chore: import upstream snapshot with attribution

contributing/samples/integrations/oauth_calendar_agent/README.md

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+# OAuth Sample
+
+## Introduction
+
+This sample tests and demos the OAuth support in ADK via two tools:
+
+- 1. list_calendar_events
+
+  This is a customized tool that calls Google Calendar API to list calendar
+  events. It passes in the client id and client secret to ADK and then get back
+  the access token from ADK. And then it uses the access token to call
+  calendar api.
+
+- 2. get_calendar_events
+
+  This is a google calendar tool that calls Google Calendar API to get the
+  details of a specific calendar. This tool is from the ADK built-in Google
+  Calendar ToolSet. Everything is wrapped and the tool user just needs to pass
+  in the client id and client secret.
+
+## How to use
+
+- 1. Follow
+     https://developers.google.com/identity/protocols/oauth2#1.-obtain-oauth-2.0-credentials-from-the-dynamic_data.setvar.console_name.
+     to get your client id and client secret. Be sure to choose "web" as your
+     client type.
+
+- 2. Configure your `.env` file to add two variables:
+
+  - OAUTH_CLIENT_ID={your client id}
+  - OAUTH_CLIENT_SECRET={your client secret}
+
+  Note: don't create a separate `.env` file , instead put it to the same
+  `.env` file that stores your Vertex AI or Dev ML credentials
+
+- 3. Follow
+     https://developers.google.com/identity/protocols/oauth2/web-server#creatingcred
+     to add http://localhost/dev-ui/ to "Authorized redirect URIs".
+
+  Note: localhost here is just a hostname that you use to access the dev ui,
+  replace it with the actual hostname you use to access the dev ui.
+
+- 4. For 1st run, allow popup for localhost in Chrome.
+
+## Sample prompt
+
+- `List all my today's meeting from 7am to 7pm.`
+- `Get the details of the first event.`

