diff --git a/ai-hub/app/api/routes.py b/ai-hub/app/api/routes.py
index 6cf3deb..23bfa68 100644
--- a/ai-hub/app/api/routes.py
+++ b/ai-hub/app/api/routes.py
@@ -5,7 +5,7 @@
 from typing import Literal
 from sqlalchemy.orm import Session
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 
 # Pydantic Models for API requests
 class ChatRequest(BaseModel):

diff --git a/ai-hub/app/api/routes.py b/ai-hub/app/api/routes.py
index 6cf3deb..23bfa68 100644
--- a/ai-hub/app/api/routes.py
+++ b/ai-hub/app/api/routes.py
@@ -5,7 +5,7 @@
 from typing import Literal
 from sqlalchemy.orm import Session
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 
 # Pydantic Models for API requests
 class ChatRequest(BaseModel):
diff --git a/ai-hub/app/app.py b/ai-hub/app/app.py
index 7b82b4b..d18d97b 100644
--- a/ai-hub/app/app.py
+++ b/ai-hub/app/app.py
@@ -10,7 +10,7 @@
 from app.core.services import RAGService
 
 # Import the new files for database and API routes
-from app.db_setup import create_db_tables
+from app.db.session import create_db_and_tables
 from app.api.routes import create_api_router
 
 # Load environment variables from a .env file
@@ -37,7 +37,7 @@
         cleanup on shutdown.
         """
         print("Initializing application services...")
-        create_db_tables()
+        create_db_and_tables()
         yield
         print("Shutting down application services...")
         vector_store.save_index()

diff --git a/ai-hub/app/api/routes.py b/ai-hub/app/api/routes.py
index 6cf3deb..23bfa68 100644
--- a/ai-hub/app/api/routes.py
+++ b/ai-hub/app/api/routes.py
@@ -5,7 +5,7 @@
 from typing import Literal
 from sqlalchemy.orm import Session
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 
 # Pydantic Models for API requests
 class ChatRequest(BaseModel):
diff --git a/ai-hub/app/app.py b/ai-hub/app/app.py
index 7b82b4b..d18d97b 100644
--- a/ai-hub/app/app.py
+++ b/ai-hub/app/app.py
@@ -10,7 +10,7 @@
 from app.core.services import RAGService
 
 # Import the new files for database and API routes
-from app.db_setup import create_db_tables
+from app.db.session import create_db_and_tables
 from app.api.routes import create_api_router
 
 # Load environment variables from a .env file
@@ -37,7 +37,7 @@
         cleanup on shutdown.
         """
         print("Initializing application services...")
-        create_db_tables()
+        create_db_and_tables()
         yield
         print("Shutting down application services...")
         vector_store.save_index()
diff --git a/ai-hub/app/config.py b/ai-hub/app/config.py
new file mode 100644
index 0000000..ab8f8f4
--- /dev/null
+++ b/ai-hub/app/config.py
@@ -0,0 +1,29 @@
+# app/config.py
+
+import os
+from dotenv import load_dotenv
+
+# Load environment variables from a .env file
+load_dotenv()
+
+class Settings:
+    # --- Database ---
+    DB_MODE: str = os.getenv("DB_MODE", "sqlite")
+    DATABASE_URL: str = (
+        "sqlite:///./data/ai_hub.db"
+        if DB_MODE == "sqlite"
+        else os.getenv("DATABASE_URL", "postgresql://user:password@localhost/ai_hub_db")
+    )
+    
+    # --- LLM API Keys & Models ---
+    DEEPSEEK_API_KEY: str = os.getenv("DEEPSEEK_API_KEY")
+    GEMINI_API_KEY: str = os.getenv("GEMINI_API_KEY")
+    DEEPSEEK_MODEL_NAME: str = os.getenv("DEEPSEEK_MODEL_NAME", "deepseek-chat")
+    GEMINI_MODEL_NAME: str = os.getenv("GEMINI_MODEL_NAME", "gemini-1.5-flash-latest")
+    
+    # --- Vector Store ---
+    FAISS_INDEX_PATH: str = os.getenv("FAISS_INDEX_PATH", "data/faiss_index.bin")
+    EMBEDDING_DIMENSION: int = int(os.getenv("EMBEDDING_DIMENSION", 768))
+
+# Instantiate the settings so they can be imported and used anywhere
+settings = Settings()
\ No newline at end of file

diff --git a/ai-hub/app/api/routes.py b/ai-hub/app/api/routes.py
index 6cf3deb..23bfa68 100644
--- a/ai-hub/app/api/routes.py
+++ b/ai-hub/app/api/routes.py
@@ -5,7 +5,7 @@
 from typing import Literal
 from sqlalchemy.orm import Session
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 
 # Pydantic Models for API requests
 class ChatRequest(BaseModel):
diff --git a/ai-hub/app/app.py b/ai-hub/app/app.py
index 7b82b4b..d18d97b 100644
--- a/ai-hub/app/app.py
+++ b/ai-hub/app/app.py
@@ -10,7 +10,7 @@
 from app.core.services import RAGService
 
 # Import the new files for database and API routes
-from app.db_setup import create_db_tables
+from app.db.session import create_db_and_tables
 from app.api.routes import create_api_router
 
 # Load environment variables from a .env file
@@ -37,7 +37,7 @@
         cleanup on shutdown.
         """
         print("Initializing application services...")
-        create_db_tables()
+        create_db_and_tables()
         yield
         print("Shutting down application services...")
         vector_store.save_index()
diff --git a/ai-hub/app/config.py b/ai-hub/app/config.py
new file mode 100644
index 0000000..ab8f8f4
--- /dev/null
+++ b/ai-hub/app/config.py
@@ -0,0 +1,29 @@
+# app/config.py
+
+import os
+from dotenv import load_dotenv
+
+# Load environment variables from a .env file
+load_dotenv()
+
+class Settings:
+    # --- Database ---
+    DB_MODE: str = os.getenv("DB_MODE", "sqlite")
+    DATABASE_URL: str = (
+        "sqlite:///./data/ai_hub.db"
+        if DB_MODE == "sqlite"
+        else os.getenv("DATABASE_URL", "postgresql://user:password@localhost/ai_hub_db")
+    )
+    
+    # --- LLM API Keys & Models ---
+    DEEPSEEK_API_KEY: str = os.getenv("DEEPSEEK_API_KEY")
+    GEMINI_API_KEY: str = os.getenv("GEMINI_API_KEY")
+    DEEPSEEK_MODEL_NAME: str = os.getenv("DEEPSEEK_MODEL_NAME", "deepseek-chat")
+    GEMINI_MODEL_NAME: str = os.getenv("GEMINI_MODEL_NAME", "gemini-1.5-flash-latest")
+    
+    # --- Vector Store ---
+    FAISS_INDEX_PATH: str = os.getenv("FAISS_INDEX_PATH", "data/faiss_index.bin")
+    EMBEDDING_DIMENSION: int = int(os.getenv("EMBEDDING_DIMENSION", 768))
+
+# Instantiate the settings so they can be imported and used anywhere
+settings = Settings()
\ No newline at end of file
diff --git a/ai-hub/app/db/database.py b/ai-hub/app/db/database.py
index cbb6b13..c2dfee1 100644
--- a/ai-hub/app/db/database.py
+++ b/ai-hub/app/db/database.py
@@ -1,54 +1,5 @@
-import os
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker, declarative_base # <-- CORRECTED IMPORT
+from sqlalchemy.orm import declarative_base
 
-# --- Configuration ---
-# Determines the database mode. Can be "postgres" or "sqlite".
-# Defaults to "postgres" if not set.
-DB_MODE = os.getenv("DB_MODE", "postgres").lower()
-
-# Default database URLs
-POSTGRES_DEFAULT_URL = "postgresql://user:password@localhost/ai_hub_db"
-SQLITE_DEFAULT_URL = "sqlite:///./data/ai_hub.db"
-
-DATABASE_URL = ""
-engine_args = {}
-
-# --- Database Initialization ---
-if DB_MODE == "sqlite":
-    print("✅ Initializing with SQLite in-file database.")
-    DATABASE_URL = SQLITE_DEFAULT_URL
-    # SQLite requires a specific argument to allow access from multiple threads,
-    # which is common in web applications.
-    engine_args = {"connect_args": {"check_same_thread": False}}
-else: # Default to postgres
-    # Use the provided DATABASE_URL or fall back to the default.
-    DATABASE_URL = os.getenv("DATABASE_URL", POSTGRES_DEFAULT_URL)
-    DB_MODE = "postgres"
-    print(f"✅ Initializing with PostgreSQL database. URL: {DATABASE_URL}")
-    # pool_pre_ping checks if a connection is still alive before using it from the pool.
-    engine_args = {"pool_pre_ping": True}
-
-
-# Create the SQLAlchemy engine with the determined settings
-engine = create_engine(DATABASE_URL, **engine_args)
-
-# SessionLocal is a factory for creating new database session objects
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
-
-# Base is a class that our database model classes will inherit from.
-Base = declarative_base()
-
-
-# --- Dependency for FastAPI ---
-def get_db():
-    """
-    FastAPI dependency that provides a database session for a single API request.
-    It ensures the session is always closed after the request is finished.
-    """
-    db = SessionLocal()
-    try:
-        yield db
-    finally:
-        db.close()
-
+# This Base class is the foundation that all your SQLAlchemy ORM models
+# (like Document, VectorMetadata, etc.) will inherit from.
+Base = declarative_base()
\ No newline at end of file

diff --git a/ai-hub/app/api/routes.py b/ai-hub/app/api/routes.py
index 6cf3deb..23bfa68 100644
--- a/ai-hub/app/api/routes.py
+++ b/ai-hub/app/api/routes.py
@@ -5,7 +5,7 @@
 from typing import Literal
 from sqlalchemy.orm import Session
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 
 # Pydantic Models for API requests
 class ChatRequest(BaseModel):
diff --git a/ai-hub/app/app.py b/ai-hub/app/app.py
index 7b82b4b..d18d97b 100644
--- a/ai-hub/app/app.py
+++ b/ai-hub/app/app.py
@@ -10,7 +10,7 @@
 from app.core.services import RAGService
 
 # Import the new files for database and API routes
-from app.db_setup import create_db_tables
+from app.db.session import create_db_and_tables
 from app.api.routes import create_api_router
 
 # Load environment variables from a .env file
@@ -37,7 +37,7 @@
         cleanup on shutdown.
         """
         print("Initializing application services...")
-        create_db_tables()
+        create_db_and_tables()
         yield
         print("Shutting down application services...")
         vector_store.save_index()
diff --git a/ai-hub/app/config.py b/ai-hub/app/config.py
new file mode 100644
index 0000000..ab8f8f4
--- /dev/null
+++ b/ai-hub/app/config.py
@@ -0,0 +1,29 @@
+# app/config.py
+
+import os
+from dotenv import load_dotenv
+
+# Load environment variables from a .env file
+load_dotenv()
+
+class Settings:
+    # --- Database ---
+    DB_MODE: str = os.getenv("DB_MODE", "sqlite")
+    DATABASE_URL: str = (
+        "sqlite:///./data/ai_hub.db"
+        if DB_MODE == "sqlite"
+        else os.getenv("DATABASE_URL", "postgresql://user:password@localhost/ai_hub_db")
+    )
+    
+    # --- LLM API Keys & Models ---
+    DEEPSEEK_API_KEY: str = os.getenv("DEEPSEEK_API_KEY")
+    GEMINI_API_KEY: str = os.getenv("GEMINI_API_KEY")
+    DEEPSEEK_MODEL_NAME: str = os.getenv("DEEPSEEK_MODEL_NAME", "deepseek-chat")
+    GEMINI_MODEL_NAME: str = os.getenv("GEMINI_MODEL_NAME", "gemini-1.5-flash-latest")
+    
+    # --- Vector Store ---
+    FAISS_INDEX_PATH: str = os.getenv("FAISS_INDEX_PATH", "data/faiss_index.bin")
+    EMBEDDING_DIMENSION: int = int(os.getenv("EMBEDDING_DIMENSION", 768))
+
+# Instantiate the settings so they can be imported and used anywhere
+settings = Settings()
\ No newline at end of file
diff --git a/ai-hub/app/db/database.py b/ai-hub/app/db/database.py
index cbb6b13..c2dfee1 100644
--- a/ai-hub/app/db/database.py
+++ b/ai-hub/app/db/database.py
@@ -1,54 +1,5 @@
-import os
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker, declarative_base # <-- CORRECTED IMPORT
+from sqlalchemy.orm import declarative_base
 
