chore: import upstream snapshot with attribution

contributing/samples/workflows/multi_triggers/README.md

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+# ADK Workflow Multi-Triggers Sample
+
+## Overview
+
+This sample demonstrates how a single node can fan out to execute multiple downstream nodes concurrently, and how multiple upstream nodes can trigger a single downstream node independently in **ADK Workflows**.
+
+In this example, the `START` node fans out to three different processing functions (`make_uppercase`, `count_characters`, and `reverse_string`). Each of these functions receives the initial user input string, processes it, and then independently outputs its result.
+
+Because the subsequent `send_message` node receives a continuous flow of outputs and does not use an aggregation mechanism (like `JoinNode`), it is triggered multiple times—once for every upstream event.
+
+## Sample Inputs
+
+- `Hello World`
+
+- `ADK workflows`
+
+- `testing concurrent nodes`
+
+## Graph
+
+```mermaid
+graph TD
+    START --> make_uppercase
+    START --> count_characters
+    START --> reverse_string
+    make_uppercase --> send_message
+    count_characters --> send_message
+    reverse_string --> send_message
+```
+
+## How To
+
+1. You can specify a tuple of nodes within an edge to create a parallel fan-out segment where the same input is provided to multiple nodes:
+
+   ```python
+   (
+       "START",
+       (make_uppercase, count_characters, reverse_string),
+       # ...
+   )
+   ```
+
+1. By continuing the sequence to another node after the tuple, the outputs of all nodes in the tuple will independently trigger that target node:
+
+   ```python
+   (
+       "START",
+       (make_uppercase, count_characters, reverse_string),
+       send_message,
+   )
+   ```
+
+   In this case, `send_message` will be executed once for `make_uppercase`'s output, once for `count_characters`'s output, and once for `reverse_string`'s output.

contributing/samples/workflows/multi_triggers/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 typing import Any
+
+from google.adk import Event
+from google.adk import Workflow
+
+
+def make_uppercase(node_input: str):
+  return node_input.upper()
+
+
+def count_characters(node_input: str):
+  return len(node_input)
+
+
+def reverse_string(node_input: str):
+  return node_input[::-1]
+
+
+async def send_message(node_input: Any):
+  yield Event(message=f"Triggered for input: {node_input}")
+
+
+root_agent = Workflow(
+    name="root_agent",
+    edges=[(
+        "START",
+        (make_uppercase, count_characters, reverse_string),
+        send_message,
+    )],
+    input_schema=str,
+)

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

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+{
+  "appName": "multi_triggers",
+  "events": [
+    {
+      "author": "user",
+      "content": {
+        "parts": [
+          {
+            "text": "go"
+          }
+        ],
+        "role": "user"
+      },
+      "id": "e-1",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": ""
+      }
+    },
+    {
+      "author": "root_agent",
+      "branch": "make_uppercase@1",
+      "id": "e-2",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "outputFor": [
+          "root_agent@1/make_uppercase@1"
+        ],
+        "path": "root_agent@1/make_uppercase@1"
+      },
+      "output": "GO"
+    },
+    {
+      "author": "root_agent",
+      "branch": "count_characters@1",
+      "id": "e-3",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "outputFor": [
+          "root_agent@1/count_characters@1"
+        ],
+        "path": "root_agent@1/count_characters@1"
+      },
+      "output": 2
+    },
+    {
+      "author": "root_agent",
+      "branch": "reverse_string@1",
+      "id": "e-4",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "outputFor": [
+          "root_agent@1/reverse_string@1"
+        ],
+        "path": "root_agent@1/reverse_string@1"
+      },
+      "output": "og"
+    },
+    {
+      "author": "root_agent",
+      "branch": "make_uppercase@1",
+      "content": {
+        "parts": [
+          {
+            "text": "Triggered for input: GO"
+          }
+        ],
+        "role": "user"
+      },
+      "id": "e-5",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": "root_agent@1/send_message@1"
+      }
+    },
+    {
+      "author": "root_agent",
+      "branch": "count_characters@1",
+      "content": {
+        "parts": [
+          {
+            "text": "Triggered for input: 2"
+          }
+        ],
+        "role": "user"
+      },
+      "id": "e-6",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": "root_agent@1/send_message@2"
+      }
+    },
+    {
+      "author": "root_agent",
+      "branch": "reverse_string@1",
+      "content": {
+        "parts": [
+          {
+            "text": "Triggered for input: og"
+          }
+        ],
+        "role": "user"
+      },
+      "id": "e-7",
+      "invocationId": "i-1",
+      "nodeInfo": {
+        "path": "root_agent@1/send_message@3"
+      }
+    }
+  ],
+  "id": "5cf6403e-fd4e-4fef-ad66-8ae78d26ba29",
+  "state": {
+    "__session_metadata__": {
+      "displayName": "go"
+    }
+  },
+  "userId": "user"
+}