Cowork: MCP tools (update_artifact/list_artifacts) disappear mid-session and do not return after app restart

Summary

In a Cowork session (remote cloud sandbox, Claude desktop app on macOS), the artifact tools exposed by the remote-devices MCP server were available and working, then silently disappeared from the tool manifest partway through the session. They did not return after refreshing the MCP servers or after restarting the desktop app. This left no way to publish or update an artifact for the rest of the session.

Environment

• Surface: Cowork (Claude desktop app), remote cloud sandbox session
• Host: darwin / arm64
• App version: 1.34493.1
• Electron: 42.9.2
• Node: 24.18.1
• Configured model: claude-opus-5

What happened

1. Earlier in the session, mcp__remote-devices__update_artifact and mcp__remote-devices__list_artifacts were present and I called them successfully three times. Each returned a success result (Artifact "<id>" updated on the connected desktop.).
2. Later in the same session, calling mcp__remote-devices__update_artifact returned: Error: No such tool available.
3. ToolSearch with select:mcp__remote-devices__update_artifact returns No matching deferred tools found.
4. RefreshMcpTools (both single-server and all-servers) reports remote-devices as status: refreshed, toolCount: 6, added: [], removed: [].

Remaining tools on remote-devices (6): get_device_info, device_bash, device_list_dir, device_stage_files, device_commit_files, device_request_folder_access.

Missing: create_artifact, update_artifact, list_artifacts.

Note that the file/shell tools on the same server continued to work correctly throughout — device_request_folder_access and device_commit_files both succeeded after the artifact tools vanished. So the connection itself is healthy; only part of the manifest is gone.

Steps tried

• RefreshMcpTools on remote-devices alone — no change
• RefreshMcpTools across all 16 servers — no added/removed on any server
• ToolSearch by exact tool name and by keyword — no match
• User restarted the Claude desktop app — tools still absent after restart
• Attempted a workaround via claude-in-chrome (see secondary issue below) — also unavailable

Secondary anomaly (possibly related)

RefreshMcpTools reports claude-in-chrome with toolCount: 22, and the tool schemas load successfully via ToolSearch. But calling mcp__claude-in-chrome__tabs_context_mcp returns:

Browser extension is not connected. Please ensure the Claude browser extension is installed and running...

So a server can report a healthy tool count while being functionally disconnected. That inconsistency may share a root cause with the missing tools above.

Expected behavior

Either tools stay registered for the lifetime of a session, or RefreshMcpTools / an app restart re-registers them. Silent partial loss of a server's manifest, with no error and no removed entry on refresh, gives no way to detect or recover from the problem.

Impact

The session's deliverable was an artifact the user needed to update and share. After the tools vanished there was no path to publish it. The workaround was writing the HTML to the user's Desktop via device_commit_files so they could republish manually.