Revert F4 runtime-fetch back to build-time fetch (P3 supply-chain hardening)

Dockerfile

@@ -5,16 +5,28 @@ WORKDIR /app
 # Copy space app files
 COPY . /app
 
-# Install dependencies (huggingface-hub is in requirements.txt for runtime dataset fetch)
+# Install dependencies
 RUN pip install --no-cache-dir -r requirements.txt
 
-# Set environment
+# Set environment for dataset download
 ENV HF_HUB_DOWNLOAD_TIMEOUT=120
+
+# Fetch benchmark tasks from Hugging Face dataset at BUILD time (immutable in image).
+# Reverted from runtime fetch (F4) back to build-time fetch per peer review C3/C5:
+# runtime fetch from a public admin-writable dataset introduced a supply-chain attack
+# surface (poisoned verify.py auto-propagating into the Space). Build-time fetch bakes
+# the dataset into the immutable Docker image — dataset updates require a deliberate
+# rebuild, which acts as a safety check.
+RUN pip install --no-cache-dir huggingface-hub && \
+    python -c "from huggingface_hub import snapshot_download; snapshot_download('hummbl-hf/governance-bench', repo_type='dataset', local_dir='/bench')"
+
+# Verify download
+RUN ls /bench/tasks/ | head -5
+
+# Set environment
 ENV BENCH_ROOT=/bench
 ENV PYTHONPATH=/bench/scripts:/app
 
-# Dataset is fetched at runtime (app startup), not build time,
-# so dataset updates surface without a space rebuild (F4 refactor).
 EXPOSE 7860
 
 CMD ["uvicorn", "app:app", "--host", "0.0.0.0", "--port", "7860"]

app.py

@@ -34,23 +34,6 @@ SCRIPTS_DIR = BENCH_ROOT / "scripts"
 TEMPLATES_DIR = Path(__file__).resolve().parent / "templates"
 STATIC_DIR = Path(__file__).resolve().parent / "static"
 
-
-def ensure_bench_downloaded() -> None:
-    """Download the benchmark dataset at runtime if BENCH_ROOT is empty/missing.
-
-    Fetches from hummbl-hf/governance-bench so dataset updates surface without
-    a space rebuild (F4 refactor — was previously baked in at Docker build time).
-    """
-    if TASKS_ROOT.exists() and any(TASKS_ROOT.iterdir()):
-        return  # already populated
-    from huggingface_hub import snapshot_download
-    snapshot_download(
-        "hummbl-hf/governance-bench",
-        repo_type="dataset",
-        local_dir=str(BENCH_ROOT),
-    )
-
-
 app = FastAPI(
     title="Governance-Bench Agent Reasoning Audit",
     description="Interactive benchmark for AI agent governance primitives",
@@ -61,11 +44,6 @@ app.mount("/static", StaticFiles(directory=str(STATIC_DIR)), name="static")
 templates = Jinja2Templates(directory=str(TEMPLATES_DIR))
 
 
-@app.on_event("startup")
-async def _startup_download_bench() -> None:
-    ensure_bench_downloaded()
-
-
 # ---------------------------------------------------------------------------
 # Data models
 # ---------------------------------------------------------------------------

requirements.txt

@@ -2,4 +2,3 @@ fastapi
 uvicorn[standard]
 jinja2
 hummbl-governance>=1.1.0
-huggingface-hub