Run first the checks most likely to fail for each second they take, so a bad change hears no as early as possible. In practice that mostly means cheapest first: format, lint, types, unit tests, then the slow and costly ones.
An agent sits idle or burns tokens while it waits, and every retry goes through the line again, so a slow first failure is paid for over and over. Good work doesn't get any faster from this. Only the bad news does, and that is where an agent spends its time.
Say it to your agent
“Order the CI pipeline by cost: format and lint first, then tsc --noEmit, then unit tests, with mutation tests only after merge. Stop at the first failure. Print how long each step took, and if the total is over 5 minutes, tell me which one to move.”