MR-JEPA: Multimodal Reasoning via Joint-Embedding Predictive Architecture

A world model for multimodal reasoning that refines a latent belief state over K=3 steps using JEPA-style prediction, evidence gating, and dense visual backbones.

Key Idea

Traditional multimodal models produce answers in a single forward pass. MR-JEPA instead models the evolution of a belief state as the system reasons about a question:

z₀ (initial evidence) → z₁ (first refinement) → z₂ (deeper reasoning) → z₃ (answer)

This trajectory is supervised by a JEPA objective: a target encoder (EMA) generates target latent states, and the online predictor learns to predict them. The JEPA loss encourages the model to learn meaningful intermediate reasoning states — not just the final answer.

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Architecture

┌──────────────┐     ┌────────────────────┐     ┌──────────────────┐     ┌───────────────┐
│  DINOv3-L/16 │────▶│   Evidence Memory  │────▶│  Latent Rollout  │────▶│ Disc. Head    │
│   (frozen)   │     │ (Perceiver Resampl)│     │  z₀→z₁→z₂→z₃    │     │ (MC scoring)  │
└──────────────┘     └────────┬───────────┘     │ (shared block)   │     └───────────────┘
                              │                 └────────┬─────────┘     ┌───────────────┐
┌──────────────┐              │                          │          ├───▶│ Gen. Decoder   │
│ Qwen3-Embed  │──────────────┘                  ┌───────┴────────┐     │ (Qwen3.5-4B)  │
│   0.6B       │                                 │ Target Encoder │     └───────────────┘
│   (frozen)   │                                 │  (EMA copy)    │
└──────────────┘                                 └────────────────┘
                                                         │
┌──────────────┐                                  JEPA Loss:
│ Phase 3 opt: │──────────┘                       SmoothL1/Cosine
│ PaddleOCR-VL │                                  + SIGReg (purist)
│ SAM 3.1      │                                  / VICReg (hybrid)
└──────────────┘

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Component Stack

Module	Primary Choice	Alternative	Notes
Visual backbone	timm/vit_large_patch16_dinov3.lvd1689m — DINOv3-L/16, 1024-dim, 300M	DINOv3-B/16 (purist); DINOv2-L/14 (ablation)	Frozen Phase 1; last 6 layers unfrozen Phase 2
Text encoder	Qwen/Qwen3-Embedding-0.6B — 1024-dim, 596M	Qwen3-Embedding-4B (heavier); EmbeddingGemma-300M (lighter)	Frozen Phase 1; last 4 layers unfrozen Phase 2
Evidence memory	Perceiver Resampler, 64 queries, 4 cross-attn layers	Q-Former as baseline	Modality-typed tokens (visual/text/OCR/layout/chart/SAM)
OCR / doc / charts	PaddlePaddle/PaddleOCR-VL-1.5 — 958M	MinerU2.5 for heavy PDF parsing	Phase 3 only, offline token extraction
Segmentation	jetjodh/sam3.1 — SAM 3.1, non-gated mirror	SAM 2.1-Large (stable)	Phase 3 optional, offline mask extraction
Latent rollout	Shared transformer predictor, 6 layers, K=3	Per-step unshared blocks (ablation)	Weight-tied across steps; sigmoid evidence gates
Target encoder	EMA copy (cosine 0.996→1.0) of evidence+rollout	Frozen target (ablation baseline)	From I-JEPA
JEPA loss	SmoothL1 + VICReg (hybrid); Cosine + SIGReg (purist)	MSE (ablation)	SIGReg emphasis in purist branch
Disc. head	MLP/bilinear scorer	Cross-encoder scorer (ablation)	Attention-pooled z_K × option embeddings
Gen. decoder	Qwen/Qwen3.5-4B — 4.7B, multimodal	HuggingFaceTB/SmolLM3-3B (cheaper); Gemma3-4B	Phase 3+, cross-attends to z_K + evidence
Teacher/baseline	InternVL3.5 / Qwen3-VL	External comparison only	NOT used as internal module

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Training Protocol

Phase 1: Reasoning Core (15–20 epochs)

• Freeze all perception (DINOv3 + Qwen3-Embedding)
• Train evidence memory + latent rollout + discriminative head
• Full JEPA loss + task loss
• LR: 3e-4, effective batch: 64

Phase 2: Perception Fine-tuning (10 epochs)

• Unfreeze last 6 DINOv3 layers + last 4 Qwen3-Embedding layers (1e-5)
• Continue training reasoning core (1e-4)

Phase 3: Enriched Evidence + Generative Decoder (10 epochs)

• Enable PaddleOCR-VL tokens, SAM 3.1 masks, layout/chart tokens
• Attach Qwen3.5-4B generative decoder for open-ended answers
• End-to-end fine-tuning, LR: 5e-5

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Target Benchmarks (9)

Benchmark	Type	Metric	Key Challenge
MMMU	MC (multi-image)	Accuracy	Multi-discipline, up to 7 images
MathVista	Mixed MC/Open	Accuracy	Mathematical reasoning
ScienceQA	MC	Accuracy	Scientific diagrams, nullable images
AI2D	MC	Accuracy	Science diagram comprehension
MMBench	MC	CircularEval Acc	General visual understanding
MMStar	MC	Accuracy	Vision-dependent questions
DocVQA	Open	ANLS	Document text extraction
TextVQA	Open	VQA Accuracy	Scene text reading
ChartQA	Open	Relaxed Accuracy	Chart data extraction

