[BUG] Frequent API Error 500 in Claude Code (claude-opus-4-6) - Unable to work

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?

I'm experiencing persistent HTTP 500 internal server errors while using Claude Code with the claude-opus-4-6 model via VS Code extension. The errors occur intermittently during normal usage (file edits, Task agent calls), making it impossible to maintain a productive workflow.

Error: API Error: 500 {"type":"error","error":{"type":"api_error","message":"Internal server error"}}

Example request_ids:

req_011CYV9xzXu7nfjGasWx2ESL
req_011CYVAhLjkZzwKy7QD9rABs
req_011CYVApEbrDM67rJst1c4CH
req_011CYVBbJt5Q8KHQ3HWpzbfy
Environment: Windows 11, VS Code extension, claude-opus-4-6 model
Date: 2026-02-25, ~18:00-19:00 GMT+1

The errors seem to happen more frequently with longer conversation contexts and when using Task subagents.

What Should Happen?

API calls should complete successfully without returning HTTP 500 internal server errors. During a normal Claude Code session (editing files, running builds, making tool calls), the API should maintain stable connectivity. Instead, I'm experiencing frequent 500 errors that interrupt my workflow, force me to restart conversations, and lose context. This makes it impossible to complete multi-step coding tasks reliably. The errors occur every few minutes, particularly when the conversation context grows larger or when using the Task (subagent) tool.

Error Messages/Logs

Steps to Reproduce

1. Open Claude Code in VS Code extension with claude-opus-4-6 model
2. Start a multi-step coding task (editing multiple files across a project)
3. After ~10-15 tool calls, API starts returning 500 errors intermittently
4. Errors increase in frequency as conversation context grows
5. Task subagent calls fail almost 100% of the time
6. Eventually the session becomes unusable and requires a new chat

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.56

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_