> For the complete documentation index, see [llms.txt](https://ura-labs-1.gitbook.io/ura-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ura-labs-1.gitbook.io/ura-documentation/capacity-protocol/model-b-sponsored-execution.md).

# Model B — Sponsored Execution

Model B is the demand and execution side of the Capacity Protocol.

An application submits a bounded request. The operator validates policy and available capacity, reserves a budget, executes the Midnight operation and records the confirmed result.

## Proven boundary

* One bounded live sponsored spend on Preprod.
* Warm-operator source/spend reconciliation.
* Local one-click sponsored user experience.

## Required controls

* Identifiable application and request.
* Explicit operation scope and budget.
* Replay and expiry handling.
* Classified retryable, rejected and terminal outcomes.
* Operator-signed receipt and on-chain inclusion evidence.
* Append-only reconciliation.

Model B can operate from Ura's own capacity while generalized Model A wallet onboarding is being completed.


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