contributing/samples/integrations/oauth_calendar_agent/__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/integrations/oauth_calendar_agent/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 datetime import datetime
+import os
+
+from dotenv import load_dotenv
+from fastapi.openapi.models import OAuth2
+from fastapi.openapi.models import OAuthFlowAuthorizationCode
+from fastapi.openapi.models import OAuthFlows
+from google.adk.agents.callback_context import CallbackContext
+from google.adk.agents.llm_agent import Agent
+from google.adk.auth.auth_credential import AuthCredential
+from google.adk.auth.auth_credential import AuthCredentialTypes
+from google.adk.auth.auth_credential import OAuth2Auth
+from google.adk.auth.auth_tool import AuthConfig
+from google.adk.tools.authenticated_function_tool import AuthenticatedFunctionTool
+from google.adk.tools.google_api_tool import CalendarToolset
+from google.adk.tools.tool_context import ToolContext
+from google.oauth2.credentials import Credentials
+from googleapiclient.discovery import build
+
+# Load environment variables from .env file
+load_dotenv()
+
+# Access the variable
+oauth_client_id = os.getenv("OAUTH_CLIENT_ID")
+oauth_client_secret = os.getenv("OAUTH_CLIENT_SECRET")
+
+
+SCOPES = ["https://www.googleapis.com/auth/calendar"]
+
+calendar_toolset = CalendarToolset(
+    # you can also replace below customized `list_calendar_events` with build-in
+    # google calendar tool by adding `calendar_events_list` in the filter list
+    client_id=oauth_client_id,
+    client_secret=oauth_client_secret,
+    tool_filter=["calendar_events_get", "calendar_events_update"],
+    tool_name_prefix="google",
+)
+
+
+# this tool will be invoked right after google_calendar_events_get returns a
+# final response to test whether adk works correctly for subsequent function
+# call right after a function call that request auth
+# see https://github.com/google/adk-python/issues/1944 for details
+def redact_event_content(event_content: str) -> str:
+  """Redact confidential information in the calendar event content
+  Args:
+      event_content: the content of the calendar event to redact
+
+  Returns:
+      str: redacted content of the calendar event
+  """
+  return event_content
+
+
+def list_calendar_events(
+    start_time: str,
+    end_time: str,
+    limit: int,
+    tool_context: ToolContext,
+    credential: AuthCredential,
+) -> list[dict]:
+  """Search for calendar events.
+
+  Example:
+
+      flights = get_calendar_events(
+          calendar_id='joedoe@gmail.com',
+          start_time='2024-09-17T06:00:00',
+          end_time='2024-09-17T12:00:00',
+          limit=10
+      )
+      # Returns up to 10 calendar events between 6:00 AM and 12:00 PM on
+      September 17, 2024.
+
+  Args:
+      calendar_id (str): the calendar ID to search for events.
+      start_time (str): The start of the time range (format is
+        YYYY-MM-DDTHH:MM:SS).
+      end_time (str): The end of the time range (format is YYYY-MM-DDTHH:MM:SS).
+      limit (int): The maximum number of results to return.
+
+  Returns:
+      list[dict]: A list of events that match the search criteria.
+  """
+
+  creds = Credentials(
+      token=credential.oauth2.access_token,
+      refresh_token=credential.oauth2.refresh_token,
+  )
+
+  service = build("calendar", "v3", credentials=creds)
+  events_result = (
+      service.events()
+      .list(
+          calendarId="primary",
+          timeMin=start_time + "Z" if start_time else None,
+          timeMax=end_time + "Z" if end_time else None,
+          maxResults=limit,
+          singleEvents=True,
+          orderBy="startTime",
+      )
+      .execute()
+  )
+  events = events_result.get("items", [])
+  return events
+
+
+def update_time(callback_context: CallbackContext):
+  # get current date time
+  now = datetime.now()
+  formatted_time = now.strftime("%Y-%m-%d %H:%M:%S")
+  callback_context.state["_time"] = formatted_time
+
+
+root_agent = Agent(
+    name="calendar_agent",
+    instruction="""
+      You are a helpful personal calendar assistant.
+      Use the provided tools to search for calendar events (use 10 as limit if user doesn't specify), and update them.
+      Use "primary" as the calendarId if users don't specify.
+
+      Scenario1:
+      The user want to query the calendar events.
+      Use list_calendar_events to search for calendar events.
+
+
+      Scenario2:
+      User want to know the details of one of the listed calendar events.
+      Use google_calendar_events_get to get the details of a calendar event and use redact_event_content to redact confidential information before sending the details to user
+
+      Scenario3:
+      User want to update calendar events.
+      Use google_calendar_events_update to update calendar events
+
+      IMPORTANT NOTE
+      Whenever you use google_calendar_events_get to the details of a calendar event ,
+      you MUST use format_calendar_redact_event_content to redact it and use the return value to reply the user.
+      This very important! Otherwise you run the risk of leaking confidential information!!!
+
+
+
+      Current user:
+      <User>
+      {userInfo?}
+      </User>
+
+      Current time: {_time}
+""",
+    tools=[
+        AuthenticatedFunctionTool(
+            func=list_calendar_events,
+            auth_config=AuthConfig(
+                auth_scheme=OAuth2(
+                    flows=OAuthFlows(
+                        authorizationCode=OAuthFlowAuthorizationCode(
+                            authorizationUrl=(
+                                "https://accounts.google.com/o/oauth2/auth"
+                            ),
+                            tokenUrl="https://oauth2.googleapis.com/token",
+                            scopes={
+                                "https://www.googleapis.com/auth/calendar": "",
+                            },
+                        )
+                    )
+                ),
+                raw_auth_credential=AuthCredential(
+                    auth_type=AuthCredentialTypes.OAUTH2,
+                    oauth2=OAuth2Auth(
+                        client_id=oauth_client_id,
+                        client_secret=oauth_client_secret,
+                    ),
+                ),
+            ),
+        ),
+        calendar_toolset,
+        redact_event_content,
+    ],
+    before_agent_callback=update_time,
+)