[Model] Opus 4.5 overwrites user's stored plan .md file when switching to unrelated task

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

1. User asked Claude to review codebase and create a plan for the original task
2. Claude created plan and user said "store this plan, I have some other changes and code commits I want to make before embarking on rewrites"
3. User then asked a separate question: "do we have a .gitignore in this repo? if not can you create a plan for generating one"

What Claude Actually Did

What Claude Actually Did:

1. Claude acknowledged storing the first plan at "bubbly-wishing-flask.md"
2. When creating the second plan (for .gitignore), Claude used the Write tool to overwrite the same file path
3. The original email hyperlinks plan was completely replaced with the gitignore plan
4. Claude did not ask for confirmation before overwriting
5. Claude did not create a new file for the separate task

Expected Behavior

Claude should have:

1. Created a new plan file with a different name for the unrelated gitignore task
2. Preserved the original plan file that the user explicitly asked to be stored
3. At minimum, asked before overwriting an existing plan file

Files Affected

\.claude\plans\bubbly-wishing-flask.md (overwritten without permission)

Permission Mode

Accept Edits was ON (auto-accepting changes)

Can You Reproduce This?

Haven't tried to reproduce

Steps to Reproduce

Steps to Reproduce:

1. Ask Claude to create a plan for Task A
2. Tell Claude to "store this plan" for later
3. Ask Claude to create a plan for unrelated Task B
4. Observe whether Claude creates a new file or overwrites the stored plan

Claude Model

Opus

Relevant Conversation

User: "store this plan, I have some other changes and code commits I want to make before embarking on rewrites"

Claude: "The plan is saved at \.claude\plans\bubbly-wishing-flask.md for future reference."

User: "do we have a .gitignore in this repo? if not can you create a plan for generating one"

[Claude investigates .gitignore, then writes new plan]

Claude's Write tool call:
  <invoke name="Write">
  <parameter name="file_path">\.claude\plans\bubbly-wishing-flask.md</parameter>
  <parameter name="content"># Plan: Comprehensive .gitignore Update
  ...

User: "you completely overwrote a different plan with the gitignore one, do you believe that's a bug that needs to be reported? I specifically wanted the prior plan written and stored, and I never asked you to overwrite with this separate gitignore task"

Claude: "You're absolutely right, and I apologize - that was my mistake, not a bug in the system. The tooling worked correctly - I explicitly told it to write to the same file path."

Impact

Medium - Extra work to undo changes

Claude Code Version

2.1.29 Claude Code

Platform

Anthropic API

Additional Context

Additional Context:

• Claude acknowledged this was an error in judgment, not a tool bug
• The random/non-descriptive filename (bubbly-wishing-flask.md) may have contributed to Claude not recognizing it as important to preserve
• User had to point out the error; Claude did not notice it had overwritten the file