chore: import upstream snapshot with attribution

contributing/samples/models/litellm_streaming/__init__.py

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+# 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.
+
+from . import agent

contributing/samples/models/litellm_streaming/agent.py

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+# 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.
+
+"""LiteLLM sample agent for SSE text streaming."""
+
+from __future__ import annotations
+
+from google.adk import Agent
+from google.adk.models.lite_llm import LiteLlm
+
+root_agent = Agent(
+    name='litellm_streaming_agent',
+    model=LiteLlm(model='gemini/gemini-2.5-flash'),
+    description='A LiteLLM agent used for streaming text responses.',
+    instruction='You are a verbose assistant',
+)

contributing/samples/models/litellm_streaming/main.py

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+# 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.
+
+"""Runs the LiteLLM streaming sample with SSE enabled."""
+
+from __future__ import annotations
+
+import asyncio
+
+from dotenv import load_dotenv
+from google.adk.agents.run_config import RunConfig
+from google.adk.agents.run_config import StreamingMode
+from google.adk.cli.utils import logs
+from google.adk.runners import InMemoryRunner
+from google.genai import types
+
+from . import agent
+
+load_dotenv(override=True)
+logs.log_to_tmp_folder()
+
+
+async def _run_prompt(
+    *,
+    runner: InMemoryRunner,
+    user_id: str,
+    session_id: str,
+    prompt: str,
+) -> None:
+  """Runs one prompt and prints partial chunks in real time."""
+  content = types.Content(
+      role='user',
+      parts=[types.Part.from_text(text=prompt)],
+  )
+
+  print(f'User: {prompt}')
+  print('Agent: ', end='', flush=True)
+  saw_text = False
+  saw_partial_text = False
+
+  # For `adk web`, enable the `Streaming` toggle in the UI to get
+  # partial SSE responses similar to this script.
+  async for event in runner.run_async(
+      user_id=user_id,
+      session_id=session_id,
+      new_message=content,
+      run_config=RunConfig(streaming_mode=StreamingMode.SSE),
+  ):
+    if not event.content:
+      continue
+    text = ''.join(part.text for part in event.content.parts if part.text)
+    if not text:
+      continue
+
+    if event.partial:
+      print(text, end='', flush=True)
+      saw_text = True
+      saw_partial_text = True
+      continue
+
+    # With SSE mode, ADK emits a final aggregated event after partial chunks.
+    if not saw_partial_text:
+      print(text, end='', flush=True)
+      saw_text = True
+
+  if saw_text:
+    print()
+  else:
+    print('(no text response)')
+  print('------------------------------------')
+
+
+async def main() -> None:
+  app_name = 'litellm_streaming_demo'
+  user_id = 'user_1'
+  runner = InMemoryRunner(agent=agent.root_agent, app_name=app_name)
+  session = await runner.session_service.create_session(
+      app_name=app_name,
+      user_id=user_id,
+  )
+  prompts = [
+      'Write an essay about the roman empire',
+      'Now summarize the essay into one sentence.',
+  ]
+
+  for prompt in prompts:
+    await _run_prompt(
+        runner=runner,
+        user_id=user_id,
+        session_id=session.id,
+        prompt=prompt,
+    )
+
+
+if __name__ == '__main__':
+  asyncio.run(main())