Description

This PR introduces a SessionManagement class to the Strands SDK that is in charge of persisting an agent to some datastore, and re-initializing the agent. The SessionManagement feature set includes:

• Introduces an agent id attribute used as a unique id for differentiating agents

• SessionManager: Interface for SessionManagers. This interface introduces a append_message_to_agent_session method that is called in the Agent class when adding a message to the agent messages array, as well as an initialize_agent class for initializing an agent

• AgentSessionManager: Implementation of the above interface for persisting a single agent to some datastore. This will also re-initialize the agent's messages and state.

• Session models: Three new models to represent different data types for session persistence:

  • Session: The overarching container to represent a strands agent, and in the future, multi-agent systems. One session can have many agents
  • SessionAgent: A persisted version of an agent, storing the agents state and messages
  • SessionMessage: A persisted version of a message

• SessionDAO: DAO Interface with CRUDL operations for each of the above new models

• FileSessionDAO: A implementation of the SessionDAO for storing a session in the local file system. This introduces the following directory and file structure to represent a Session:

  • <storage_dir>/session_<session_id>/
    • session.json # Stores session related data
    • agents/agent_<agent_id>/
      • agent.json # Stores agent related data
      • messages/messages_<message_id>.json # Stores message content

• S3SessionDAO: Same as the above FileSessionDAO, but stores sessions in S3

Things that still need to be addressed:

• all unit tests are vibe-coded, need to do a more thorough review
• Integ tests
• Update message after guardrail triggers
• Order event files
• Review docstrings (some seem to be out of date)
• Add tests for EventLoopMetric ser/de
• Respect created_at time for DAO Update methods

Changes for a follow-up pr:

• Support ConversationManager refreshing (SummarizationConversationManager)

#246

Documentation PR

TODO:

Type of Change

New feature

Testing

How have you tested the change?

• Vibecoded unit tests and local testing
• Still needs:
  • Thorough review of unit tests
  • Integration tests

• [x] I ran hatch run prepare

Checklist

• [x] I have read the CONTRIBUTING document
• [x] I have added any necessary tests that prove my fix is effective or my feature works
• [ ] I have updated the documentation accordingly
• [ ] I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• [x] My changes generate no new warnings
• [x] Any dependent changes have been merged and published

Additional Notes:
N/A

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