[BUG] Claude Code doesn't work when using Amazon Bedrock and not defined model in settings.json

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

When ”CLAUDE_CODE_USE_BEDROCK” is set to "1" and no model is specified in settings.json, the default model is set to us.anthropic.claude-sonnet-4-5-20250929-v1:0, but it should be global.anthropic.claude-sonnet-4-5-20250929-v1:0.
I believe this is because AWS changed the prefix rule starting with Sonnet 4.5.

ref. https://aws.amazon.com/jp/blogs/aws/introducing-claude-sonnet-4-5-in-amazon-bedrock-anthropics-most-intelligent-model-best-for-coding-and-complex-agents/

What Should Happen?

Default model should be global.anthropic.claude-sonnet-4-5-20250929-v1:0

Error Messages/Logs

> hi!
  ⎿  403 You don't have access to the model with the specified model ID.

Steps to Reproduce

settings.json

{
  "env": {
    "AWS_PROFILE": "xxx",
    "CLAUDE_CODE_USE_BEDROCK": "1",
  }
}

and launch claude.

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.0.1 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

_No response_