`if change > 0` created a change output for any leftover at all. Below the
P2WPKH dust threshold (294 sat: the output's 31 vbytes plus the 67 needed to
spend it, at the 3000 sat/kvB dust relay fee) relaying nodes reject the whole
transaction, so the bet or withdrawal failed at broadcast with an error the user
could do nothing about — and which arrived as a 500 (BUGS.md B-06).
Sub-dust change now goes to the fee in both builders, and a sub-dust
recipient/winner/commission amount is refused up front with its own error code.
The fee estimate already assumed two outputs, so dropping one never underpays.
Cross-checked against PalladiumWallet, the source of truth for PLM parameters:
it delegates to NBitcoin's TransactionBuilder (same 294 sat threshold) and has
an explicit test — Un_resto_sotto_la_soglia_dust_viene_assorbito_nella_fee —
asserting the same behaviour, so both the value and the semantics match the
reference implementation.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
davideandClaude Opus 5
b4d70385a6