Express, Foundation and Frontier. Your plan sets the highest tier you can pick. You pick one for each prompt.
Every question you ask has a tier: Express, Foundation, Frontier. The tier sets which engines fill the seats. Your plan sets the highest tier you can reach. Inside that limit, you choose per prompt.
A plan gives you access to a tier, and you pick the tier for each question. How the ceiling applies depends on where you call from.
| Where | Ceiling |
|---|---|
| Chat | Signed out reaches Express. Signed in on Free reaches Foundation. Plus and Pro reach Frontier. A Free account that picks Foundation keeps the Express roster in the seats, and the panel convenes for that question. |
| API key | tier defaults to Foundation (plus). Any of the three values below is accepted. |
| Connected app on your plan | Your plan's own tier. A higher tier returns tier_not_permitted with the highest tier your plan allows. |
A Pro subscriber can run Express all day and choose Frontier for the hardest questions. In Chat, the selector next to the composer is headed Who Deliberates. It shows the tier in force, and your pick is kept for next time.
| Tier | Seats |
|---|---|
| Express | Small, fast engines. The cheapest and quickest. |
| Foundation | Mid-range engines. |
| Frontier | Frontier engines. The dearest and slowest. |
The tier decides who sits. The Mode decides how the panel works. A Mode can turn on the express lane, where an easy question gets one seat's answer with no judge and no synthesis. In Chat, choosing Foundation or Frontier convenes the panel for that question.
Pick Express for everyday work. Pick Foundation when you want the panel to debate the question. Pick Frontier when a wrong answer is expensive.
tier on deliberate, or tier on the request body. The API and MCP tier parameter takes three values that name the seat roster, listed in the API reference. With an API key, any listed tier is accepted. In a connected app billed to your plan, a value above your plan returns tier_not_permitted, with the highest tier your plan allows.| Tier | Send tier as |
|---|---|
| Express | "experience" |
| Foundation | "plus" |
| Frontier | "pro" |
On the REST API, any other value returns invalid_tier.
The receipt on every answer shows which engines ran and whether a deliberation happened. Open it with get_receipt or from the answer in Chat.