Hugging Face Model Deployment Guide

Production operating guide for loading models from the Hugging Face Hub and running local inference.

Authentication & Secrets

Parameter	Description
hf_token	Hugging Face access token. Required for private or gated repos.
token	Alias accepted by some integrations.

Tokens must be sourced from a secret store in production. For public, non-gated models the token is optional; for private / gated repos (Llama, most Mistral checkpoints), the token is required.

Token Discovery Fallback

When hf_token is unset, the loader falls back to the HF_TOKEN environment variable, then HF_HUB_TOKEN, then the Hugging Face token file ($HF_HOME/token, default ~/.cache/huggingface/token, written by huggingface-cli login). This makes local development portable but should be explicitly set in production via the secret store to avoid surprise auth behavior across environments.

Resilience Controls

Download & Cache

Models are downloaded on first use into the standard Hugging Face Hub cache, resolved in this order: HF_HUB_CACHE, then $HF_HOME/hub, then ~/.cache/huggingface/hub. Blobs already present in that cache are reused on subsequent starts. Download requests use bearer auth when a token is configured. Set HF_HUB_CACHE (or HF_HOME) to place the cache on a volume with enough space and to share it between restarts or replicas.

Revision Pinning

Model IDs support explicit revision pinning by appending a colon and the revision to the from value — from: huggingface:huggingface.co/<org>/<model>:<revision> (see from format). The revision is passed to the Hub verbatim, so it must name a real branch, tag or commit SHA on the repo; latest is not translated to main and fails unless the repo actually has a latest ref. An @ is not a valid separator: org/model@revision fails the from pattern and the model does not load. Pin revisions to a commit SHA in production to guarantee reproducibility — the default branch is a moving target.

Retry Behavior

Download retries follow the shared HTTP-client policy with exponential/fibonacci backoff on transient failures. Models are downloaded and instantiated during startup, so a slow or large download delays the model reaching Ready rather than slowing the first request. For very large models over slow networks, pre-download into the cache directory with the Hugging Face CLI (passing --revision when the from pins one).

Capacity & Sizing

Device Selection

Local inference uses the first available backend in order:

1. CUDA (if compiled with CUDA support and a device is present)
2. Metal (if compiled with Metal support — macOS / Apple Silicon)
3. CPU fallback

Install the CUDA-enabled Spice build on GPU hosts; the standard build uses CPU-only inference which is significantly slower for models over a few billion parameters.

Memory Footprint

Model size on disk is close to RAM/VRAM footprint at load. Quantized GGUF models (Q4, Q5, Q8) reduce footprint roughly proportional to their bit-width. For a 7B parameter model:

• f16: ~14 GB
• Q8: ~7.5 GB
• Q5: ~5 GB
• Q4: ~4 GB

Add ~20–30% headroom for KV cache and working memory during inference.

Concurrency

The runtime rate limiter defaults to max_concurrency=1 for local models (HuggingFace, filesystem) — local inference is compute-bound and benefits little from request-level parallelism on a single accelerator. Override via max_concurrency for multi-GPU / large-core CPU hosts.

Metrics

Shared LLM metrics apply (see the OpenAI Model Deployment Guide for the full metric list): llm_requests, llm_failures, llm_internal_request_duration_ms, llm_prompt_tokens_total, llm_completion_tokens_total.

See Component Metrics for enabling and exporting metrics.

Task History

Local inference operations emit ai_completion spans (and health spans for probes) in task history, mirroring the OpenAI-path spans. captured_output and token usage fields are logged.

Known Limitations

• Single-process loading: A model is loaded into the Spice process — it cannot be shared across process instances without a dedicated inference server.
• No hot reload: Switching model revisions requires a spicepod reload.
• Limited Responses API support: Responses API routing is currently tied to specific providers (OpenAI, xAI); a local HF-loaded model does not serve the Responses API.
• Quantized formats: Support depends on the local loader (mistral / candle). Verify the format is supported before production deployment.
• Disk-space requirements: First-run downloads can be multi-GB; ensure the Hub cache directory (HF_HUB_CACHE, $HF_HOME/hub, or ~/.cache/huggingface/hub) has adequate space.

Troubleshooting

Symptom	Likely cause	Resolution
401 Unauthorized on download	Missing or invalid hf_token; gated model.	Set hf_token; accept the model's license on Hugging Face; verify token has read scope.
OOM on model load	Model size exceeds device memory.	Choose a smaller quantized variant; switch to CPU + larger system RAM; use multi-GPU if supported.
Inference falls back to CPU unexpectedly	CUDA / Metal unavailable or not detected.	Use a CUDA-enabled Spice build on GPU hosts; verify nvidia-smi shows devices; for macOS, use Apple Silicon build.
Model output changes between restarts	Revision unpinned (default branch).	Pin the revision with a colon: from: huggingface:huggingface.co/org/model:<commit_sha>.
Model stays Initializing for a long time after startup	First-run download. Models are fetched and instantiated during startup (load_models), not lazily on the first inference request, so the model is unavailable until the download completes.	Pre-warm the Hub cache with huggingface-cli download <org>/<model> --revision <revision> — passing the same revision the from pins — and point HF_HOME / HF_HUB_CACHE at the directory Spice uses.
Model fails to load with an invalid-from error	from does not match the HuggingFace pattern — most often an @ used as the revision separator, or a character outside [A-Za-z0-9_.-] in the revision.	Use from: huggingface:huggingface.co/<org>/<model>:<revision>; the revision accepts word characters, digits, dashes and dots, so commit SHAs are safe.