A cheaper model is not cheaper if it silently breaks the workflow. That is the trap many AI product teams are walking into as open-weight models get stronger. A model looks good in a leaderboard, a demo feels fast, and the per-token price looks friendly. Then production traffic arrives. Support answers lose citations. JSON starts drifting. Tool calls become noisy. A workflow that looked 40% cheaper now needs retries, escalations, and manual cleanup. The safer path is not "use the biggest m...