-# --- Configuration ---
-# Determines the database mode. Can be "postgres" or "sqlite".
-# Defaults to "postgres" if not set.
-DB_MODE = os.getenv("DB_MODE", "postgres").lower()
-
-# Default database URLs
-POSTGRES_DEFAULT_URL = "postgresql://user:password@localhost/ai_hub_db"
-SQLITE_DEFAULT_URL = "sqlite:///./data/ai_hub.db"
-
-DATABASE_URL = ""
-engine_args = {}
-
-# --- Database Initialization ---
-if DB_MODE == "sqlite":
-    print("✅ Initializing with SQLite in-file database.")
-    DATABASE_URL = SQLITE_DEFAULT_URL
-    # SQLite requires a specific argument to allow access from multiple threads,
-    # which is common in web applications.
-    engine_args = {"connect_args": {"check_same_thread": False}}
-else: # Default to postgres
-    # Use the provided DATABASE_URL or fall back to the default.
-    DATABASE_URL = os.getenv("DATABASE_URL", POSTGRES_DEFAULT_URL)
-    DB_MODE = "postgres"
-    print(f"✅ Initializing with PostgreSQL database. URL: {DATABASE_URL}")
-    # pool_pre_ping checks if a connection is still alive before using it from the pool.
-    engine_args = {"pool_pre_ping": True}
-
-
-# Create the SQLAlchemy engine with the determined settings
-engine = create_engine(DATABASE_URL, **engine_args)
-
-# SessionLocal is a factory for creating new database session objects
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
-
-# Base is a class that our database model classes will inherit from.
-Base = declarative_base()
-
-
-# --- Dependency for FastAPI ---
-def get_db():
-    """
-    FastAPI dependency that provides a database session for a single API request.
-    It ensures the session is always closed after the request is finished.
-    """
-    db = SessionLocal()
-    try:
-        yield db
-    finally:
-        db.close()
-
+# This Base class is the foundation that all your SQLAlchemy ORM models
+# (like Document, VectorMetadata, etc.) will inherit from.
+Base = declarative_base()
\ No newline at end of file
diff --git a/ai-hub/app/db/session.py b/ai-hub/app/db/session.py
new file mode 100644
index 0000000..26e8938
--- /dev/null
+++ b/ai-hub/app/db/session.py
@@ -0,0 +1,44 @@
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from app.config import settings
+from app.db.database import Base
+
+# Determine engine arguments based on the database mode from the central config
+engine_args = {}
+if settings.DB_MODE == "sqlite":
+    # This argument is required for SQLite to allow it to be used by multiple threads,
+    # which is the case in a web application like FastAPI.
+    engine_args["connect_args"] = {"check_same_thread": False}
+else:
+    # 'pool_pre_ping' checks if a database connection is still alive before using it.
+    # This prevents errors from connections that have been timed out by the DB server.
+    engine_args["pool_pre_ping"] = True
+
+# Create the SQLAlchemy engine using the centralized URL and determined arguments
+engine = create_engine(settings.DATABASE_URL, **engine_args)
+
+# SessionLocal is a factory for creating new database session objects.
+# It's the standard way to interact with the database in SQLAlchemy.
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+def create_db_and_tables():
+    """
+    Creates all database tables defined by models inheriting from Base.
+    This is typically called once on application startup.
+    """
+    print("Creating database tables...")
+    # Base.metadata contains all the schema information from your models.
+    Base.metadata.create_all(bind=engine)
+
+def get_db():
+    """
+    FastAPI dependency that provides a database session for a single API request.
+    
+    This pattern ensures that the database session is always closed after the
+    request is finished, even if an error occurs.
+    """
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
\ No newline at end of file

diff --git a/ai-hub/app/api/routes.py b/ai-hub/app/api/routes.py
index 6cf3deb..23bfa68 100644
--- a/ai-hub/app/api/routes.py
+++ b/ai-hub/app/api/routes.py
@@ -5,7 +5,7 @@
 from typing import Literal
 from sqlalchemy.orm import Session
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 
 # Pydantic Models for API requests
 class ChatRequest(BaseModel):
diff --git a/ai-hub/app/app.py b/ai-hub/app/app.py
index 7b82b4b..d18d97b 100644
--- a/ai-hub/app/app.py
+++ b/ai-hub/app/app.py
@@ -10,7 +10,7 @@
 from app.core.services import RAGService
 
 # Import the new files for database and API routes
-from app.db_setup import create_db_tables
+from app.db.session import create_db_and_tables
 from app.api.routes import create_api_router
 
 # Load environment variables from a .env file
@@ -37,7 +37,7 @@
         cleanup on shutdown.
         """
         print("Initializing application services...")
-        create_db_tables()
+        create_db_and_tables()
         yield
         print("Shutting down application services...")
         vector_store.save_index()
diff --git a/ai-hub/app/config.py b/ai-hub/app/config.py
new file mode 100644
index 0000000..ab8f8f4
--- /dev/null
+++ b/ai-hub/app/config.py
@@ -0,0 +1,29 @@
+# app/config.py
+
+import os
+from dotenv import load_dotenv
+
+# Load environment variables from a .env file
+load_dotenv()
+
+class Settings:
+    # --- Database ---
+    DB_MODE: str = os.getenv("DB_MODE", "sqlite")
+    DATABASE_URL: str = (
+        "sqlite:///./data/ai_hub.db"
+        if DB_MODE == "sqlite"
+        else os.getenv("DATABASE_URL", "postgresql://user:password@localhost/ai_hub_db")
+    )
+    
+    # --- LLM API Keys & Models ---
+    DEEPSEEK_API_KEY: str = os.getenv("DEEPSEEK_API_KEY")
+    GEMINI_API_KEY: str = os.getenv("GEMINI_API_KEY")
+    DEEPSEEK_MODEL_NAME: str = os.getenv("DEEPSEEK_MODEL_NAME", "deepseek-chat")
+    GEMINI_MODEL_NAME: str = os.getenv("GEMINI_MODEL_NAME", "gemini-1.5-flash-latest")
+    
+    # --- Vector Store ---
+    FAISS_INDEX_PATH: str = os.getenv("FAISS_INDEX_PATH", "data/faiss_index.bin")
+    EMBEDDING_DIMENSION: int = int(os.getenv("EMBEDDING_DIMENSION", 768))
+
+# Instantiate the settings so they can be imported and used anywhere
+settings = Settings()
\ No newline at end of file
diff --git a/ai-hub/app/db/database.py b/ai-hub/app/db/database.py
index cbb6b13..c2dfee1 100644
--- a/ai-hub/app/db/database.py
+++ b/ai-hub/app/db/database.py
@@ -1,54 +1,5 @@
-import os
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker, declarative_base # <-- CORRECTED IMPORT
+from sqlalchemy.orm import declarative_base
 
-# --- Configuration ---
-# Determines the database mode. Can be "postgres" or "sqlite".
-# Defaults to "postgres" if not set.
-DB_MODE = os.getenv("DB_MODE", "postgres").lower()
-
-# Default database URLs
-POSTGRES_DEFAULT_URL = "postgresql://user:password@localhost/ai_hub_db"
-SQLITE_DEFAULT_URL = "sqlite:///./data/ai_hub.db"
-
-DATABASE_URL = ""
-engine_args = {}
-
-# --- Database Initialization ---
-if DB_MODE == "sqlite":
-    print("✅ Initializing with SQLite in-file database.")
-    DATABASE_URL = SQLITE_DEFAULT_URL
-    # SQLite requires a specific argument to allow access from multiple threads,
-    # which is common in web applications.
-    engine_args = {"connect_args": {"check_same_thread": False}}
-else: # Default to postgres
-    # Use the provided DATABASE_URL or fall back to the default.
-    DATABASE_URL = os.getenv("DATABASE_URL", POSTGRES_DEFAULT_URL)
-    DB_MODE = "postgres"
-    print(f"✅ Initializing with PostgreSQL database. URL: {DATABASE_URL}")
-    # pool_pre_ping checks if a connection is still alive before using it from the pool.
-    engine_args = {"pool_pre_ping": True}
-
-
-# Create the SQLAlchemy engine with the determined settings
-engine = create_engine(DATABASE_URL, **engine_args)
-
-# SessionLocal is a factory for creating new database session objects
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
-
-# Base is a class that our database model classes will inherit from.
-Base = declarative_base()
-
-
-# --- Dependency for FastAPI ---
-def get_db():
-    """
-    FastAPI dependency that provides a database session for a single API request.
-    It ensures the session is always closed after the request is finished.
-    """
-    db = SessionLocal()
-    try:
-        yield db
-    finally:
-        db.close()
-
+# This Base class is the foundation that all your SQLAlchemy ORM models
+# (like Document, VectorMetadata, etc.) will inherit from.
+Base = declarative_base()
\ No newline at end of file
diff --git a/ai-hub/app/db/session.py b/ai-hub/app/db/session.py
new file mode 100644
index 0000000..26e8938
--- /dev/null
+++ b/ai-hub/app/db/session.py
@@ -0,0 +1,44 @@
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from app.config import settings
+from app.db.database import Base
+
+# Determine engine arguments based on the database mode from the central config
+engine_args = {}
+if settings.DB_MODE == "sqlite":
+    # This argument is required for SQLite to allow it to be used by multiple threads,
+    # which is the case in a web application like FastAPI.
+    engine_args["connect_args"] = {"check_same_thread": False}
+else:
+    # 'pool_pre_ping' checks if a database connection is still alive before using it.
+    # This prevents errors from connections that have been timed out by the DB server.
+    engine_args["pool_pre_ping"] = True
+
+# Create the SQLAlchemy engine using the centralized URL and determined arguments
+engine = create_engine(settings.DATABASE_URL, **engine_args)
+
+# SessionLocal is a factory for creating new database session objects.
+# It's the standard way to interact with the database in SQLAlchemy.
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+def create_db_and_tables():
+    """
+    Creates all database tables defined by models inheriting from Base.
+    This is typically called once on application startup.
+    """
+    print("Creating database tables...")
+    # Base.metadata contains all the schema information from your models.
+    Base.metadata.create_all(bind=engine)
+
+def get_db():
+    """
+    FastAPI dependency that provides a database session for a single API request.
+    
+    This pattern ensures that the database session is always closed after the
+    request is finished, even if an error occurs.
+    """
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
\ No newline at end of file
diff --git a/ai-hub/app/db_setup.py b/ai-hub/app/db_setup.py
deleted file mode 100644
index 63a64a6..0000000
--- a/ai-hub/app/db_setup.py
+++ /dev/null
@@ -1,36 +0,0 @@
-import os
-from dotenv import load_dotenv
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker, Session
-from app.db.database import Base # Assuming `Base` is in this file
-
-# Load environment variables from a .env file
-load_dotenv()
-
-# --- Database Connection Setup ---
-# This configuration allows for easy switching between SQLite and PostgreSQL.
-DB_MODE = os.getenv("DB_MODE", "sqlite")
-if DB_MODE == "sqlite":
-    DATABASE_URL = "sqlite:///./data/ai_hub.db"
-    # The connect_args are needed for SQLite to work with FastAPI's multiple threads
-    engine = create_engine(DATABASE_URL, connect_args={"check_same_thread": False})
-else:
-    DATABASE_URL = os.getenv("DATABASE_URL", "postgresql://user:password@localhost/ai_hub_db")
-    engine = create_engine(DATABASE_URL)
-
-# Create a database session class
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
-
-def create_db_tables():
-    """Create all database tables based on the models."""
-    print("Creating database tables...")
-    Base.metadata.create_all(bind=engine)
-
-# The dependency to get a database session
-def get_db():
-    """Dependency that provides a database session."""
-    db = SessionLocal()
-    try:
-        yield db
-    finally:
-        db.close()
\ No newline at end of file

diff --git a/ai-hub/app/api/routes.py b/ai-hub/app/api/routes.py
index 6cf3deb..23bfa68 100644
--- a/ai-hub/app/api/routes.py
+++ b/ai-hub/app/api/routes.py
@@ -5,7 +5,7 @@
 from typing import Literal
 from sqlalchemy.orm import Session
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 
 # Pydantic Models for API requests
 class ChatRequest(BaseModel):
diff --git a/ai-hub/app/app.py b/ai-hub/app/app.py
index 7b82b4b..d18d97b 100644
--- a/ai-hub/app/app.py
+++ b/ai-hub/app/app.py
@@ -10,7 +10,7 @@
 from app.core.services import RAGService
 
