feat: move hook event firing into reduce_context methods

Fire BeforeReduceContextEvent and AfterReduceContextEvent inside each
reduce_context() implementation instead of at the call site in the agent's
event loop. This ensures hooks are triggered for all reduce_context calls:
- From ContextWindowOverflowException handling in event loop
- From ConversationManager.apply_management() for proactive reduction

Hook callbacks are now synchronous (invoke_callbacks) since reduce_context
is synchronous and may be called from sync contexts.

Files modified:
- agent.py: Remove hook firing from _execute_event_loop_cycle()
- sliding_window_conversation_manager.py: Add sync hook calls
- summarizing_conversation_manager.py: Add sync hook calls
- null_conversation_manager.py: Add sync before hook

Addresses reviewer feedback: hooks now fire regardless of reduction source.

Author: Zelys-DFKH

src/strands/agent/agent.py

@@ -35,10 +35,8 @@
 from ..handlers.callback_handler import PrintingCallbackHandler, null_callback_handler
 from ..hooks import (
     AfterInvocationEvent,
-    AfterReduceContextEvent,
     AgentInitializedEvent,
     BeforeInvocationEvent,
-    BeforeReduceContextEvent,
     HookCallback,
     HookProvider,
     HookRegistry,
@@ -965,13 +963,9 @@ async def _execute_event_loop_cycle(
                 yield event
 
         except ContextWindowOverflowException as e:
-            await self.hooks.invoke_callbacks_async(BeforeReduceContextEvent(agent=self, exception=e))
-
             # Try reducing the context size and retrying
             self.conversation_manager.reduce_context(self, e=e)
 
-            await self.hooks.invoke_callbacks_async(AfterReduceContextEvent(agent=self))
-
             # Sync agent after reduce_context to keep conversation_manager_state up to date in the session
             if self._session_manager:
                 self._session_manager.sync_agent(self)

src/strands/agent/conversation_manager/null_conversation_manager.py

@@ -40,6 +40,9 @@ def reduce_context(self, agent: "Agent", e: Exception | None = None, **kwargs: A
             e: If provided.
             ContextWindowOverflowException: If e is None.
         """
+        # Fire before event
+        agent.hooks.invoke_callbacks(BeforeReduceContextEvent(agent=agent, exception=e))
+
         if e:
             raise e
         else:

src/strands/agent/conversation_manager/sliding_window_conversation_manager.py

@@ -6,7 +6,7 @@
 if TYPE_CHECKING:
     from ...agent.agent import Agent
 
-from ...hooks import BeforeModelCallEvent, HookRegistry
+from ...hooks import BeforeModelCallEvent, BeforeReduceContextEvent, AfterReduceContextEvent, HookRegistry
 from ...types.content import ContentBlock, Messages
 from ...types.exceptions import ContextWindowOverflowException
 from ...types.tools import ToolResultContent
@@ -171,6 +171,9 @@ def reduce_context(self, agent: "Agent", e: Exception | None = None, **kwargs: A
                 Such as when the conversation is already minimal or when tool result messages cannot be properly
                 converted.
         """
+        # Fire before event
+        agent.hooks.invoke_callbacks(BeforeReduceContextEvent(agent=agent, exception=e))
+
         messages = agent.messages
 
         # Try to truncate the tool result first
@@ -213,6 +216,9 @@ def reduce_context(self, agent: "Agent", e: Exception | None = None, **kwargs: A
         # Overwrite message history
         messages[:] = messages[trim_index:]
 
+        # Fire after event
+        agent.hooks.invoke_callbacks(AfterReduceContextEvent(agent=agent))
+
     def _truncate_tool_results(self, messages: Messages, msg_idx: int) -> bool:
         """Truncate tool results and replace image blocks in a message to reduce context size.
 

src/strands/agent/conversation_manager/summarizing_conversation_manager.py

@@ -13,6 +13,7 @@
 from ...types.exceptions import ContextWindowOverflowException
 from ...types.tools import AgentTool
 from .conversation_manager import ConversationManager
+from ...hooks import BeforeReduceContextEvent, AfterReduceContextEvent
 
 if TYPE_CHECKING:
     from ..agent import Agent
@@ -135,6 +136,9 @@ def reduce_context(self, agent: "Agent", e: Exception | None = None, **kwargs: A
         Raises:
             ContextWindowOverflowException: If the context cannot be summarized.
         """
+        # Fire before event
+        agent.hooks.invoke_callbacks(BeforeReduceContextEvent(agent=agent, exception=e))
+
         try:
             # Calculate how many messages to summarize
             messages_to_summarize_count = max(1, int(len(agent.messages) * self.summary_ratio))
@@ -171,6 +175,9 @@ def reduce_context(self, agent: "Agent", e: Exception | None = None, **kwargs: A
             # Replace the summarized messages with the summary
             agent.messages[:] = [self._summary_message] + remaining_messages
 
+            # Fire after event
+            agent.hooks.invoke_callbacks(AfterReduceContextEvent(agent=agent))
+
         except Exception as summarization_error:
             logger.error("Summarization failed: %s", summarization_error)
             raise summarization_error from e