ScriptPubKey scripts containing OP_VERIF (0x65) or OP_VERNOTIF (0x66) are permanently unspendable because these opcodes unconditionally abort script execution — even when they appear inside an unexecuted OP_IF branch.

Abstract

Bitcoin's script interpreter has a small set of opcodes that cause immediate, unconditional failure regardless of the execution context. OP_VERIF (0x65) and OP_VERNOTIF (0x66) are two such opcodes. Unlike most disabled opcodes (which only abort when actually executed), the interpreter checks for these two opcodes before the branch-execution test — meaning that even if the opcode sits inside an OP_IF 0 OP_ELSE ... OP_ENDIF branch that would never be reached, its mere presence in the script causes the transaction to be invalid.

Any output whose scriptPubKey contains one of these bytes (as an opcode, not as push data) can never be spent.

Detection

The helper containsAbortOpcode walks the script byte-by-byte, correctly skipping over push-data payloads so that 0x65 or 0x66 bytes embedded inside data pushes do not produce false positives.

function containsAbortOpcode(hex) {
    let pos = 0;
    while (pos + 1 < hex.length) {
        const opcode = parseInt(hex.slice(pos, pos + 2), 16);
        pos += 2;
        if (opcode === 0x65 || opcode === 0x66) return true;
        if (opcode >= 0x01 && opcode <= 0x4b) {
            pos += opcode * 2;         // skip N data bytes
        } else if (opcode === 0x4c) {  // OP_PUSHDATA1
            if (pos + 2 > hex.length) break;
            const len = parseInt(hex.slice(pos, pos + 2), 16);
            pos += 2 + len * 2;
        } else if (opcode === 0x4d) {  // OP_PUSHDATA2 (little-endian)
            if (pos + 4 > hex.length) break;
            const len = parseInt(hex.slice(pos, pos + 2), 16) +
                        parseInt(hex.slice(pos + 2, pos + 4), 16) * 256;
            pos += 4 + len * 2;
        } else if (opcode === 0x4e) {  // OP_PUSHDATA4: break for safety
            break;
        }
    }
    return false;
}

This check is placed between Proposal 004 (OP_RETURN) and the outer else block (Proposals 005+), so it is evaluated before any per-script-type analysis.

Scope Notes

• Only OP_VERIF and OP_VERNOTIF are covered here. Other unconditionally-failing opcodes (e.g. OP_RESERVED, OP_VER) require execution context and are not included.
• The parser handles OP_PUSHDATA1 and OP_PUSHDATA2 to avoid false positives from data payloads. OP_PUSHDATA4 (0x4e) terminates the scan early; any script using OP_PUSHDATA4 to encode a payload containing 0x65/0x66 would itself be non-standard for other reasons.