 # Import the new files for database and API routes
-from app.db_setup import create_db_tables
+from app.db.session import create_db_and_tables
 from app.api.routes import create_api_router
 
 # Load environment variables from a .env file
@@ -37,7 +37,7 @@
         cleanup on shutdown.
         """
         print("Initializing application services...")
-        create_db_tables()
+        create_db_and_tables()
         yield
         print("Shutting down application services...")
         vector_store.save_index()
diff --git a/ai-hub/app/config.py b/ai-hub/app/config.py
new file mode 100644
index 0000000..ab8f8f4
--- /dev/null
+++ b/ai-hub/app/config.py
@@ -0,0 +1,29 @@
+# app/config.py
+
+import os
+from dotenv import load_dotenv
+
+# Load environment variables from a .env file
+load_dotenv()
+
+class Settings:
+    # --- Database ---
+    DB_MODE: str = os.getenv("DB_MODE", "sqlite")
+    DATABASE_URL: str = (
+        "sqlite:///./data/ai_hub.db"
+        if DB_MODE == "sqlite"
+        else os.getenv("DATABASE_URL", "postgresql://user:password@localhost/ai_hub_db")
+    )
+    
+    # --- LLM API Keys & Models ---
+    DEEPSEEK_API_KEY: str = os.getenv("DEEPSEEK_API_KEY")
+    GEMINI_API_KEY: str = os.getenv("GEMINI_API_KEY")
+    DEEPSEEK_MODEL_NAME: str = os.getenv("DEEPSEEK_MODEL_NAME", "deepseek-chat")
+    GEMINI_MODEL_NAME: str = os.getenv("GEMINI_MODEL_NAME", "gemini-1.5-flash-latest")
+    
+    # --- Vector Store ---
+    FAISS_INDEX_PATH: str = os.getenv("FAISS_INDEX_PATH", "data/faiss_index.bin")
+    EMBEDDING_DIMENSION: int = int(os.getenv("EMBEDDING_DIMENSION", 768))
+
+# Instantiate the settings so they can be imported and used anywhere
+settings = Settings()
\ No newline at end of file
diff --git a/ai-hub/app/db/database.py b/ai-hub/app/db/database.py
index cbb6b13..c2dfee1 100644
--- a/ai-hub/app/db/database.py
+++ b/ai-hub/app/db/database.py
@@ -1,54 +1,5 @@
-import os
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker, declarative_base # <-- CORRECTED IMPORT
+from sqlalchemy.orm import declarative_base
 
-# --- Configuration ---
-# Determines the database mode. Can be "postgres" or "sqlite".
-# Defaults to "postgres" if not set.
-DB_MODE = os.getenv("DB_MODE", "postgres").lower()
-
-# Default database URLs
-POSTGRES_DEFAULT_URL = "postgresql://user:password@localhost/ai_hub_db"
-SQLITE_DEFAULT_URL = "sqlite:///./data/ai_hub.db"
-
-DATABASE_URL = ""
-engine_args = {}
-
-# --- Database Initialization ---
-if DB_MODE == "sqlite":
-    print("✅ Initializing with SQLite in-file database.")
-    DATABASE_URL = SQLITE_DEFAULT_URL
-    # SQLite requires a specific argument to allow access from multiple threads,
-    # which is common in web applications.
-    engine_args = {"connect_args": {"check_same_thread": False}}
-else: # Default to postgres
-    # Use the provided DATABASE_URL or fall back to the default.
-    DATABASE_URL = os.getenv("DATABASE_URL", POSTGRES_DEFAULT_URL)
-    DB_MODE = "postgres"
-    print(f"✅ Initializing with PostgreSQL database. URL: {DATABASE_URL}")
-    # pool_pre_ping checks if a connection is still alive before using it from the pool.
-    engine_args = {"pool_pre_ping": True}
-
-
-# Create the SQLAlchemy engine with the determined settings
-engine = create_engine(DATABASE_URL, **engine_args)
-
-# SessionLocal is a factory for creating new database session objects
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
-
-# Base is a class that our database model classes will inherit from.
-Base = declarative_base()
-
-
-# --- Dependency for FastAPI ---
-def get_db():
-    """
-    FastAPI dependency that provides a database session for a single API request.
-    It ensures the session is always closed after the request is finished.
-    """
-    db = SessionLocal()
-    try:
-        yield db
-    finally:
-        db.close()
-
+# This Base class is the foundation that all your SQLAlchemy ORM models
+# (like Document, VectorMetadata, etc.) will inherit from.
+Base = declarative_base()
\ No newline at end of file
diff --git a/ai-hub/app/db/session.py b/ai-hub/app/db/session.py
new file mode 100644
index 0000000..26e8938
--- /dev/null
+++ b/ai-hub/app/db/session.py
@@ -0,0 +1,44 @@
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from app.config import settings
+from app.db.database import Base
+
+# Determine engine arguments based on the database mode from the central config
+engine_args = {}
+if settings.DB_MODE == "sqlite":
+    # This argument is required for SQLite to allow it to be used by multiple threads,
+    # which is the case in a web application like FastAPI.
+    engine_args["connect_args"] = {"check_same_thread": False}
+else:
+    # 'pool_pre_ping' checks if a database connection is still alive before using it.
+    # This prevents errors from connections that have been timed out by the DB server.
+    engine_args["pool_pre_ping"] = True
+
+# Create the SQLAlchemy engine using the centralized URL and determined arguments
+engine = create_engine(settings.DATABASE_URL, **engine_args)
+
+# SessionLocal is a factory for creating new database session objects.
+# It's the standard way to interact with the database in SQLAlchemy.
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+def create_db_and_tables():
+    """
+    Creates all database tables defined by models inheriting from Base.
+    This is typically called once on application startup.
+    """
+    print("Creating database tables...")
+    # Base.metadata contains all the schema information from your models.
+    Base.metadata.create_all(bind=engine)
+
+def get_db():
+    """
+    FastAPI dependency that provides a database session for a single API request.
+    
+    This pattern ensures that the database session is always closed after the
+    request is finished, even if an error occurs.
+    """
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
\ No newline at end of file
diff --git a/ai-hub/app/db_setup.py b/ai-hub/app/db_setup.py
deleted file mode 100644
index 63a64a6..0000000
--- a/ai-hub/app/db_setup.py
+++ /dev/null
@@ -1,36 +0,0 @@
-import os
-from dotenv import load_dotenv
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker, Session
-from app.db.database import Base # Assuming `Base` is in this file
-
-# Load environment variables from a .env file
-load_dotenv()
-
-# --- Database Connection Setup ---
-# This configuration allows for easy switching between SQLite and PostgreSQL.
-DB_MODE = os.getenv("DB_MODE", "sqlite")
-if DB_MODE == "sqlite":
-    DATABASE_URL = "sqlite:///./data/ai_hub.db"
-    # The connect_args are needed for SQLite to work with FastAPI's multiple threads
-    engine = create_engine(DATABASE_URL, connect_args={"check_same_thread": False})
-else:
-    DATABASE_URL = os.getenv("DATABASE_URL", "postgresql://user:password@localhost/ai_hub_db")
-    engine = create_engine(DATABASE_URL)
-
-# Create a database session class
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
-
-def create_db_tables():
-    """Create all database tables based on the models."""
-    print("Creating database tables...")
-    Base.metadata.create_all(bind=engine)
-
-# The dependency to get a database session
-def get_db():
-    """Dependency that provides a database session."""
-    db = SessionLocal()
-    try:
-        yield db
-    finally:
-        db.close()
\ No newline at end of file
diff --git a/ai-hub/tests/api/test_routes.py b/ai-hub/tests/api/test_routes.py
index b98fdbf..fdee764 100644
--- a/ai-hub/tests/api/test_routes.py
+++ b/ai-hub/tests/api/test_routes.py
@@ -8,7 +8,7 @@
 
 # Import the dependencies and router factory
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 from app.api.routes import create_api_router
 
 @pytest.fixture

diff --git a/ai-hub/app/api/routes.py b/ai-hub/app/api/routes.py
index 6cf3deb..23bfa68 100644
--- a/ai-hub/app/api/routes.py
+++ b/ai-hub/app/api/routes.py
@@ -5,7 +5,7 @@
 from typing import Literal
 from sqlalchemy.orm import Session
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 
 # Pydantic Models for API requests
 class ChatRequest(BaseModel):
diff --git a/ai-hub/app/app.py b/ai-hub/app/app.py
index 7b82b4b..d18d97b 100644
--- a/ai-hub/app/app.py
+++ b/ai-hub/app/app.py
@@ -10,7 +10,7 @@
 from app.core.services import RAGService
 
 # Import the new files for database and API routes
-from app.db_setup import create_db_tables
+from app.db.session import create_db_and_tables
 from app.api.routes import create_api_router
 
 # Load environment variables from a .env file
@@ -37,7 +37,7 @@
         cleanup on shutdown.
         """
         print("Initializing application services...")
-        create_db_tables()
+        create_db_and_tables()
         yield
         print("Shutting down application services...")
         vector_store.save_index()
diff --git a/ai-hub/app/config.py b/ai-hub/app/config.py
new file mode 100644
index 0000000..ab8f8f4
--- /dev/null
+++ b/ai-hub/app/config.py
@@ -0,0 +1,29 @@
+# app/config.py
+
+import os
+from dotenv import load_dotenv
+
+# Load environment variables from a .env file
+load_dotenv()
+
+class Settings:
+    # --- Database ---
+    DB_MODE: str = os.getenv("DB_MODE", "sqlite")
+    DATABASE_URL: str = (
+        "sqlite:///./data/ai_hub.db"
+        if DB_MODE == "sqlite"
+        else os.getenv("DATABASE_URL", "postgresql://user:password@localhost/ai_hub_db")
+    )
+    
+    # --- LLM API Keys & Models ---
+    DEEPSEEK_API_KEY: str = os.getenv("DEEPSEEK_API_KEY")
+    GEMINI_API_KEY: str = os.getenv("GEMINI_API_KEY")
+    DEEPSEEK_MODEL_NAME: str = os.getenv("DEEPSEEK_MODEL_NAME", "deepseek-chat")
+    GEMINI_MODEL_NAME: str = os.getenv("GEMINI_MODEL_NAME", "gemini-1.5-flash-latest")
+    
+    # --- Vector Store ---
+    FAISS_INDEX_PATH: str = os.getenv("FAISS_INDEX_PATH", "data/faiss_index.bin")
+    EMBEDDING_DIMENSION: int = int(os.getenv("EMBEDDING_DIMENSION", 768))
+
+# Instantiate the settings so they can be imported and used anywhere
+settings = Settings()
\ No newline at end of file
diff --git a/ai-hub/app/db/database.py b/ai-hub/app/db/database.py
index cbb6b13..c2dfee1 100644
--- a/ai-hub/app/db/database.py
+++ b/ai-hub/app/db/database.py
@@ -1,54 +1,5 @@
-import os
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker, declarative_base # <-- CORRECTED IMPORT
+from sqlalchemy.orm import declarative_base
 
