[BUG] Cowork: Custom uploaded plugin commands hang on / invocation — skills and natural language work fine

Description

Custom uploaded plugin commands hang indefinitely when invoked via /plugin-name:command-name in Cowork. The spinner appears and the session becomes unresponsive. However, the same commands work perfectly when triggered through natural language (e.g., typing "daily brief" instead of /recirq-chief-ops:daily-brief).

Skills from the same plugin load and fire correctly in conversation. Official marketplace plugin commands (e.g., Slack plugin's /channel-digest) work fine via / invocation.

Reproduction Steps

1. Create a plugin with .claude-plugin/plugin.json, commands/, and skills/ directories
2. Commands are short (10-15 lines) with only description and argument-hint in frontmatter
3. Upload as .zip via Cowork → Customize
4. Plugin installs successfully — skills appear and fire correctly in conversation
5. Type /plugin-name:command-name (e.g., /recirq-chief-ops:daily-brief)
6. Result: Session hangs — spinner appears, no response, requires force-quit or new session
7. Type the command name naturally (e.g., "run the daily brief") in a new session
8. Result: Works — Claude reads the command file, loads relevant skills, proceeds normally

Expected Behavior

/plugin-name:command-name should invoke the command the same way natural language does — read the command file and proceed.

Environment

• Platform: macOS (Apple Silicon)
• Plans tested: Pro and Teams — same behavior on both
• Claude Desktop: Latest version as of March 2026
• Plugin format: Standard .zip with .claude-plugin/plugin.json manifest

Notes

• Tested with commands of varying lengths (10 lines to 70 lines) — all hang via /
• Skills from the same plugin work perfectly (progressive loading, reference files, etc.)
• Official marketplace plugins' commands do NOT hang — only custom uploaded plugins
• The plugin structure follows the same format as anthropics/knowledge-work-plugins

🤖 Generated with Claude Code