[BUG] v2.1.96: Claude Code GitHub Action fails with AWS authentication

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?

Since upgrading to Claude Code v2.1.96, the Claude Code GitHub Action (Bedrock) fails with a 403 authentication error.

Error: Action failed with error: SDK execution error: Error: Claude Code returned an error result: Failed to authenticate. API Error: 403 Authorization header requires 'Credential' parameter. Authorization header requires 'Signature' parameter. Authorization header requires 'SignedHeaders' parameter. (Hashed with SHA-256 and encoded with Base64) Authorization=xxx
Fetching issue comment xxxx

What Should Happen?

Claude Code Action should authenticate with AWS Bedrock successfully
and complete the assigned task.

Error Messages/Logs

Error: Action failed with error: SDK execution error: Error: Claude Code returned an error result: Failed to authenticate. API Error: 403 Authorization header requires 'Credential' parameter. Authorization header requires 'Signature' parameter. Authorization header requires 'SignedHeaders' parameter. (Hashed with SHA-256 and encoded with Base64) Authorization=xxx
Fetching issue comment xxxx

Steps to Reproduce

1. Configure Claude Code Action with AWS Bedrock
2. Trigger the action on a GitHub issue or PR

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.92

Claude Code Version

2.1.96

Platform

AWS Bedrock

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_