chore: import upstream snapshot with attribution

contributing/samples/context_management/rewind_session/__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/context_management/rewind_session/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.
+
+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,
+    ],
+)

contributing/samples/context_management/rewind_session/main.py

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+#!/usr/bin/env python3
+"""Simple test script for Rewind Session agent."""
+
+# 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 asyncio
+import logging
+
+import agent
+from google.adk.agents.run_config import RunConfig
+from google.adk.cli.utils import logs
+from google.adk.events.event import Event
+from google.adk.runners import InMemoryRunner
+from google.genai import types
+
+APP_NAME = "rewind_test_app"
+USER_ID = "test_user"
+
+logs.setup_adk_logger(level=logging.ERROR)
+logging.getLogger("google_genai.types").setLevel(logging.ERROR)
+
+
+# ANSI color codes for terminal output
+COLOR_RED = "\x1b[31m"
+COLOR_BLUE = "\x1b[34m"
+COLOR_YELLOW = "\x1b[33m"
+COLOR_BOLD = "\x1b[1m"
+RESET = "\x1b[0m"
+
+
+def highlight(text: str) -> str:
+  """Adds color highlights to tool responses and agent text."""
+  text = str(text)
+  return (
+      text.replace("'red'", f"'{COLOR_RED}red{RESET}'")
+      .replace('"red"', f'"{COLOR_RED}red{RESET}"')
+      .replace("'blue'", f"'{COLOR_BLUE}blue{RESET}'")
+      .replace('"blue"', f'"{COLOR_BLUE}blue{RESET}"')
+      .replace("'version1'", f"'{COLOR_BOLD}{COLOR_YELLOW}version1{RESET}'")
+      .replace("'version2'", f"'{COLOR_BOLD}{COLOR_YELLOW}version2{RESET}'")
+  )
+
+
+async def call_agent_async(
+    runner: InMemoryRunner, user_id: str, session_id: str, prompt: str
+) -> list[Event]:
+  """Helper function to call the agent and return events."""
+  print(f"\n👤 User: {prompt}")
+  content = types.Content(
+      role="user", parts=[types.Part.from_text(text=prompt)]
+  )
+  events = []
+  try:
+    async for event in runner.run_async(
+        user_id=user_id,
+        session_id=session_id,
+        new_message=content,
+        run_config=RunConfig(),
+    ):
+      events.append(event)
+      if event.content and event.author and event.author != "user":
+        for part in event.content.parts:
+          if part.text:
+            print(f"  🤖 Agent: {highlight(part.text)}")
+          elif part.function_call:
+            print(f"    🛠️ Tool Call: {part.function_call.name}")
+          elif part.function_response:
+            print(
+                "    📦 Tool Response:"
+                f" {highlight(part.function_response.response)}"
+            )
+  except Exception as e:
+    print(f"❌ Error during agent call: {e}")
+    raise
+  return events
+
+
+async def main():
+  """Demonstrates session rewind."""
+  print("🚀 Testing Rewind Session Feature")
+  print("=" * 50)
+
+  runner = InMemoryRunner(
+      agent=agent.root_agent,
+      app_name=APP_NAME,
+  )
+
+  # Create a session
+  session = await runner.session_service.create_session(
+      app_name=APP_NAME, user_id=USER_ID
+  )
+  print(f"Created session: {session.id}")
+
+  # 1. Initial agent calls to set state and artifact
+  print("\n\n===== INITIALIZING STATE AND ARTIFACT =====")
+  await call_agent_async(
+      runner, USER_ID, session.id, "set state `color` to red"
+  )
+  await call_agent_async(
+      runner, USER_ID, session.id, "save artifact file1 with content version1"
+  )
+
+  # 2. Check current state and artifact
+  print("\n\n===== STATE BEFORE UPDATE =====")
+  await call_agent_async(
+      runner, USER_ID, session.id, "what is the value of state `color`?"
+  )
+  await call_agent_async(runner, USER_ID, session.id, "load artifact file1")
+
+  # 3. Update state and artifact - THIS IS THE POINT WE WILL REWIND BEFORE
+  print("\n\n===== UPDATING STATE AND ARTIFACT =====")
+  events_update_state = await call_agent_async(
+      runner, USER_ID, session.id, "update state key color to blue"
+  )
+  rewind_invocation_id = events_update_state[0].invocation_id
+  print(f"Will rewind before invocation: {rewind_invocation_id}")
+
+  await call_agent_async(
+      runner, USER_ID, session.id, "save artifact file1 with content version2"
+  )
+
+  # 4. Check state and artifact after update
+  print("\n\n===== STATE AFTER UPDATE =====")
+  await call_agent_async(
+      runner, USER_ID, session.id, "what is the value of state key color?"
+  )
+  await call_agent_async(runner, USER_ID, session.id, "load artifact file1")
+
+  # 5. Perform rewind
+  print(f"\n\n===== REWINDING SESSION to before {rewind_invocation_id} =====")
+  await runner.rewind_async(
+      user_id=USER_ID,
+      session_id=session.id,
+      rewind_before_invocation_id=rewind_invocation_id,
+  )
+  print("✅ Rewind complete.")
+
+  # 6. Check state and artifact after rewind
+  print("\n\n===== STATE AFTER REWIND =====")
+  await call_agent_async(
+      runner, USER_ID, session.id, "what is the value of state `color`?"
+  )
+  await call_agent_async(runner, USER_ID, session.id, "load artifact file1")
+
+  print("\n" + "=" * 50)
+  print("✨ Rewind testing complete!")
+  print(
+      "🔧 If rewind was successful, color should be 'red' and file1 content"
+      " should contain 'version1' in the final check."
+  )
+
+
+if __name__ == "__main__":
+  asyncio.run(main())