-# --- Configuration ---
-# Determines the database mode. Can be "postgres" or "sqlite".
-# Defaults to "postgres" if not set.
-DB_MODE = os.getenv("DB_MODE", "postgres").lower()
-
-# Default database URLs
-POSTGRES_DEFAULT_URL = "postgresql://user:password@localhost/ai_hub_db"
-SQLITE_DEFAULT_URL = "sqlite:///./data/ai_hub.db"
-
-DATABASE_URL = ""
-engine_args = {}
-
-# --- Database Initialization ---
-if DB_MODE == "sqlite":
-    print("✅ Initializing with SQLite in-file database.")
-    DATABASE_URL = SQLITE_DEFAULT_URL
-    # SQLite requires a specific argument to allow access from multiple threads,
-    # which is common in web applications.
-    engine_args = {"connect_args": {"check_same_thread": False}}
-else: # Default to postgres
-    # Use the provided DATABASE_URL or fall back to the default.
-    DATABASE_URL = os.getenv("DATABASE_URL", POSTGRES_DEFAULT_URL)
-    DB_MODE = "postgres"
-    print(f"✅ Initializing with PostgreSQL database. URL: {DATABASE_URL}")
-    # pool_pre_ping checks if a connection is still alive before using it from the pool.
-    engine_args = {"pool_pre_ping": True}
-
-
-# Create the SQLAlchemy engine with the determined settings
-engine = create_engine(DATABASE_URL, **engine_args)
-
-# SessionLocal is a factory for creating new database session objects
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
-
-# Base is a class that our database model classes will inherit from.
-Base = declarative_base()
-
-
-# --- Dependency for FastAPI ---
-def get_db():
-    """
-    FastAPI dependency that provides a database session for a single API request.
-    It ensures the session is always closed after the request is finished.
-    """
-    db = SessionLocal()
-    try:
-        yield db
-    finally:
-        db.close()
-
+# This Base class is the foundation that all your SQLAlchemy ORM models
+# (like Document, VectorMetadata, etc.) will inherit from.
+Base = declarative_base()
\ No newline at end of file
diff --git a/ai-hub/app/db/session.py b/ai-hub/app/db/session.py
new file mode 100644
index 0000000..26e8938
--- /dev/null
+++ b/ai-hub/app/db/session.py
@@ -0,0 +1,44 @@
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from app.config import settings
+from app.db.database import Base
+
+# Determine engine arguments based on the database mode from the central config
+engine_args = {}
+if settings.DB_MODE == "sqlite":
+    # This argument is required for SQLite to allow it to be used by multiple threads,
+    # which is the case in a web application like FastAPI.
+    engine_args["connect_args"] = {"check_same_thread": False}
+else:
+    # 'pool_pre_ping' checks if a database connection is still alive before using it.
+    # This prevents errors from connections that have been timed out by the DB server.
+    engine_args["pool_pre_ping"] = True
+
+# Create the SQLAlchemy engine using the centralized URL and determined arguments
+engine = create_engine(settings.DATABASE_URL, **engine_args)
+
+# SessionLocal is a factory for creating new database session objects.
+# It's the standard way to interact with the database in SQLAlchemy.
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+def create_db_and_tables():
+    """
+    Creates all database tables defined by models inheriting from Base.
+    This is typically called once on application startup.
+    """
+    print("Creating database tables...")
+    # Base.metadata contains all the schema information from your models.
+    Base.metadata.create_all(bind=engine)
+
+def get_db():
+    """
+    FastAPI dependency that provides a database session for a single API request.
+    
+    This pattern ensures that the database session is always closed after the
+    request is finished, even if an error occurs.
+    """
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
\ No newline at end of file
diff --git a/ai-hub/app/db_setup.py b/ai-hub/app/db_setup.py
deleted file mode 100644
index 63a64a6..0000000
--- a/ai-hub/app/db_setup.py
+++ /dev/null
@@ -1,36 +0,0 @@
-import os
-from dotenv import load_dotenv
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker, Session
-from app.db.database import Base # Assuming `Base` is in this file
-
-# Load environment variables from a .env file
-load_dotenv()
-
-# --- Database Connection Setup ---
-# This configuration allows for easy switching between SQLite and PostgreSQL.
-DB_MODE = os.getenv("DB_MODE", "sqlite")
-if DB_MODE == "sqlite":
-    DATABASE_URL = "sqlite:///./data/ai_hub.db"
-    # The connect_args are needed for SQLite to work with FastAPI's multiple threads
-    engine = create_engine(DATABASE_URL, connect_args={"check_same_thread": False})
-else:
-    DATABASE_URL = os.getenv("DATABASE_URL", "postgresql://user:password@localhost/ai_hub_db")
-    engine = create_engine(DATABASE_URL)
-
-# Create a database session class
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
-
-def create_db_tables():
-    """Create all database tables based on the models."""
-    print("Creating database tables...")
-    Base.metadata.create_all(bind=engine)
-
-# The dependency to get a database session
-def get_db():
-    """Dependency that provides a database session."""
-    db = SessionLocal()
-    try:
-        yield db
-    finally:
-        db.close()
\ No newline at end of file
diff --git a/ai-hub/tests/api/test_routes.py b/ai-hub/tests/api/test_routes.py
index b98fdbf..fdee764 100644
--- a/ai-hub/tests/api/test_routes.py
+++ b/ai-hub/tests/api/test_routes.py
@@ -8,7 +8,7 @@
 
 # Import the dependencies and router factory
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 from app.api.routes import create_api_router
 
 @pytest.fixture
diff --git a/ai-hub/tests/app.py b/ai-hub/tests/app.py
new file mode 100644
index 0000000..b7e6fb3
--- /dev/null
+++ b/ai-hub/tests/app.py
@@ -0,0 +1,56 @@
+import os
+from contextlib import asynccontextmanager
+from fastapi import FastAPI
+from dotenv import load_dotenv
+from typing import List
+
+# Import core application logic
+from app.core.vector_store import FaissVectorStore
+from app.core.retrievers import FaissDBRetriever, Retriever
+from app.core.services import RAGService
+
+# Import the new files for database and API routes
+from app.db.session import create_db_tables
+from app.api.routes import create_api_router
+
+# Load environment variables from a .env file
+load_dotenv()
+
+# --- Application Factory Function ---
+def create_app() -> FastAPI:
+    """
+    Factory function to create and configure the FastAPI application.
+    This encapsulates all setup logic, making the main entry point clean.
+    """
+    # Initialize core services for RAG
+    # CORRECTED: Now passing the required arguments to FaissVectorStore
+    vector_store = FaissVectorStore(index_file_path="data/faiss_index.bin", dimension=768)
+    retrievers: List[Retriever] = [
+        FaissDBRetriever(vector_store=vector_store),
+    ]
+    rag_service = RAGService(vector_store=vector_store, retrievers=retrievers)
+
+    @asynccontextmanager
+    async def lifespan(app: FastAPI):
+        """
+        Initializes the database and vector store on startup and handles
+        cleanup on shutdown.
+        """
+        print("Initializing application services...")
+        create_db_tables()
+        yield
+        print("Shutting down application services...")
+        vector_store.save_index()
+
+    app = FastAPI(
+        title="AI Model Hub Service",
+        description="A extensible hub to route requests to various LLMs with RAG capabilities.",
+        version="0.0.0",
+        lifespan=lifespan
+    )
+
+    # Create and include the API router
+    api_router = create_api_router(rag_service=rag_service)
+    app.include_router(api_router)
+
+    return app

diff --git a/ai-hub/app/api/routes.py b/ai-hub/app/api/routes.py
index 6cf3deb..23bfa68 100644
--- a/ai-hub/app/api/routes.py
+++ b/ai-hub/app/api/routes.py
@@ -5,7 +5,7 @@
 from typing import Literal
 from sqlalchemy.orm import Session
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 
 # Pydantic Models for API requests
 class ChatRequest(BaseModel):
diff --git a/ai-hub/app/app.py b/ai-hub/app/app.py
index 7b82b4b..d18d97b 100644
--- a/ai-hub/app/app.py
+++ b/ai-hub/app/app.py
@@ -10,7 +10,7 @@
 from app.core.services import RAGService
 
 # Import the new files for database and API routes
-from app.db_setup import create_db_tables
+from app.db.session import create_db_and_tables
 from app.api.routes import create_api_router
 
 # Load environment variables from a .env file
@@ -37,7 +37,7 @@
         cleanup on shutdown.
         """
         print("Initializing application services...")
-        create_db_tables()
+        create_db_and_tables()
         yield
         print("Shutting down application services...")
         vector_store.save_index()
diff --git a/ai-hub/app/config.py b/ai-hub/app/config.py
new file mode 100644
index 0000000..ab8f8f4
--- /dev/null
+++ b/ai-hub/app/config.py
@@ -0,0 +1,29 @@
+# app/config.py
+
+import os
+from dotenv import load_dotenv
+
+# Load environment variables from a .env file
+load_dotenv()
+
+class Settings:
+    # --- Database ---
+    DB_MODE: str = os.getenv("DB_MODE", "sqlite")
+    DATABASE_URL: str = (
+        "sqlite:///./data/ai_hub.db"
+        if DB_MODE == "sqlite"
+        else os.getenv("DATABASE_URL", "postgresql://user:password@localhost/ai_hub_db")
+    )
+    
+    # --- LLM API Keys & Models ---
+    DEEPSEEK_API_KEY: str = os.getenv("DEEPSEEK_API_KEY")
+    GEMINI_API_KEY: str = os.getenv("GEMINI_API_KEY")
+    DEEPSEEK_MODEL_NAME: str = os.getenv("DEEPSEEK_MODEL_NAME", "deepseek-chat")
+    GEMINI_MODEL_NAME: str = os.getenv("GEMINI_MODEL_NAME", "gemini-1.5-flash-latest")
+    
+    # --- Vector Store ---
+    FAISS_INDEX_PATH: str = os.getenv("FAISS_INDEX_PATH", "data/faiss_index.bin")
+    EMBEDDING_DIMENSION: int = int(os.getenv("EMBEDDING_DIMENSION", 768))
+
+# Instantiate the settings so they can be imported and used anywhere
+settings = Settings()
\ No newline at end of file
diff --git a/ai-hub/app/db/database.py b/ai-hub/app/db/database.py
index cbb6b13..c2dfee1 100644
--- a/ai-hub/app/db/database.py
+++ b/ai-hub/app/db/database.py
@@ -1,54 +1,5 @@
-import os
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker, declarative_base # <-- CORRECTED IMPORT
+from sqlalchemy.orm import declarative_base
 
