hugging-face-vision-trainer — quality + safety report

---
source: "https://github.com/huggingface/skills/tree/main/skills/huggingface-vision-trainer"
name: hugging-face-vision-trainer
description: Train or fine-tune vision models on Hugging Face Jobs for detection, classification, and SAM or SAM2 segmentation.
risk: unknown
---

# Vision Model Training on Hugging Face Jobs

Train object detection, image classification, and SAM/SAM2 segmentation models on managed cloud GPUs. No local GPU setup required—results are automatically saved to the Hugging Face Hub.

## When to Use This Skill

Use this skill when users want to:
- Fine-tune object detection models (D-FINE, RT-DETR v2, DETR, YOLOS) on cloud GPUs or local
- Fine-tune image classification models (timm: MobileNetV3, MobileViT, ResNet, ViT/DINOv3, or any Transformers classifier) on cloud GPUs or local
- Fine-tune SAM or SAM2 models for segmentation / image matting using bbox or point prompts
- Train bounding-box detectors on custom datasets
- Train image classifiers on custom datasets
- Train segmentation models on custom mask datasets with prompts
- Run vision training jobs on Hugging Face Jobs infrastructure
- Ensure trained vision models are permanently saved to the Hub

## Related Skills

- **`hugging-face-jobs`** — General HF Jobs infrastructure: token authentication, hardware flavors, timeout management, cost estimation, secrets, environment variables, scheduled jobs, and result persistence. **Refer to the Jobs skill for any non-training-specific Jobs questions** (e.g., "how do secrets work?", "what hardware is available?", "how do I pass tokens?").
- **`hugging-face-model-trainer`** — TRL-based language model training (SFT, DPO, GRPO). Use that skill for text/language model fine-tuning.

## Local Script Execution

Helper scripts use PEP 723 inline dependencies. Run them with `uv run`:
```bash
uv run scripts/dataset_inspector.py --dataset username/dataset-name --split train
uv run scripts/estimate_cost.py --help
```

## Prerequisites Checklist

Before starting any training job, verify:

### Account & Authentication
- Hugging Face Account with [Pro](https://hf.co/pro), [Team](https://hf.co/enterprise), or [Enterprise](https://hf.co/enterprise) plan (Jobs require paid plan)
- Authenticated login: Check with `hf_whoami()` (tool) or `hf auth whoami` (terminal)
- Token has **write** permissions
- **MUST pass token in job secrets** — see directive #3 below for syntax (MCP tool vs Python API)

### Dataset Requirements — Object Detection
- Dataset must exist on Hub
- Annotations must use the `objects` column with `bbox`, `category` (and optionally `area`) sub-fields
- Bboxes can be in **xywh (COCO)** or **xyxy (Pascal VOC)** format — auto-detected and converted
- Categories can be **integers or strings** — strings are auto-remapped to integer IDs
- `image_id` column is **optional** — generated automatically if missing
- **ALWAYS validate unknown datasets** before GPU training (see Dataset Validation section)

### Dataset Requirements — Image Classification
- Dataset must exist on Hub
- Must have an **`image` column** (PIL images) and a **`label` column** (integer class IDs or strings)
- The label column can be `ClassLabel` type (with names) or plain integers/strings — strings are auto-remapped
- Common column names auto-detected: `label`, `labels`, `class`, `fine_label`
- **ALWAYS validate unknown datasets** before GPU training (see Dataset Validation section)

### Dataset Requirements — SAM/SAM2 Segmentation
- Dataset must exist on Hub
- Must have an **`image` column** (PIL images) and a **`mask` column** (binary ground-truth segmentation mask)
- Must have a **prompt** — either:
  - A **`prompt` column** with JSON containing `{"bbox": [x0,y0,x1,y1]}` or `{"point": [x,y]}`
  - OR a dedicated **`bbox`** column with `[x0,y0,x1,y1]` values
  - OR a dedicated **`point`** column with `[x,y]` or `[[x,y],...]` values
- Bboxes should be in **xyxy** format (absolute pixel coordinates)
- Example dataset: `merve/MicroMat-mini` (image matting with bbox prompts)
- **ALWAYS validate unknown datasets** before GPU training (see Dataset Validation section)

