chore: import upstream snapshot with attribution

contributing/samples/core/abort/README.md

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+# Abort Agent Sample
+
+## Overview
+
+This sample demonstrates a standalone ADK agent designed specifically to showcase cooperative task cancellation on client disconnections.
+
+The agent leverages a custom tool that counts from 1 to a target number requested by the user, pausing 1 second between each count and printing the progress directly to the server's stdout terminal. This delay allows you to easily trigger connection drops (by cancelling client requests mid-execution) and visually observe that background agent execution halts immediately in the server terminal, resolving resource leaks.
+
+## Sample Inputs
+
+- `Count to 10 seconds`
+
+  The agent will call the `count_seconds` tool with a target count of 10, pausing 1 second between each increment.
+
+- `Please count up to 20`
+
+  The agent will invoke the tool to count to 20. If you close the client connection (such as pressing `Ctrl+C` in a cURL window or closing your browser tab) while the loop is running, counting halts immediately.
+
+## Graph
+
+```mermaid
+graph TD
+    START --> AbortAgent
+    AbortAgent --> |"Invoke Tool"| count_seconds
+    count_seconds --> |"Abort if Disconnected / Done"| AbortAgent
+    AbortAgent --> ANSWER
+```
+
+## How To
+
+### 1. Running Locally via the CLI
+
+To interact with the agent in your local shell terminal:
+
+```bash
+adk run contributing/samples/core/abort/
+```
+
+Type `count to 10` at the `[user]:` prompt. Pressing `Ctrl+C` mid-run will abort counting and exit.
+
+### 2. Running via HTTP Server and cURL
+
+To verify connection-drop abortion over network protocols (e.g. simple HTTP REST request):
+
+1. Start the local development server to watch the sample workspace:
+   ```bash
+   adk web --allow_origins=http://localhost:4200 contributing/samples/
+   ```
+1. In a separate terminal, register the test session (local CLI development servers run with `--auto_create_session` set to `False` by default):
+   ```bash
+   curl -X POST http://localhost:8000/apps/abort_agent/users/user/sessions \
+     -H "Content-Type: application/json" \
+     -d '{"session_id": "8b24e6ed-1fff-4f0c-a06a-e065692a446e"}'
+   ```
+1. Initiate the count request (this blocks waiting for a response):
+   ```bash
+   curl -X POST http://localhost:8000/run \
+     -H "Content-Type: application/json" \
+     -d '{
+       "app_name": "abort_agent",
+       "user_id": "user",
+       "session_id": "8b24e6ed-1fff-4f0c-a06a-e065692a446e",
+       "new_message": {
+         "role": "user",
+         "parts": [{"text": "count to 100"}]
+       }
+     }'
+   ```
+1. Observe your `adk web` terminal window. You will see the counting progress logging.
+1. **Trigger the Abort**: Press `Ctrl+C` in your cURL terminal window to close the client connection.
+1. Observe the server console window. Counting halts instantly and prints:
+   ```text
+   [Counting Tool] Count was ABORTED mid-run at progress: X/100 (Client Disconnected)!
+   ```
+
+### 3. Running and Testing via ADK Web (Dev UI)
+
+To observe cooperative aborts interactively in the web-based developer interface:
+
+1. Start the local development server:
+   ```bash
+   adk web --allow_origins=http://localhost:4200 contributing/samples/
+   ```
+1. Open the ADK Web interface (`http://localhost:4200`) in your web browser.
+1. Select the **`abort_agent`** app from the left sidebar panel.
+1. Type `count to 100` in the message input box and click submit.
+1. **Trigger the Abort**: Simply close your browser tab, refresh the page, or navigate away from the chat panel.
+1. Observe the server's stdout terminal console. You will see that counting halts immediately and logs:
+   ```text
+   [Counting Tool] Count was ABORTED mid-run (Client Disconnected)!
+   ```

contributing/samples/core/abort/__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/core/abort/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.
+
+import asyncio
+import logging
+
+from google.adk import Agent
+
+logger = logging.getLogger("google_adk." + __name__)
+
+
+async def count_seconds(target: int) -> str:
+  """Counts from 1 to the target number, pausing 1 second between counts, and prints each count.
+
+  Args:
+    target: The target number to count to.
+  """
+  logger.info("Starting count from 1 to %d...", target)
+  print(
+      f"\n[Counting Tool] Starting counting up to {target} in console...",
+      flush=True,
+  )
+
+  i = 0
+  try:
+    for i in range(1, target + 1):
+      await asyncio.sleep(1)
+      # Print to standard stdout so it shows directly in the server terminal
+      print(f"[Counting Tool] Progress: {i}/{target}", flush=True)
+      logger.info("Counted: %d/%d", i, target)
+
+    print(
+        f"[Counting Tool] Finished counting up to {target}.\n",
+        flush=True,
+    )
+    return f"Successfully counted from 1 to {target} in the console."
+  except asyncio.CancelledError:
+    print(
+        f"\n[Counting Tool] Count was ABORTED mid-run at progress: {i}/{target}"
+        " (Client Disconnected)!\n",
+        flush=True,
+    )
+    logger.warning("Counting tool was cancelled mid-run.")
+    raise
+
+
+root_agent = Agent(
+    name="abort_agent",
+    description=(
+        "An agent designed to demonstrate how ADK handles client disconnects"
+        " and aborts agent executions mid-run using a counting loop with a"
+        " 1-second delay."
+    ),
+    instruction="""You are an abort coordinator.
+Your goal is to demonstrate cooperative task abortion.
+When asked to count to a number (or count for a number of seconds), invoke the `count_seconds` tool with the target number.
+Do not try to count by yourself; always delegate counting to the `count_seconds` tool so that progress is accurately printed and logs can show task cancellation when a disconnect happens.""",
+    tools=[count_seconds],
+)