[BUG] [Claude Desktop / macOS] App freezes (OS-level disk-write throttle) on any video upload — 1.4758.0

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?

> Filed here per Anthropic support guidance. This is about the Claude Desktop macOS app (Electron), not the Claude Code CLI — please re-route if there is a more appropriate repository.

## Summary
Claude Desktop 1.4758.0 freezes / becomes unresponsive when uploading any video file in chat. macOS suspends the process via the disk-write throttle: ~8.5 GB of dirty file-backed memory written in 10
minutes. Started ~2 weeks ago; identical workflow worked reliably before. 5 reproductions in the past 4 days, all sharing the same disk writes crash signature.

## Environment

• Claude Desktop 1.4758.0 (Electron 40.4.1, Chrome 144.0.7559.173, Node 24.13.0)
• macOS 26.2 (Tahoe, Build 25C56, Darwin 25.2.0)
• Hardware: MacBook Air M3, 8 GB RAM
• Locale: pt-BR

What Should Happen?

Reproduction (100%)

1. Open a fresh chat in Claude Desktop
2. Upload any video file (MOV or MP4)
3. Send any prompt referencing the video (e.g. "describe this video")
4. UI becomes unresponsive within seconds; Force Quit required

Reproduces with both:

• Original MOV: 265 MB, 2938×1598, H.264 60fps, 198 s, no audio (a screen recording)
• Locally transcoded MP4 via ffmpeg: 11 MB, 1600×870, H.264 30 fps — still freezes

## Smoking gun (from Claude_2026-04-26-214202_*.diag)

``
Event: disk writes
Action taken: none
Writes: 8593.47 MB of file backed memory dirtied over 610 seconds
(14.09 MB/s average), exceeding limit of 99.42 KB/s over 86400s
Footprint: 218.53 MB → 354.95 MB (+136.42 MB) (max 550.81 MB)
Heaviest stack: thread_start → _pthread_start → uv_cancel (Electron Framework) → write
``

App is not crashing in the JS sense — macOS is throttling/suspending it for excessive disk I/O caused by aggressive paging. The small Footprint (≤550 MB) vs huge cumulative Writes (8.5 GB) = swap
thrashing. Stack roots in libuv inside the Electron framework. Strongly suggests native allocation runaway in the upload/decode path, not a JS heap leak.

## Regression
Same machine, same account, same workflow (upload screen recording, ask for analysis) was reliable ~2 weeks ago. All 5 crash diagnostics from 2026-04-23 through 2026-04-26 share the identical disk writes
throttle signature.

## Attachments

• 5× Claude*.diag files from /Library/Logs/DiagnosticReports/
• system-info.txt from ~/Library/Logs/Claude/
• console-claude-2026-04-26.log — Console.app filtered to process == "Claude" OR process BEGINSWITH "Claude Helper", window 21:30–21:45 around the most recent freeze (4592 lines)

Anexos: abre o Finder em ~/Desktop/claude-bug-report/, seleciona os 7 arquivos e arrasta na área de anexos do GitHub (campo "Attach files by dragging & dropping...").

Error Messages/Logs

Steps to Reproduce

## Steps tried

• Local transcode to small MP4 (11 MB) → still freezes
• Help → Troubleshooting → Clear Cache and Restart → not attempted yet (wanted to preserve diagnostic state for this report)
• /heapdump from inside Claude Desktop → cannot capture; the chat input becomes unresponsive before the slash command can be submitted. The "before" baseline could be captured on app open, but not the

"after" state during the freeze.

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.119 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_