Field note
Fees for Liveness: First Price, a Posted Reserve, and No Native Token
A private Action still consumes proving, aggregation, data, and L1 inclusion capacity. If no one is paid to carry it through the epoch, privacy and correctness do not create liveness by themselves.
The vault models this obligation as a dedicated FeeV1 kind. Every Action contains exactly one non-empty fee partition. Its circuit requires one positive output, an approved fee asset, and the genesis-pinned AggregatorFeeVault as owner. The fee asset and amount are public so aggregators can order candidate Actions without learning their hidden value or application kind.
Why the rule stays thin
The universal layer should not decide what every application charges. FeeV1 pays for protocol liveness. A kind may separately route a fraction of its own conserved value to a collector. On PayMoney Solve, for example, FiatOfferV1 splits the selected escrow asset between the taker and PayMoney's collector under immutable offer terms, rounding toward the taker.
Keeping those two fees separate prevents an application's business rule from becoming a vault-wide semantic assumption.
First price with a reserve
Candidates publish a fee and the aggregator prefers more valuable inclusion work: a first-price market. First price is not strategy-proof. Users may shade or raise bids based on expected demand, and the winning payment need not equal the opportunity cost imposed on the next candidate.
The target pairs this with a minimum posted reserve. A wallet can present that reserve as the lowest currently admissible price rather than forcing a user to guess whether zero will be ignored. The reserve improves the interaction; it does not transform the auction into a truthful mechanism.
Why there is no EIP-1559-style burn
The vault has no native token whose monetary policy could absorb a base-fee burn. Approved assets such as USDC fund the aggregator vault directly. Introducing a burn merely to imitate another fee market would add value semantics and governance the architecture deliberately avoids.
Hidden kinds and amounts remove content-extraction opportunities that depend on reading an Action's business details. They do not remove fee-based inclusion, exclusion, or censorship. Rotation and forced-inclusion mechanisms bound that residual power.
No numerical fee is defensible before measured proving, bandwidth, and L1 costs exist. The design fixes the mechanism; deployment evidence must calibrate the reserve and wallet policy.