chore: import upstream snapshot with attribution

contributing/samples/models/litellm_with_fallback_models/agent.py

@@ -0,0 +1,88 @@
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import random
+
+from google.adk import Agent
+from google.adk.models.lite_llm import LiteLlm
+from google.adk.tools.tool_context import ToolContext
+from google.genai import types
+
+
+def roll_die(sides: int, tool_context: ToolContext) -> int:
+  """Roll a die and return the rolled result.
+
+  Args:
+    sides: The integer number of sides the die has.
+    tool_context: The tool context to use for the die roll.
+
+  Returns:
+    An integer of the result of rolling the die.
+    The result is also stored in the tool context for future use.
+  """
+  result = random.randint(1, sides)
+  if 'rolls' not in tool_context.state:
+    tool_context.state['rolls'] = []
+
+  tool_context.state['rolls'] = tool_context.state['rolls'] + [result]
+  return result
+
+
+async def before_model_callback(callback_context, llm_request):
+  print('@before_model_callback')
+  print(f'Beginning model choice: {llm_request.model}')
+  callback_context.state['beginning_model_choice'] = llm_request.model
+  return None
+
+
+async def after_model_callback(callback_context, llm_response):
+  print('@after_model_callback')
+  print(f'Final model choice: {llm_response.model_version}')
+  callback_context.state['final_model_choice'] = llm_response.model_version
+  return None
+
+
+root_agent = Agent(
+    model=LiteLlm(
+        model='gemini/gemini-2.5-pro',
+        fallbacks=[
+            'anthropic/claude-sonnet-4-5-20250929',
+            'openai/gpt-4o',
+        ],
+    ),
+    name='resilient_agent',
+    description=(
+        'hello world agent that can roll a dice of given number of sides.'
+    ),
+    instruction="""
+      You roll dice and answer questions about the outcome of the dice rolls.
+      You can roll dice of different sizes.
+      It is ok to discuss previous dice roles, and comment on the dice rolls.
+      When you are asked to roll a die, you must call the roll_die tool with the number of sides. Be sure to pass in an integer. Do not pass in a string.
+      You should never roll a die on your own.
+    """,
+    tools=[
+        roll_die,
+    ],
+    generate_content_config=types.GenerateContentConfig(
+        safety_settings=[
+            types.SafetySetting(  # avoid false alarm about rolling dice.
+                category=types.HarmCategory.HARM_CATEGORY_DANGEROUS_CONTENT,
+                threshold=types.HarmBlockThreshold.OFF,
+            ),
+        ]
+    ),
+    before_model_callback=before_model_callback,
+    after_model_callback=after_model_callback,
+)