The pool normally holds exactly the round's bet outputs and the payout spent them all for
exactly the pool amount, so it had no change output: bump_fee could never accelerate it,
and a payout stuck in a mempool (never abandoned while a server knows it) kept the round in
`paying_out` and the whole lottery stopped.
- build_payout_transaction always has three outputs: winner, fee address, and a bump reserve
of max(DUST_LIMIT_SATS, estimate_vsize(inputs, 3) * 10 sat/vB) paid to the reserve address
m/84'/746'/0'/1/0. The reserve comes out of the platform's 30%, the network fee still out
of the winner's 70%. Input value beyond winner share + commission (only rounds opened
before the per-round pool address) is folded into the reserve output if >= dust, left to
the network fee otherwise. `change_address` is replaced by `reserve_address`.
- `rounds.bump_reserve_sats` (Alembic e5a91c3d7b26, plain add_column) is written with the
payout intent before the broadcast; /admin/rounds returns it.
- bump_fee takes the increase from the reserve output for a payout
(_find_reducible_output; a payout already in flight with a change to the pool still falls
back to that), never from the winner or fee-address outputs.
- payout_config_problem / rounds_can_open (RND-40): a bet amount and fee rate under which a
round of 1 or of MAX_PARTICIPANTS_PER_ROUND participants could not cover the network fee,
the reserve and dust outputs opens no round (lottery_configured=false); PUT /admin/config
refuses such a bet amount or fee rate with 422 config_not_payable, judged on the resulting
values, since the payout reads the fee rate live.
Ambiguity resolved: the reserve output and any excess input are one output (RND-23 says one
output to the reserve address), and bump_reserve_sats records that output's initial value.
DAT-22's "abandon clears all amounts" stays with B-96.
Tests changed because the spec changed: the four test_payout_builder tests asserted the old
two/three-output shape with change to the pool and the fee address receiving the whole 30%;
the whitespace fee_address test now spells out the amounts rounds_can_open reads. New: reserve
sizing, payout with 1 and with 400 participants (inputs = outputs + fee to the satoshi),
exact commission/reserve/dust boundary, excess folded or left to the fee, a real payout bumped
out of its reserve with the other outputs byte-identical and bumped five times, the old
reserve-less shape still raising RbfError, the scheduler output addresses and recorded
amounts, payability boundaries found independently by bisection, no round / unconfigured flag
for an unpayable config, a round in progress surviving it, PUT /admin/config refusals and the
migration column. Mutation-checked: dropping the reserve lookup in bump_fee and the payability
check in rounds_can_open each fail tests.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
The payout has to spend one pool UTXO per bet, so reusing MAX_TX_INPUTS (50)
for it made any round past ~50 players unpayable: select_utxos raised
too_many_inputs, the round stayed "paying_out" retrying every 60s forever, and
since no new round may open while one is active, the whole lottery stopped with
the pool stuck. The cap was being enforced on the payout side, i.e. discovered
once the money was already committed and there was no way back.
Two halves:
- select_utxos takes the cap as a parameter. Bets and withdrawals keep
MAX_TX_INPUTS = 50, which protects a user from a fee that eats into the amount
they are moving; the payout uses MAX_PAYOUT_TX_INPUTS = 500, where that
argument doesn't apply — 400 inputs at 1 sat/vB cost ~0.00027 PLM out of the
winner's 70% share. What actually bounds it is relay policy: 500 inputs is
~34 kvB against the 100 kvB standardness limit, and signing that many measures
~0.4s, once per round, inside a background task.
- place_bet refuses the 401st bet with a new round_full error (translated into
all 7 languages), so "a round can always be paid out" is an invariant checked
before any money moves. MAX_PARTICIPANTS_PER_ROUND sits below the input cap to
leave the payout headroom for pool change from earlier rounds, and counts every
participant row rather than only confirmed ones, since a failed bet frees a slot.
A round already wedged past the old cap now pays out on the next retry tick.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
BIP84 derivation of per-user P2WPKH addresses and the pool address from
the encrypted master xprv (app/wallet/hd.py, keystore.py), the PLM
mainnet chain params (plm_network.py), and PSBT construction for bets/
payouts/withdrawals with change-output and fee-estimation logic
(psbt_builder.py).
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
davideandClaude Sonnet 5.5