Help us improve
Share bugs, ideas, or general feedback.
From huggingface-skills
Guides writing Gradio Spaces using Hugging Face ZeroGPU hardware: `@spaces.GPU`, duration/quotas, pickle isolation, CUDA builds, and common errors like `illegal duration` or wheel build failures.
npx claudepluginhub huggingface/skills --plugin huggingface-zerogpuHow this skill is triggered — by the user, by Claude, or both
Slash command
/huggingface-skills:huggingface-zerogpuThe summary Claude sees in its skill listing — used to decide when to auto-load this skill
Rules and patterns for ML demos on Hugging Face Spaces with **ZeroGPU** hardware. Covers `@spaces.GPU`, duration and quota tuning, process isolation, the CUDA availability model, concurrency safety, and CUDA build constraints.
Runs Python workloads on Hugging Face Jobs with managed CPUs, GPUs, TPUs, secrets, and Hub persistence. Use for batch inference, data processing, ML experiments, and testing without local GPU setup.
Deploys and runs Python code on Modal's serverless GPU infrastructure. Use for AI/ML model serving, GPU-accelerated workloads, web endpoints, batch jobs, and scheduled tasks.
Packages and builds custom AI models with Cog for Replicate deployment. Creates cog.yaml and predict.py, builds Docker images, handles GPU/CUDA setup, and ports Hugging Face models.
Share bugs, ideas, or general feedback.
Rules and patterns for ML demos on Hugging Face Spaces with ZeroGPU hardware. Covers @spaces.GPU, duration and quota tuning, process isolation, the CUDA availability model, concurrency safety, and CUDA build constraints.
This skill is for Gradio SDK Spaces using ZeroGPU hardware. Docker and Static Spaces cannot schedule onto ZeroGPU, and Streamlit apps now run as Docker Spaces — so this skill applies only to Gradio. For general Gradio coding (components, layouts, event listeners), see the huggingface-gradio skill in this repo. The authoritative ZeroGPU docs live at https://huggingface.co/docs/hub/spaces-zerogpu — refer to them for the current backing GPU, runtime version lists, and tier thresholds, all of which change over time.
| Reference | When to read |
|---|---|
references/concurrency.md | Always read alongside SKILL.md when writing ZeroGPU code — handlers run in parallel by default |
references/how-zerogpu-works.md | When reasoning about cold-starts, worker reuse, why module-scope warmup does not carry to requests, or why returning CUDA tensors hangs |
references/how-quota-works.md | When choosing duration values, debugging illegal duration vs quota exceeded errors, or explaining why default 60s blocks short tasks |
references/cuda-and-deps.md | When installing CUDA-dependent packages (e.g. flash-attn), pinning torch side-cars, or reading wheel filename tags |
ZeroGPU exposes two GPU sizes that map to a fraction of the backing card:
size | Slice of backing GPU | Quota cost |
|---|---|---|
large (default) | Half | 1x |
xlarge | Full | 2x |
Default large gives half a physical GPU, so memory bandwidth and compute are significantly lower than the full card's specs. Use xlarge only when the workload genuinely needs the extra memory or compute.
Backing GPU changes without notice. ZeroGPU has already migrated across GPU generations several times; older write-ups may name A100 or H200, but those are outdated. For the current backing GPU and exact per-size VRAM, always check the ZeroGPU docs before sizing workloads.
import spaces
import torch
from transformers import pipeline
pipe = pipeline("text-generation", model="...", device="cuda")
@spaces.GPU
def generate(prompt: str) -> str:
return pipe(prompt, max_new_tokens=100)[0]["generated_text"]
Key rules:
.to("cuda") eagerly. ZeroGPU handles the actual device mapping transparently (see CUDA availability model below).@spaces.GPU. The decorator is a no-op outside ZeroGPU, so it is safe to keep in all environments.duration to match the realistic worst-case workload (default 60s). The platform pre-checks requested duration against the user's remaining quota — not against the actual run time — so a 10-second task left at the 60s default fails with quota exceeded as soon as the user's remaining quota drops below 60s. Smaller declared duration also ranks higher in the node-level queue. See "Duration and Quota" below.torch.compile is NOT supported. Use PyTorch ahead-of-time compilation (AoTI) (torch 2.8+) instead.size="xlarge" sparingly. It allocates the full backing GPU, but costs 2x quota and tends to queue longer.@spaces.GPU(duration=120)
def generate_image(prompt: str):
return pipe(prompt).images[0]
Real GPU access is only available inside @spaces.GPU-decorated functions. Outside those functions, the GPU is not attached to the process.
