Author: Will Tygart

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.

Claude Cowork Error Quick-Reference

Claude Cowork issues: quick diagnosis

Claude Cowork Error Quick-Reference

Claude Cowork Error Quick-Reference

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.

Anthropic now offers two distinct modes of working with Claude — the familiar chat interface and Cowork, a persistent task and agent environment. They look similar but serve fundamentally different purposes. Using the wrong one creates friction; knowing which to reach for first saves significant time.

What Cowork Actually Is

Cowork is a persistent agent environment inside Claude Desktop. It gives Claude access to your local filesystem, a sandboxed Linux VM with bash execution, your installed MCP servers, and a scheduler. Tasks you set up in Cowork can run on a schedule — daily, weekly, whenever you trigger them — without you being in the conversation. Claude operates autonomously against your instructions until the task is done.

What Claude Chat Actually Is

Claude Chat (claude.ai or the Claude app) is a stateless, interactive conversation interface. Each session is fresh. Claude has no persistent memory across sessions beyond what you’ve configured in memory settings. It’s optimized for real-time back-and-forth: you ask, Claude responds, you refine. The bash environment in Chat (used for file operations and code execution) is sandboxed and resets between sessions.

Side-by-Side Comparison

When to Use Claude Chat

Chat is the right tool when you’re actively involved in the work — drafting, editing, analyzing, strategizing. If you need to go back and forth, refine an output, or make judgment calls mid-task, Chat’s interactive model is faster and more natural. It’s also better for any task that’s genuinely one-off: you do it once, you’re done, there’s nothing to schedule or automate.

Chat also runs in the cloud, meaning it doesn’t compete with your machine’s other processes and doesn’t run into the local VM disk limitations that Cowork can hit with heavy workloads.

When to Use Cowork

Cowork shines for work that should happen without you: daily newsroom publishing, weekly SEO reports, nightly data syncs, any pipeline that follows the same steps every run. If you find yourself doing the same Claude Chat session more than twice a week, it’s a candidate for a Cowork task.

Cowork also makes sense for tasks that need direct access to files on your machine — reading from a local folder, processing downloads, interacting with local applications — since Chat requires you to explicitly upload files each session.

Known Cowork Limitation to Be Aware Of

Cowork runs on a local VM (the sessiondata.img file) with a fixed 8.5GB disk. Heavy users with many skills installed will periodically hit a disk-full error that prevents new sessions from launching. This is a known bug (GitHub #30751) with a manual workaround. See Claude Cowork useradd Failed Error: How to Fix It for the fix.

If every Cowork task is failing with useradd: cannot create directory /sessions/friendly-youthful-thompson or a similar error, your Cowork VM’s internal disk is full. This is not something you broke — it’s a known Anthropic bug that affects power users consistently. Here’s exactly what’s happening and how to fix it in under two minutes.

What’s Causing the Error

Cowork runs on a local VM with a fixed 8.5GB disk image called sessiondata.img. Every Cowork conversation creates a new directory under /sessions/<name>/ inside that VM and caches all your installed plugins and skills there. Those directories are never cleaned up automatically. Once the disk fills — roughly 80 sessions for light users, 40–50 sessions for users with many skills installed — every new task fails immediately with a useradd error. The session simply can’t be provisioned.

If you have 20+ skills installed (the Tygart Media stack runs 40+), you’ll hit the cap significantly faster than the average user.

The Fix: Move the Image File

The fix is the same on macOS and Windows: move sessiondata.img out of its location so Claude Desktop rebuilds it fresh on next launch.

Windows

Quit Claude Desktop completely. Open Run (Win + R), paste this path and press Enter:

Find sessiondata.img and move it to your Desktop as a backup. Relaunch Claude Desktop — it will recreate a fresh image automatically. Your first Cowork session after the reset may take slightly longer while plugins reinstall.

macOS

Quit Claude Desktop. In Finder, press Cmd + Shift + G and go to:

Move sessiondata.img to your Desktop. Relaunch Claude Desktop.

What Gets Wiped vs What’s Preserved

How Often Will You Need to Do This?

Until Anthropic ships automatic session cleanup, this is a recurring task. With a heavy skill load, plan on running the fix every 4–6 weeks or whenever you see the useradd error return. Setting a calendar reminder is the most reliable approach.

The Longer-Term Fix: Move Heavy Operations Off Cowork

The root cause is that Cowork was designed for lighter, conversational task automation — not running dozens of skills across many parallel sessions. If you’re running content pipelines, batch WordPress operations, or multi-step automation workflows, moving those operations to a GCP Cloud Run cron job or Compute Engine VM eliminates the local VM bottleneck entirely. Cowork’s local sandbox competes for your machine’s resources; GCP runs isolated, always-on, and never fills up your laptop’s disk.

Every few months, a new wave of “Claude 5 release date” searches spikes — and it makes sense. Anthropic moves fast, the gaps between major generations have been shortening, and early signals like Vertex AI log leaks have given the community something to speculate on. Here’s an honest breakdown of what’s confirmed, what’s leaked, and what the pattern suggests.

Claude 5 Expected Specs vs Current Models (June 2026)

Claude 5 specs are unconfirmed as of June 9, 2026. All information is based on industry signals and Anthropic research publications — not official announcements.

