feat: add Gemini 2.0 Flash as primary LLM (native vision+audio) — Groq/HF fallback

app.py

@@ -437,6 +437,20 @@ _tools = [
 ]
 
 
+def _build_gemini_llm():
+    """Build Gemini 2.0 Flash — multimodal, free, best for vision+audio+text."""
+    from langchain_google_genai import ChatGoogleGenerativeAI
+    google_key = os.environ.get("GOOGLE_API_KEY")
+    if not google_key:
+        raise ValueError("GOOGLE_API_KEY not set")
+    return ChatGoogleGenerativeAI(
+        model="gemini-2.0-flash",
+        temperature=0,
+        google_api_key=google_key,
+        max_tokens=8192,
+    )
+
+
 def _build_groq_llm():
     """Build Groq LLM (fast, free, excellent tool calling)."""
     from langchain_groq import ChatGroq
@@ -469,24 +483,40 @@ def _build_hf_llm():
 
 
 def build_graph():
-    """Build and return a compiled LangGraph ReAct agent. Tries Groq first, then HF."""
-    # Try Groq first (better tool calling, free)
+    """Build LangGraph ReAct agent. Priority: Gemini → Groq → HuggingFace."""
     llm = None
     provider_used = None
+
+    # 1st choice: Gemini 2.0 Flash (multimodal — handles images + audio natively)
     try:
-        llm = _build_groq_llm()
-        provider_used = "Groq (llama-3.3-70b-versatile)"
+        llm = _build_gemini_llm()
+        provider_used = "Gemini 2.0 Flash (multimodal)"
         print(f"✅ Using LLM: {provider_used}")
     except Exception as e:
-        print(f"⚠️  Groq not available: {e}. Trying HuggingFace...")
+        print(f"⚠️  Gemini not available: {e}")
+
+    # 2nd choice: Groq Llama-3.3-70B (excellent tool calling, free)
+    if llm is None:
+        try:
+            llm = _build_groq_llm()
+            provider_used = "Groq (llama-3.3-70b-versatile)"
+            print(f"✅ Using LLM: {provider_used}")
+        except Exception as e:
+            print(f"⚠️  Groq not available: {e}")
+
+    # 3rd choice: HuggingFace endpoint
+    if llm is None:
         try:
             llm = _build_hf_llm()
             provider_used = "HuggingFace (Qwen2.5-Coder-32B)"
             print(f"✅ Using LLM: {provider_used}")
-        except Exception as e2:
+        except Exception as e:
             raise RuntimeError(
-                f"No LLM available. Set GROQ_API_KEY or HF_TOKEN.\n"
-                f"Groq error: {e}\nHF error: {e2}"
+                "No LLM available. Please set one of:\n"
+                "  GOOGLE_API_KEY  (recommended — aistudio.google.com)\n"
+                "  GROQ_API_KEY    (groq.com)\n"
+                "  HF_TOKEN        (huggingface.co)\n"
+                f"Last error: {e}"
             )
 
     llm_with_tools = llm.bind_tools(_tools)

requirements.txt

@@ -10,6 +10,7 @@ langchain-core>=0.3.0
 langchain-community>=0.3.0
 langchain-huggingface>=0.1.0
 langchain-groq>=0.2.0
+langchain-google-genai>=2.0.0
 langgraph>=0.2.0
 
 # HuggingFace