[Bug] API ERROR 529 Overload with sonnet 4.6 model

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?

Claude Code 2.1.183 running Sonnet 4.6 consistently fails with 529 Overloaded during long-running code migration audits after ~20–25 minutes of analysis.

<img width="1920" height="1080" alt="Image" src="https://github.com/user-attachments/assets/76ecbf10-1b0f-49ec-8679-94409b79e59d" />

What Should Happen?

While performing a large Vue-to-React migration audit, Claude Code should complete the analysis successfully or provide a reliable resume/checkpoint mechanism. It should not terminate with a 529 Overloaded error after extensive processing and retry attempts.

Error Messages/Logs

Steps to Reproduce

1. Open Claude Code (version 2.1.183).
2. Use Sonnet 4.6 model.
3. Open a large codebase containing Vue and React projects.
4. Ask Claude to perform a comprehensive migration audit between the Vue and React implementations.
5. The audit should include:

• API comparison
• Payload comparison
• Validation comparison
• Watchers/useEffect analysis
• Business logic audit
• Edit/Create flow analysis

1. Allow Claude to analyze the codebase for an extended period (approximately 20–25 minutes).
2. Observe Claude repeatedly updating its plan and continuing analysis.
3. Eventually Claude displays:

"API Error: 529 Overloaded"

1. Automatic retries occur until reaching:

"Retrying attempt 10/10"

1. The audit fails to complete and progress is lost.

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.183

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_