Browsing early Taproot transactions, I came across this one (block 709,911, ~280 blocks after Taproot activation):
https://mempool.space/tx/ef72502f5d2509f519be33304e385bdf9d1bed5e4cd19f7a254700299db2ba91
What caught my eye:
- It’s a P2TR keypath spend, single input, single output, dust-level
amount (1943 → 1803 sats) - The witness signature is 65 bytes ending in 0x02 — i.e.,
SIGHASH_NONE (not SIGHASH_NONE|ANYONECANPAY which is 0x82) - nSequence is 0x9f (= 159), which under BIP68 would imply a relative
timelock of 159 blocks
Plain SIGHASH_NONE (without ANYONECANPAY) on a 1-input-1-output transaction seems strange to me — the signer is essentially saying “I authorize spending this UTXO regardless of where the output goes,” but there’s only one output. Anyone seeing this in mempool could in principle replace the output and rebroadcast.
Questions:
- Is there a known wallet or protocol that signs P2TR keypath with plain SIGHASH_NONE (0x02)? I’d expect 0x82 (NONE|ANYONECANPAY) for any kind of cooperative signing flow, not 0x02 alone.
- Is the combination with the unusual nSequence=0x9f indicative of a specific test framework or early development tool from late 2021?
Curious whether this is a known pattern or just a one-off oddity.
