[BUG] API Error 400: data retention mode 'default' is not available for this model via AWS Bedrock

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 using Claude Code connected through AWS Bedrock, every prompt fails with:

API Error: 400 data retention mode 'default' is not available for this model

This appears similar to other Bedrock compatibility issues where Claude Code sends API parameters (e.g., thinking.type.enabled, output_config.effort, beta flags) that the Bedrock endpoint does not recognize for certain model configurations.

The error occurs immediately on any message (e.g., hi), making Claude Code completely unusable via Bedrock.

<img width="1614" height="916" alt="Image" src="https://github.com/user-attachments/assets/4e16d6ba-3268-49db-b060-86afa0830600" />

What Should Happen?

Claude Code should either:

• Not send the data_retention parameter when the model/Bedrock configuration doesn't support it, OR
• Gracefully handle the error and suggest a workaround

Expected: Normal conversation flow without 400 errors.

Error Messages/Logs

API Error: 400 data retention mode 'default' is not available for this model

Steps to Reproduce

1. Configure Claude Code to use AWS Bedrock (export CLAUDE_CODE_USE_BEDROCK=1)
2. Run claude and send any message, e.g., hi
3. Error: ⏺ API Error: 400 data retention mode 'default' is not available for this model

Claude Model

Model: global.anthropic.claude-fable-5

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.170

Platform

AWS Bedrock

Operating System

macOS

Terminal/Shell

iTerm2

Additional Information

_No response_