[FEATURE] Support Claude 4.6 Adaptive Thinking and Effort Parameter

[statefb]

Problem Statement

Claude 4.6 introduces new thinking features that deprecate the current budget_tokens approach:

Deprecated (will be removed in future models):

• thinking: {type: "enabled", budget_tokens: N}

New recommended approach:

• thinking: {type: "adaptive"} - Claude dynamically decides when and how much to think
• effort parameter (low, medium, high, max) - Controls thinking depth

Currently, Strands SDK only supports the deprecated budget_tokens via additional_request_fields, with no native support for the new
Claude 4.6 features.

Reference: https://platform.claude.com/docs/en/about-claude/models/whats-new-claude-4-6

Proposed Solution

No response

Use Case

1. Agentic Applications with Dynamic Reasoning

• Agents that need to think deeply on complex tasks but skip thinking for simple ones
• thinking: {type: "adaptive"} with effort: "high" provides optimal cost/quality balance

2. Cost Optimization

• effort: "low" for simple queries (faster, cheaper)
• effort: "max" for complex reasoning tasks (best quality)

3. Future-Proofing

• budget_tokens will be removed in future Claude models
• Applications using Strands need a migration path to the new API

Example usage:

from strands import Agent                                                                                                                  
from strands.models import BedrockModel
                                                                                                                                           
model = BedrockModel(
    model_id="anthropic.claude-opus-4-6-20250514-v1:0",                                                                                    
    additional_request_fields={                                                                                                            
        "thinking": {"type": "adaptive"},
        "effort": "high"
    }
)

agent = Agent(model=model, tools=[...])
result = agent("Solve this complex problem...")

Alternatives Solutions

No response

Additional Context

No response

[mkmeral]

Currently, Strands SDK only supports the deprecated budget_tokens via additional_request_fields, with no native support for the new

You can also pass the "thinking": {"type": "adaptive"}, just like you have done in your example. This feature works the same way for both parameters. In fact your code sample should work as is.

I will take consider this ticket as DevX improvement to bring adaptive thinking parameters to Bedrock Model provider.

About the new field request, I don't think that is a good idea, mainly because Bedrock supports so many models with different configurations, and each have their own style. Even Claude (like you are saying) has recently changed it, and they are deprecating their old way. This will essentially become a cat-and-mouse game where we will have to play catch-up with what models are supported in Bedrock and how they are configured, and it only brings a small DevX improvement (note that the feature can actually be used today). I don't think this is a scalable mechanism for the SDK.

I will add won't-fix and autoclose labels. If you disagree, feel free to respond on the ticket and we can discuss further

[statefb]

Thank you, well understood. Let me close