Parsing the leaf version from control block:

TapLeaf:

- leaf_version: 1 byte

- script: variable length

TapLeaf hash:
hash = tagged_hash("TapLeaf", leaf_version_byte + compact_size(len(script)) + script)

Control block structure:

- (leaf_version | parity_bit): 1 byte
  └── High 7 bits: leaf version (e.g., 0xc0 >> 1 = 0x60)
  └── Low 1 bit: parity of the internal key's y-coordinate

- internal_pubkey: 32 bytes

- merkle_path: 0 to 128 × 32 bytes (the branch hashes to the root)
python
# Parsing the leaf version from control block:
control_block = witness_stack[-1]  # Last item (before annex if present)
leaf_version = control_block[0] & 0xfe  # Mask off the parity bit
# leaf_version should be 0xc0 for standard Tapscript

0xc0  → BIP 342 Tapscript (the only currently defined version)
0x00  → Reserved (would be confusable with OP_0, avoided)
0x02–0xbe (even values) → Reserved for future use
0xc2–0xfe (even values) → Reserved for future use

Future possibility:

Leaf version 0xc2: "Tapscript v2"

- Could re-enable OP_CAT natively (not via OP_SUCCESS soft fork)

- Could introduce new numeric ranges (5-byte script numbers)

- Could change stack item size limits

- Could add new opcodes without the OP_SUCCESS mechanism

Leaf version 0xc4: "Simplicity" (the functional scripting language)

- A completely different language with formal verification properties

- Already designed to be deployed via a Taproot leaf version

# Building a TapLeaf in Python (using python-bitcoinlib or similar):
def make_tap_leaf(script_bytes, leaf_version=0xc0):
    """Create a TapLeaf with the specified version."""
    return tagged_hash(
        "TapLeaf",
        bytes([leaf_version]) + compact_size(len(script_bytes)) + script_bytes
    )