sessiondata.img). Second most common: a scheduled task depends on a local process that stops when your machine sleeps. Both are fixable in minutes.Claude Cowork stops working for a small set of predictable reasons. This page covers the five most common failures, how to diagnose which one you’re hitting, and the exact fix for each.
Error 1: “useradd failed: exit status 12”
What it means: The Cowork VM’s internal disk (sessiondata.img) is full. No new sessions can be provisioned.
Fix: Quit Claude Desktop. Move sessiondata.img from %APPDATA%\Claude\vm_bundles\claudevm.bundle\ (Windows) or ~/Library/Application Support/Claude/vm_bundles/claudevm.bundle/ (macOS) to your Desktop. Relaunch Claude Desktop — it recreates a fresh image. Full walkthrough: Claude Cowork useradd Failed Error Fix.
Error 2: Scheduled Tasks Stop Running
What it means: Tasks that were running on schedule suddenly stop firing. Often appears as tasks last running a few days ago with no new entries.
Causes: Machine went to sleep, Claude Desktop was quit, or the local runner process died. Cowork tasks require Claude Desktop to be open and running on an active machine. They are not fully cloud-hosted — they depend on the local Cowork environment being live.
Fix: Reopen Claude Desktop and manually trigger one task to verify it runs. For tasks that need to run reliably without the machine being awake, move them to a GCP Cloud Run cron job or a cloud VM instead of Cowork’s local scheduler.
Error 3: MCP Tools Not Available in Cowork
What it means: Cowork tasks can’t access Notion, Gmail, or other connected services that work fine in Chat.
Fix: MCP servers must be configured in claude_desktop_config.json — the same config file Claude Desktop uses. If an MCP server appears in Chat but not in Cowork, verify it’s listed in the desktop config, not just the web interface. Restart Claude Desktop after any config changes.
Error 4: File Access Denied or Path Not Found
What it means: A Cowork task fails trying to read or write a file that should be accessible.
Fix: Cowork’s VM mounts specific directories from your machine. If the file is outside a mounted path, Cowork can’t reach it. Check that the file path is within your configured working directories. On Windows, path separator issues (\ vs /) inside the Linux VM can also cause this — use forward slashes or escape backslashes in task prompts.
Error 5: Tasks Run but Produce Wrong Output
What it means: Cowork is running but the results are stale, wrong, or missing context from previous runs.
Fix: Cowork tasks don’t have memory of previous runs by default. If your task depends on knowing what happened last time — what was published, what changed — you need to build that context explicitly into the task prompt, typically by reading a log from Notion or a local file at the start of each run. The task prompt is the only persistent instruction; Claude doesn’t remember prior task outputs.
Why did Cowork tasks stop running overnight?
Cowork requires Claude Desktop to be running on an active machine. If your computer slept, hibernated, or Claude Desktop was closed, scheduled tasks won’t fire. For always-on reliability, route tasks through a cloud runner instead.
Why can Cowork not find my files?
Cowork’s Linux VM only has access to directories you’ve configured as mount points. Files outside those paths are invisible to the VM. Verify your working directory configuration in Claude Desktop settings.
Does Cowork work on Windows?
Yes, Cowork is available on both Windows and macOS via Claude Desktop. The VM behavior and file paths differ slightly between platforms but the core functionality is the same.
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