feat(hooks): add AgentResult to AfterInvocationEvent

Author: Ratish1

src/strands/agent/agent.py

@@ -733,6 +733,7 @@ async def _run_loop(
         """
         await self.hooks.invoke_callbacks_async(BeforeInvocationEvent(agent=self))
 
+        agent_result: AgentResult | None = None
         try:
             yield InitEventLoopEvent()
 
@@ -761,9 +762,13 @@ async def _run_loop(
                         self._session_manager.redact_latest_message(self.messages[-1], self)
                 yield event
 
+            # Capture the result from the final event if available
+            if hasattr(event, "__getitem__") and "stop" in event:
+                agent_result = AgentResult(*event["stop"])
+
         finally:
             self.conversation_manager.apply_management(self)
-            await self.hooks.invoke_callbacks_async(AfterInvocationEvent(agent=self))
+            await self.hooks.invoke_callbacks_async(AfterInvocationEvent(agent=self, result=agent_result))
 
     async def _execute_event_loop_cycle(
         self, invocation_state: dict[str, Any], structured_output_context: StructuredOutputContext | None = None

src/strands/hooks/events.py

@@ -5,10 +5,13 @@
 
 import uuid
 from dataclasses import dataclass
-from typing import Any, Optional
+from typing import TYPE_CHECKING, Any, Optional
 
 from typing_extensions import override
 
+if TYPE_CHECKING:
+    from ..agent.agent_result import AgentResult
+
 from ..types.content import Message
 from ..types.interrupt import _Interruptible
 from ..types.streaming import StopReason
@@ -60,8 +63,15 @@ class AfterInvocationEvent(HookEvent):
       - Agent.__call__
       - Agent.stream_async
       - Agent.structured_output
+
+    Attributes:
+        result: The result of the agent invocation, if available. This will be None
+            when invoked from structured_output methods, as those return typed output
+            directly rather than AgentResult.
     """
 
+    result: Optional["AgentResult"] = None
+
     @property
     def should_reverse_callbacks(self) -> bool:
         """True to invoke callbacks in reverse order."""

tests/strands/agent/hooks/test_events.py

@@ -2,6 +2,7 @@
 
 import pytest
 
+from strands.agent.agent_result import AgentResult
 from strands.hooks import (
     AfterInvocationEvent,
     AfterToolCallEvent,
@@ -10,6 +11,7 @@
     BeforeToolCallEvent,
     MessageAddedEvent,
 )
+from strands.types.content import Message
 from strands.types.tools import ToolResult, ToolUse
 
 
@@ -138,3 +140,46 @@ def test_after_tool_invocation_event_cannot_write_properties(after_tool_event):
         after_tool_event.invocation_state = {}
     with pytest.raises(AttributeError, match="Property exception is not writable"):
         after_tool_event.exception = Exception("test")
+
+
+def test_after_invocation_event_has_optional_result(agent):
+    """Test that AfterInvocationEvent has optional result field."""
+    # Test with no result (structured_output case)
+    event_without_result = AfterInvocationEvent(agent=agent)
+    assert event_without_result.result is None
+
+    # Test with result (normal invocation case)
+    mock_message: Message = {"role": "assistant", "content": [{"text": "test"}]}
+    mock_result = AgentResult(
+        stop_reason="end_turn",
+        message=mock_message,
+        metrics={},
+        state={},
+    )
+    event_with_result = AfterInvocationEvent(agent=agent, result=mock_result)
+    assert event_with_result.result == mock_result
+    assert event_with_result.result.stop_reason == "end_turn"
+
+
+def test_after_invocation_event_result_not_writable(agent):
+    """Test that result property is not writable after initialization."""
+    mock_message: Message = {"role": "assistant", "content": [{"text": "test"}]}
+    mock_result = AgentResult(
+        stop_reason="end_turn",
+        message=mock_message,
+        metrics={},
+        state={},
+    )
+
+    event = AfterInvocationEvent(agent=agent, result=None)
+
+    with pytest.raises(AttributeError, match="Property result is not writable"):
+        event.result = mock_result
+
+
+def test_after_invocation_event_agent_not_writable(agent):
+    """Test that agent property is not writable."""
+    event = AfterInvocationEvent(agent=agent)
+
+    with pytest.raises(AttributeError, match="Property agent is not writable"):
+        event.agent = Mock()

tests/strands/agent/test_agent_hooks.py

@@ -197,7 +197,10 @@ def test_agent__call__hooks(agent, hook_provider, agent_tool, mock_model, tool_u
     )
     assert next(events) == MessageAddedEvent(agent=agent, message=agent.messages[3])
 
-    assert next(events) == AfterInvocationEvent(agent=agent)
+    after_invocation_event = next(events)
+    assert isinstance(after_invocation_event, AfterInvocationEvent)
+    assert after_invocation_event.agent == agent
+    assert after_invocation_event.result is not None
 
     assert len(agent.messages) == 4
 
@@ -261,7 +264,10 @@ async def test_agent_stream_async_hooks(agent, hook_provider, agent_tool, mock_m
     )
     assert next(events) == MessageAddedEvent(agent=agent, message=agent.messages[3])
 
-    assert next(events) == AfterInvocationEvent(agent=agent)
+    after_invocation_event = next(events)
+    assert isinstance(after_invocation_event, AfterInvocationEvent)
+    assert after_invocation_event.agent == agent
+    assert after_invocation_event.result is not None
 
     assert len(agent.messages) == 4