Serving stack and optional Tier 3 calls

The engine reports the stack and stages used for a request. The stack declaration is the source of truth for which components are available; see the Models & Licences view in Studio or the deployed engine health response. Do not infer a component or capability from a product label.

Tier 3 is an optional third-party operation. It does not run because a confidence value falls below a threshold. A caller requests it explicitly with supervisor or finalize; if no Tier 3 provider is configured, the response reports that it was skipped. Third-party output is labelled in the response. See the SDK contract for the request options.

Request path

flowchart LR
    Request[Application request] --> Engine[Declared serving stack]
    Engine --> Result[Decision and available evidence]
    Result --> App[Application checks permissions and acts]
    Result -. explicit caller option .-> Tier3[Optional third-party supervisor or final response]

The application decides whether to execute a returned tool call. A response outcome or may_act field does not grant access to customer data or authorize an external side effect.

Inspect the live stack

Use the health endpoint and request trace for the engine you actually run. Record the stack identifier alongside any evaluation. Results from another stack or an unverified local build do not describe the deployed engine.