For this particular error, the standard suspects are double length-prefixing or by accident together with the annex. Double-prefixing is the one I see most frequently.
The management block needs to be one witness stack ingredient, uncooked bytes. Format:
<1 byte: leaf_version | parity>
<32 bytes: inside key>
<32 bytes × depth: merkle path hashes>
(parity comes from the tweaked pubkey’s y-coordinate odd/even—you may have it for those who derived Q accurately.) No compactSize inside. No splitting.
Your ser_string name — that is the issue. Witness serialization already length-prefixes every stack merchandise. So whenever you do ser_string(control_block)you are including an additional prefix. The node checks (len - 33) % 32 == 0; one additional byte and that examine fails, therefore Invalid Taproot management block dimension. Simply concatenate:
control_block = b''.be part of([
bytes([leaf_version | parity]),
internal_pubkey,
merkle_hash_1,
merkle_hash_2
])
witness_stack = [preimage_or_sig, script, control_block]
Splitting into separate parts — additionally flawed. The node takes the final ingredient because the management block. In the event you cut up, it solely sees hash2 (32 bytes) or no matter is final, so the scale examine fails. You too can hit bad-witness-nonstandard earlier than script validation, relying on coverage.
Helpful approach to consider it: layer 1 is BIP 341’s management block format (33+32m bytes, validated by that (len-33)%32==0 examine). Layer 2 is witness encoding (size prefix per ingredient). You solely outline layer 1; layer 2 is computerized. Do not combine them.
If dropping ser_string and utilizing a single blob fixes it, that was the problem. I’ve reproduced this on regtest—toggle solely the management block construct and the conduct matches.
