[FEATURE] RouterModel — dynamic model selection and routing for Strands agents

[umeshchandani]

Problem Statement

Problem

Every Strands agent today hardcodes a single BedrockModel. An internal survey
of multiple Strands repositories found almost all instances of this pattern with zero
routing, zero fallback, and zero cost tracking.

Proposed Solution

A RouterModel class that implements the same Model interface as BedrockModel
and is a zero-code-change drop-in:

  # Before
  Agent(model=BedrockModel(model_id="us.anthropic.claude-sonnet-4-6"))

  # After
  Agent(model=RouterModel(deployments=[...], strategy="rate-limit-aware"))

Key routing strategies:

• rate-limit-aware: TPM/RPM-aware dispatch with cross-region fallback
• bedrock-ipr: passes Prompt Router ARN as model_id (bridges IPR gap)
• cost-based: token cost minimization
• latency-based: TTL-cached response time

Use Case

Prior Art

LiteLLM Router (https://docs.litellm.ai/docs/routing) solves this for
OpenAI-compatible providers. No equivalent exists for Strands.

Bedrock Intelligent Prompt Routing exists as a managed service but is
inaccessible to Strands agents today — this PR would close that gap.

Alternatives Solutions

No response

Additional Context

Questions for Maintainers

1. Is this on your roadmap?
2. Would you prefer this upstream in sdk-python or as a separate package?
3. Should Bedrock-specific strategies (bedrock-ipr) live separately from
   provider-agnostic strategies (rate-limit-aware, cost-based)?

I Am Willing To Contribute

Yes — I have a detailed design doc and can begin with a focused PR for
the provider-agnostic RouterModel core.