IME when supplementing Lion's Mane I can enjoy rather large amounts, like multiple quad shots of espresso in a day, without getting too jittery and impatient/agro/short-tempered.

It also seems to largely eliminate the withdrawal symptoms of quitting caffeine cold-turkey. So I'll go on it hard for couple weeks, and as it starts becoming less fun/useful thanks to tolerance developing, I just stop. There's one day of lethargy just because I'm off stimulants, but no persistent headache/hangover, nothing. Dry out for a week or two before riding the caffeine train again.

Without Lion's Mane in the loop I get miserable multi-day headaches and hangover-like effects when I quit caffeine cold turkey.

This was all just accidentally discovered, but it's highly repeatable for me and honestly is the one interaction that clearly demonstrates Lion's Mane is not just a placebo.

It feels like caffeine is part poison, and Lion's Mane delivers the antidote for that undesirable part. Back when I first started using the combination this way, searches revealed that I wasn't the only one - there's even mushroom-adulterated coffee beans marketed now.