feat: Add UiWidget to EventActions for supporting new experimental UI Widgets feature

vishwa180 · copybara-github · commit 530ff06ece61 · 2026-03-09T16:42:17.000-07:00
Co-authored-by: Vishwa Murugan &lt;vishwamurugan@google.com&gt;
PiperOrigin-RevId: 881099147
diff --git a/src/google/adk/events/event_actions.py b/src/google/adk/events/event_actions.py
@@ -25,6 +25,7 @@
 
 from ..auth.auth_tool import AuthConfig
 from ..tools.tool_confirmation import ToolConfirmation
+from .ui_widget import UiWidget
 
 
 class EventCompaction(BaseModel):
@@ -108,3 +109,6 @@ class EventActions(BaseModel):
 
   rewind_before_invocation_id: Optional[str] = None
   """The invocation id to rewind to. This is only set for rewind event."""
+
+  render_ui_widgets: Optional[list[UiWidget]] = None
+  """List of UI widgets to be rendered by the UI."""
diff --git a/src/google/adk/events/ui_widget.py b/src/google/adk/events/ui_widget.py
@@ -0,0 +1,59 @@
+# 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 __future__ import annotations
+
+from typing import Any
+
+from pydantic import alias_generators
+from pydantic import BaseModel
+from pydantic import ConfigDict
+from pydantic import Field
+
+
+class UiWidget(BaseModel):
+  """Rendering metadata for a UI widget associated with an event.
+
+  When present on an Event.actions, the UI renders the widget using the
+  specified provider's renderer component.
+  """
+
+  model_config = ConfigDict(
+      extra='forbid',
+      alias_generator=alias_generators.to_camel,
+      populate_by_name=True,
+  )
+
+  id: str
+  """The unique identifier of the UI widget."""
+
+  provider: str
+  """Widget provider identifier. Determines which rendering strategy
+  the UI uses.
+
+  Known values:
+    - 'mcp': MCP App iframe, rendered with the MCP Apps AppBridge.
+  """
+
+  payload: dict[str, Any] = Field(default_factory=dict)
+  """Provider-specific data required for rendering.
+
+  If provider is 'mcp', the payload is a dictionary with the following fields:
+  {
+    "resource_uri: "ui://...",
+    "tool": {...},
+    "tool_args": {...}
+  }
+  Future providers can have their set of payload fields.
+  """
