System & Access Errors

Claude Cowork runs in a sandboxed environment on your computer. When it cannot reach the file system, execute a shell command, or connect to a local integration, the problem usually falls into one of three categories: permissions, PATH resolution, or network connectivity. This page groups every system-and-access error we have documented, explains what each one means at a glance, and links to the full fix.

How System Errors Differ from Logic Errors

System errors are environmental: the agent is fine, but the machine, the OS, or the network is blocking it. Logic errors (context drift, hallucinations) happen inside the model's reasoning. The quickest diagnostic question is:

"Did this work before, and did something change on my machine?"

If the answer is yes, you are almost certainly looking at a system error on this page.

Errors in This Category

Permission Denied / File Access

Claude cannot read or write to a specific folder. On macOS this is usually caused by Privacy & Security settings that restrict which directories each app may touch. On Windows it can be a read-only attribute or a folder owned by a different user account.

Typical message: Permission denied or Cannot read file at path /Users/...

Quick check: Did you grant Claude access to this specific folder during setup? Cowork only sees folders you explicitly allowlisted.

Full fix: Permission Denied / File Access →

Tool Execution Failed (Exit Code 127)

The agent tried to run a shell command but the binary was not found. Exit code 127 means "command not found." This happens because Cowork runs commands in a non-interactive shell that does not load your .zshrc, .bash_profile, or NVM initialization scripts.

Typical message: /bin/sh: python: command not found or npm: command not found

Quick check: Run which <tool> in your own terminal, then compare that path with what Cowork sees.

Full fix: Tool Execution Failed (127) →

MCP Connection Failed

You configured a Model Context Protocol server (a local database, file system bridge, or third-party integration), but Claude cannot reach it. The server may not be running, the port may be wrong, or a corporate VPN may be blocking localhost traffic.

Typical message: Failed to connect to MCP server or Connection refused at localhost:3000

Quick check: Is the MCP server process actually running? Open a terminal and look for the listening port.

Full fix: MCP Connection Failed →

General Troubleshooting Order

When you hit a system error, work through these steps in order — they resolve the majority of cases within five minutes:

  1. Restart Claude Desktop. Many permission and PATH issues clear after a full quit-and-relaunch (not just close-the-window).
  2. Verify the folder is in your allowlist. Open Cowork settings and confirm the target directory is listed.
  3. Check OS privacy settings. On macOS: System Settings → Privacy & Security → Files and Folders → Claude. On Windows: right-click the folder → Properties → Security.
  4. Test the command manually. Open a terminal and run the exact command Claude tried. If it fails for you too, the problem is not Cowork.
  5. Disable VPN/firewall temporarily. If the error is network-related (MCP, API), rule out corporate network restrictions.

When to Contact Support

If none of the above resolves the issue, collect the following before reaching out:

  • The exact error message (copy-paste, not a screenshot).
  • Your OS version and Claude Desktop version (Settings → About).
  • The folder path you granted Claude access to.
  • The command or task you were trying to run.
  • Whether the issue reproduces after a restart.

Send these to Anthropic support or post in the Claude community for faster help.

Platform-Specific Notes

macOS

macOS has the most layered permission model of the platforms Cowork supports, and it is the source of most "permission denied" reports we see.

  • Full Disk Access vs. Files and Folders. Granting Claude access to a specific folder through Cowork's picker is usually enough. But if the folder lives inside a protected location (Desktop, Documents, Downloads, iCloud Drive), macOS may still block access unless Claude has Full Disk Access or the specific folder is listed under Privacy & Security → Files and Folders → Claude. If a folder you granted keeps returning permission errors, check this first.
  • Translocation. If you downloaded Claude Desktop and ran it directly from the DMG without dragging it to Applications, macOS runs it in a randomized read-only location called a "translocated" path. This breaks file access and plugin loading. The fix is to drag Claude Desktop into /Applications and launch it from there.
  • Gatekeeper. After a Claude Desktop update, macOS may re-prompt for accessibility and screen recording permissions. This is normal — the OS treats the updated binary as a new app. Re-grant the permissions and restart.

Windows

  • Path length. Windows has a 260-character path limit by default. If your workspace folder is deeply nested (e.g., C:\Users\name\OneDrive\Company\Projects\2026\Q2\Client Deliverables\Final Versions\...), Cowork may hit "file not found" errors on files that clearly exist. Move the workspace closer to the root (e.g., C:\cowork-workspace\) to avoid this.
  • Antivirus interference. Some antivirus products quarantine files that Claude creates or block the Claude Desktop process from writing to disk. If files disappear after Cowork reports success, add an exclusion for the Claude Desktop executable and your workspace folder.
  • OneDrive sync conflicts. If your workspace is inside a OneDrive-synced folder, OneDrive may lock files for upload while Claude tries to write to them. Use a folder that is not synced, or pause sync during long Cowork runs.

Linux (Community)

Cowork does not officially support Linux, but some users run it through compatibility layers. The most common system errors on this setup are missing libraries (libgtk, libnss) and broken file dialog integrations. These are environment issues, not Cowork bugs — if you go this route, expect to troubleshoot the compatibility layer yourself.

Preventing System Errors Before They Happen

Most system errors are preventable with a few habits:

  1. Keep your workspace folder shallow and local. Avoid network drives, cloud-synced folders, and deeply nested paths. A local folder like ~/cowork-workspace or C:\cowork-workspace eliminates a whole class of path and sync issues.
  2. Pin your tool versions. If Cowork runs a Python or Node script, make sure the version it finds on PATH is the one you tested with. A silent version upgrade can break a script that worked yesterday.
  3. Restart Claude Desktop after OS updates. OS updates often reset privacy permissions or change security policies. A restart surfaces these immediately, rather than mid-task.
  4. Keep MCP server startup scripts in version control. When an MCP connection fails, the cause is often a config drift between your local setup and what the server expects. A committed startup script makes the configuration reproducible.
  5. Test in a small folder first. Before running a workflow on 500 files, run it on 5. System errors surface faster and are cheaper to debug on a small sample.