fix: route workflow IDs and retry jitter through platform seams

src/google/adk/events/request_input.py

@@ -15,13 +15,13 @@
 
 from typing import Any
 from typing import Optional
-import uuid
 
 from pydantic import alias_generators
 from pydantic import BaseModel
 from pydantic import ConfigDict
 from pydantic import Field
 
+from ..platform import uuid as platform_uuid
 from ..utils._schema_utils import SchemaType
 
 
@@ -39,7 +39,7 @@ class RequestInput(BaseModel):
           "The ID of the interrupt, usually a function call ID. This is used"
           " to identify the interrupt that the input is for."
       ),
-      default_factory=lambda: str(uuid.uuid4()),
+      default_factory=platform_uuid.new_uuid,
   )
   """The ID of the interrupt, usually a function call ID.
 

src/google/adk/platform/__init__.py

@@ -11,3 +11,13 @@
 # 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 ._random import get_random
+from ._random import reset_random_provider
+from ._random import set_random_provider
+
+__all__ = [
+    'get_random',
+    'reset_random_provider',
+    'set_random_provider',
+]

src/google/adk/platform/_random.py

@@ -0,0 +1,46 @@
+# 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.
+
+"""Platform module for abstracting random number generation."""
+
+from __future__ import annotations
+
+from contextvars import ContextVar
+import random
+from typing import Callable
+
+_default_random: random.Random = random.Random()
+_default_random_provider: Callable[[], random.Random] = lambda: _default_random
+_random_provider_context_var: ContextVar[Callable[[], random.Random]] = (
+    ContextVar("random_provider", default=_default_random_provider)
+)
+
+
+def set_random_provider(provider: Callable[[], random.Random]) -> None:
+  """Sets the provider for the random number generator.
+
+  Args:
+    provider: A callable that returns the `random.Random` instance to use.
+  """
+  _random_provider_context_var.set(provider)
+
+
+def reset_random_provider() -> None:
+  """Resets the random provider to its default implementation."""
+  _random_provider_context_var.set(_default_random_provider)
+
+
+def get_random() -> random.Random:
+  """Returns the random number generator."""
+  return _random_provider_context_var.get()()

src/google/adk/workflow/_tool_node.py

@@ -19,7 +19,6 @@
 from collections.abc import AsyncGenerator
 import json
 from typing import Any
-import uuid
 
 from google.genai import types
 from pydantic import ConfigDict
@@ -28,6 +27,7 @@
 
 from ..agents.context import Context
 from ..events.event import Event
+from ..platform import uuid as platform_uuid
 from ..tools.base_tool import BaseTool
 from ..tools.tool_context import ToolContext
 from ..utils.content_utils import extract_text_from_content
@@ -66,7 +66,7 @@ async def _run_impl(
   ) -> AsyncGenerator[Any, None]:
     tool_context = ToolContext(
         invocation_context=ctx.get_invocation_context(),
-        function_call_id=str(uuid.uuid4()),
+        function_call_id=platform_uuid.new_uuid(),
     )
 
     args = node_input

src/google/adk/workflow/utils/_retry_utils.py

@@ -16,8 +16,7 @@
 
 """Utility functions for retrying nodes in a workflow."""
 
-import random
-
+from ...platform import _random as platform_random
 from .._node_state import NodeState
 from .._retry_config import RetryConfig
 
@@ -82,7 +81,9 @@ def _get_retry_delay(
   delay = min(delay, max_delay)
 
   if jitter > 0.0:
-    random_offset = random.uniform(-jitter * delay, jitter * delay)
+    random_offset = platform_random.get_random().uniform(
+        -jitter * delay, jitter * delay
+    )
     delay = max(0.0, delay + random_offset)
 
