diff --git a/server/auth.py b/server/auth.py
index 4781808..9c3a2ce 100644
--- a/server/auth.py
+++ b/server/auth.py
@@ -35,15 +35,15 @@ async def _verify_firebase_id_token(token: str) -> FirebaseIDTokenData:
         auth.InvalidIdTokenError,
         auth.ExpiredIdTokenError,
         auth.RevokedIdTokenError,
-    ) as e:
+    ):
         raise HTTPException(
             status_code=status.HTTP_401_UNAUTHORIZED, detail="Invalid or expired token"
         )
-    except auth.UserDisabledError as e:
+    except auth.UserDisabledError:
         raise HTTPException(
             status_code=status.HTTP_404_NOT_FOUND, detail="User disabled"
         )
-    except (ValueError, auth.CertificateFetchError, auth.FirebaseError) as e:
+    except (ValueError, auth.CertificateFetchError, auth.FirebaseError):
         raise HTTPException(
             status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
             detail="Internal server error",
diff --git a/server/fastapi_server.py b/server/fastapi_server.py
index 6d01da8..705453a 100644
--- a/server/fastapi_server.py
+++ b/server/fastapi_server.py
@@ -4,6 +4,7 @@
 import traceback
 import logging
 import asyncio
+import re
 
 from fastapi import FastAPI, Request, HTTPException, Depends, Header
 from fastapi.middleware.cors import CORSMiddleware
@@ -81,21 +82,51 @@ def create_fastapi_app() -> FastAPI:
     app = FastAPI()
 
     # Configure CORS
+    # FastAPI CORSMiddleware doesn't support regex patterns, so we list all allowed origins
+    allowed_origins = [
+        "https://bitquant.io",
+        "https://www.bitquant.io",
+        # Localhost ports for development
+        "http://localhost:3000",
+        "http://localhost:3001",
+        "http://localhost:3002",
+        "http://localhost:4000",
+        "http://localhost:4200",
+        "http://localhost:5000",
+        "http://localhost:5173",
+        "http://localhost:8000",
+        "http://localhost:8080",
+        "http://localhost:8081",
+        "http://localhost:9000",
+    ]
+    
+    # Vercel preview deployments pattern (will be checked in custom middleware)
+    vercel_pattern = re.compile(r"^https://defi-chat-hub-git-[\w-]+-open-gradient\.vercel\.app$")
+    
     app.add_middleware(
         CORSMiddleware,
-        allow_origins=[
-            "https://bitquant.io",
-            "https://www.bitquant.io",
-            r"^http://localhost:(3000|3001|3002|4000|4200|5000|5173|8000|8080|8081|9000)$",
-            r"^https://defi-chat-hub-git-[\w-]+-open-gradient\.vercel\.app$",
-        ],
+        allow_origins=allowed_origins,
         allow_credentials=True,
         allow_methods=["*"],
         allow_headers=["*"],
     )
-
+    
     # Add Datadog metrics middleware
     app.add_middleware(DatadogMetricsMiddleware)
+    
+    # Add custom CORS check for Vercel preview deployments
+    # This middleware runs after CORSMiddleware to handle regex patterns
+    @app.middleware("http")
+    async def cors_vercel_middleware(request: Request, call_next):
+        origin = request.headers.get("origin")
+        if origin and vercel_pattern.match(origin):
+            response = await call_next(request)
+            response.headers["Access-Control-Allow-Origin"] = origin
+            response.headers["Access-Control-Allow-Credentials"] = "true"
+            response.headers["Access-Control-Allow-Methods"] = "*"
+            response.headers["Access-Control-Allow-Headers"] = "*"
+            return response
+        return await call_next(request)
 
     # Initialize DynamoDB session
     database_manager = DatabaseManager()
diff --git a/server/service.py b/server/service.py
index 831985d..6383d90 100644
--- a/server/service.py
+++ b/server/service.py
@@ -5,24 +5,32 @@
 
 
 def verify_solana_signature(verify_request: SolanaVerifyRequest) -> str:
-    try:
-        public_key = b58decode(verify_request.address)
-        signature = b58decode(verify_request.signature)
-        message = verify_request.message.encode("utf-8")
+    """Verify Solana signature and create Firebase custom token.
+    
+    Args:
+        verify_request: Solana verification request containing address, signature, and message.
+        
+    Returns:
+        Firebase custom token as string.
+        
+    Raises:
+        ValueError: If signature verification fails or token creation fails.
+    """
+    public_key = b58decode(verify_request.address)
+    signature = b58decode(verify_request.signature)
+    message = verify_request.message.encode("utf-8")
 
-        verify_key = VerifyKey(public_key)
-        verify_key.verify(message, signature)
+    verify_key = VerifyKey(public_key)
+    verify_key.verify(message, signature)
 
-        uid = f"wallet_{verify_request.address}"
-        custom_token = auth.create_custom_token(uid)
+    uid = f"wallet_{verify_request.address}"
+    custom_token = auth.create_custom_token(uid)
 
-        if isinstance(custom_token, bytes):
-            token_bytes = custom_token
-        elif isinstance(custom_token, str):
-            token_bytes = custom_token.encode("utf-8")
-        else:
-            token_bytes = str(custom_token).encode("utf-8")
+    if isinstance(custom_token, bytes):
+        token_bytes = custom_token
+    elif isinstance(custom_token, str):
+        token_bytes = custom_token.encode("utf-8")
+    else:
+        token_bytes = str(custom_token).encode("utf-8")
 
-        return token_bytes.decode("utf-8")
-    except Exception:
-        raise
+    return token_bytes.decode("utf-8")