diff --git a/samples/python/src/common/function_call_resolver.py b/samples/python/src/common/function_call_resolver.py
index 49356429..4db51323 100644
--- a/samples/python/src/common/function_call_resolver.py
+++ b/samples/python/src/common/function_call_resolver.py
@@ -26,6 +26,8 @@
 from google import genai
 from google.genai import types
 
+from common.system_utils import LLM_MODEL
+
 
 DataPartContent = dict[str, Any]
 Tool = Callable[[list[DataPartContent], TaskUpdater, Task | None], Any]
@@ -81,7 +83,7 @@ def determine_tool_to_use(self, prompt: str) -> str:
     """
 
     response = self._client.models.generate_content(
-        model="gemini-2.5-flash",
+        model=LLM_MODEL,
         contents=prompt,
         config=self._config,
     )
diff --git a/samples/python/src/common/retrying_llm_agent.py b/samples/python/src/common/retrying_llm_agent.py
index c5e50e2c..fa6afaae 100644
--- a/samples/python/src/common/retrying_llm_agent.py
+++ b/samples/python/src/common/retrying_llm_agent.py
@@ -39,7 +39,7 @@ async def _retry_async(
           author=ctx.agent.name,
           invocation_id=ctx.invocation_id,
           error_message=(
-              "Maximum retries exhausted. The remote Gemini server failed to"
+              "Maximum retries exhausted. The remote LLM server failed to"
               " respond. Please try again later."
           ),
       )
@@ -51,7 +51,7 @@ async def _retry_async(
         yield Event(
             author=ctx.agent.name,
             invocation_id=ctx.invocation_id,
-            error_message="Gemini server error. Retrying...",
+            error_message="LLM server error. Retrying...",
             custom_metadata={"error": str(e)},
         )
         async for event in self._retry_async(ctx, retries_left - 1):
diff --git a/samples/python/src/common/system_utils.py b/samples/python/src/common/system_utils.py
index f9403935..1968a60c 100644
--- a/samples/python/src/common/system_utils.py
+++ b/samples/python/src/common/system_utils.py
@@ -14,6 +14,10 @@
 
 """Helper functions related to the system."""
 
+import os
+
+LLM_MODEL = os.environ.get("MODEL", "gemini-2.5-flash")
+
 DEBUG_MODE_INSTRUCTIONS = """
     This is really important! If the agent or user asks you to be verbose or if debug_mode is True, do the following:
       1. If this is the the start of a new task, explain who you are, what you are going to do, what tools you use, and what agents you delegate to.
diff --git a/samples/python/src/roles/merchant_agent/sub_agents/catalog_agent.py b/samples/python/src/roles/merchant_agent/sub_agents/catalog_agent.py
index b40f72e0..87ebd999 100644
--- a/samples/python/src/roles/merchant_agent/sub_agents/catalog_agent.py
+++ b/samples/python/src/roles/merchant_agent/sub_agents/catalog_agent.py
@@ -44,6 +44,7 @@
 from ap2.types.payment_request import PaymentRequest
 from common import message_utils
 from common.system_utils import DEBUG_MODE_INSTRUCTIONS
+from common.system_utils import LLM_MODEL
 
 
 async def find_items_workflow(
@@ -68,7 +69,7 @@ async def find_items_workflow(
         """ % DEBUG_MODE_INSTRUCTIONS
 
   llm_response = llm_client.models.generate_content(
-      model="gemini-2.5-flash",
+      model=LLM_MODEL,
       contents=prompt,
       config={
           "response_mime_type": "application/json",
diff --git a/samples/python/src/roles/shopping_agent/agent.py b/samples/python/src/roles/shopping_agent/agent.py
index 37c91a31..f9cfbdb7 100644
--- a/samples/python/src/roles/shopping_agent/agent.py
+++ b/samples/python/src/roles/shopping_agent/agent.py
@@ -28,11 +28,12 @@
 from .subagents.shopper.agent import shopper
 from common.retrying_llm_agent import RetryingLlmAgent
 from common.system_utils import DEBUG_MODE_INSTRUCTIONS
+from common.system_utils import LLM_MODEL
 
 
 root_agent = RetryingLlmAgent(
     max_retries=5,
-    model="gemini-2.5-flash",
+    model=LLM_MODEL,
     name="root_agent",
     instruction="""
           You are a shopping agent responsible for helping users find and
diff --git a/samples/python/src/roles/shopping_agent/subagents/payment_method_collector/agent.py b/samples/python/src/roles/shopping_agent/subagents/payment_method_collector/agent.py
index 446f83fe..7f2d6192 100644
--- a/samples/python/src/roles/shopping_agent/subagents/payment_method_collector/agent.py
+++ b/samples/python/src/roles/shopping_agent/subagents/payment_method_collector/agent.py
@@ -28,10 +28,11 @@
 from . import tools
 from common.retrying_llm_agent import RetryingLlmAgent
 from common.system_utils import DEBUG_MODE_INSTRUCTIONS
+from common.system_utils import LLM_MODEL
 
 
 payment_method_collector = RetryingLlmAgent(
-    model="gemini-2.5-flash",
+    model=LLM_MODEL,
     name="payment_method_collector",
     max_retries=5,
     instruction="""
diff --git a/samples/python/src/roles/shopping_agent/subagents/shipping_address_collector/agent.py b/samples/python/src/roles/shopping_agent/subagents/shipping_address_collector/agent.py
index 0407b2b6..a9bbefb6 100644
--- a/samples/python/src/roles/shopping_agent/subagents/shipping_address_collector/agent.py
+++ b/samples/python/src/roles/shopping_agent/subagents/shipping_address_collector/agent.py
@@ -29,9 +29,10 @@
 from . import tools
 from common.retrying_llm_agent import RetryingLlmAgent
 from common.system_utils import DEBUG_MODE_INSTRUCTIONS
+from common.system_utils import LLM_MODEL
 
 shipping_address_collector = RetryingLlmAgent(
-    model="gemini-2.5-flash",
+    model=LLM_MODEL,
     name="shipping_address_collector",
     max_retries=5,
     instruction="""
diff --git a/samples/python/src/roles/shopping_agent/subagents/shopper/agent.py b/samples/python/src/roles/shopping_agent/subagents/shopper/agent.py
index d380fac7..8d33b27d 100644
--- a/samples/python/src/roles/shopping_agent/subagents/shopper/agent.py
+++ b/samples/python/src/roles/shopping_agent/subagents/shopper/agent.py
@@ -27,10 +27,11 @@
 from . import tools
 from common.retrying_llm_agent import RetryingLlmAgent
 from common.system_utils import DEBUG_MODE_INSTRUCTIONS
+from common.system_utils import LLM_MODEL
 
 
 shopper = RetryingLlmAgent(
-    model="gemini-2.5-flash",
+    model=LLM_MODEL,
     name="shopper",
     max_retries=5,
     instruction="""