-- +goose Up

-- What the BOOK had already cost before this attempt started.
--
-- The engine's `committed_usd` is a lifetime total per BOOK — `SELECT SUM(committed_usd) FROM spend
-- WHERE book_id = ?` — not the cost of the run that just ended. Settling with it verbatim charges an
-- account for every earlier run of the same book again, every time. So the attempt records where the
-- meter stood when it began, and settlement charges the DIFFERENCE.
--
-- Null means the baseline was never captured, which is not a state any current path produces: the
-- spawn refuses to start an attempt whose baseline it could not read, precisely because a paid run
-- that cannot be billed correctly is worse than a run that starts a sweep later. It stays nullable
-- for the rows that predate this column.
alter table run_attempts add column spend_baseline_micro_usd bigint;

-- +goose Down
alter table run_attempts drop column spend_baseline_micro_usd;