[BUG] Randomly Hitting “Malformed input request” (HTTP 400) Error on AWS Bedrock with Claude CLI ≥ 0.2.107

Environment

• Platform (select one):
• [ ] Anthropic API
• [X] AWS Bedrock
• [ ] Google Vertex AI
• [ ] Other
• Claude CLI version: 0.2.115
• Operating System: macOS 15.3.2 (24D81)
• Terminal: Warp

Bug Description

Every Claude CLI release after 0.2.106 randomly fails on AWS Bedrock with API Error: 400 Malformed input request, please reformat your input and try again..

Only downgrading to 0.2.106 or below restores the functionality.

Steps to Reproduce

1. npm i -g @anthropic-ai/claude-code@0.2.115 (or any version ≥ 0.2.107).
2. Ensure Bedrock is being used, e.g. export CLAUDE_CODE_USE_BEDROCK=1.
3. Start an interactive shell: claude.
4. Send a request (or a couple) to claude.
5. Sometimes, the 400 error appears on the very first request. Other times, it may be after 2-3 requests 🤷‍♂.
6. Downgrade: npm i -g @anthropic-ai/claude-code@0.2.106 → issue disappears.

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Expected Behavior

The CLI should work as expected with AWS Bedrock.

Actual Behavior

Requests fail with the above error.