BIP 342 — Validation of Taproot Scripts

BIP 342 (Validation of Taproot Scripts) defines tapscript, the script rules for Taproot script-path spends: signature checks use BIP 340 Schnorr, OP_CHECKMULTISIG is replaced by the batch-friendly OP_CHECKSIGADD, and a set of OP_SUCCESS opcodes are reserved so future opcodes can be added by soft fork. Repository status: Deployed.

Debate relevance: The OP_SUCCESS upgrade hooks are the standing answer to 'how would OP_CAT or CTV-style opcodes actually deploy'; that makes BIP 342 background material for nearly every covenant debate. Common misstatements: Confusing the Taproot trio: BIP 340 is the signature scheme, BIP 341 the output/spending rules, BIP 342 the script rules. Also, "multisig is gone in Taproot" — CHECKMULTISIG is replaced in tapscript by CHECKSIGADD, and key aggregation (MuSig2) offers an off-script alternative.