   return delay

tests/unittests/events/test_request_input.py

@@ -0,0 +1,57 @@
+# 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.
+
+"""Unit tests for the RequestInput event model."""
+
+from __future__ import annotations
+
+import uuid
+
+from google.adk.events.request_input import RequestInput
+from google.adk.platform import uuid as platform_uuid
+
+
+class TestRequestInputInterruptId:
+
+  def teardown_method(self) -> None:
+    platform_uuid.reset_id_provider()
+
+  def test_default_interrupt_id_is_a_uuid(self):
+    """Without a custom provider, the default interrupt_id is a uuid."""
+    request = RequestInput()
+
+    # Should be parseable as uuid
+    uuid.UUID(request.interrupt_id)
+
+  def test_default_interrupt_id_uses_platform_id_provider(self):
+    """The default interrupt_id is minted via the platform uuid seam.
+
+    Embedders can install a custom id provider to control how IDs are
+    generated (e.g. seeded or sequential IDs for reproducible runs); the
+    default interrupt_id must come from that provider because recorded
+    user responses reference it by value.
+    """
+    platform_uuid.set_id_provider(lambda: "deterministic-id")
+
+    request = RequestInput()
+
+    assert request.interrupt_id == "deterministic-id"
+
+  def test_explicit_interrupt_id_is_preserved(self):
+    """An explicitly provided interrupt_id bypasses the provider."""
+    platform_uuid.set_id_provider(lambda: "deterministic-id")
+
+    request = RequestInput(interrupt_id="explicit-id")
+
+    assert request.interrupt_id == "explicit-id"

tests/unittests/platform/test_random.py

@@ -0,0 +1,51 @@
+# 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.
+
+"""Unit tests for the platform random module."""
+
+import random
+import unittest
+
+from google.adk import platform as adk_platform
+
+
+class TestRandom(unittest.TestCase):
+
+  def tearDown(self) -> None:
+    # Reset provider to default after each test
+    adk_platform.reset_random_provider()
+
+  def test_default_random_provider(self) -> None:
+    # Verify it returns a random.Random instance producing values in range
+    rng = adk_platform.get_random()
+    self.assertIsInstance(rng, random.Random)
+    value = rng.uniform(0.0, 1.0)
+    self.assertGreaterEqual(value, 0.0)
+    self.assertLessEqual(value, 1.0)
+
+  def test_custom_random_provider(self) -> None:
+    # Test override
+    seeded = random.Random(42)
+    adk_platform.set_random_provider(lambda: seeded)
+    self.assertIs(adk_platform.get_random(), seeded)
+    expected = random.Random(42).uniform(0.0, 1.0)
+    self.assertEqual(adk_platform.get_random().uniform(0.0, 1.0), expected)
+
+  def test_reset_random_provider(self) -> None:
+    seeded = random.Random(42)
+    adk_platform.set_random_provider(lambda: seeded)
+    adk_platform.reset_random_provider()
+    self.assertIsNot(adk_platform.get_random(), seeded)
+    # Default provider returns a stable module-level instance
+    self.assertIs(adk_platform.get_random(), adk_platform.get_random())

tests/unittests/workflow/test_node_runner_failure.py

@@ -20,6 +20,7 @@
 from typing import AsyncGenerator
 from unittest import mock
 
+from google.adk import platform as adk_platform
 from google.adk.agents.context import Context
 from google.adk.events.event import Event
 from google.adk.runners import Runner
@@ -715,20 +716,23 @@ async def test_retry_applies_random_jitter(request: pytest.FixtureRequest):
   session = await ss.create_session(app_name=agent.name, user_id='u')
   msg = types.Content(parts=[types.Part(text='start')], role='user')
 
-  with (
-      mock.patch('asyncio.sleep', new_callable=mock.AsyncMock) as mock_sleep,
-      mock.patch('random.uniform', return_value=-1.0) as mock_random,
-  ):
-    events = []
-    async for event in runner.run_async(
-        user_id='u', session_id=session.id, new_message=msg
-    ):
-      events.append(event)
-
-    # 4.0 + (-1.0) = 3.0
-    mock_sleep.assert_any_await(3.0)
-    # Called with -0.5 * 4.0, 0.5 * 4.0
-    mock_random.assert_called_once_with(-2.0, 2.0)
+  mock_random = mock.Mock()
+  mock_random.uniform = mock.Mock(return_value=-1.0)
+  adk_platform.set_random_provider(lambda: mock_random)
+  try:
+    with mock.patch('asyncio.sleep', new_callable=mock.AsyncMock) as mock_sleep:
+      events = []
+      async for event in runner.run_async(
+          user_id='u', session_id=session.id, new_message=msg
+      ):
+        events.append(event)
+
+      # 4.0 + (-1.0) = 3.0
+      mock_sleep.assert_any_await(3.0)
+      # Called with -0.5 * 4.0, 0.5 * 4.0
+      mock_random.uniform.assert_called_once_with(-2.0, 2.0)
+  finally:
+    adk_platform.reset_random_provider()
 
   results = simplify_events_with_node(events)
   filtered_results = [

tests/unittests/workflow/test_tool_node.py

@@ -14,9 +14,12 @@
 
 """Tests for ToolNode input parsing and execution."""
 
