Generate a reproducible, runnable PyTorch training repo for a medical-imaging task — segmentation, classification, detection, image-to-image synthesis, self-supervised pretraining, or fine-tuning a pretrained backbone (transfer learning) — the missing middle link between choosing an architecture and validating a trained model. Emits a patient-level seed-locked split as an auditable artifact, a task-appropriate model, train and evaluate scripts that seed every RNG and infer under eval mode, a config, requirements, a reproducibility record, and a Methods stub with VERIFY placeholders (no fabricated numbers). Fine-tuning mode adds a frozen-then-unfrozen schedule, discriminative learning rates, and a pretrained-weight provenance record. The reproducibility guarantees hold by construction, so the build is leakage-safe before any training runs. Integrates with MONAI, nnU-Net, TorchIO, timm, and torchvision — it does not reimplement them.
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name
model-scaffold
description
Generate a reproducible, runnable PyTorch training repo for a medical-imaging task — segmentation, classification, detection, image-to-image synthesis, self-supervised pretraining, or fine-tuning a pretrained backbone (transfer learning) — the missing middle link between choosing an architecture and validating a trained model. Emits a patient-level seed-locked split as an auditable artifact, a task-appropriate model, train and evaluate scripts that seed every RNG and infer under eval mode, a config, requirements, a reproducibility record, and a Methods stub with VERIFY placeholders (no fabricated numbers). Fine-tuning mode adds a frozen-then-unfrozen schedule, discriminative learning rates, and a pretrained-weight provenance record. The reproducibility guarantees hold by construction, so the build is leakage-safe before any training runs. Integrates with MONAI, nnU-Net, TorchIO, timm, and torchvision — it does not reimplement them.
triggers
model scaffold, scaffold a model, training repo, PyTorch repo, build a model, train a model, fine-tune, finetune, transfer learning, pretrained backbone, MedSAM, SAM adaptation, segmentation, classification, detection, image synthesis, self-supervised, SimCLR, Pix2Pix, Faster R-CNN, U-Net, UNet, nnU-Net, MONAI, timm, torchvision, dataloader, train.py, patient-level split, reproducible training, seed everything, generate training code, medical imaging model
tools
Read, Write, Edit, Bash, Grep, Glob
model
inherit
Model-Scaffold Skill
Purpose
This skill stamps out a runnable PyTorch training repo for a medical-imaging task — --tasksegmentation (U-Net), classification (CNN / timm backbone), detection (torchvision Faster
R-CNN / FPN), synthesis (Pix2Pix generator + PatchGAN), ssl (SimCLR encoder), or finetune
(transfer-learning a pretrained backbone with a frozen→unfrozen schedule + a provenance record) —
with the reproducibility guarantees baked in by construction — so the build is leakage-safe and
reproducible before a single epoch runs. It is the imaging analogue of how /analyze-stats generates
runnable statistical code: the generator produces the repo, you run the training on your GPU / Colab,
and the lane's deterministic gates verify the network-free parts.
It is the missing middle link in the lane: /architecture-zoo (choose) → model-scaffold (build)
→ /model-validation (validate the split / design) → /model-evaluation + /analyze-stats (metrics)
→ /write-paper + /check-reporting (publish). It integrates MONAI / nnU-Net / TorchIO (referenced
in the generated requirements.txt); it does not reimplement them.
When to use
You have a data manifest (one row per image, with a patient/subject ID) and want a reproducible,
leakage-safe starting repo for a segmentation model.
You want to fine-tune a pretrained backbone (transfer learning — the common clinician workflow:
a timm / MONAI / MedSAM checkpoint adapted to your collected clinical data) with the freeze schedule,
discriminative learning rates, and pretrained-weight provenance recorded (--task finetune).
When NOT to use
Auditing an already-trained model's validation design → /model-validation.
Choosing the architecture for the research question → /architecture-zoo (when available).
Reimplementing MONAI / nnU-Net → out of scope (the scaffold integrates them).
LLM / MLLM evaluation → /mllm-eval.
Workflow
Phase 1 — Prepare the manifest
A CSV with one row per image and a patient/subject ID column (patient_id / subject_id /
case_id), plus image and label path columns. The ID column is load-bearing: the split is done at the
patient level off this column.
