[BUG] Cannot Open and Download .pptx Files

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 am using a project with claude desktop to generate a monthly deck and now every time I try to download the final .pptx output. It doesn't let me open or download the file. I could only download the .txt logs file.

<img width="428" height="121" alt="Image" src="https://github.com/user-attachments/assets/51a77843-ffb4-4f9f-a1dc-0e3c06e5bc1c" />

When I tried to download the file in claude web I had 0 issues.

I am using a:

• Windows 11 Enterprise
• LENOVO_MT_21MM_BU_Think_FM_ThinkPad T14 Gen 5
• Processor: Intel(R) Core(TM) Ultra 5 135U, 1600 Mhz, 12 Core(s), 14 Logical Processor(s)
• 32GB RAM

What Should Happen?

It should let me download all the files in Claude desktop.

Error Messages/Logs

Steps to Reproduce

I cannot share my code for legal reasons

1. Create a PowerPoint and an excel
2. Populate the PowerPoint slide with the excel information.
3. Tell the "Agent" in Claude Project to output the generated PowerPoint.
4. Try to open/download the file with Claude Desktop and then Claude Web.

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

I don't remember the version, but 1 week ago it worked.

Claude Code Version

Claude Code v2.1.198

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

_No response_