BIP 65 — OP_CHECKLOCKTIMEVERIFY

BIP 65 (OP_CHECKLOCKTIMEVERIFY) is a consensus soft fork adding an opcode that makes an output unspendable until a specified absolute time or block height, activated in late 2015. It enables trust-minimized escrows, payment channels, and the timeout paths used in Lightning HTLCs. Repository status: Deployed.

Debate relevance: Cited in any timelock discussion and in Lightning architecture explanations. Often paired (and confused) with BIP 112. Common misstatements: Mixing up CLTV and CSV — BIP 65 is absolute locktime ('not before block X / time T'); BIP 112 (CHECKSEQUENCEVERIFY) is relative ('not until N blocks after confirmation').