Smooth Migration Strategy to Claude 4 Sonnet on Amazon Bedrock

Introduction

With the release of Anthropic’s Claude 4 Sonnet on Amazon Bedrock, AI-powered applications can upgrade their capabilities and face the impending deprecation of Claude 3.5 Sonnet (v1 and v2). Whether your system supports chatbots, document summarization, legal analysis, or code generation, this migration is not optional. It ensures stability, support, and access to major improvements.

This guide explains what’s new, how to prepare, and the best practices for a smooth transition, illustrated with practical examples.

What’s Different in Claude 4 Sonnet

Claude 4 is more than an incremental update. Its changes affect how you design and run AI systems.

Key Considerations Before Migration

Prerequisites & Region Availability

• Request access for Claude 4 Sonnet in Amazon Bedrock and accept the new EULA.
• Verify that your AWS Region supports Claude 4 or plan for cross-Region inference.

2. API / Code Changes

• For InvokeModel, update the modelId from anthropic.claude-3-5-sonnet-20240620-v1:0 to anthropic.claude-4-sonnet-20240514-v1:0.
• If you use Converse (recommended), formats remain consistent, but tool names differ.
• For example, replace the old text editor tool with text_editor_20250124 (str_replace_based_edit_tool) and remove unsupported commands like undo_edit.

3. Prompt Engineering & Behavior Changes

• Claude 4 follows instructions more strictly, sometimes producing shorter outputs unless you explicitly request detail.
• Use tags (e.g., XML) to separate input sections clearly.
• Adjust persona prompts if you rely on conversational style.

4. New Reasoning Features

• Add the thinking field in API calls to enable extended reasoning.
• Reasoning tokens count toward output, increasing cost and latency.
• Use extended thinking for complex planning or legal/scientific analysis, not for simple lookups.

5. Evaluation & Validation

• Build or reuse a benchmark suite of representative prompts and expected outputs.
• Automate evaluation with CI/CD integration or Amazon Bedrock evaluation tools.
• Compare outputs, latency, cost, and safety behavior across models.

6. Safety & Deployment

• Guardrails may trigger differently with Claude 4; test carefully.
• Deploy gradually using shadow testing, A/B, or canary strategies.
• Always maintain a rollback plan.

Migration in Action: Example Scenarios

Legal Document Review

With Claude 3.5, long contracts had to be split into chunks. Claude 4’s million-token context lets you analyze entire documents in one pass. Interleaved thinking allows it to call a legal dictionary and risk classifier mid-analysis for richer insights.

Educational Tutoring Bot
Suppose previously the bot used chain-of-thought via prompt engineering to guide students step by step, with Claude 4. In that case, you might enable extended thinking so that the model reasons in multiple steps behind the scenes, and then you present a more concise, coherent answer. You might also adjust the bot’s persona prompt to remain encouraging and pedagogical, but without over-verbosity.

Code Review & Generation

A system reviewing large codebases previously lost track of dependencies. With Claude 4’s context, entire modules can be processed together. Parallel tool use (analyzer, formatter, documentation generator) streamlines results.

Step-by-Step Migration Plan

1. Inventory & Audit
   Identify all Claude 3.5 use cases. Collect representative prompts and outcomes.
2. Enable Access
   Request Claude 4 access and confirm region support.
3. Update API / Code
   Replace model IDs, update tool definitions, and remove deprecated commands.
   Handle the new refusal stop reason when handling errors.
4. Prompt Adjustments
   Add tags or explicit wording for clarity.
   Test with and without extended thinking to balance cost and latency.
5. Build & Run Benchmarks
   Run suites on both models, comparing accuracy, latency, cost, and safety.
6. Safe Deployment
   Shadow deploy first, then move to A/B or canary rollout. Keep rollback options ready.
7. Monitor & Iterate
   After rollout, monitor performance and adjust prompts or integration as needed.

Conclusion

Migrating from Claude 3.5 Sonnet to Claude 4 Sonnet is a critical upgrade. The new model brings a massive context window, advanced reasoning modes, richer tool integration, and stricter instruction adherence. These improvements can enhance performance and reliability only if migration is planned carefully.

Drop a query if you have any questions regarding Claude and we will get back to you quickly.

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