Phase 2 — Generate the repo
python3 ${CLAUDE_SKILL_DIR}/scripts/scaffold.py \
--manifest <manifest.csv> --task segmentation --out model_repo --seed 42 \
--in-channels 1 --out-channels 1
# --task = segmentation | classification | detection | synthesis | ssl | finetune# (out-channels = num classes for classification/finetune, target channels for synthesis)# fine-tuning a pretrained backbone (transfer learning) on collected clinical data:
python3 ${CLAUDE_SKILL_DIR}/scripts/scaffold.py \
--manifest <manifest.csv> --task finetune --out model_repo --seed 42 \
--out-channels <num_classes> --from-pretrained timm:resnet50.a1_in1k
# emits PRETRAINED.md (provenance) + a frozen→unfrozen train.py with discriminative LRs;# record the exact pretrained source so the fine-tune is reproducible.
This writes model_repo/ with config.yaml, model.py (the task's model — U-Net / CNN / Faster R-CNN
/ Pix2Pix / SimCLR encoder), dataset.py (reads the frozen split), losses.py (task-appropriate),
train.py, evaluate.py, requirements.txt,
REPRODUCIBILITY.md, methods_stub.md, and — the key artifact — splits/split_assignment.csv +
splits/split_seed.txt. The split is patient-disjoint by construction (a deterministic group split)
and the emitted code seeds every RNG, sets cuDNN deterministic, builds the training loader from the
train split only, and infers under model.eval() + torch.no_grad().
Phase 3 — Verify the build (network-free)
# this skill's own training-hygiene gate
python3 ${CLAUDE_SKILL_DIR}/scripts/check_training_hygiene.py --repo model_repo --strict
# the split-leakage gate (proves patient disjointness) — owned by /model-validation
Route the emitted splits/split_assignment.csv to /model-validation
(check_split_leakage.py --splits model_repo/splits/split_assignment.csv --strict) for the
patient-disjointness proof, and (optionally, locally with torch installed)
bash ${CLAUDE_SKILL_DIR}/scripts/scaffold_challenge/verify.sh to smoke the forward pass.
Phase 4 — Plug in your data and train
Implement dataset.py's _load_image / _load_label for your modality (DICOM / NIfTI / TIFF via
nibabel / pydicom / tifffile / TorchIO / MONAI transforms). For production, swap model.py for MONAI
UNet / SegResNet or an nnU-Net plan (see ${CLAUDE_SKILL_DIR}/references/training_guide.md). For a
fine-tuning repo (--task finetune), fill PRETRAINED.md and set the freeze schedule / discriminative
learning rates (see ${CLAUDE_SKILL_DIR}/references/finetuning_guide.md, which also covers MedSAM/SAM
adaptation and train-only diffusion augmentation). Run python train.py (best model selected on the
val split), then python evaluate.py (predictions on the test split, touched once).
Phase 5 — Validate, evaluate, publish
Hand off to /model-validation (validation-tier + comparator + metric-selection audit),
/model-evaluation + /analyze-stats (Dice + HD95/NSD with CIs), /make-figures, and /write-paper
(fill the methods_stub.md[VERIFY] placeholders) + /check-reporting (CLAIM 2024 / TRIPOD+AI). For
reproducibility-safe wiring of experiment tracking (W&B / MLflow), config / data / environment
versioning, and the MLOps reporting checklist, see ${CLAUDE_SKILL_DIR}/references/mlops_guide.md
(a wiring + reporting reference — it points to the frameworks, it does not replace them).
Runnability — honest contract
The generated repo is runnable, but runnability is not a CI guarantee. The default gates prove
the network-free properties (the emitted split is patient-disjoint + seeded; the emitted training code
is hygienic) by parsing the produced artifacts — no torch is executed. A torch forward-pass smoke
(build + forward shape + gradients flow + reproducible loss) is a self-skipping tier in the
challenge verify.sh and a documented local command; it is never counted as CI coverage of
runnability.
Anti-Hallucination
Never fabricate training or evaluation metrics. The scaffold emits [VERIFY] placeholders;
every number must come from the user's executed run and from /model-evaluation + /analyze-stats.
Never emit a split that is not patient-disjoint or not seed-locked. The generator does this by
construction; do not hand-edit the split table to introduce overlap or remove the seed.
Never claim the generated repo was trained or that it achieved a result — it is a starting point
the user runs.
If a library API, default, or architecture detail is uncertain, flag [VERIFY] and ask rather than
guessing.
Deterministic gates
scripts/scaffold.py — the generator (stdlib + numpy; deterministic given manifest + seed).
scripts/check_training_hygiene.py — AST linter: all RNGs seeded, cuDNN deterministic,
eval() + no_grad() inference, no training on a non-train split, and (fine-tuning) a
recorded pretrained-weight provenance when pretrained weights are loaded
(PRETRAINED_PROVENANCE_MISSING).