Wild mushrooms — Food safety facts
Do not feed · Cats · full breakdown on the linked food page
Never feed wild mushrooms — several species cause liver failure or death. Even store mushrooms are best cooked.
Short answer
Treat this as an emergency. Several species of wild mushrooms can cause rapid liver failure or death in cats, and it's impossible to identify safe ones at a glance. Even a small nibble can be dangerous. Contact your vet or an emergency clinic right away; if possible, bring a sample or photo of the mushroom. Do not wait for symptoms, as they can be delayed and severe.