-
69.2
74.2
73.3
58.5
69.6
SQA img
-
74.8
78.3
78.3
89.2
91.6
SEED img
-
-
72.5
-
68.2
70.5
Table 4: Main performance comparison with MLLMs. We report the LLM backbone, model size, and training data scales (4T* denotes 4T tokens, otherwise samples). Note that backbones are detailed in Table 2 . MMB: MMBench (En) dev split; SQA img : ScienceQA-Img; SEED img : SEED-Bench-Img; RWQA: RealWorldQA; TVQA: TextVQA; CQA: ChartQA; DVQA: DocVQA; POPE; Missing entries indicate unavailable results.
Benchmark
Baseline (r=1)
Ours w/o Hier (r=32)
Ours w/ Hier (r=32)
MMStar
33.28
48.44
49.79
SEED img
42.37
70.46
70.48
MMB dev
21.74
68.04
69.59
RWQA
41.44
57.52
57.91
SQA img
60.09
89.39
91.57
Avg.
39.78
66.77
67.87
Table 5: Results on benchmarks for three variants. Bold text indicates the best performance among these models. MMB: MMBench (En) dev split; SQA img : ScienceQA-Img; SEED img : SEED-Bench-Img; RWQA: RealWorldQA; TVQA: TextVQA; DVQA: DocVQA; MathV: MathVista; POPE
Figure 3: Building upon Huginn, we integrate a Vision Transformer (ViT) and propose a hierarchical latent-space reasoning framework. Specifically, we argue that latent-space reasoning with visual information should be hierarchical rather than merely iterative. The figure shows our comparison results on ScienceQA img .
Figure 4: MMBench detailed results. LR denotes logic reasoning. FC denotes fine-grained perception (cross-instance). AR denotes attribute reasoning. RR denotes relation reasoning. FI denotes fine-grained perception (instance-level). CP denotes coarse perception.
Figure 5: Distribution of inference steps for the first token generation across multiple-choice benchmarks. We evaluate the impact of hierarchical cue injection on the recurrent steps. The results demonstrate that incorporating these cues causes a distinct leftward shift in the distribution, indicating a reduction in computation during inference.
Appendix figures & tables7 assets
Supplementary material from the paper’s appendix.
Appendix
Figure 6: The details of our training datasets.
Figure 7: A case from ScienceQA, where the question has been modified as a QA.
Figure 8: The visualization shows the evolution of latent states as a function of token position (vertical axis) and iteration depth (horizontal axis) in the model variant (r=32, w/o Hier,). Each cell represents the distance between a given iterate and its corresponding steady state, approximated at r=32 .
Figure 9: The visualization shows the evolution of latent states as a function of token position (vertical axis) and iteration depth (horizontal axis) in the HIVE . Each cell represents the distance between a given iterate and its corresponding steady state, approximated at r=32 .
Figure 10: Visualization of hidden state trajectories in the model variant (r=32 w/o Hier.) during inference.
Figure 11: Visualization of hidden state trajectories in HIVE during inference.