zu-huggingface 0.3.1

Zu HuggingFace adapter: task models as typed tools/detectors/validators, behind the supply-chain guards

zu-huggingface

HuggingFace models behind Zu's typed ports. HuggingFace is not a model — it is the largest hub of open models across every modality — so "supporting it" means three different things, and this package draws the line cleanly (Engineering Design §8.3–8.5).

Chat / vision-language models as the policy — no code here

A chat or vision-language model that is the brain speaks the OpenAI chat API on all three HuggingFace serving surfaces (the router's /v1, a dedicated Endpoint's /v1, or a local vLLM server). So a HuggingFace model as the policy is the existing openai-compatible provider pointed at a HuggingFace base URL — the OpenRouter story exactly, no new adapter:

# agent.yaml — a HuggingFace multimodal model as the policy
model:    meta-llama/Llama-Vision-...        # any chat / VLM id on the Hub
provider: openai-compatible
options:
  base_url: https://router.huggingface.co/v1  # or an Endpoint, or local vLLM
  api_key_env: HF_TOKEN

The three serving surfaces are one adapter + config — only the base_url changes (the path is always <base_url>/chat/completions):

Surface	base_url
Inference Providers router	https://router.huggingface.co/v1
Dedicated Inference Endpoint	https://<id>.<region>.aws.endpoints.huggingface.cloud/v1
Local vLLM	http://localhost:8000/v1

A VLM policy (an image in the chat request) rides the same adapter+config: a multimodal content list ({type:"text"} + {type:"image_url", image_url:{url: "data:<mime>;base64,…"}}) passes straight through to the wire. This is proven offline by zu-providers/tests/test_hf_router_policy.py (an httpx.MockTransport asserting the request path, the Bearer from HF_TOKEN, the body, and that the response parses identically across all three base URLs — no live call).

Task models as tools, detectors, validators — this package

Most HuggingFace models are not chat models (OCR, ASR, detection, embeddings, classification, …), so they enter through the non-policy ports by their role (the port is the role, assigned per agent — §4.5):

Role	Class	Task
Tool	Transcribe (hf_transcribe)	speech → text (ASR)
Tool	ImageToText (hf_image_to_text)	image → text (OCR / caption)
Tool	DetectObjects (hf_detect)	image → labelled boxes
Tool	Embed (hf_embed)	text → vector (retrieval / grounding)
Tool	Classify (hf_classify)	text → labels
Tool	ZeroShotClassify (hf_zero_shot)	text + labels → scores
Tool	Summarize (hf_summarize)	text → text
Tool	Translate (hf_translate)	text → text
Tool	SegmentImage (hf_segment)	image → labelled masks
Tool	EstimateDepth (hf_depth)	image → depth map (base64 PNG)
Tool	AskDocument (hf_doc_qa)	document image + question → answer
Tool	AskImage (hf_vqa)	image + question → answer (VQA)
Tool	Speak (hf_speak)	text → audio (base64 WAV)
Tool	ClassifyAudio (hf_classify_audio)	audio → labels (same shape as Classify)
Tool	VlmDescribe (hf_vlm)	image + text prompt → text (VLM-as-tool)
Tool	AskTable (hf_table_qa)	table + question → answer
Tool	ClassifyTable (hf_tabular_classify)	rows → label per row (hosted-only)
Tool	PredictTable (hf_tabular_regress)	rows → number per row (hosted-only)
Detector	HfClassifierDetector	classify an observation → ESCALATE/stop
Validator	HfClassifierValidator	classify the result → fail/RETRY

VLM-as-tool. VlmDescribe exposes a vision-language model's vision as a verb (not the policy): a text policy can call hf_vlm(image, prompt) to get a description/answer about a picture and then reason over it. It rides the client's image_text_to_text path — a multimodal chat call hosted (a text + image_url data-URL message), an image-text-to-text pipeline local — over the one HfClient seam, exactly like every other tool.

Tabular (ClassifyTable/PredictTable) is hosted-only: tabular models are sklearn/tabular-backed on the Hub and served via the Inference API, so the local PipelineBackend raises a clear hosted-only error rather than fetch a model (it therefore cannot bypass the supply-chain guard).

Each is parameterised by a model id (and the role wrappers by the labels that matter), so they are wired by reference in config per agent rather than as zero-config entry points:

tools:
  - ref: zu_huggingface.tools:Transcribe
    args: { model: openai/whisper-large-v3 }
  - ref: zu_huggingface.tools:Embed
    args: { model: BAAI/bge-large-en-v1.5 }
detectors:
  - ref: zu_huggingface.roles:HfClassifierDetector
    args: { model: facebook/bart-large-mnli, candidate_labels: ["safe","unsafe"], escalate_on: ["unsafe"] }

The typed multimodal Content (Text/Image/Audio) from zu_core.content is the currency in and out — which is what lets a non-chat model slot into the loop as cleanly as a chat one.

Hosted vs local — one seam

Every tool depends only on the HfClient seam, so the same tool works:

• Hosted — InferenceClientBackend wraps huggingface_hub.InferenceClient (the serverless router or a dedicated Endpoint). Egresses to router.huggingface.co; HF_TOKEN is read from the environment inside the backend. pip install 'zu-huggingface[hosted]'.
• Local — PipelineBackend wraps transformers.pipeline for the air-gapped / on-prem case. Reaches no network. Every pipeline is built through the supply-chain guards. pip install 'zu-huggingface[local]' (plus a backend such as torch).

The supply chain — safe by default (§8.3)

Pulling a model from the Hub is a supply-chain surface. supply_chain.py enforces, by default:

• Pin + hash. A ModelPin should carry a full commit-sha revision; verify_file_hash checks a downloaded file's sha256.
• safetensors, not pickle. verify_model_source rejects .bin/.pt/.ckpt checkpoints (which execute on deserialisation) unless explicitly allowed.
• No remote code. safe_pipeline_kwargs forces trust_remote_code=False; assert_no_remote_code raises if it is relaxed.

The safe configuration is the default — there is nothing to turn on to be safe, only flags a reviewed case may relax.

Tests

Offline, no network, no model download: the tools and role wrappers are exercised against a fake HfClient, and the supply-chain guards are pure. uv run pytest packages/zu-huggingface.