[MODEL] sonnet 4.6

Preflight Checklist

• [x] I have searched existing issues for similar behavior reports
• [x] This report does NOT contain sensitive information (API keys, passwords, etc.)

Type of Behavior Issue

Claude modified files I didn't ask it to modify

What You Asked Claude to Do

Claude Code modifies production files without explicit per-change user approval

What Claude Actually Did

Claude Code repeatedly edited a production Python file (general4.py) across multiple sessions without asking for explicit approval before each modification. It made substantive
▎ code changes — including restructuring a core algorithm — and only created a backup after being prompted by the user. This behavior is risky: the user relies on this file for
▎ ongoing HPC computations, and unauthorized edits could corrupt results or break running jobs.

Expected Behavior

Expected behavior: Before modifying any existing file, Claude Code should clearly state what it intends to change, ask for confirmation, and create a timestamped backup
▎ proactively — not reactively.

Files Affected

Permission Mode

Accept Edits was ON (auto-accepting changes)

Can You Reproduce This?

Yes, every time with the same prompt

Steps to Reproduce

_No response_

Claude Model

Sonnet

Relevant Conversation

Impact

Critical - Data loss or corrupted project

Claude Code Version

2.1.152 (Claude Code)

Platform

Anthropic API

Additional Context

Observed behavior: Changes were made immediately upon identifying a fix, backup was only offered after the user explicitly asked whether one existed.