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Experimental Branches

Hybrid-main (competitive)

• DINOv3-L backbone, SmoothL1 + VICReg, K=3
• Full enriched evidence in Phase 3
• Target: state-of-the-art on all benchmarks

Purist-side (scientific validation)

• DINOv3-B backbone, Cosine + SIGReg, K=5
• No enriched evidence, pure JEPA reasoning
• Target: demonstrate JEPA contributes beyond perception

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Ablation Experiments

Each experiment maps 1:1 to a CLI flag in train_mrjepa.py.

Experiment	CLI flag	Modification	Purpose
hybrid_main	(default)	Full model	Baseline
no_jepa	--no_jepa	Remove L_JEPA, task loss only	Validate JEPA objective
no_rollout	--no_rollout	K=0, use z₀ directly	Validate iterative refinement
no_gate	--no_evidence_gate	Remove evidence gating	Validate adaptive evidence flow
K1 / K5 / K7	--K 1/5/7	Vary rollout depth	Find optimal depth
dinov2_ablation	--backbone dinov2	DINOv2-L/14 backbone	DINOv3 vs DINOv2
mse_loss	--loss_fn mse	MSE (L2) JEPA loss	Original I-JEPA loss
cosine_loss	--loss_fn cosine	Cosine similarity JEPA loss	Purist-style loss
no_sigreg	--no_sigreg	Disable SIGReg anti-collapse	Test regularization
vicreg_only	--no_sigreg --use_vicreg	VICReg only	Alternative anti-collapse
purist	--purist	DINOv3-B, K=5, Cosine+SIGReg	Isolate JEPA contribution

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Project Structure

MR-JEPA/
├── README.md                    # This file
├── train_mrjepa.py              # Complete training script (CLI, all ablations)
├── test_architecture.py         # Architecture validation tests (synthetic data)
│
├── mr_jepa/
│   ├── __init__.py
│   ├── ARCHITECTURE.md          # Detailed architecture specification
│   │
│   ├── configs/
│   │   ├── __init__.py
│   │   └── model_config.py      # All hyperparameter dataclasses
│   │
│   ├── models/
│   │   ├── __init__.py
│   │   ├── mr_jepa.py           # Main model (integrates all components)
│   │   ├── backbones.py         # Visual (DINOv3/v2) + Text (Qwen3-Embedding)
│   │   ├── evidence_memory.py   # Perceiver Resampler multimodal fusion
│   │   ├── latent_rollout.py    # K-step shared predictor + evidence gates
│   │   ├── target_encoder.py    # EMA encoder + JEPA/SIGReg/VICReg losses
│   │   └── answer_heads.py      # Discriminative (MC) + Generative (open-ended)
│   │
│   ├── data/
│   │   ├── __init__.py
│   │   ├── unified_dataset.py   # 9-benchmark unified loader with format quirks
│   │   └── data_utils.py        # Collator, dataloader factory, benchmark configs
│   │
│   ├── training/
│   │   ├── __init__.py
│   │   ├── trainer.py           # 3-phase training loop
│   │   └── phase_scheduler.py   # Phase transitions, LR scheduling
│   │
│   ├── evaluation/
│   │   ├── __init__.py
│   │   └── metrics.py           # Accuracy, ANLS, VQA Acc, Relaxed Acc
│   │
│   └── utils/
│       ├── __init__.py
│       ├── visualization.py     # Trajectory PCA, gate analysis
│       └── ablation.py          # Systematic ablation runner
│
├── results/                     # Training results (auto-pushed)
│   ├── hybrid_main.json
│   ├── no_jepa.json
│   ├── no_rollout.json
│   └── ...
│
└── checkpoints/                 # Best model checkpoints (auto-pushed)
    ├── hybrid_main_best.pt
    └── ...

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Paper Contribution

A world model for multimodal reasoning: We demonstrate that modeling the evolution of a latent belief state via JEPA-style prediction improves performance on static multimodal benchmarks compared to single-pass baselines. The evidence-gated rollout with K=3 steps learns meaningful intermediate reasoning states, validated through ablation studies across 9 benchmarks. The JEPA objective (not human chain-of-thought) supervises a latent trajectory generated by an EMA target encoder, showing that self-supervised dynamics training transfers to discriminative reasoning tasks.

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Key References

1. I-JEPA (Assran et al., 2023) — arxiv:2301.08243: JEPA architecture, EMA target encoder, L2 prediction loss, narrow predictor
2. LeWorldModel (Maes et al., 2025) — arxiv:2603.19312: SIGReg anti-collapse, end-to-end JEPA
3. Coconut (Yu et al., 2024) — arxiv:2412.06769: Chain of Continuous Thought, latent reasoning
4. DINOv3 (Meta, 2025) — arxiv:2508.10104: Dense SSL with RoPE + Gram anchoring
5. SoftCoT++ (Xu et al., 2025) — arxiv:2505.11484: Soft chain-of-thought with contrastive learning

License

Apache-2.0