Where errands come from
Errands arrive at a configurable rate (the default is 8 per sim-minute) as a per-tick spawn probability, so arrivals are irregular in a natural way. Each errand is a ferry from a random reed bed to a random delivery dock. The reward is 14 credits plus 0.9 per cell of distance plus up to 10 of noise, and it opens an auction with a 4.5 second window.
Bidding down
This is a procurement auction: the frogs are selling their labor, so the lowest bid wins. The first bidder opens just under the reward. After that, each round a frog undercuts the standing best bid by its personal step, between 1 and 3 credits depending on personality. No frog ever goes below its own bid floor, and each keeps exactly one standing bid per auction.
Timing is part of strategy. The sniper does not enter at all until 55% of the window has passed, then bids into whatever spread is left. On the pond you can watch this as the bid fan: lines from each bidder to the errand, tightening as the window runs out.
Clearing
When the window closes, the lowest standing bid from a frog that is still idle wins. (A frog that won a different auction a second earlier is skipped, and the next-cheapest bid takes it.) The winner gets the errand and a deadline of roughly three times its estimated travel time plus 30 seconds. Payment lands on delivery, not on award: a frog that wins at 17 credits and fails collects nothing.
Every bidder learns something from the result. The learner frog adjusts its margin after each auction it participated in, up on wins, down on losses. The details are on the cost model page.
When nobody bids
An errand can close with no takers, usually because everyone is busy, low on stamina, or the price is below everyone's floor. The market's answer is to raise the price: the reward is multiplied by 1.2 (capped at 90 credits) and the errand is relisted with a fresh 3 second window. An errand that stays unclaimed for 150 seconds total finally expires. In practice the sweetener finds a buyer well before that, which is the point: scarcity shows up as price, not as a stuck queue.
Failure and relisting
An assigned errand fails in two ways: the deadline passes, or the carrier's stamina drops below 5% and it has to abandon the job. Either way the frog pays a 5 credit fine, loses 4 reputation, and the errand goes back on the market at 1.15 times its reward. The premium on a relisted errand usually finds a taker fast.