Plugins can deny resuming an agent, and Claude Code tells you when they do

What

Plugins are add-ons that extend Claude Code. Some plugins run hooks, small programs that run at set moments such as before or after a tool call. An agent is a separate worker Claude can start, and it can be paused and later resumed or woken by queued messages.

• A plugin can now deny resuming an agent, or waking one because messages are waiting for it (deniedByPlugin).
• When a resume is denied, the waiting message is dropped and the wake is not retried. The failure is reported as not_reachable.
• Resuming a local agent task that a plugin denies now stops there and shows a notification instead of continuing.
• Failed delivery of queued messages to an agent now uses a shared notification instead of the old inline warning "Failed to deliver queued message to agent", with a new branch for plugin denials.
• Notices about skipped hooks gain "call refused" and "result withheld" versions.
• When a plugin withholds the result of a PostToolUse hook, which runs after a tool call succeeds, the notice now reads "ran, and a plugin withheld its result".

Why

Plugins now have more say over when agents run again and what results Claude sees. If an agent does not pick up a message you sent it, a plugin may have blocked the resume, and the notification tells you so.