I went looking for a flag that could cap the amount spent on a session on DeepAgents. The kind of hard spending cap that stops an agent loop before it burns through a budget. What exists instead is a warning, and the gap between "warning" and "stopping" turned out to be the more interesting story. What Already Exists: A Number With No Teethdeepagents-code has a CostTrackingMiddleware that owns a thread's cumulative spend. This is a real, checkpointed dollar figure priced from actual per-request token usage, not an estimate. A separate feature built on top of that number, merged earlier, adds a one-time warning once the total crosses a configured threshold (default $50):