a node's mempool is configurable as a portion of the machines RAM. there's no hard limit except infrastructure a node is running on
Discussion
Indeed. I recall mempool.space had to increase their official node's mempool limit since transactions weren't showing up with the default limit.
so which "indeed" is it? your two seem mutually exclusive to me. is there a hard limit or is it configurable?
https://bitcoincore.org/en/doc/29.0.0/rpc/blockchain/getmempoolinfo/
I think our wires are getting crossed. When Bill said "mempool already has a hard cap", he meant the size of blocks is limited, by consensus. The size of the mempool (the *entire* mempool, including the backlog) is configurable per-node.