How Do You Control AI Coding Agent Spend?

Short answer. Controlling AI coding agent spend means setting a hard ceiling on tokens, dollars, or tool calls for a given change and having the tool itself refuse to continue once that ceiling is crossed — not just a dashboard that reports spend after the fact. A number you can look up after the run is observability. A number that blocks the run is control.

Reporting versus enforcing

Every AI coding tool can show you how much a session cost after it finished. Far fewer will actually stop a run before it doubles that cost. The difference is whether spend is checked during the loop, against a ceiling that was configured before it started.

How Maistik Forge does it

The spend budget is one of Forge's enforced controls and bounds cost the way the verify circuit-breaker bounds iterations. Each change keeps its own ledger (.forge/changes/<c>/budget.yaml):

forge budget record --change <c>   # add reported spend, enforce ceiling
forge budget check  --change <c>   # read-only verdict
forge budget reset  --change <c>   # clear the ledger

record returns a non-zero exit with BUDGET EXCEEDED the moment a configured ceiling — --max-tokens, --max-usd, or --max-tool-calls — is strictly crossed. With no ceiling set, the ledger accumulates spend and never blocks; enforcement only turns on once you give it a number to enforce.

Questions people actually ask

Does Forge meter tokens itself, or does it trust the agent to report them?

Forge is not inside the model's inference loop, so it does not meter tokens on its own. Whoever holds the real numbers — a host hook or the agent — reports spend into the ledger, and Forge enforces the ceiling against what was reported. Tool-call count is the most reliably reportable figure, since a PostToolUse hook can increment it once per call. See the honest limit for the full explanation of what this does and does not guarantee.

What happens exactly at the limit — does the last request still go through?

Reaching exactly the configured ceiling is within budget; only strictly exceeding it blocks. 1000/1000 passes, 1001/1000 blocks.