[Cowork] User-created skills stored in ephemeral session dirs — silently deleted on cleanup

This is a real problem — skills created in Cowork sessions are ephemeral by design but users expect them to persist.

Prevention: Stop hook to backup skills

#!/bin/bash
# backup-skills.sh — save skills before session cleanup
# TRIGGER: Stop

PERSISTENT_DIR="$HOME/.claude/skills"
mkdir -p "$PERSISTENT_DIR"

# Find and copy skills from ephemeral session dirs
for skill_dir in /tmp/claude-*/local_*/.claude/skills/*/; do
  if [ -d "$skill_dir" ]; then
    SKILL_NAME=$(basename "$skill_dir")
    if [ ! -d "$PERSISTENT_DIR/$SKILL_NAME" ]; then
      cp -r "$skill_dir" "$PERSISTENT_DIR/$SKILL_NAME"
      echo "📋 Backed up skill: $SKILL_NAME" >&2
    fi
  fi
done
exit 0

Manual recovery

After a Cowork session, check for ephemeral skill dirs before they're cleaned up:

find /tmp -path '*/local_*/.claude/skills/*/SKILL.md' 2>/dev/null
# Copy to persistent storage:
# cp -r /tmp/claude-XXX/local_YYY/.claude/skills/my-skill ~/.claude/skills/

Best practice

When creating skills in Cowork, immediately copy them to ~/.claude/skills/ or your project's .claude/skills/ directory before ending the session.

Cowork just doesn't seem like it's production-ready for a lot of reasons, and this is the latest for me. Adding what I found after spending a lot of tokens (and a lot of hours) chasing this down, because the skills storage model in Cowork is completely undocumented and the debugging cost is on paying customers.

What appears to actually be happening

Cowork does not load skills from ~/.claude/skills/. That's the path every bit of documentation and every intuition points to, and it is wrong.

The actual location on macOS is:

~/Library/Application Support/Claude/local-agent-mode-sessions/skills-plugin/<plugin-uuid>/<session-uuid>/skills/

That's where the Cowork Personal skills panel reads from. The directory is user-owned and writable (drwxr-xr-x, 755). But the timestamps on every SKILL.md in there match within seconds of each other, which points to Cowork re-hydrating the directory from some upstream source on session or app startup. I have not been able to identify the source from outside. The Claude.app bundle contains no skills (confirmed via find /Applications/Claude.app -type d -name skills), and the bundled data under ~/Library/Application Support/Claude/vm_bundles/ doesn't obviously contain them either.

Inside the Cowork sandbox, there are two skill mounts:

• /sessions/<id>/mnt/.claude/skills/ (read-only) maps to the skills-plugin/.../skills/ location above. This is what the Personal panel loads.
• /sessions/<id>/mnt/skills/ (writable) maps to the user's host ~/.claude/skills/. This is where any in-session edits land.

The user-observable consequence: edits made from inside a Cowork session to skills (via the Edit tool, the skill-creator skill, or anything else) are written to the host ~/.claude/skills/. Cowork never loads from there. So the edits appear to vanish the moment the session ends, even though they persist on disk in the wrong location for Cowork's purposes.

Why this matters as a customer issue

I pay for Claude. I built workflows on top of Cowork skills, assuming that editing a skill from inside the product would persist to the product. It doesn't.

None of this is documented. Nothing in the Cowork product surfaces the skills-plugin directory, warns that in-session edits go to a different location, or explains the re-sync behavior. The result is that any customer who tries to customize their Cowork skills will burn time and tokens chasing a ghost, and most of them will reasonably conclude the feature is broken and stop using it.

Requests

1. Document the skills storage architecture publicly. Specifically: where Cowork loads skills from, where user edits are written, whether the load location is managed or free, and how to persist customizations.
2. If skills-plugin/.../skills/ gets re-hydrated from an upstream source, say so explicitly and document how to contribute to that source.
3. Ideally, unify skill storage between Cowork and Claude Code CLI so that ~/.claude/skills/ is the single source of truth. The current split is confusing and wastes customer time.
4. At minimum, add a warning in the Cowork UI when a user edits a skill from within a session, noting that the edit may not persist to the location Cowork loads from.

Happy to share the specific paths, timestamps, and tool output from my investigation if that would help the triage pass. I'd just like to stop paying Anthropic to debug Anthropic's product.

Real hassle - even though I specified skills to be saved globally for all sessions, they were persisted into the ephemeral session. Manually copied into the central library which seems to work, but I have to double check skill versioning, etc. myself.