[BUG] Model abandons first version mid-output and restarts with different content in same response

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 generating long-form content (e.g. 4000+ character text), Claude sometimes
abandons its first version partway through and starts over with completely different content
in the same response. The user sees both versions concatenated together.

This is NOT a UI rendering duplicate — the two outputs have different content/structure.
The model appears to internally "change its mind" about the approach mid-generation
and restarts from the beginning without stopping to ask the user.

This wastes tokens (user pays for both versions) and breaks the reading experience.

What Should Happen?

Claude should commit to one version of output per response. If the model is unsatisfied with its current output mid-generation, it should finish the current version first, then ask the user if they want a revision — not silently restart and output a second different version in the same response.

Error Messages/Logs

No error messages. This is a behavioral issue, not a crash.
The model outputs Version A (partial) followed by Version B (complete) in a single response.
Both versions have different content — this is not a UI rendering duplicate.

Steps to Reproduce

1. Ask Claude to write a long piece of content (4000+ characters,)
2. Observe the streaming output — Claude begins writing version A
3. Midway through, Claude stops version A and begins writing version B from the start
4. Both versions appear in the same response with different content

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.92

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_