@chaizhenhua By the design last year, the pagespeed_body_filter will copy the content to proxy fetch. If you call the top_body_fitler, this pagespeed body_filter will be called again. It may be in an infinite loop between this one and proxy fetch.

But I think your question is reasonable. You could do an conditional judgement in this pagespeed body filter. If it's the optimized response, you could just ignore it.