However, import spaces monkey-patches torch so that:
torch.cuda.is_available() returns True globally..to("cuda") / device="cuda" calls at module scope succeed without error.This is intentional. Module-scope model.to("cuda") calls register tensors with the ZeroGPU backend, which writes them to a disk offload directory at a startup "pack" step and frees the corresponding RAM. When a @spaces.GPU call lands, a forked GPU worker process streams those weights from disk into VRAM via a pinned-memory pipeline. Warm workers (reused across requests on the same GPU slot) keep weights resident on the GPU and skip the disk → VRAM step. The user-facing rule: write device="cuda" at module scope and it works — see references/how-zerogpu-works.md for the full lifecycle.
| Action | Where | Why |
|---|---|---|
model.to("cuda") / pipe(..., device="cuda") | Module scope | ZeroGPU registers the tensor and manages device migration |
| Actual CUDA computation (inference, etc.) | Inside @spaces.GPU | Real GPU is only attached during the decorated call |
Branching on torch.cuda.is_available() | Avoid relying on it | Always returns True due to the monkey-patch |
Do not run inference or CUDA kernels at module scope — the real GPU is not attached, so operations either silently run on CPU or fail.
The standard idiom remains correct under ZeroGPU:
device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
model = AutoModel.from_pretrained("...").to(device)
is_available() is True (monkey-patched), so the model is registered for automatic device migration.is_available() is genuinely True."cpu".Do not hardcode device="cuda" — it breaks on CPU-only environments.
Load models at module scope, not lazily on first request. The Space process starts before any user arrives, so cold-start cost is paid once. Lazy loading (global model; if model is None: ..., @lru_cache wrappers, factory functions instantiating on first call) just pushes that cost onto the first user.
spacesDo not wrap import spaces in try/except and redefine spaces.GPU as a no-op fallback for local runs. Off-ZeroGPU, the spaces package is already a true no-op:
SPACES_ZERO_GPU env var, set only on ZeroGPU.@spaces.GPU returns the undecorated function unchanged off-ZeroGPU.import spaces performs only lightweight imports.The Gradio SDK base image installs spaces on every hardware tier. So even after duplicating a Space onto a dedicated GPU (T4, L4, A10G, etc.) or CPU basic, no code changes are needed — import spaces still succeeds and @spaces.GPU becomes a transparent passthrough.
try:
import spaces
except ImportError:
class spaces: # type: ignore
@staticmethod
def GPU(func=None, **kwargs):
return func if func else (lambda f: f)
Problems:
@spaces.GPU call shape — bare decorator, duration=..., size=..., generators, aoti_* helpers — and drifts as the spaces API grows.spaces from requirements.txt, even though the Space needs it at deploy time.Add spaces to dependencies and import it unconditionally:
import spaces
@spaces.GPU
def generate(prompt: str) -> str:
...
Three things happen when you declare @spaces.GPU(duration=N):
duration cap. Declaring duration larger than the cap fails immediately with ZeroGPU illegal duration, regardless of remaining quota. (Tier numbers change over time — see the ZeroGPU docs.)requested duration against the user's remaining quota. If remaining < requested, the call fails with ZeroGPU quota exceeded — even if the actual work would have fit. The error message shows the explicit numbers, e.g. "60s requested vs. 30s left". A 10-second task left at the default 60s therefore blocks the user once their remaining quota drops below 60s.duration ranks higher.All three favor declaring the smallest realistic duration — including for short tasks. Explicit @spaces.GPU(duration=15) on a 10-second task avoids premature quota exceeded rejections and ranks higher in the queue.
xlargedoubles the request.requested = N * 2whensize="xlarge", both for the tier-max check and the quota pre-check. So@spaces.GPU(duration=60, size="xlarge")is internally a 120s request.
For workloads whose runtime depends on inputs, pass a callable that estimates per request. A static high duration locks out low-tier users (whose tier cap may be smaller than the static value) and unnecessarily reserves quota for light inputs.
def estimate_duration(prompt, steps):
return int(steps * 3.5)
@spaces.GPU(duration=estimate_duration)
def generate(prompt, steps):
return pipe(prompt, num_inference_steps=steps).images[0]
For the full distinction between illegal duration vs quota exceeded, runs-per-day limits, the 24h quota window, and pay-as-you-go billing, see references/how-quota-works.md.
@spaces.GPU-decorated functions run in a separate process managed by the ZeroGPU scheduler. Arguments and return values cross the process boundary via pickle serialization.
Consequences:
PicklingError.torch.cuda._lazy_init(), which ZeroGPU blocks. Convert to CPU first: return tensor.cpu() or tensor.cpu().numpy().gr.State semantics across the boundaryBecause handlers run in a separate process, gr.State values are pickled on every yield — they are NOT shared by reference.
id() differs from the caller's).gr.update() for a gr.State slot skips the update — other handlers continue to see the pre-yield value.Practical guidance:
gr.State on ZeroGPU. Code that mutates state in a generator and expects another handler to see those mutations will silently use stale data.gr.State value triggers a full pickle round-trip. For large state (model sessions, frame buffers), minimize how often you yield it — ideally once at the end. Use gr.update() for the state slot on intermediate yields.torch.cuda._lazy_init() issue as above.Handlers run concurrently by default on ZeroGPU. This is not opt-in. Code that worked in single-user testing can silently corrupt or leak data in production.
