diff --git a/server.py b/server.py
index bf2ac6c1..7b54d5e6 100644
--- a/server.py
+++ b/server.py
@@ -122,6 +122,10 @@ def format(self, record):
     "gemini-2.5-pro"
 ]
 
+def is_gemini_model(model_name: str) -> bool:
+    """Check if a model name is a Gemini model (known list or starts with 'gemini')."""
+    return model_name in GEMINI_MODELS or model_name.startswith("gemini")
+
 # Helper function to clean schema for Gemini
 def clean_gemini_schema(schema: Any) -> Any:
     """Recursively removes unsupported fields from a JSON schema for Gemini."""
@@ -222,7 +226,7 @@ def validate_model_field(cls, v, info): # Renamed to avoid conflict
 
         # Map Haiku to SMALL_MODEL based on provider preference
         elif 'haiku' in clean_v.lower():
-            if PREFERRED_PROVIDER == "google" and SMALL_MODEL in GEMINI_MODELS:
+            if PREFERRED_PROVIDER == "google" and is_gemini_model(SMALL_MODEL):
                 new_model = f"gemini/{SMALL_MODEL}"
                 mapped = True
             else:
@@ -231,7 +235,7 @@ def validate_model_field(cls, v, info): # Renamed to avoid conflict
 
         # Map Sonnet to BIG_MODEL based on provider preference
         elif 'sonnet' in clean_v.lower():
-            if PREFERRED_PROVIDER == "google" and BIG_MODEL in GEMINI_MODELS:
+            if PREFERRED_PROVIDER == "google" and is_gemini_model(BIG_MODEL):
                 new_model = f"gemini/{BIG_MODEL}"
                 mapped = True
             else:
@@ -240,7 +244,7 @@ def validate_model_field(cls, v, info): # Renamed to avoid conflict
 
         # Add prefixes to non-mapped models if they match known lists
         elif not mapped:
-            if clean_v in GEMINI_MODELS and not v.startswith('gemini/'):
+            if is_gemini_model(clean_v) and not v.startswith('gemini/'):
                 new_model = f"gemini/{clean_v}"
                 mapped = True # Technically mapped to add prefix
             elif clean_v in OPENAI_MODELS and not v.startswith('openai/'):
@@ -295,7 +299,7 @@ def validate_model_token_count(cls, v, info): # Renamed to avoid conflict
         mapped = False
         # Map Haiku to SMALL_MODEL based on provider preference
         if 'haiku' in clean_v.lower():
-            if PREFERRED_PROVIDER == "google" and SMALL_MODEL in GEMINI_MODELS:
+            if PREFERRED_PROVIDER == "google" and is_gemini_model(SMALL_MODEL):
                 new_model = f"gemini/{SMALL_MODEL}"
                 mapped = True
             else:
@@ -304,7 +308,7 @@ def validate_model_token_count(cls, v, info): # Renamed to avoid conflict
 
         # Map Sonnet to BIG_MODEL based on provider preference
         elif 'sonnet' in clean_v.lower():
-            if PREFERRED_PROVIDER == "google" and BIG_MODEL in GEMINI_MODELS:
+            if PREFERRED_PROVIDER == "google" and is_gemini_model(BIG_MODEL):
                 new_model = f"gemini/{BIG_MODEL}"
                 mapped = True
             else:
@@ -313,7 +317,7 @@ def validate_model_token_count(cls, v, info): # Renamed to avoid conflict
 
         # Add prefixes to non-mapped models if they match known lists
         elif not mapped:
-            if clean_v in GEMINI_MODELS and not v.startswith('gemini/'):
+            if is_gemini_model(clean_v) and not v.startswith('gemini/'):
                 new_model = f"gemini/{clean_v}"
                 mapped = True # Technically mapped to add prefix
             elif clean_v in OPENAI_MODELS and not v.startswith('openai/'):