fix(space): set PYTHONPATH and prefer Gemini 3.1 with 2.5 fallback

Dockerfile

@@ -13,6 +13,7 @@ COPY . .
 ENV MODEL_CACHE_DIR=/data/models
 ENV TOKENIZERS_PARALLELISM=false
 ENV PYTHONUNBUFFERED=1
+ENV PYTHONPATH=/app
 
 EXPOSE 7860
 CMD ["python", "spaces/app.py"]

requirements.txt

@@ -24,6 +24,7 @@ torch-geometric>=2.5.0
 scipy>=1.13.0
 
 # Explainability - Gemini
+google-genai>=1.0.0
 google-generativeai>=0.8.0
 
 # HuggingFace

src/explainability/explainer.py

@@ -27,8 +27,13 @@ SYSTEM_INSTRUCTION = (
 )
 
 MODEL_CANDIDATES = (
+    # Preferred order: Gemini 3.1 first, then 2.5 and legacy fallbacks.
+    "gemini-3.1-pro-preview",
+    "gemini-3.1-pro-preview-customtools",
     "gemini-2.5-pro",
-    "gemini-2.5-pro-latest",
+    "gemini-2.5-flash",
+    "gemini-2.5-flash-lite",
+    # Legacy/compatibility fallbacks.
     "gemini-2.0-flash",
     "gemini-1.5-pro",
     "gemini-1.5-pro-latest",