+import itertools
+import re
 from typing import Any
 
 from google.adk.events.event import Event
+from google.adk.platform import uuid as platform_uuid
 from google.adk.tools.base_tool import BaseTool
 from google.adk.workflow import START
 from google.adk.workflow._tool_node import _ToolNode as ToolNode
@@ -139,3 +142,48 @@ async def test_tool_node_rejects_non_dict_content():
       TypeError, match="The input to ToolNode must be a dictionary"
   ):
     await _run_tool_node_wf(content)
+
+
+@pytest.mark.asyncio
+async def test_tool_node_function_call_id_uses_platform_id_provider():
+  """Tests that the tool's function_call_id is minted via the platform seam.
+
+  Embedders can install a custom id provider to control how IDs are
+  generated; the function_call_id handed to the tool must come from that
+  provider, matching how flows/llm_flows/functions.py mints the same IDs.
+  """
+  captured_ids: list[str] = []
+
+  class CapturingTool(BaseTool):
+    """A tool that records the function_call_id it was invoked with."""
+
+    def __init__(self):
+      super().__init__(name="capturing_tool", description="Captures ids")
+
+    async def run_async(self, *, args: dict[str, Any], tool_context) -> Any:
+      captured_ids.append(tool_context.function_call_id)
+      return {}
+
+  tool_node = ToolNode(tool=CapturingTool())
+
+  def start_node():
+    return Event(output={"param_a": 1})
+
+  wf = Workflow(
+      name="tool_node_id_wf",
+      edges=[
+          (START, start_node),
+          (start_node, tool_node),
+      ],
+  )
+  counter = itertools.count()
+  platform_uuid.set_id_provider(lambda: f"fixed-{next(counter)}")
+  try:
+    app_instance = testing_utils.App(name="test_app", root_agent=wf)
+    runner = testing_utils.InMemoryRunner(app=app_instance)
+    await runner.run_async("start")
+  finally:
+    platform_uuid.reset_id_provider()
+
+  assert len(captured_ids) == 1
+  assert re.fullmatch(r"fixed-\d+", captured_ids[0])

tests/unittests/workflow/test_workflow_failures.py

@@ -19,6 +19,7 @@
 from typing import AsyncGenerator
 from unittest import mock
 
+from google.adk import platform as adk_platform
 from google.adk.agents.context import Context
 from google.adk.apps.app import App
 from google.adk.events.event import Event
@@ -586,13 +587,16 @@ async def test_retry_with_jitter(request: pytest.FixtureRequest):
   app = App(name=request.function.__name__, root_agent=agent)
   runner = testing_utils.InMemoryRunner(app=app)
 
-  with (
-      mock.patch('asyncio.sleep', new_callable=mock.AsyncMock) as mock_sleep,
-      mock.patch('random.uniform', return_value=-1.0) as mock_random,
-  ):
-    events = await runner.run_async(testing_utils.get_user_content('start'))
-    mock_sleep.assert_any_await(3.0)
-    mock_random.assert_called_once_with(-2.0, 2.0)
+  mock_random = mock.Mock()
+  mock_random.uniform = mock.Mock(return_value=-1.0)
+  adk_platform.set_random_provider(lambda: mock_random)
+  try:
+    with mock.patch('asyncio.sleep', new_callable=mock.AsyncMock) as mock_sleep:
+      events = await runner.run_async(testing_utils.get_user_content('start'))
+      mock_sleep.assert_any_await(3.0)
+      mock_random.uniform.assert_called_once_with(-2.0, 2.0)
+  finally:
+    adk_platform.reset_random_provider()
 
   assert simplify_events_with_node(events) == [
       (