# Anthropic: Major incident: Degraded functionality for Claude Cowork on Windows

**Summary:** Claude Cowork on Windows could not run local commands after a September 8 Windows update blocked workspace access to the computer’s drive; chat and file reading/editing still worked for most users. Anthropic rated the incident major, from 2026-09-10 15:54 UTC to 2026-09-14 19:14 UTC (4 days 3 h). Microsoft’s September 14 Windows update fixed it. _(machine-written, sol)_
- Kind: Major incident · Label: degradation (model (Jev))
- Changed: 2026-09-10 15:54 UTC · Detected: 2026-10-17 18:21 UTC
- [Source: https://stspg.io/5yp3rhhztm30](https://stspg.io/5yp3rhhztm30)
- [Company: Anthropic](https://rewindex.com/company/anthropic.md)
- Versions: before (none: first archived) → after incident\_version:1/r1pqn1kb4hvk@41ae511da1fa
- Change 1 of 1 for this incident

## What changed

**1. Added: Title**

```diff
+ Degraded functionality for Claude Cowork on Windows
```

**2. Added: Impact**

```diff
+ major
```

**3. Added: Status**

```diff
+ resolved
```

**4. Added: Start time**

```diff
+ 2026-09-10 15:54 UTC
```

**5. Added: Resolved time**

```diff
+ 2026-09-14 19:14 UTC
```

**6. Added: Affected components**

```diff
+ Claude Cowork
```

**7. Added: Update** (identified) · 2026-09-10 15:54 UTC

```diff
+ A Windows update released September 8 has left Claude Cowork on Windows unable to run local commands, because its workspace can no longer reach your computer's drive. For most users, chat and file reading and editing still work. There's no in-app workaround yet, and restarting or reinstalling won't help. Microsoft has developed a fix and is working to release it. We'll post an update when we have more to share.
```

**8. Added: Update** (resolved) · 2026-09-14 19:14 UTC

```diff
+ This issue has been resolved. Microsoft has released a September 14 Windows update that fixes it: https://support.microsoft.com/en-us/servicing/os/windows-11/2026/09/kb5129195-windows-11-24h2-25h2-security-update
```

## History of this incident

| When (UTC) | Change | Label |
| --- | --- | --- |
| 2026-09-10 15:54 UTC | Major incident: Degraded functionality for Claude Cowork on Windows (this change) | degradation |

All Anthropic changes: [timeline](https://rewindex.com/company/anthropic/changes.md)
_Diff excerpts are shown on normalized text: dates, counters and tokens appear as ‹date›, ‹count›, ‹tok›; noise-only edits are hidden. Rewindex shows the changed passages, not a copy of the page._


---
Canonical: https://rewindex.com/change/i9bed555e7669fc · Markdown: https://rewindex.com/change/i9bed555e7669fc.md · JSON: https://rewindex.com/api/v1/changes/i9bed555e7669fc · Generated 2026-10-18T02:28:22.443Z