strands-context-manager

name	strands-context-manager
description	Strands conversation/context manager patterns, including sliding window with summarization. Use when building agents with context management, preventing session pollution, or implementing conversation compaction.
license	MIT
metadata	{"author":"sample-skills-for-builders","version":"1.0.0"}

Strands Context Manager (Sliding Window with Summarization)

Strands Agents SDK conversation manager combining sliding window and summarization strategies.

When to Apply

Reference this skill when:

• Building Strands agents with long conversations
• Implementing context window management
• Preventing session pollution in multi-turn dialogs
• Combining sliding window with summarization

Critical Pitfalls

1. Inheritance Pitfall

DON'T inherit from SummarizingConversationManager. DO inherit from base ConversationManager.

2. Infinite Recursion

Use _is_summarizing flag with try/finally to prevent recursion during summarization calls.

3. Hook Closure Problem (MOST CRITICAL)

Lambda closures capture session_manager references during initialization. Create summarization agent WITHOUT session_manager, hooks, or persistence.

Implementation Pattern

class SlidingWindowWithSummarizationManager(ConversationManager):
    def __init__(self, window_size=40, summarization_agent=None, summarization_system_prompt=None):
        self._is_summarizing = False
        self._summarization_agent = summarization_agent  # Lazy init when None

    def _get_summarization_agent(self):
        # Create clean agent without session_manager
        return Agent(
            # NO session_manager, NO hooks
        )

Usage

from conversation_manager import SlidingWindowWithSummarizationManager

manager = SlidingWindowWithSummarizationManager(
    window_size=20,
)

Critical Test

def test_no_session_pollution():
    # Verify internal messages don't persist
    # Verify no "Please summarize" in session

References

• Architecture - Detailed design and testing