-# --- Configuration ---
-# Determines the database mode. Can be "postgres" or "sqlite".
-# Defaults to "postgres" if not set.
-DB_MODE = os.getenv("DB_MODE", "postgres").lower()
-
-# Default database URLs
-POSTGRES_DEFAULT_URL = "postgresql://user:password@localhost/ai_hub_db"
-SQLITE_DEFAULT_URL = "sqlite:///./data/ai_hub.db"
-
-DATABASE_URL = ""
-engine_args = {}
-
-# --- Database Initialization ---
-if DB_MODE == "sqlite":
-    print("✅ Initializing with SQLite in-file database.")
-    DATABASE_URL = SQLITE_DEFAULT_URL
-    # SQLite requires a specific argument to allow access from multiple threads,
-    # which is common in web applications.
-    engine_args = {"connect_args": {"check_same_thread": False}}
-else: # Default to postgres
-    # Use the provided DATABASE_URL or fall back to the default.
-    DATABASE_URL = os.getenv("DATABASE_URL", POSTGRES_DEFAULT_URL)
-    DB_MODE = "postgres"
-    print(f"✅ Initializing with PostgreSQL database. URL: {DATABASE_URL}")
-    # pool_pre_ping checks if a connection is still alive before using it from the pool.
-    engine_args = {"pool_pre_ping": True}
-
-
-# Create the SQLAlchemy engine with the determined settings
-engine = create_engine(DATABASE_URL, **engine_args)
-
-# SessionLocal is a factory for creating new database session objects
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
-
-# Base is a class that our database model classes will inherit from.
-Base = declarative_base()
-
-
-# --- Dependency for FastAPI ---
-def get_db():
-    """
-    FastAPI dependency that provides a database session for a single API request.
-    It ensures the session is always closed after the request is finished.
-    """
-    db = SessionLocal()
-    try:
-        yield db
-    finally:
-        db.close()
-
+# This Base class is the foundation that all your SQLAlchemy ORM models
+# (like Document, VectorMetadata, etc.) will inherit from.
+Base = declarative_base()
\ No newline at end of file
diff --git a/ai-hub/app/db/session.py b/ai-hub/app/db/session.py
new file mode 100644
index 0000000..26e8938
--- /dev/null
+++ b/ai-hub/app/db/session.py
@@ -0,0 +1,44 @@
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from app.config import settings
+from app.db.database import Base
+
+# Determine engine arguments based on the database mode from the central config
+engine_args = {}
+if settings.DB_MODE == "sqlite":
+    # This argument is required for SQLite to allow it to be used by multiple threads,
+    # which is the case in a web application like FastAPI.
+    engine_args["connect_args"] = {"check_same_thread": False}
+else:
+    # 'pool_pre_ping' checks if a database connection is still alive before using it.
+    # This prevents errors from connections that have been timed out by the DB server.
+    engine_args["pool_pre_ping"] = True
+
+# Create the SQLAlchemy engine using the centralized URL and determined arguments
+engine = create_engine(settings.DATABASE_URL, **engine_args)
+
+# SessionLocal is a factory for creating new database session objects.
+# It's the standard way to interact with the database in SQLAlchemy.
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+def create_db_and_tables():
+    """
+    Creates all database tables defined by models inheriting from Base.
+    This is typically called once on application startup.
+    """
+    print("Creating database tables...")
+    # Base.metadata contains all the schema information from your models.
+    Base.metadata.create_all(bind=engine)
+
+def get_db():
+    """
+    FastAPI dependency that provides a database session for a single API request.
+    
+    This pattern ensures that the database session is always closed after the
+    request is finished, even if an error occurs.
+    """
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
\ No newline at end of file
diff --git a/ai-hub/app/db_setup.py b/ai-hub/app/db_setup.py
deleted file mode 100644
index 63a64a6..0000000
--- a/ai-hub/app/db_setup.py
+++ /dev/null
@@ -1,36 +0,0 @@
-import os
-from dotenv import load_dotenv
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker, Session
-from app.db.database import Base # Assuming `Base` is in this file
-
-# Load environment variables from a .env file
-load_dotenv()
-
-# --- Database Connection Setup ---
-# This configuration allows for easy switching between SQLite and PostgreSQL.
-DB_MODE = os.getenv("DB_MODE", "sqlite")
-if DB_MODE == "sqlite":
-    DATABASE_URL = "sqlite:///./data/ai_hub.db"
-    # The connect_args are needed for SQLite to work with FastAPI's multiple threads
-    engine = create_engine(DATABASE_URL, connect_args={"check_same_thread": False})
-else:
-    DATABASE_URL = os.getenv("DATABASE_URL", "postgresql://user:password@localhost/ai_hub_db")
-    engine = create_engine(DATABASE_URL)
-
-# Create a database session class
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
-
-def create_db_tables():
-    """Create all database tables based on the models."""
-    print("Creating database tables...")
-    Base.metadata.create_all(bind=engine)
-
-# The dependency to get a database session
-def get_db():
-    """Dependency that provides a database session."""
-    db = SessionLocal()
-    try:
-        yield db
-    finally:
-        db.close()
\ No newline at end of file
diff --git a/ai-hub/tests/api/test_routes.py b/ai-hub/tests/api/test_routes.py
index b98fdbf..fdee764 100644
--- a/ai-hub/tests/api/test_routes.py
+++ b/ai-hub/tests/api/test_routes.py
@@ -8,7 +8,7 @@
 
 # Import the dependencies and router factory
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 from app.api.routes import create_api_router
 
 @pytest.fixture
diff --git a/ai-hub/tests/app.py b/ai-hub/tests/app.py
new file mode 100644
index 0000000..b7e6fb3
--- /dev/null
+++ b/ai-hub/tests/app.py
@@ -0,0 +1,56 @@
+import os
+from contextlib import asynccontextmanager
+from fastapi import FastAPI
+from dotenv import load_dotenv
+from typing import List
+
+# Import core application logic
+from app.core.vector_store import FaissVectorStore
+from app.core.retrievers import FaissDBRetriever, Retriever
+from app.core.services import RAGService
+
+# Import the new files for database and API routes
+from app.db.session import create_db_tables
+from app.api.routes import create_api_router
+
+# Load environment variables from a .env file
+load_dotenv()
+
+# --- Application Factory Function ---
+def create_app() -> FastAPI:
+    """
+    Factory function to create and configure the FastAPI application.
+    This encapsulates all setup logic, making the main entry point clean.
+    """
+    # Initialize core services for RAG
+    # CORRECTED: Now passing the required arguments to FaissVectorStore
+    vector_store = FaissVectorStore(index_file_path="data/faiss_index.bin", dimension=768)
+    retrievers: List[Retriever] = [
+        FaissDBRetriever(vector_store=vector_store),
+    ]
+    rag_service = RAGService(vector_store=vector_store, retrievers=retrievers)
+
+    @asynccontextmanager
+    async def lifespan(app: FastAPI):
+        """
+        Initializes the database and vector store on startup and handles
+        cleanup on shutdown.
+        """
+        print("Initializing application services...")
+        create_db_tables()
+        yield
+        print("Shutting down application services...")
+        vector_store.save_index()
+
+    app = FastAPI(
+        title="AI Model Hub Service",
+        description="A extensible hub to route requests to various LLMs with RAG capabilities.",
+        version="0.0.0",
+        lifespan=lifespan
+    )
+
+    # Create and include the API router
+    api_router = create_api_router(rag_service=rag_service)
+    app.include_router(api_router)
+
+    return app
diff --git a/ai-hub/tests/db/test_database.py b/ai-hub/tests/db/test_database.py
index 8287067..a070625 100644
--- a/ai-hub/tests/db/test_database.py
+++ b/ai-hub/tests/db/test_database.py
@@ -1,91 +1,13 @@
-import os
 import pytest
-import importlib
-from sqlalchemy.orm import Session
-from sqlalchemy.exc import ResourceClosedError
-from sqlalchemy import text
-from unittest.mock import patch
+from sqlalchemy.orm import declarative_base
 
-def test_sqlite_mode_initialization(monkeypatch):
+def test_base_is_declarative_base():
     """
-    Tests if the database initializes in SQLite mode correctly.
+    Tests if the Base object in app.db.database is a SQLAlchemy declarative_base.
     """
-    # Arrange: Set environment variable for SQLite mode
-    monkeypatch.setenv("DB_MODE", "sqlite")
+    # Arrange: Import the Base object from the module
+    from app.db.database import Base
 
-    # Act: Reload the module to apply the monkeypatched env vars
-    from app.db import database
-    importlib.reload(database)
-
-    # Assert: Check if the configuration is correct for SQLite
-    assert database.DB_MODE == "sqlite"
-    assert "sqlite:///./data/ai_hub.db" in database.DATABASE_URL
-    assert "connect_args" in database.engine_args
-    assert database.engine_args["connect_args"] == {"check_same_thread": False}
-
-    # Cleanup the created SQLite file after test, if it exists
-    if os.path.exists("ai_hub.db"):
-        os.remove("ai_hub.db")
-
-def test_postgres_mode_initialization(monkeypatch):
-    """
-    Tests if the database initializes in PostgreSQL mode with a custom URL.
-    """
-    # Arrange: Set env vars for PostgreSQL mode and a specific URL
-    monkeypatch.setenv("DB_MODE", "postgres")
-    monkeypatch.setenv("DATABASE_URL", "postgresql://test_user:test_password@testhost/test_db")
-
-    # Act: Reload the module to apply the monkeypatched env vars
-    from app.db import database
-    importlib.reload(database)
-
-    # Assert: Check if the configuration is correct for PostgreSQL
-    assert database.DB_MODE == "postgres"
-    assert database.DATABASE_URL == "postgresql://test_user:test_password@testhost/test_db"
-    assert "pool_pre_ping" in database.engine_args
-
-def test_default_to_postgres_mode(monkeypatch):
-    """
-    Tests if the system defaults to PostgreSQL mode when DB_MODE is not set.
-    """
-    # Arrange: Ensure DB_MODE is not set
-    monkeypatch.delenv("DB_MODE", raising=False)
-
-    # Act: Reload the module to apply the monkeypatched env vars
-    from app.db import database
-    importlib.reload(database)
-
-    # Assert: Check that it defaulted to postgres
-    assert database.DB_MODE == "postgres"
-    assert "postgresql://user:password@localhost/ai_hub_db" in database.DATABASE_URL
-
-@patch('app.db.database.SessionLocal')
-def test_get_db_yields_and_closes_session(mock_session_local, monkeypatch):
-    """
-    Tests if the get_db() dependency function yields a valid, active session
-    and correctly closes it afterward by mocking the session object.
-    """
-    # Arrange: Get the actual get_db function from the module
-    from app.db import database
-    
-    # Configure the mock session returned by SessionLocal()
-    mock_session = mock_session_local.return_value
-
-    db_generator = database.get_db()
-    
-    # Act
-    # 1. Get the session object from the generator
-    db_session_instance = next(db_generator)
-
-    # Assert
-    # 2. Check that the yielded object is our mock session
-    assert db_session_instance is mock_session
-    mock_session.close.assert_not_called() # The session should not be closed yet
-
-    # 3. Exhaust the generator to trigger the 'finally' block
-    with pytest.raises(StopIteration):
-        next(db_generator)
-
-    # 4. Assert that the close() method was called exactly once.
-    mock_session.close.assert_called_once()
-
+    # Assert: Check that the Base object's metaclass is the same as a new declarative_base's metaclass.
+    # This confirms it's the correct type of object for SQLAlchemy models to inherit from.
+    assert type(Base) == type(declarative_base())
\ No newline at end of file

diff --git a/ai-hub/app/api/routes.py b/ai-hub/app/api/routes.py
index 6cf3deb..23bfa68 100644
--- a/ai-hub/app/api/routes.py
+++ b/ai-hub/app/api/routes.py
@@ -5,7 +5,7 @@
 from typing import Literal
 from sqlalchemy.orm import Session
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 
 # Pydantic Models for API requests
 class ChatRequest(BaseModel):
diff --git a/ai-hub/app/app.py b/ai-hub/app/app.py
index 7b82b4b..d18d97b 100644
--- a/ai-hub/app/app.py
+++ b/ai-hub/app/app.py
@@ -10,7 +10,7 @@
 from app.core.services import RAGService
 
