chore: import upstream snapshot with attribution

contributing/samples/context_management/rewind_session/agent.py

@@ -0,0 +1,70 @@
+# 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 google.adk import Agent
+from google.adk.tools.tool_context import ToolContext
+from google.genai import types
+
+
+async def update_state(tool_context: ToolContext, key: str, value: str) -> dict:
+  """Updates a state value."""
+  tool_context.state[key] = value
+  return {"status": f"Updated state '{key}' to '{value}'"}
+
+
+async def load_state(tool_context: ToolContext, key: str) -> dict:
+  """Loads a state value."""
+  return {key: tool_context.state.get(key)}
+
+
+async def save_artifact(
+    tool_context: ToolContext, filename: str, content: str
+) -> dict:
+  """Saves an artifact with the given filename and content."""
+  artifact_bytes = content.encode("utf-8")
+  artifact_part = types.Part(
+      inline_data=types.Blob(mime_type="text/plain", data=artifact_bytes)
+  )
+  version = await tool_context.save_artifact(filename, artifact_part)
+  return {"status": "success", "filename": filename, "version": version}
+
+
+async def load_artifact(tool_context: ToolContext, filename: str) -> dict:
+  """Loads an artifact with the given filename."""
+  artifact = await tool_context.load_artifact(filename)
+  if not artifact:
+    return {"error": f"Artifact '{filename}' not found"}
+  content = artifact.inline_data.data.decode("utf-8")
+  return {"filename": filename, "content": content}
+
+
+# Create the agent
+root_agent = Agent(
+    name="state_agent",
+    instruction="""You are an agent that manages state and artifacts.
+
+    You can:
+    - Update state value
+    - Load state value
+    - Save artifact
+    - Load artifact
+
+    Use the appropriate tool based on what the user asks for.""",
+    tools=[
+        update_state,
+        load_state,
+        save_artifact,
+        load_artifact,
+    ],
+)