[BUG] .skill file "Save and Replace" does not overwrite existing skill files in Cowork

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

[BUG] .skill file "Save and Replace" does not overwrite existing skill files in Cowork

Environment

• OS: macOS
• App: Claude Desktop (Cowork mode)
• Date: 2026-04-11

Description

When installing a .skill file that has the same name as an already-installed skill, clicking "Save and Replace" does not overwrite the existing skill's files. The old SKILL.md (and other files) remain unchanged on disk.

Steps to reproduce

1. Have an existing skill installed at ~/.claude/skills/wiki-curator/ (520 lines in SKILL.md)
2. Create an updated version of the skill with new content (549 lines, new sections added)
3. Package it as wiki-curator.skill (a zip with wiki-curator/SKILL.md inside)
4. Open the .skill file in Claude Desktop
5. Click "Save and Replace" when prompted
6. Check ~/.claude/skills/wiki-curator/SKILL.md — the old version is still there

Expected behavior

The .skill install should overwrite all files in ~/.claude/skills/wiki-curator/ with the contents of the .skill package.

Actual behavior

The install appears to succeed (no error), but the files on disk are unchanged. The old SKILL.md remains. The new content (added sections, changed text) is not present.

Evidence

Inside the .skill package (correct, updated):

Archive:  wiki-curator.skill
  Length      Date    Time    Name
---------  ---------- -----   ----
    22471  2026-04-11 22:12   wiki-curator/SKILL.md        <-- 549 lines, has "Autonomous operation" section
     2771  2026-04-11 22:12   wiki-curator/references/wiki-structure.md
    10879  2026-04-11 22:12   wiki-curator/scripts/detect_changes.py
    14086  2026-04-11 22:12   wiki-curator/scripts/generate_sitemap.py
---------                     -------
    50207                     4 files

Installed on disk after "Save and Replace" (old, unchanged):

~/.claude/skills/wiki-curator/SKILL.md   <-- still 520 lines, missing "Autonomous operation" section

Grep for content that should exist after install returns no matches:

grep -n "spidernic\|Autonomous\|pre-approved" ~/.claude/skills/wiki-curator/SKILL.md
# (no output — these strings exist in the .skill package but not in the installed file)

Additional notes

• The Cowork session VM sees the skill at /sessions/.../mnt/.claude/skills/wiki-curator/SKILL.md as read-only, confirming the old version persists
• This was tested with both a correctly-named package (wiki-curator/ inside the zip) and a misnamed one (wiki-curator-edit/). Neither resulted in the installed skill being updated.
• Multiple install attempts with "Save and Replace" had no effect

Workaround

None found from within Cowork. The user would need to manually delete ~/.claude/skills/wiki-curator/ and then re-install the .skill file.

Related issues

• #26172 — Skills not loading to Claude Cowork on Mac
• #26254 — SKILL.md files not mounted in container
• #26998 — Skills not saving/loading on Windows

What Should Happen?

The skill should replace the old one.

Error Messages/Logs

Steps to Reproduce

[BUG] .skill file "Save and Replace" does not overwrite existing skill files in Cowork

Environment

• OS: macOS
• App: Claude Desktop (Cowork mode)
• Date: 2026-04-11

Description

When installing a .skill file that has the same name as an already-installed skill, clicking "Save and Replace" does not overwrite the existing skill's files. The old SKILL.md (and other files) remain unchanged on disk.

Steps to reproduce

1. Have an existing skill installed at ~/.claude/skills/wiki-curator/ (520 lines in SKILL.md)
2. Create an updated version of the skill with new content (549 lines, new sections added)
3. Package it as wiki-curator.skill (a zip with wiki-curator/SKILL.md inside)
4. Open the .skill file in Claude Desktop
5. Click "Save and Replace" when prompted
6. Check ~/.claude/skills/wiki-curator/SKILL.md — the old version is still there

Expected behavior

The .skill install should overwrite all files in ~/.claude/skills/wiki-curator/ with the contents of the .skill package.

Actual behavior

The install appears to succeed (no error), but the files on disk are unchanged. The old SKILL.md remains. The new content (added sections, changed text) is not present.

Evidence

Inside the .skill package (correct, updated):

Archive:  wiki-curator.skill
  Length      Date    Time    Name
---------  ---------- -----   ----
    22471  2026-04-11 22:12   wiki-curator/SKILL.md        <-- 549 lines, has "Autonomous operation" section
     2771  2026-04-11 22:12   wiki-curator/references/wiki-structure.md
    10879  2026-04-11 22:12   wiki-curator/scripts/detect_changes.py
    14086  2026-04-11 22:12   wiki-curator/scripts/generate_sitemap.py
---------                     -------
    50207                     4 files

Installed on disk after "Save and Replace" (old, unchanged):

~/.claude/skills/wiki-curator/SKILL.md   <-- still 520 lines, missing "Autonomous operation" section

Grep for content that should exist after install returns no matches:

grep -n "spidernic\|Autonomous\|pre-approved" ~/.claude/skills/wiki-curator/SKILL.md
# (no output — these strings exist in the .skill package but not in the installed file)

Additional notes

• The Cowork session VM sees the skill at /sessions/.../mnt/.claude/skills/wiki-curator/SKILL.md as read-only, confirming the old version persists
• This was tested with both a correctly-named package (wiki-curator/ inside the zip) and a misnamed one (wiki-curator-edit/). Neither resulted in the installed skill being updated.
• Multiple install attempts with "Save and Replace" had no effect

Workaround

None found from within Cowork. The user would need to manually delete ~/.claude/skills/wiki-curator/ and then re-install the .skill file.

Related issues

• #26172 — Skills not loading to Claude Cowork on Mac
• #26254 — SKILL.md files not mounted in container
• #26998 — Skills not saving/loading on Windows

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude Code version 2.1.92.

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Other

Additional Information

I did it from the Claude App in MacOs