 # Import the new files for database and API routes
-from app.db_setup import create_db_tables
+from app.db.session import create_db_and_tables
 from app.api.routes import create_api_router
 
 # Load environment variables from a .env file
@@ -37,7 +37,7 @@
         cleanup on shutdown.
         """
         print("Initializing application services...")
-        create_db_tables()
+        create_db_and_tables()
         yield
         print("Shutting down application services...")
         vector_store.save_index()
diff --git a/ai-hub/app/config.py b/ai-hub/app/config.py
new file mode 100644
index 0000000..ab8f8f4
--- /dev/null
+++ b/ai-hub/app/config.py
@@ -0,0 +1,29 @@
+# app/config.py
+
+import os
+from dotenv import load_dotenv
+
+# Load environment variables from a .env file
+load_dotenv()
+
+class Settings:
+    # --- Database ---
+    DB_MODE: str = os.getenv("DB_MODE", "sqlite")
+    DATABASE_URL: str = (
+        "sqlite:///./data/ai_hub.db"
+        if DB_MODE == "sqlite"
+        else os.getenv("DATABASE_URL", "postgresql://user:password@localhost/ai_hub_db")
+    )
+    
+    # --- LLM API Keys & Models ---
+    DEEPSEEK_API_KEY: str = os.getenv("DEEPSEEK_API_KEY")
+    GEMINI_API_KEY: str = os.getenv("GEMINI_API_KEY")
+    DEEPSEEK_MODEL_NAME: str = os.getenv("DEEPSEEK_MODEL_NAME", "deepseek-chat")
+    GEMINI_MODEL_NAME: str = os.getenv("GEMINI_MODEL_NAME", "gemini-1.5-flash-latest")
+    
+    # --- Vector Store ---
+    FAISS_INDEX_PATH: str = os.getenv("FAISS_INDEX_PATH", "data/faiss_index.bin")
+    EMBEDDING_DIMENSION: int = int(os.getenv("EMBEDDING_DIMENSION", 768))
+
+# Instantiate the settings so they can be imported and used anywhere
+settings = Settings()
\ No newline at end of file
diff --git a/ai-hub/app/db/database.py b/ai-hub/app/db/database.py
index cbb6b13..c2dfee1 100644
--- a/ai-hub/app/db/database.py
+++ b/ai-hub/app/db/database.py
@@ -1,54 +1,5 @@
-import os
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker, declarative_base # <-- CORRECTED IMPORT
+from sqlalchemy.orm import declarative_base
 
-# --- Configuration ---
-# Determines the database mode. Can be "postgres" or "sqlite".
-# Defaults to "postgres" if not set.
-DB_MODE = os.getenv("DB_MODE", "postgres").lower()
-
-# Default database URLs
-POSTGRES_DEFAULT_URL = "postgresql://user:password@localhost/ai_hub_db"
-SQLITE_DEFAULT_URL = "sqlite:///./data/ai_hub.db"
-
-DATABASE_URL = ""
-engine_args = {}
-
-# --- Database Initialization ---
-if DB_MODE == "sqlite":
-    print("✅ Initializing with SQLite in-file database.")
-    DATABASE_URL = SQLITE_DEFAULT_URL
-    # SQLite requires a specific argument to allow access from multiple threads,
-    # which is common in web applications.
-    engine_args = {"connect_args": {"check_same_thread": False}}
-else: # Default to postgres
-    # Use the provided DATABASE_URL or fall back to the default.
-    DATABASE_URL = os.getenv("DATABASE_URL", POSTGRES_DEFAULT_URL)
-    DB_MODE = "postgres"
-    print(f"✅ Initializing with PostgreSQL database. URL: {DATABASE_URL}")
-    # pool_pre_ping checks if a connection is still alive before using it from the pool.
-    engine_args = {"pool_pre_ping": True}
-
-
-# Create the SQLAlchemy engine with the determined settings
-engine = create_engine(DATABASE_URL, **engine_args)
-
-# SessionLocal is a factory for creating new database session objects
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
-
-# Base is a class that our database model classes will inherit from.
-Base = declarative_base()
-
-
-# --- Dependency for FastAPI ---
-def get_db():
-    """
-    FastAPI dependency that provides a database session for a single API request.
-    It ensures the session is always closed after the request is finished.
-    """
-    db = SessionLocal()
-    try:
-        yield db
-    finally:
-        db.close()
-
+# This Base class is the foundation that all your SQLAlchemy ORM models
+# (like Document, VectorMetadata, etc.) will inherit from.
+Base = declarative_base()
\ No newline at end of file
diff --git a/ai-hub/app/db/session.py b/ai-hub/app/db/session.py
new file mode 100644
index 0000000..26e8938
--- /dev/null
+++ b/ai-hub/app/db/session.py
@@ -0,0 +1,44 @@
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from app.config import settings
+from app.db.database import Base
+
+# Determine engine arguments based on the database mode from the central config
+engine_args = {}
+if settings.DB_MODE == "sqlite":
+    # This argument is required for SQLite to allow it to be used by multiple threads,
+    # which is the case in a web application like FastAPI.
+    engine_args["connect_args"] = {"check_same_thread": False}
+else:
+    # 'pool_pre_ping' checks if a database connection is still alive before using it.
+    # This prevents errors from connections that have been timed out by the DB server.
+    engine_args["pool_pre_ping"] = True
+
+# Create the SQLAlchemy engine using the centralized URL and determined arguments
+engine = create_engine(settings.DATABASE_URL, **engine_args)
+
+# SessionLocal is a factory for creating new database session objects.
+# It's the standard way to interact with the database in SQLAlchemy.
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+def create_db_and_tables():
+    """
+    Creates all database tables defined by models inheriting from Base.
+    This is typically called once on application startup.
+    """
+    print("Creating database tables...")
+    # Base.metadata contains all the schema information from your models.
+    Base.metadata.create_all(bind=engine)
+
+def get_db():
+    """
+    FastAPI dependency that provides a database session for a single API request.
+    
+    This pattern ensures that the database session is always closed after the
+    request is finished, even if an error occurs.
+    """
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
\ No newline at end of file
diff --git a/ai-hub/app/db_setup.py b/ai-hub/app/db_setup.py
deleted file mode 100644
index 63a64a6..0000000
--- a/ai-hub/app/db_setup.py
+++ /dev/null
@@ -1,36 +0,0 @@
-import os
-from dotenv import load_dotenv
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker, Session
-from app.db.database import Base # Assuming `Base` is in this file
-
-# Load environment variables from a .env file
-load_dotenv()
-
-# --- Database Connection Setup ---
-# This configuration allows for easy switching between SQLite and PostgreSQL.
-DB_MODE = os.getenv("DB_MODE", "sqlite")
-if DB_MODE == "sqlite":
-    DATABASE_URL = "sqlite:///./data/ai_hub.db"
-    # The connect_args are needed for SQLite to work with FastAPI's multiple threads
-    engine = create_engine(DATABASE_URL, connect_args={"check_same_thread": False})
-else:
-    DATABASE_URL = os.getenv("DATABASE_URL", "postgresql://user:password@localhost/ai_hub_db")
-    engine = create_engine(DATABASE_URL)
-
-# Create a database session class
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
-
-def create_db_tables():
-    """Create all database tables based on the models."""
-    print("Creating database tables...")
-    Base.metadata.create_all(bind=engine)
-
-# The dependency to get a database session
-def get_db():
-    """Dependency that provides a database session."""
-    db = SessionLocal()
-    try:
-        yield db
-    finally:
-        db.close()
\ No newline at end of file
diff --git a/ai-hub/tests/api/test_routes.py b/ai-hub/tests/api/test_routes.py
index b98fdbf..fdee764 100644
--- a/ai-hub/tests/api/test_routes.py
+++ b/ai-hub/tests/api/test_routes.py
@@ -8,7 +8,7 @@
 
 # Import the dependencies and router factory
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 from app.api.routes import create_api_router
 
 @pytest.fixture
diff --git a/ai-hub/tests/app.py b/ai-hub/tests/app.py
new file mode 100644
index 0000000..b7e6fb3
--- /dev/null
+++ b/ai-hub/tests/app.py
@@ -0,0 +1,56 @@
+import os
+from contextlib import asynccontextmanager
+from fastapi import FastAPI
+from dotenv import load_dotenv
+from typing import List
+
+# Import core application logic
+from app.core.vector_store import FaissVectorStore
+from app.core.retrievers import FaissDBRetriever, Retriever
+from app.core.services import RAGService
+
+# Import the new files for database and API routes
+from app.db.session import create_db_tables
+from app.api.routes import create_api_router
+
+# Load environment variables from a .env file
+load_dotenv()
+
+# --- Application Factory Function ---
+def create_app() -> FastAPI:
+    """
+    Factory function to create and configure the FastAPI application.
+    This encapsulates all setup logic, making the main entry point clean.
+    """
+    # Initialize core services for RAG
+    # CORRECTED: Now passing the required arguments to FaissVectorStore
+    vector_store = FaissVectorStore(index_file_path="data/faiss_index.bin", dimension=768)
+    retrievers: List[Retriever] = [
+        FaissDBRetriever(vector_store=vector_store),
+    ]
+    rag_service = RAGService(vector_store=vector_store, retrievers=retrievers)
+
+    @asynccontextmanager
+    async def lifespan(app: FastAPI):
+        """
+        Initializes the database and vector store on startup and handles
+        cleanup on shutdown.
+        """
+        print("Initializing application services...")
+        create_db_tables()
+        yield
+        print("Shutting down application services...")
+        vector_store.save_index()
+
+    app = FastAPI(
+        title="AI Model Hub Service",
+        description="A extensible hub to route requests to various LLMs with RAG capabilities.",
+        version="0.0.0",
+        lifespan=lifespan
+    )
+
+    # Create and include the API router
+    api_router = create_api_router(rag_service=rag_service)
+    app.include_router(api_router)
+
+    return app
diff --git a/ai-hub/tests/db/test_database.py b/ai-hub/tests/db/test_database.py
index 8287067..a070625 100644
--- a/ai-hub/tests/db/test_database.py
+++ b/ai-hub/tests/db/test_database.py
@@ -1,91 +1,13 @@
-import os
 import pytest
-import importlib
-from sqlalchemy.orm import Session
-from sqlalchemy.exc import ResourceClosedError
-from sqlalchemy import text
-from unittest.mock import patch
+from sqlalchemy.orm import declarative_base
 
-def test_sqlite_mode_initialization(monkeypatch):
+def test_base_is_declarative_base():
     """
-    Tests if the database initializes in SQLite mode correctly.
+    Tests if the Base object in app.db.database is a SQLAlchemy declarative_base.
     """
-    # Arrange: Set environment variable for SQLite mode
-    monkeypatch.setenv("DB_MODE", "sqlite")
+    # Arrange: Import the Base object from the module
+    from app.db.database import Base
 
