chore: import upstream snapshot with attribution

contributing/samples/workflows/retry/README.md

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+# ADK Workflow Sample: Node Retries
+
+## Overview
+
+In real-world applications, interacting with external APIs, databases, or third-party services can occasionally result in transient failures (e.g., temporary network outages, rate limits, or bad gateways).
+
+The ADK framework allows you to easily handle these scenarios by wrapping the unreliable logic in a `@node` decorator configured with `RetryConfig`. If the node raises one of the expected exceptions, the workflow engine automatically pauses, waits for a backoff delay, and reschedules the node for another attempt.
+
+When a node raises an exception, the framework automatically emits an error event (with `error_code` and `error_message`) so the error is visible in the event stream. If the node has retry configured, it will be retried after the backoff delay.
+
+This sample demonstrates a `get_weather` node that intentionally fails randomly (70% chance) by raising an `HTTPError` representing a 500 Internal Server error. The framework gracefully recovers and eventually succeeds, passing the result to `report_weather`.
+
+## Graph
+
+```mermaid
+graph TD
+    START --> get_weather[get_weather <br/>Retries on HTTPError]
+    get_weather --> report_weather
+```
+
+## How To
+
+1. **Import `RetryConfig`**: Ensure you import the configuration class to set your retry parameters.
+
+   ```python
+   from google.adk.workflow import RetryConfig
+   ```
+
+1. **Configure the Decorator**: Apply the `@node` decorator to your Python function and specify the `retry_config` parameter with your desired logic (e.g., `max_attempts`, `initial_delay`).
+
+   ```python
+   @node(retry_config=RetryConfig(max_attempts=5, initial_delay=1))
+   def get_weather(ctx: Context) -> str:
+       # ... flaky logic here ...
+   ```
+
+   When an exception like `HTTPError` occurs, the ADK framework catches it, emits an error event, and processes the backoff delay automatically. As long as `max_attempts` hasn't been exceeded, the node executes again.
+
+1. **Track Retries (Optional)**: If you need to know which attempt the node is currently running, you can access `ctx.attempt_count` from the `Context`.
+
+   ```python
+   yield Event(message=f"Getting weather... attempt {ctx.attempt_count}")
+   ```

contributing/samples/workflows/retry/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 random
+from urllib.error import HTTPError
+
+from google.adk import Context
+from google.adk import Event
+from google.adk import Workflow
+from google.adk.workflow import node
+from google.adk.workflow import RetryConfig
+
+
+@node(retry_config=RetryConfig(max_attempts=5, initial_delay=1))
+def get_weather(ctx: Context) -> str:
+  """A mock task that fails randomly."""
+
+  yield Event(message=f"Getting weather... attempt {ctx.attempt_count}")
+  if random.random() < 0.7:  # 70% chance of failure
+    raise HTTPError(
+        url="http://mock-api.example.com",
+        code=500,
+        msg="Internal Server Error",
+        hdrs={},
+        fp=None,
+    )
+
+  yield "sunny"
+
+
+def report_weather(node_input: str):
+  yield Event(message=f"The weather is {node_input}")
+
+
+root_agent = Workflow(
+    name="root_agent",
+    edges=[("START", get_weather, report_weather)],
+)

contributing/samples/workflows/retry/tests/go.json

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+{
+  "appName": "retry",
+  "events": [
+    {
+      "author": "user",
+      "content": {
+        "parts": [
+          {
+            "text": "go"
+          }
+        ],
+        "role": "user"
+      },
+      "id": "e-1",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": ""
+      }
+    },
+    {
+      "author": "root_agent",
+      "content": {
+        "parts": [
+          {
+            "text": "Getting weather... attempt 1"
+          }
+        ],
+        "role": "user"
+      },
+      "id": "e-2",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": "root_agent@1/get_weather@1"
+      }
+    },
+    {
+      "author": "root_agent",
+      "errorCode": "HTTPError",
+      "errorMessage": "HTTP Error 500: Internal Server Error",
+      "id": "e-3",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": "root_agent@1/get_weather@1"
+      }
+    },
+    {
+      "author": "root_agent",
+      "content": {
+        "parts": [
+          {
+            "text": "Getting weather... attempt 2"
+          }
+        ],
+        "role": "user"
+      },
+      "id": "e-4",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": "root_agent@1/get_weather@1"
+      }
+    },
+    {
+      "author": "root_agent",
+      "errorCode": "HTTPError",
+      "errorMessage": "HTTP Error 500: Internal Server Error",
+      "id": "e-5",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": "root_agent@1/get_weather@1"
+      }
+    },
+    {
+      "author": "root_agent",
+      "content": {
+        "parts": [
+          {
+            "text": "Getting weather... attempt 3"
+          }
+        ],
+        "role": "user"
+      },
+      "id": "e-6",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": "root_agent@1/get_weather@1"
+      }
+    },
+    {
+      "author": "root_agent",
+      "id": "e-7",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "outputFor": [
+          "root_agent@1/get_weather@1"
+        ],
+        "path": "root_agent@1/get_weather@1"
+      },
+      "output": "sunny"
+    },
+    {
+      "author": "root_agent",
+      "content": {
+        "parts": [
+          {
+            "text": "The weather is sunny"
+          }
+        ],
+        "role": "user"
+      },
+      "id": "e-8",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": "root_agent@1/report_weather@1"
+      }
+    }
+  ],
+  "id": "c0e0c167-1e63-4e18-84b6-ad64ba59376f",
+  "mocks": {
+    "random.random": [
+      0.5,
+      0.5,
+      0.8
+    ]
+  },
+  "state": {
+    "__session_metadata__": {
+      "displayName": "go"
+    }
+  },
+  "userId": "user"
+}