feat: add startup environment validator to ensure critical secrets are present

backend/config.py

@@ -0,0 +1,38 @@
+import os
+from pydantic import Field, SecretStr
+from pydantic_settings import BaseSettings, SettingsConfigDict
+
+class Settings(BaseSettings):
+    # Required for LLM
+    google_api_key: SecretStr = Field(..., alias="GOOGLE_API_KEY")
+
+    # Required for Vector Search (Vertex AI)
+    gcp_project_id: str = Field(..., alias="GCP_PROJECT_ID")
+    index_endpoint_id_full: str = Field(..., alias="INDEX_ENDPOINT_ID_FULL")
+    deployed_index_id: str = Field(..., alias="DEPLOYED_INDEX_ID")
+
+    # Optional with Defaults
+    gcp_region: str = Field("europe-west4", alias="GCP_REGION")
+    bq_dataset_id: str = Field("ks_metadata", alias="BQ_DATASET_ID")
+    bq_table_id: str = Field("docstore", alias="BQ_TABLE_ID")
+
+    # Load from .env file
+    model_config = SettingsConfigDict(
+        env_file=".env", 
+        env_file_encoding="utf-8", 
+        extra="ignore"
+    )
+
+def validate_config():
+    """Validates presence of critical env vars at startup."""
+    try:
+        settings = Settings()
+        print("✅ Environment variables validated successfully.")
+        return settings
+    except Exception as e:
+        print("\n❌ CRITICAL ERROR: Missing or Invalid Environment Variables")
+        print("Please check your .env file or system environment.")
+        print(f"Details: {e}")
+        # Exit the process to prevent 'zombie' deployment
+        import sys
+        sys.exit(1)

backend/main.py

@@ -4,7 +4,7 @@
 import asyncio
 from typing import Optional, Dict, Any
 from datetime import datetime
-
+from config import validate_config
 from dotenv import load_dotenv
 from fastapi import FastAPI, HTTPException
 from fastapi.middleware.cors import CORSMiddleware
@@ -16,6 +16,8 @@
 
 load_dotenv()
 
+validate_config()
+
 # FastAPI app + CORS
 app = FastAPI(
     title="KnowledgeSpace AI",