-    # Act: Reload the module to apply the monkeypatched env vars
-    from app.db import database
-    importlib.reload(database)
-
-    # Assert: Check if the configuration is correct for SQLite
-    assert database.DB_MODE == "sqlite"
-    assert "sqlite:///./data/ai_hub.db" in database.DATABASE_URL
-    assert "connect_args" in database.engine_args
-    assert database.engine_args["connect_args"] == {"check_same_thread": False}
-
-    # Cleanup the created SQLite file after test, if it exists
-    if os.path.exists("ai_hub.db"):
-        os.remove("ai_hub.db")
-
-def test_postgres_mode_initialization(monkeypatch):
-    """
-    Tests if the database initializes in PostgreSQL mode with a custom URL.
-    """
-    # Arrange: Set env vars for PostgreSQL mode and a specific URL
-    monkeypatch.setenv("DB_MODE", "postgres")
-    monkeypatch.setenv("DATABASE_URL", "postgresql://test_user:test_password@testhost/test_db")
-
-    # Act: Reload the module to apply the monkeypatched env vars
-    from app.db import database
-    importlib.reload(database)
-
-    # Assert: Check if the configuration is correct for PostgreSQL
-    assert database.DB_MODE == "postgres"
-    assert database.DATABASE_URL == "postgresql://test_user:test_password@testhost/test_db"
-    assert "pool_pre_ping" in database.engine_args
-
-def test_default_to_postgres_mode(monkeypatch):
-    """
-    Tests if the system defaults to PostgreSQL mode when DB_MODE is not set.
-    """
-    # Arrange: Ensure DB_MODE is not set
-    monkeypatch.delenv("DB_MODE", raising=False)
-
-    # Act: Reload the module to apply the monkeypatched env vars
-    from app.db import database
-    importlib.reload(database)
-
-    # Assert: Check that it defaulted to postgres
-    assert database.DB_MODE == "postgres"
-    assert "postgresql://user:password@localhost/ai_hub_db" in database.DATABASE_URL
-
-@patch('app.db.database.SessionLocal')
-def test_get_db_yields_and_closes_session(mock_session_local, monkeypatch):
-    """
-    Tests if the get_db() dependency function yields a valid, active session
-    and correctly closes it afterward by mocking the session object.
-    """
-    # Arrange: Get the actual get_db function from the module
-    from app.db import database
-    
-    # Configure the mock session returned by SessionLocal()
-    mock_session = mock_session_local.return_value
-
-    db_generator = database.get_db()
-    
-    # Act
-    # 1. Get the session object from the generator
-    db_session_instance = next(db_generator)
-
-    # Assert
-    # 2. Check that the yielded object is our mock session
-    assert db_session_instance is mock_session
-    mock_session.close.assert_not_called() # The session should not be closed yet
-
-    # 3. Exhaust the generator to trigger the 'finally' block
-    with pytest.raises(StopIteration):
-        next(db_generator)
-
-    # 4. Assert that the close() method was called exactly once.
-    mock_session.close.assert_called_once()
-
+    # Assert: Check that the Base object's metaclass is the same as a new declarative_base's metaclass.
+    # This confirms it's the correct type of object for SQLAlchemy models to inherit from.
+    assert type(Base) == type(declarative_base())
\ No newline at end of file
diff --git a/ai-hub/tests/db/test_session.py b/ai-hub/tests/db/test_session.py
new file mode 100644
index 0000000..17b020a
--- /dev/null
+++ b/ai-hub/tests/db/test_session.py
@@ -0,0 +1,68 @@
+import pytest
+import importlib
+from unittest.mock import patch
+
+# --- Test Suite for app.db.session ---
+
+def test_sqlite_mode_initialization(monkeypatch):
+    """
+    Tests if the session module correctly configures the SQLAlchemy engine for SQLite.
+    """
+    # Arrange
+    monkeypatch.setenv("DB_MODE", "sqlite")
+
+    # Act
+    from app import config
+    from app.db import session
+    importlib.reload(config)
+    importlib.reload(session)
+
+    # Assert
+    assert session.engine.dialect.name == "sqlite"
+    assert session.engine.url.database == "./data/ai_hub.db"
+
+def test_postgres_mode_initialization(monkeypatch):
+    """
+    Tests if the session module correctly configures the SQLAlchemy engine for PostgreSQL.
+    """
+    # Arrange
+    monkeypatch.setenv("DB_MODE", "postgres")
+    custom_url = "postgresql://test_user:test_password@testhost/test_db"
+    monkeypatch.setenv("DATABASE_URL", custom_url)
+
+    # Act
+    from app import config
+    from app.db import session
+    importlib.reload(config)
+    importlib.reload(session)
+
+    # Assert
+    assert session.engine.url.drivername == "postgresql"
+    assert session.engine.url.username == "test_user"
+    assert session.engine.url.host == "testhost"
+    assert session.engine.url.database == "test_db"
+
+@patch('app.db.session.SessionLocal')
+def test_get_db_yields_and_closes_session(mock_session_local):
+    """
+    Tests if the get_db() dependency function yields a session and then closes it.
+    """
+    # Arrange
+    from app.db.session import get_db
+    # FIX: Correctly assign the mock session from the mock factory's return_value
+    mock_session = mock_session_local.return_value
+    db_generator = get_db()
+    
+    # Act (Yield)
+    db_session_instance = next(db_generator)
+
+    # Assert (Yield)
+    assert db_session_instance is mock_session
+    mock_session.close.assert_not_called()
+
+    # Act (Close)
+    with pytest.raises(StopIteration):
+        next(db_generator)
+
+    # Assert (Close)
+    mock_session.close.assert_called_once()
\ No newline at end of file

diff --git a/ai-hub/app/api/routes.py b/ai-hub/app/api/routes.py
index 6cf3deb..23bfa68 100644
--- a/ai-hub/app/api/routes.py
+++ b/ai-hub/app/api/routes.py
@@ -5,7 +5,7 @@
 from typing import Literal
 from sqlalchemy.orm import Session
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 
 # Pydantic Models for API requests
 class ChatRequest(BaseModel):
diff --git a/ai-hub/app/app.py b/ai-hub/app/app.py
index 7b82b4b..d18d97b 100644
--- a/ai-hub/app/app.py
+++ b/ai-hub/app/app.py
@@ -10,7 +10,7 @@
 from app.core.services import RAGService
 
 # Import the new files for database and API routes
-from app.db_setup import create_db_tables
+from app.db.session import create_db_and_tables
 from app.api.routes import create_api_router
 
 # Load environment variables from a .env file
@@ -37,7 +37,7 @@
         cleanup on shutdown.
         """
         print("Initializing application services...")
-        create_db_tables()
+        create_db_and_tables()
         yield
         print("Shutting down application services...")
         vector_store.save_index()
diff --git a/ai-hub/app/config.py b/ai-hub/app/config.py
new file mode 100644
index 0000000..ab8f8f4
--- /dev/null
+++ b/ai-hub/app/config.py
@@ -0,0 +1,29 @@
+# app/config.py
+
+import os
+from dotenv import load_dotenv
+
+# Load environment variables from a .env file
+load_dotenv()
+
+class Settings:
+    # --- Database ---
+    DB_MODE: str = os.getenv("DB_MODE", "sqlite")
+    DATABASE_URL: str = (
+        "sqlite:///./data/ai_hub.db"
+        if DB_MODE == "sqlite"
+        else os.getenv("DATABASE_URL", "postgresql://user:password@localhost/ai_hub_db")
+    )
+    
+    # --- LLM API Keys & Models ---
+    DEEPSEEK_API_KEY: str = os.getenv("DEEPSEEK_API_KEY")
+    GEMINI_API_KEY: str = os.getenv("GEMINI_API_KEY")
+    DEEPSEEK_MODEL_NAME: str = os.getenv("DEEPSEEK_MODEL_NAME", "deepseek-chat")
+    GEMINI_MODEL_NAME: str = os.getenv("GEMINI_MODEL_NAME", "gemini-1.5-flash-latest")
+    
+    # --- Vector Store ---
+    FAISS_INDEX_PATH: str = os.getenv("FAISS_INDEX_PATH", "data/faiss_index.bin")
+    EMBEDDING_DIMENSION: int = int(os.getenv("EMBEDDING_DIMENSION", 768))
+
+# Instantiate the settings so they can be imported and used anywhere
+settings = Settings()
\ No newline at end of file
diff --git a/ai-hub/app/db/database.py b/ai-hub/app/db/database.py
index cbb6b13..c2dfee1 100644
--- a/ai-hub/app/db/database.py
+++ b/ai-hub/app/db/database.py
@@ -1,54 +1,5 @@
-import os
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker, declarative_base # <-- CORRECTED IMPORT
+from sqlalchemy.orm import declarative_base
 
-# --- Configuration ---
-# Determines the database mode. Can be "postgres" or "sqlite".
-# Defaults to "postgres" if not set.
-DB_MODE = os.getenv("DB_MODE", "postgres").lower()
-
-# Default database URLs
-POSTGRES_DEFAULT_URL = "postgresql://user:password@localhost/ai_hub_db"
-SQLITE_DEFAULT_URL = "sqlite:///./data/ai_hub.db"
-
-DATABASE_URL = ""
-engine_args = {}
-
-# --- Database Initialization ---
-if DB_MODE == "sqlite":
-    print("✅ Initializing with SQLite in-file database.")
-    DATABASE_URL = SQLITE_DEFAULT_URL
-    # SQLite requires a specific argument to allow access from multiple threads,
-    # which is common in web applications.
-    engine_args = {"connect_args": {"check_same_thread": False}}
-else: # Default to postgres
-    # Use the provided DATABASE_URL or fall back to the default.
-    DATABASE_URL = os.getenv("DATABASE_URL", POSTGRES_DEFAULT_URL)
-    DB_MODE = "postgres"
-    print(f"✅ Initializing with PostgreSQL database. URL: {DATABASE_URL}")
-    # pool_pre_ping checks if a connection is still alive before using it from the pool.
-    engine_args = {"pool_pre_ping": True}
-
-
-# Create the SQLAlchemy engine with the determined settings
-engine = create_engine(DATABASE_URL, **engine_args)
-
-# SessionLocal is a factory for creating new database session objects
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
-
-# Base is a class that our database model classes will inherit from.
-Base = declarative_base()
-
-
-# --- Dependency for FastAPI ---
-def get_db():
-    """
-    FastAPI dependency that provides a database session for a single API request.
-    It ensures the session is always closed after the request is finished.
-    """
-    db = SessionLocal()
-    try:
-        yield db
-    finally:
-        db.close()
-
+# This Base class is the foundation that all your SQLAlchemy ORM models
+# (like Document, VectorMetadata, etc.) will inherit from.
+Base = declarative_base()
\ No newline at end of file
diff --git a/ai-hub/app/db/session.py b/ai-hub/app/db/session.py
new file mode 100644
index 0000000..26e8938
--- /dev/null
+++ b/ai-hub/app/db/session.py
@@ -0,0 +1,44 @@
+from sqlalchemy import create_engine
+from sqlalchemy.orm import sessionmaker
+from app.config import settings
+from app.db.database import Base
+
+# Determine engine arguments based on the database mode from the central config
+engine_args = {}
+if settings.DB_MODE == "sqlite":
+    # This argument is required for SQLite to allow it to be used by multiple threads,
+    # which is the case in a web application like FastAPI.
+    engine_args["connect_args"] = {"check_same_thread": False}
+else:
+    # 'pool_pre_ping' checks if a database connection is still alive before using it.
+    # This prevents errors from connections that have been timed out by the DB server.
+    engine_args["pool_pre_ping"] = True
+
+# Create the SQLAlchemy engine using the centralized URL and determined arguments
+engine = create_engine(settings.DATABASE_URL, **engine_args)
+
+# SessionLocal is a factory for creating new database session objects.
+# It's the standard way to interact with the database in SQLAlchemy.
+SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
+
+def create_db_and_tables():
+    """
+    Creates all database tables defined by models inheriting from Base.
+    This is typically called once on application startup.
+    """
+    print("Creating database tables...")
+    # Base.metadata contains all the schema information from your models.
+    Base.metadata.create_all(bind=engine)
+
+def get_db():
+    """
+    FastAPI dependency that provides a database session for a single API request.
+    
+    This pattern ensures that the database session is always closed after the
+    request is finished, even if an error occurs.
+    """
+    db = SessionLocal()
+    try:
+        yield db
+    finally:
+        db.close()
\ No newline at end of file
diff --git a/ai-hub/app/db_setup.py b/ai-hub/app/db_setup.py
deleted file mode 100644
index 63a64a6..0000000
--- a/ai-hub/app/db_setup.py
+++ /dev/null
@@ -1,36 +0,0 @@
-import os
-from dotenv import load_dotenv
-from sqlalchemy import create_engine
-from sqlalchemy.orm import sessionmaker, Session
-from app.db.database import Base # Assuming `Base` is in this file
-
-# Load environment variables from a .env file
-load_dotenv()
-
-# --- Database Connection Setup ---
-# This configuration allows for easy switching between SQLite and PostgreSQL.
-DB_MODE = os.getenv("DB_MODE", "sqlite")
-if DB_MODE == "sqlite":
-    DATABASE_URL = "sqlite:///./data/ai_hub.db"
-    # The connect_args are needed for SQLite to work with FastAPI's multiple threads
-    engine = create_engine(DATABASE_URL, connect_args={"check_same_thread": False})
-else:
-    DATABASE_URL = os.getenv("DATABASE_URL", "postgresql://user:password@localhost/ai_hub_db")
-    engine = create_engine(DATABASE_URL)
-
-# Create a database session class
-SessionLocal = sessionmaker(autocommit=False, autoflush=False, bind=engine)
-
-def create_db_tables():
-    """Create all database tables based on the models."""
-    print("Creating database tables...")
-    Base.metadata.create_all(bind=engine)
-
-# The dependency to get a database session
-def get_db():
-    """Dependency that provides a database session."""
-    db = SessionLocal()
-    try:
-        yield db
-    finally:
-        db.close()
\ No newline at end of file
diff --git a/ai-hub/tests/api/test_routes.py b/ai-hub/tests/api/test_routes.py
index b98fdbf..fdee764 100644
--- a/ai-hub/tests/api/test_routes.py
+++ b/ai-hub/tests/api/test_routes.py
@@ -8,7 +8,7 @@
 
