What
A new hook event fires when a subagent finishes, complementing the existing Stop event which fires when the main conversation agent finishes. The hook output's additionalContext field is delivered back to the subagent so it can continue and act on the feedback.
Details
- Event name:
SubagentStop - Available for command-based and prompt-based hooks
- Hook output schema:
{ hookEventName: "SubagentStop", additionalContext?: string } additionalContextis non-error feedback; the subagent continues execution so it can act on it- Prompt-based hooks now also explicitly support
SubagentStopalongsideStop,UserPromptSubmit, andPreToolUse
Evidence
Schema literal for the new event (search for "Hook-specific output for the SubagentStop event")
Strings lifted out of the shipped bundle, so the claim above can be checked against them.