Function hookOutput

hooks_src/external-action-gate.js:42–54

(hookName, action, message, data = {})

const CITADEL_UI = process.env.CITADEL_UI === 'true';

// For CITADEL_UI (desktop app): structured JSON to stdout.
// For CLI: human-readable message to stderr — Claude Code includes stderr in the
// hook error that the agent reads, so this is what surfaces as the block reason.
function hookOutput(hookName, action, message, data = {}) {
  if (CITADEL_UI) {
    process.stdout.write(JSON.stringify({
      hook: hookName,
      action,
      message,
      timestamp: new Date().toISOString(),
      data,
    }));
  } else {
    process.stderr.write(message);
  }
}