 # Import the dependencies and router factory
 from app.core.services import RAGService
-from app.db_setup import get_db
+from app.db.session import get_db
 from app.api.routes import create_api_router
 
 @pytest.fixture
diff --git a/ai-hub/tests/app.py b/ai-hub/tests/app.py
new file mode 100644
index 0000000..b7e6fb3
--- /dev/null
+++ b/ai-hub/tests/app.py
@@ -0,0 +1,56 @@
+import os
+from contextlib import asynccontextmanager
+from fastapi import FastAPI
+from dotenv import load_dotenv
+from typing import List
+
+# Import core application logic
+from app.core.vector_store import FaissVectorStore
+from app.core.retrievers import FaissDBRetriever, Retriever
+from app.core.services import RAGService
+
+# Import the new files for database and API routes
+from app.db.session import create_db_tables
+from app.api.routes import create_api_router
+
+# Load environment variables from a .env file
+load_dotenv()
+
+# --- Application Factory Function ---
+def create_app() -> FastAPI:
+    """
+    Factory function to create and configure the FastAPI application.
+    This encapsulates all setup logic, making the main entry point clean.
+    """
+    # Initialize core services for RAG
+    # CORRECTED: Now passing the required arguments to FaissVectorStore
+    vector_store = FaissVectorStore(index_file_path="data/faiss_index.bin", dimension=768)
+    retrievers: List[Retriever] = [
+        FaissDBRetriever(vector_store=vector_store),
+    ]
+    rag_service = RAGService(vector_store=vector_store, retrievers=retrievers)
+
+    @asynccontextmanager
+    async def lifespan(app: FastAPI):
+        """
+        Initializes the database and vector store on startup and handles
+        cleanup on shutdown.
+        """
+        print("Initializing application services...")
+        create_db_tables()
+        yield
+        print("Shutting down application services...")
+        vector_store.save_index()
+
+    app = FastAPI(
+        title="AI Model Hub Service",
+        description="A extensible hub to route requests to various LLMs with RAG capabilities.",
+        version="0.0.0",
+        lifespan=lifespan
+    )
+
+    # Create and include the API router
+    api_router = create_api_router(rag_service=rag_service)
+    app.include_router(api_router)
+
+    return app
diff --git a/ai-hub/tests/db/test_database.py b/ai-hub/tests/db/test_database.py
index 8287067..a070625 100644
--- a/ai-hub/tests/db/test_database.py
+++ b/ai-hub/tests/db/test_database.py
@@ -1,91 +1,13 @@
-import os
 import pytest
-import importlib
-from sqlalchemy.orm import Session
-from sqlalchemy.exc import ResourceClosedError
-from sqlalchemy import text
-from unittest.mock import patch
+from sqlalchemy.orm import declarative_base
 
-def test_sqlite_mode_initialization(monkeypatch):
+def test_base_is_declarative_base():
     """
-    Tests if the database initializes in SQLite mode correctly.
+    Tests if the Base object in app.db.database is a SQLAlchemy declarative_base.
     """
-    # Arrange: Set environment variable for SQLite mode
-    monkeypatch.setenv("DB_MODE", "sqlite")
+    # Arrange: Import the Base object from the module
+    from app.db.database import Base
 
-    # Act: Reload the module to apply the monkeypatched env vars
-    from app.db import database
-    importlib.reload(database)
-
-    # Assert: Check if the configuration is correct for SQLite
-    assert database.DB_MODE == "sqlite"
-    assert "sqlite:///./data/ai_hub.db" in database.DATABASE_URL
-    assert "connect_args" in database.engine_args
-    assert database.engine_args["connect_args"] == {"check_same_thread": False}
-
-    # Cleanup the created SQLite file after test, if it exists
-    if os.path.exists("ai_hub.db"):
-        os.remove("ai_hub.db")
-
-def test_postgres_mode_initialization(monkeypatch):
-    """
-    Tests if the database initializes in PostgreSQL mode with a custom URL.
-    """
-    # Arrange: Set env vars for PostgreSQL mode and a specific URL
-    monkeypatch.setenv("DB_MODE", "postgres")
-    monkeypatch.setenv("DATABASE_URL", "postgresql://test_user:test_password@testhost/test_db")
-
-    # Act: Reload the module to apply the monkeypatched env vars
-    from app.db import database
-    importlib.reload(database)
-
-    # Assert: Check if the configuration is correct for PostgreSQL
-    assert database.DB_MODE == "postgres"
-    assert database.DATABASE_URL == "postgresql://test_user:test_password@testhost/test_db"
-    assert "pool_pre_ping" in database.engine_args
-
-def test_default_to_postgres_mode(monkeypatch):
-    """
-    Tests if the system defaults to PostgreSQL mode when DB_MODE is not set.
-    """
-    # Arrange: Ensure DB_MODE is not set
-    monkeypatch.delenv("DB_MODE", raising=False)
-
-    # Act: Reload the module to apply the monkeypatched env vars
-    from app.db import database
-    importlib.reload(database)
-
-    # Assert: Check that it defaulted to postgres
-    assert database.DB_MODE == "postgres"
-    assert "postgresql://user:password@localhost/ai_hub_db" in database.DATABASE_URL
-
-@patch('app.db.database.SessionLocal')
-def test_get_db_yields_and_closes_session(mock_session_local, monkeypatch):
-    """
-    Tests if the get_db() dependency function yields a valid, active session
-    and correctly closes it afterward by mocking the session object.
-    """
-    # Arrange: Get the actual get_db function from the module
-    from app.db import database
-    
-    # Configure the mock session returned by SessionLocal()
-    mock_session = mock_session_local.return_value
-
-    db_generator = database.get_db()
-    
-    # Act
-    # 1. Get the session object from the generator
-    db_session_instance = next(db_generator)
-
-    # Assert
-    # 2. Check that the yielded object is our mock session
-    assert db_session_instance is mock_session
-    mock_session.close.assert_not_called() # The session should not be closed yet
-
-    # 3. Exhaust the generator to trigger the 'finally' block
-    with pytest.raises(StopIteration):
-        next(db_generator)
-
-    # 4. Assert that the close() method was called exactly once.
-    mock_session.close.assert_called_once()
-
+    # Assert: Check that the Base object's metaclass is the same as a new declarative_base's metaclass.
+    # This confirms it's the correct type of object for SQLAlchemy models to inherit from.
+    assert type(Base) == type(declarative_base())
\ No newline at end of file
diff --git a/ai-hub/tests/db/test_session.py b/ai-hub/tests/db/test_session.py
new file mode 100644
index 0000000..17b020a
--- /dev/null
+++ b/ai-hub/tests/db/test_session.py
@@ -0,0 +1,68 @@
+import pytest
+import importlib
+from unittest.mock import patch
+
+# --- Test Suite for app.db.session ---
+
+def test_sqlite_mode_initialization(monkeypatch):
+    """
+    Tests if the session module correctly configures the SQLAlchemy engine for SQLite.
+    """
+    # Arrange
+    monkeypatch.setenv("DB_MODE", "sqlite")
+
+    # Act
+    from app import config
+    from app.db import session
+    importlib.reload(config)
+    importlib.reload(session)
+
+    # Assert
+    assert session.engine.dialect.name == "sqlite"
+    assert session.engine.url.database == "./data/ai_hub.db"
+
+def test_postgres_mode_initialization(monkeypatch):
+    """
+    Tests if the session module correctly configures the SQLAlchemy engine for PostgreSQL.
+    """
+    # Arrange
+    monkeypatch.setenv("DB_MODE", "postgres")
+    custom_url = "postgresql://test_user:test_password@testhost/test_db"
+    monkeypatch.setenv("DATABASE_URL", custom_url)
+
+    # Act
+    from app import config
+    from app.db import session
+    importlib.reload(config)
+    importlib.reload(session)
+
+    # Assert
+    assert session.engine.url.drivername == "postgresql"
+    assert session.engine.url.username == "test_user"
+    assert session.engine.url.host == "testhost"
+    assert session.engine.url.database == "test_db"
+
+@patch('app.db.session.SessionLocal')
+def test_get_db_yields_and_closes_session(mock_session_local):
+    """
+    Tests if the get_db() dependency function yields a session and then closes it.
+    """
+    # Arrange
+    from app.db.session import get_db
+    # FIX: Correctly assign the mock session from the mock factory's return_value
+    mock_session = mock_session_local.return_value
+    db_generator = get_db()
+    
+    # Act (Yield)
+    db_session_instance = next(db_generator)
+
+    # Assert (Yield)
+    assert db_session_instance is mock_session
+    mock_session.close.assert_not_called()
+
+    # Act (Close)
+    with pytest.raises(StopIteration):
+        next(db_generator)
+
+    # Assert (Close)
+    mock_session.close.assert_called_once()
\ No newline at end of file
diff --git a/ai-hub/tests/test_app.py b/ai-hub/tests/test_app.py
index 6e08da0..6b25640 100644
--- a/ai-hub/tests/test_app.py
+++ b/ai-hub/tests/test_app.py
@@ -3,7 +3,7 @@
 from sqlalchemy.orm import Session
 
 from app.app import create_app
-from app.db_setup import get_db
+from app.db.session import get_db
 
 # --- Dependency Override for Testing ---
 mock_db = MagicMock(spec=Session)