Three rules. Full treatment with examples in references/concurrency.md.
tempfile for unique paths.Each entry into a @spaces.GPU function carries non-trivial cost — pickle round-trip across the process boundary, worker warm-up, CUDA re-attach, and a fresh pass through the node-level queue. Calling a decorated function from inside a hot loop multiplies these costs and adds a new failure mode: a later iteration may fail to acquire a GPU slot, stalling the whole job mid-way.
Decorate the outer function that owns the loop, not the per-iteration worker:
# Avoid — N GPU entries for N frames
def process_video(frames):
return [process_frame(f) for f in frames]
@spaces.GPU(duration=...)
def process_frame(frame):
...
# Prefer — one GPU entry for the whole video
@spaces.GPU(duration=...)
def process_video(frames):
return [process_frame(f) for f in frames]
def process_frame(frame):
...
If the loop mixes heavy CPU work with GPU work, wrapping the whole loop charges that CPU time against the user's quota. When that cost is material, batching the GPU work so CPU pre/post-processing stays outside the decorator is a situational optimization — not the default.
HF Spaces builds Docker images in a CPU-only environment. On ZeroGPU, the build phase has no nvcc because the base image is python:3.13 (dedicated-GPU Spaces use nvidia/cuda:*-devel-* and have nvcc at build time). A CUDA-dependent package whose only distribution is sdist — e.g. bare flash-attn — therefore cannot be installed via requirements.txt on ZeroGPU. Only pre-built wheels work.
ZeroGPU runtime does have nvcc available, mounted from a CUDA devel image at /cuda-image since 2025-07 (originally added for AoTI support). This is what makes torch.export / AoTI workflows possible inside @spaces.GPU calls.
Bottom line: install every CUDA-dependent package from a pre-built wheel. If no wheel is available on PyPI, build one externally (e.g. host on HF Hub) and pin the URL. For flash-attn, the upstream releases page ships a fairly complete wheel matrix covering most Python × CUDA × torch combinations.
For wheel-tag reading (cxx11 ABI, cu12torch2.X, cp3XX), torch-family side-car drift, and the kernels-community fallback, see references/cuda-and-deps.md.
gr.Examples behavior is environment-dependent. On ZeroGPU specifically:
cache_examples defaults to True (Spaces sets GRADIO_CACHE_EXAMPLES=true).cache_mode defaults to "lazy" (Spaces sets GRADIO_CACHE_MODE=lazy only on ZeroGPU).ZeroGPU defaults to lazy because eager caching pre-runs every example at app startup, but ZeroGPU has no GPU attached at startup — only during request handling. Eager caching of GPU-bound examples would fail there.
When cache_examples=True, the run_on_click / run_examples_on_click parameter is silently ignored. If your app relies on click-populates-only behavior, set cache_examples=False explicitly to preserve it.
To reproduce ZeroGPU example-caching behavior locally:
GRADIO_CACHE_EXAMPLES=true GRADIO_CACHE_MODE=lazy python app.py
python_version pin in README frontmatterPinning python_version is effectively required for ZeroGPU. The runtime default is currently Python 3.10, so a local environment using 3.11+ will fail to install on the Space without an explicit pin. Pin to a ZeroGPU-supported version (3.12 is a reasonable default); the authoritative supported list lives in the ZeroGPU docs — do not hardcode the full list, refer to the docs.
# README.md frontmatter
python_version: "3.12"
Both "3.12" and "3.12.12" forms are accepted.
spaces in requirements.txtThe Space platform pins its own spaces version. A conflicting pin in requirements.txt causes pip resolution to fail at build time.
Rule: Do not include
spacesinrequirements.txt.
How to achieve this depends on your tooling:
requirements.txt: simply omit spaces.pyproject.toml-managed): declare spaces in pyproject.toml so uv co-resolves transitive constraints (notably psutil, which spaces pins), then exclude it from the export:
uv export --no-hashes --no-dev --no-emit-package spaces -o requirements.txt
Without spaces in pyproject.toml, uv cannot see its transitive constraints and may resolve incompatible versions at build time.pip-compile) / Poetry: use the equivalent exclude mechanism.torch to match wheel tagsIf you install a CUDA-dependent wheel via direct URL, the wheel filename encodes the torch major.minor it was built against (e.g. cu12torch2.8). Pin torch==X.Y.Z in requirements.txt to match — otherwise pip may resolve torch to a different version and the Space fails on first import. Details and the kernels-community alternative are in references/cuda-and-deps.md.