### Critical Settings
- **Timeout must exceed expected training time** — Default 30min is TOO SHORT. See directive #6 for recommended values.
- **Hub push must be enabled** — `push_to_hub=True`, `hub_model_id="username/model-name"`, token in `secrets`

## Dataset Validation

**Validate dataset format BEFORE launching GPU training to prevent the #1 cause of training failures: format mismatches.**

**ALWAYS validate for** unknown/custom datasets or any dataset you haven't trained with before. **Skip for** `cppe-5` (the default in the training script).

### Running the Inspector

**Option 1: Via HF Jobs (recommended — avoids local SSL/dependency issues):**
```python
hf_jobs("uv", {
    "script": "path/to/dataset_inspector.py",
    "script_args": ["--dataset", "username/dataset-name", "--split", "train"]
})
```

**Option 2: Locally:**
```bash
uv run scripts/dataset_inspector.py --dataset username/dataset-name --split train
```

**Option 3: Via `HfApi().run_uv_job()` (if hf_jobs MCP unavailable):**
```python
from huggingface_hub import HfApi
api = HfApi()
api.run_uv_job(
    script="scripts/dataset_inspector.py",
    script_args=["--dataset", "username/dataset-name", "--split", "train"],
    flavor="cpu-basic",
    timeout=300,
)
```

### Reading Results

- **`✓ READY`** — Dataset is compatible, use directly
- **`✗ NEEDS FORMATTING`** — Needs preprocessing (mapping code provided in output)

## Automatic Bbox Preprocessing

The object detection training script (`scripts/object_detection_training.py`) automatically handles bbox format detection (xyxy→xywh conversion), bbox sanitization, `image_id` generation, string category→integer remapping, and dataset truncation. **No manual preprocessing needed** — just ensure the dataset has `objects.bbox` and `objects.category` columns.

## Training workflow

Copy this checklist and track progress:

```
Training Progress:
- [ ] Step 1: Verify prerequisites (account, token, dataset)
- [ ] Step 2: Validate dataset format (run dataset_inspector.py)
- [ ] Step 3: Ask user about dataset size and validation split
- [ ] Step 4: Prepare training script (OD: scripts/object_detection_training.py, IC: scripts/image_classification_training.py, SAM: scripts/sam_segmentation_training.py)
- [ ] Step 5: Save script locally, submit job, and report details
```

**Step 1: Verify prerequisites**

Follow the Prerequisites Checklist above.

**Step 2: Validate dataset**

Run the dataset inspector BEFORE spending GPU time. See "Dataset Validation" section above.

**Step 3: Ask user preferences**

ALWAYS use the AskUserQuestion tool with option-style format:

```python
AskUserQuestion({
    "questions": [
        {
            "question": "Do you want to run a quick test with a subset of the data first?",
            "header": "Dataset Size",
            "options": [
                {"label": "Quick test run (10% of data)", "description": "Faster, cheaper (~30-60 min, ~$2-5) to validate setup"},
                {"label": "Full dataset (Recommended)", "description": "Complete training for best model quality"}
            ],
            "multiSelect": false
        },
        {
            "question": "Do you want to create a validation split from the training data?",
            "header": "Split data",
            "options": [
                {"label": "Yes (Recommended)", "description": "Automatically split 15% of training data for validation"},
                {"label": "No", "description": "Use existing validation split from dataset"}
            ],
            "multiSelect": false
        },
        {
            "question": "Which GPU hardware do you want to use?",
            "header": "Hardware Flavor",
            "options": [
                {"label": "t4-small ($0.40/hr)", "description": "1x T4, 16 GB VRAM — sufficient for all OD models under 100M params"},
                {"label": "l4x1 ($0.80/hr)", "description": "1x L4, 24 GB VRAM — more headroom for large images or batch sizes"},
                {"label": "a10g-large ($1.50/hr)", "description": "1x A10G, 24 GB VRAM — faster training, more CPU/RAM"},
                {"label": "a100-large ($2.50/hr)", "description": "1x A100, 80 GB VRAM — fastest, for very large datasets or image sizes"}
            ],
            "multiSelect": false
        }
    ]
})
```

