Plugin bin/ on PATH (Claude Code): claude.ai and Cowork refuse a plugin with a bin/ directory.
userConfig prompts at install time (Claude Code): deferred.
PostToolBatch, additionalContext on Stop, and exec-form args (Claude Code): no current use.
MessageDisplay (Claude Code): it only changes what the terminal shows. It cannot block a message or send text to Claude, so text between tool calls stays unchecked.
TaskCreated (Claude Code): the PreToolUse hook on TaskCreate reads the same subject and description.