What’s Confirmed About Claude 5

As of April 2026, Anthropic has not officially announced Claude 5 by name in any public release notes, API documentation, or blog post. The company’s official model table shows the Claude 4.x family as current. No countdown page exists. No API model string beginning with claude-5 has appeared in public documentation.

What is confirmed: Anthropic is actively deprecating the original Claude 4.0 models (retiring June 15, 2026), recommending migration to Claude Sonnet 4.6 and Opus 4.6. This is a routine generational housekeeping move, not a Claude 5 announcement.

The Evidence For a Q2–Q3 2026 Release

The strongest early signal came in early February 2026, when a model identifier — claude-sonnet-5@20260203 — appeared briefly in Google Vertex AI error logs. Independent sources cross-verified the leak, and the codename “Fennec” circulated alongside claimed benchmark scores of around 80.9% on SWE-bench Verified, compared to Opus 4.6’s current scores.

Beyond the leak, the pattern is consistent: Anthropic has released a new major model generation roughly every 12–14 months since Claude 3. Claude 4.5 (the highest-capability 4.x model) reached 77.2% on SWE-bench Verified. A Claude 5 release that clearly exceeds that — not just marginally — would justify a major version bump and align with Anthropic’s stated commitment to releasing models that represent genuine capability leaps, not incremental updates.

Anthropic’s Release Pattern

A 12-month gap from the Claude 4 launch (May 2025) points to May–July 2026 as the earliest likely window. Anthropic has been explicit that they won’t rush a release — Claude 5 would need to clearly establish a new capability tier to justify the version number.

What Claude 5 Is Expected to Improve

Based on leaked benchmark data and Anthropic’s public research direction, the Claude 5 generation is expected to push forward on: extended thinking and multi-step reasoning (building on the chain-of-thought work in Claude 3.5+), larger context handling, improved agentic reliability for long-horizon tasks, and faster inference at the Sonnet tier. Pricing is expected to follow the established pattern — Claude 5 Sonnet likely priced at or below current Opus 4.6 rates while outperforming it on most tasks.

The Current Models Are Excellent — Don’t Wait

If you’re evaluating whether to build on Claude now or wait for Claude 5, the answer is build now. Claude Sonnet 4.6 and Opus 4.6 are capable, stable, and well-documented. The 4.x API will remain live well after Claude 5 launches — Anthropic maintains parallel model availability for enterprise predictability. Waiting costs you months of production time for a model that may arrive on an uncertain schedule.

For current model specs and API strings, see Claude API Model Strings — Complete Reference. For pricing on current models, see Claude AI Pricing: Every Plan Explained.

If you are still running the original Claude Sonnet 4 or Opus 4 model strings in production, you have a hard deadline: June 15, 2026. After that date, calls to claude-sonnet-4-20250514 and claude-opus-4-20250514 return an error — there is no automatic failover to a newer model. Here is exactly what is retiring, what to migrate to, and the breaking changes to plan for.

Claude Model Lifecycle Status (June 2026)

Alias trap: the dateless aliases claude-opus-4-0 and claude-sonnet-4-0 resolve to the retiring ...-20250514 snapshots — they go offline too. Claude Opus 4.6, Opus 4.7, Opus 4.5, and Sonnet 4.5 are separate, still-active models and are not affected by this retirement.

What’s Being Deprecated

Anthropic is retiring the original Claude 4.0 model versions — the ones that shipped in May 2025. These are distinct from the 4.x versions released since. The specific API strings going offline:

These are not the latest Claude 4 models. If you have been on Anthropic’s recommended alias endpoints, you are likely already on a current model. This deprecation primarily affects teams that pinned the specific 20250514 version strings in their API calls.

What to Migrate To

Anthropic’s recommended replacement within the same tier:

These are major upgrades, not just version bumps. Both current models ship a 1 million token context window at standard API pricing (no long-context premium), and the Opus line has advanced two full generations — 4.6, then 4.7, then 4.8 — since the original 4.0. For the most capable tier overall, Anthropic now offers Claude Fable 5 (claude-fable-5), a new tier that sits above Opus.

Breaking Changes When You Migrate

Moving off the original 4.0 strings is usually a model-ID swap, but the current models removed several request parameters. If you are jumping to Opus 4.8 or Fable 5, plan for these — each returns a 400 if left in:

On Sonnet 4.6 and Opus 4.6 the fixed thinking budget is deprecated but still functional; on Fable 5, Opus 4.7, and Opus 4.8 it is fully removed. A global search for 20250514 in your codebase is the fastest way to find every call that needs changing.

How This Fits the Claude Model Timeline

What If You Don’t Migrate Before June 15?

API calls to claude-sonnet-4-20250514 or claude-opus-4-20250514 after June 15, 2026 will return errors. There is no automatic failover to a newer model — the call simply fails. If you have any production systems, scheduled jobs, or automated pipelines using these version strings, audit them now. A global search for 20250514 in your codebase is the fastest way to find your exposure.

What Comes After Claude 4.x

The “after” is already here. Since the original Claude 4.0 launched in May 2025, the Opus line has shipped 4.5, 4.6, 4.7, and now 4.8, and Anthropic introduced Claude Fable 5 as a new top tier above Opus. As of June 2026 there is no separately branded “Claude 5” generation; the cadence has been steady point releases within the 4.x Opus, Sonnet, and Haiku families, plus the new Fable tier. The practical takeaway: migrating off the retiring 4.0 strings puts you on models that are materially more capable, with a 1M-token context window as the new baseline.