Maestro
The Model Router
The Model Router gives each task to the model that does it best at the lowest price, checks what comes back, and hands the result to the next model with its context intact.
The Model Router is Maestro choosing the model. It reads each task as it starts and routes it to one of the models on the board, and behind them, 300+ AI model endpoints across 14 leading model providers.
How it routes
- Routine tasks go to the cheapest model that passes the checks.
- Complex tasks go to the strongest model for the job.
- Images go to a model that makes images.
- Failed checks send the task to another model. The retry and its cost go in the record.
A sponsored model costs nothing, so it takes every task it does well. Quality still decides: when another model does a task better, that one is used, and the record shows the cost.
One task, followed through the Router
An abandoned-cart email for Northwick Candle Co., our example store, which sells in two currencies. Each step shows its model and its cost. One test fails. Only the fix moves to a stronger model.
| Step | Model | Why this model | Cost |
|---|---|---|---|
| Write the task spec | Fable | Best at specs | $0.22 |
| Plan the files | GPT | Drafting and planning | $0.03 |
| Write the code, four files | DeepSeek | Strong code at a low price | $0.04 |
| Write the tests | Sonnet | Testing | $0.05 |
| One test failed. Re-routed to the next model up. | Opus | Stronger model for the fix | $0.08 |
| Review the change | Opus | Review by a model that did not write the code | $0.07 |
| Write the email copy and subject lines | GPT | Copy | $0.01 |
| Merge and deploy a preview | ZB Cloud | Hosting | $0.00 |
| Total | $0.52 |
The same task with everything on one model: $1.45. List prices on 10 October 2026. The deploy step is part of hosting, charged separately; the 5% fee is separate too.
The same build at scale
Northwick Candle Co. is a storefront, an AI shopping assistant and the eighteen systems behind them: 3,559 AI tasks across twelve models.
| How it ran | Cost |
|---|---|
| Fable, one model for everything | $720.00 |
| Opus, one model for everything | $290.97 |
| ZB Stack, routed by the Model Router, with the 5% fee | $29.10 |
That is 90% less than Opus and 96% less than Fable. Seventy-nine tasks failed a check and were re-routed; their retries are inside the $29.10. This is our example build, not a customer result.
Five ideas behind it
| Idea | Meaning |
|---|---|
| Task | One piece of work with one result: a spec, a file of code, an image, a reply to a customer |
| Rule | Where a task may go and how much it may spend. Set once, applied to every task it covers |
| Route | The Router's choice of model for a task, made as the task starts |
| Check | A test, a review or a rule that the result must pass, run by something that did not produce it |
| Record | Every task with its model, the reason, the check and the cost |
You never have to choose a model. You can choose one yourself on any task: see Routing rules.