---
license: other
tags:
  - video
  - world-model
  - jepa
  - vjepa2
  - cosmos
  - wts
  - video-generation
base_model:
  - facebook/vjepa2-vitl-fpc64-384
  - meta-llama/Llama-3.2-1B
  - nvidia/Cosmos-Reason1-7B
pipeline_tag: other
---

# JEPA-Guidance → Cosmos context predictor (`jepa-guided-diffusion`)

JEPA-Guidance is a lightweight **predictor bridge** that maps a WTS traffic video (plus a text
query) into the frozen **Cosmos-Reason1 `(512, 1024)` context space**, so the predicted
embedding can condition **Cosmos-Predict2.5** video generation *without running the 7B
Reason1 text encoder at inference time*.

- **Input:** video / frame directory + a WTS-format query.
- **Output:** a `(512, 1024)` context tensor (the Cosmos cross-attention conditioning set).
- **Objective:** permutation-invariant **set-match Hungarian MSE** — Cosmos consumes the
  context as an unordered set, so the predicted 512 tokens are matched to the target 512
  tokens (Hungarian assignment) before MSE.

## Architecture

| Part | Role | Source |
|------|------|--------|
| **X-Encoder** (frozen) | VJEPA 2.1 ViT-L/384 (`vjepa2_1_vit_large_384`), video mode → visual tokens | torch.hub (`facebookresearch/vjepa2`) |
| **Compressor** (trained) | BLIP-2-style **QFormer**: 512 query tokens, 4 layers, cross-attn every layer | in `model.pt` |
| **Backbone** (trained) | **last 4 layers of Llama-3.2-1B**, made bidirectional | arch from hub, weights in `model.pt` |
| **Head** (trained) | `output_projection` → `(512, 1024)` | in `model.pt` |
| **Y-Encoder** (frozen, target only) | Cosmos-Reason1-7B `full_concat` + `crossattn_proj` | not needed at inference |

Only the compressor, the last 4 Llama layers, the vision projection, and the output
projection are trained; VJEPA2 and Reason1 are frozen.

## Training metrics

Full logs for the run that produced these weights are in `training_metrics/`. Training ran
**28 epochs**; the published `best_model/` is **epoch 24**, selected on minimum validation
set-match MSE.

| Metric (epoch 24) | Value |
|---|---|
| Train set-match MSE | 5.8287 |
| **Val set-match MSE** | **6.7279** |
| Retrieval top-1 | 0.3606 |
| Retrieval MRR | 0.4954 |
| Set top-1 | 0.3613 |
| Set MRR | 0.5049 |
| Alignment diag | 0.1603 |
| Alignment off-diag | 0.1561 |
| LR at best epoch | 2.40e-05 |

Validation set-match MSE fell from **21.50** (epoch 1) to **6.73** (epoch 24).

```
training_metrics/epoch_metrics.csv    # 28 rows — per-epoch loss, MSE, LR, grad-norm, retrieval/alignment
training_metrics/batch_metrics.csv    # 4452 rows — per-step trace
training_metrics/events.out.tfevents.*  # TensorBoard event file
```

```bash
tensorboard --logdir training_metrics
```

Note that `align_diag` (0.160) and `align_offdiag` (0.156) sit close together: the cached
Reason1 targets are strongly anisotropic, so a large shared mean dominates every vector.
Training subtracts a precomputed all-token mean before normalization to recover the
per-caption residual.

## Repo layout

```
config.yaml                         # full model/eval config the loader reads
best_model/model.pt                 # trained weights (predictor only)
best_model/model_config.yaml        # model config sidecar
best_model/query_tokenizer/         # Llama query tokenizer
fixed/negative_<view>.pt            # the two fixed negative embeddings (vehicle / overhead)
training_metrics/                   # per-epoch + per-batch CSVs and the TensorBoard events
```

## Usage

Install the [JEPA-Guidance](https://github.com/AlterraFa/VLJEPA-WTS) package (uv-managed), then
pass this repo id as `--checkpoint` — it is downloaded and cached automatically:

```bash
# whole test set: writes <scenario>/embedding.pt for the Cosmos handoff
uv run jepa-guidance seq-infer --checkpoint AlterraLaniakea/jepa-guided-diffusion --test-root wts/test

# single scenario -> print the (512,1024) embedding
uv run jepa-guidance infer \
  --checkpoint AlterraLaniakea/jepa-guided-diffusion \
  --visual-path wts/test/<scenario>/input \
  --output embedding \
  --query "The current preset is from overhead view with 2 target subjects. Pedestrian: A man in his 30s stands on the road facing the oncoming vehicle. Vehicle: The vehicle goes straight at a constant speed."
```

**Query format.** For in-distribution embeddings, use the same query format as training
(`seq-infer` builds this automatically from `caption.json`):

```
The current preset is from <overhead|vehicle> view with <N> target subject(s). Pedestrian: <ped caption> Vehicle: <veh caption>
```

- `<overhead|vehicle>` — `overhead` for CCTV, `vehicle` for dashcam (`video*`) clips.
- `<N>` — subject types present: `1` (pedestrian or vehicle) or `2` (both).

## Requirements

- **Gated Llama-3.2-1B**: run `hf auth login` (or export `HF_TOKEN`) before first use — the
  loader rebuilds the Llama backbone architecture from the hub and overlays the trained
  weights. (Set `hf_token: true` in `config.yaml`, or provide the token via env.)
- **VJEPA2** is fetched from `facebookresearch/vjepa2` (torch.hub / GitHub source).
- A GPU is recommended; VJEPA2 runs at crop size 384.

## Downstream

Feed the predicted `embedding.pt` into Cosmos-Predict2.5 via `scripts/generate_cosmos.py`
(see the repo README) to generate the WTS video for each scenario.