**Step 4: Prepare training script**

For object detection, use [scripts/object_detection_training.py](scripts/object_detection_training.py) as the production-ready template. For image classification, use [scripts/image_classification_training.py](scripts/image_classification_training.py). For SAM/SAM2 segmentation, use [scripts/sam_segmentation_training.py](scripts/sam_segmentation_training.py). All scripts use `HfArgumentParser` — all configuration is passed via CLI arguments in `script_args`, NOT by editing Python variables. For timm model details, see [references/timm_trainer.md](references/timm_trainer.md). For SAM2 training details, see [references/finetune_sam2_trainer.md](references/finetune_sam2_trainer.md).

**Step 5: Save script, submit job, and report**

1. **Save the script locally** to `submitted_jobs/` in the workspace root (create if needed) with a descriptive name like `training_<dataset>_<YYYYMMDD_HHMMSS>.py`. Tell the user the path.
2. **Submit** using `hf_jobs` MCP tool (preferred) or `HfApi().run_uv_job()` — see directive #1 for both methods. Pass all config via `script_args`.
3. **Report** the job ID (from `.id` attribute), monitoring URL, Trackio dashboard (`https://huggingface.co/spaces/{username}/trackio`), expected time, and estimated cost.
4. **Wait for user** to request status checks — don't poll automatically. Training jobs run asynchronously and can take hours.

## Critical directives

These rules prevent common failures. Follow them exactly.

### 1. Job submission: `hf_jobs` MCP tool vs Python API

**`hf_jobs()` is an MCP tool, NOT a Python function.** Do NOT try to import it from `huggingface_hub`. Call it as a tool:

```
hf_jobs("uv", {"script": training_script_content, "flavor": "a10g-large", "timeout": "4h", "secrets": {"HF_TOKEN": "$HF_TOKEN"}})
```

**If `hf_jobs` MCP tool is unavailable**, use the Python API directly:

```python
from huggingface_hub import HfApi, get_token
api = HfApi()
job_info = api.run_uv_job(
    script="path/to/training_script.py",  # file PATH, NOT content
    script_args=["--dataset_name", "cppe-5", ...],
    flavor="a10g-large",
    timeout=14400,  # seconds (4 hours)
    env={"PYTHONUNBUFFERED": "1"},
    secrets={"HF_TOKEN": get_token()},  # MUST use get_token(), NOT "$HF_TOKEN"
)
print(f"Job ID: {job_info.id}")
```

**Critical differences between the two methods:**

| | `hf_jobs` MCP tool | `HfApi().run_uv_job()` |
|---|---|---|
| `script` param | Python code string or URL (NOT local paths) | File path to `.py` file (NOT content) |
| Token in secrets | `"$HF_TOKEN"` (auto-replaced) | `get_token()` (actual token value) |
| Timeout format | String (`"4h"`) | Seconds (`14400`) |

**Rules for both methods:**
- The training script MUST include PEP 723 inline metadata with dependencies
- Do NOT use `image` or `command` parameters (those belong to `run_job()`, not `run_uv_job()`)

### 2. Authentication via job secrets + explicit hub_token injection

**Job config** MUST include the token in secrets — syntax depends on submission method (see table above).

**Training script requirement:** The Transformers `Trainer` calls `create_repo(token=self.args.hub_token)` during `__init__()` when `push_to_hub=True`. The training script MUST inject `HF_TOKEN` into `training_args.hub_token` AFTER parsing args but BEFORE creating the `Trainer`. The template `scripts/object_detection_training.py` already includes this:

```python
hf_token = os.environ.get("HF_TOKEN")
if training_args.push_to_hub and not training_args.hub_token:
    if hf_token:
        training_args.hub_t

… (truncated)