AgentCoreMemorySessionManager does not support extended thinking

[joshg4096]

Describe the bug
Multi-turn interaction with an agent using a model with extended thinking does not work

An error occurred (ValidationException) when calling the ConverseStream operation: The model returned the following errors: messages.11.content.0.type: Expected `thinking` or `redacted_thinking`, but found `text`. When `thinking` is enabled, a final `assistant` message must start with a thinking block. We recommend you include thinking blocks from previous turns. 

To Reproduce
Steps to reproduce the behavior:

• Create a Strands Agent with AgentCoreMemorySessionManager and with Claude Sonnet 4.5 with extended thinking enabled

additional_request_fields={
    "thinking": {"type": "enabled", "budget_tokens": 4096}
}

• Interact with the agent twice in the same session

Expected behavior
Multi-turn interaction works without an error