Saving an enabled plugin threw away hot_reload_plugin's (ok, message), so a plugin that failed to load live read "Enabled, not loaded" with nothing more. Now: - a live-load failure is recorded with its reason, as a boot failure is, and logged; a later success clears it; - any save of an enabled plugin that isn't running tries to start it, not only the off-to-on toggle; - enabling one already running is a success, not a failure; - the plugin's page offers "Restart to load" while it is enabled and not running. Quart never marks the app as having served its first request, so register_blueprint after startup is allowed: hot-loading is not refused wholesale, as #6087 suspected. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>