SIGHASH_ANYPREVOUT (OP_APO), proposed in BIP-118, modifies Bitcoin’s signature hashing to allow inputs to commit to scriptPubKey without specific UTXO, enabling efficient off-chain protocols like eltoo. It’s been tested on signet since 2022, with active community discussion for Lightning Network enhancements.

OP_CAT, proposed in BIP-347 and activated on signet in 2024, re-enables concatenation of stack elements in Bitcoin Script, previously disabled by Satoshi Nakamoto. It supports complex smart contracts, covenants, and trustless bridges, with significant on-chain usage (74K transactions).

OP_CHECKSIGFROMSTACK (OP_CSFS), proposed in BIP-348 in November 2024, verifies signatures against stack-provided public keys and arbitrary messages, enhancing script flexibility for dynamic transactions and covenants. Actively discussed for vault and oracle use cases.

OP_CHECKTEMPLATEVERIFY (OP_CTV), proposed in BIP-119, is a covenant opcode enforcing transaction structure constraints, enabling payment channels, vaults, and congestion control. Actively discussed since 2020, it’s tested on signet with growing developer support for activation.

OP_TXHASH, a proposed opcode, enables flexible transaction introspection by hashing specific transaction fields, supporting covenants and smart contracts. Actively discussed as an alternative to OP_CTV and OP_CSFS for generalized scripting.

OP_VAULT, proposed in BIP-345, introduces specialized opcodes (OP_VAULT, OP_VAULT_RECOVER) for secure custody vaults, allowing delayed spending with recovery paths. Combined with OP_CTV, it enhances vault functionality and is actively discussed for activation.

Schnorr Signatures, activated in November 2021 via BIP-340 as part of Taproot, enable signature aggregation, improving Bitcoin’s efficiency, privacy, and complex script support.

SegWit, activated in August 2017 via BIP-141, restructures Bitcoin transaction data to increase block capacity, fix transaction malleability, and enable Layer 2 solutions like Lightning.

Taproot, activated in November 2021 via BIPs 340-342, introduces Schnorr signatures, Pay-to-Taproot (P2TR) outputs, and Tapscript, enhancing privacy, efficiency, and smart contract capabilities.

Taproot Leaf Update Verify (TLUV), an experimental opcode proposal, allows dynamic modification of Taproot script trees, enabling advanced covenants and fraud-proof smart contracts. Under active discussion for flexible scripting.