Price per token is the wrong cost metric for agents

The useful cost unit for an agent isn't a token, or even a model call. It's the run that clears the schema, tests, and whatever business check actually matters. That changes the routing question. A strong planner can define the constraints, split the work, and take the weird cases. A faster executor can handle repetitive tool calls while the harness owns pass/fail. Pretty standard idea, but most cost comparisons still stop at input and output pricing. Ling-3.0-flash is interesting in that slot because its published design targets low-latency, tool-using execution. The limitation is part of the setup: it still benefits from explicit validation nodes and structured error feedback. Those validators change the math. A cheap call followed by three blind retries is not cheap. A more expensive call that passes the gate on the first attempt might be. And a faster executor can still be a bad trade if someone has to inspect every output by hand. One thing I haven't settled is the escalation rule. Do you hand the task back to the planner after two failed validations? Only on a schema failure? Or do you set a hard budget per accepted result and let the router decide? For people running multi-model agents, which boundary has held up best: task type, failure count, or budget?