BIP 118 — SIGHASH_ANYPREVOUT for Taproot Scripts

BIP 118 (SIGHASH_ANYPREVOUT for Taproot Scripts) proposes new signature-hash modes that let a signature remain valid regardless of which specific output it spends, enabling protocols where transactions can be 'rebound' to updated states. Its flagship use case is LN-Symmetry (formerly eltoo), a Lightning channel design without penalty transactions. Repository status: Draft — not activated.

Debate relevance: A fixture of the covenant/soft-fork-wishlist debate and of Lightning-improvement discussions. Often bundled rhetorically with CTV and OP_CAT despite being a sighash flag, not an opcode. Common misstatements: "Eltoo/LN-Symmetry is live" — it requires BIP 118, which remains a Draft with no scheduled activation. Calling APO 'a covenant opcode' — it is a signature-hash mode; covenant-like behavior is an emergent use.