Preemption Budget for Rate-Limited Override

Mechanism

Each actuation unit binds, at credentialing time, a preemption budget specifying the maximum number of in-flight actions the unit may preempt within a defined window, the maximum duration each preemption may extend, the replenishment policy by which budget units return to the unit, and the credentialing authority empowered to issue the budget within its scope. The budget is not advisory; it is enforced by the actuation gate itself, in the same code path that evaluates ordinary admissibility.

When a high-priority request arrives at an actuation unit that has in-flight actions of lower priority, the unit evaluates whether the new request can be satisfied by reordering, deferring, or aborting one or more in-flight actions. If preemption is required, the unit consumes one budget unit per preempted action and emits a credentialed preemption event recording the preempted action, the preempting request, the credentialing authority of the preemption, and the budget level after consumption. The preempted action is recorded in lineage in the state at which it was interrupted; the preempting request commits under emergency-accelerated mode and accrues against its own admissibility lineage.

When the budget is exhausted and a further preemption is contemplated, the actuation gate does not violate. It applies backpressure. The high-priority request is not silently dropped; it is held against an explicit backpressure signal that propagates upstream as a credentialed observation. The upstream layer — a planner, an arbiter, or an operator interface — observes that the unit has saturated its preemption envelope and must respond by re-prioritizing, deferring, routing the request elsewhere, or escalating to a higher credentialing authority that can issue a supplementary budget under explicit accountability. Exhaustion is therefore not a failure mode; it is a credentialed condition that surfaces upstream rather than being absorbed silently within the actuation unit.

Operating Parameters

The window over which budget is counted is policy-defined and may be temporal, action-counted, or mission-scoped. A drone delivery system may carry a per-flight budget that resets only on landing; an autonomous vehicle may carry a per-trip budget; a collaborative robot in a manufacturing cell may carry a per-shift budget. The window choice is a credentialing decision and is recorded in the unit's binding so that downstream auditors may reconstruct exactly under what envelope the unit operated.

The maximum duration per preemption bounds how far any one preemption may extend. A preemption that would hold a lower-priority action in the interrupted state beyond its duration bound forces the unit to either commit the preempted action's safe-state procedure or escalate to an upstream authority. The duration bound prevents preemption from being used to indefinitely suspend an action under the cover of a single budget unit.

Replenishment policy governs how budget units return. Temporal replenishment returns a budget unit at a defined cadence regardless of system events. Explicit-replenishment returns budget only upon a credentialed event from the issuing authority, requiring affirmative attention to budget restoration. Mission-scoped replenishment returns budget only at boundary events such as completion of a mission segment. The disclosed apparatus contemplates all three; selection is a policy decision recorded in the unit's credential.

Credentialing authority governs who may issue, revoke, or supplement a unit's budget. The authority is itself a credentialed identity in the mesh, and its issuance of budget is a credentialed observation visible to auditors. A unit may carry multiple budgets credentialed by distinct authorities, each scoped to a class of preempting events; an emergency-services authority may issue an emergency-class budget while an operations authority issues a routine-priority budget, and the unit consumes from the appropriate pool.

Excessive consumption — defined as a rate of budget consumption exceeding a policy threshold — itself emits a governance-flagged credentialed event. The event propagates as an observation through the mesh and may be consumed by upstream policy components to throttle the originating priority source, request human review, or trigger a supplementary credentialing decision. A unit whose preemption budget is being consumed near its envelope is therefore visible to the broader system long before the budget is exhausted.

Alternative Embodiments

Embodiments differ in granularity. A coarse-grained embodiment counts preemptions as integer units regardless of the cost of each. A fine-grained embodiment weights each preemption by an estimated cost — the energy expended in aborting an in-flight motion, the safety margin consumed by the reorder, the downstream impact on dependent actions — and consumes budget proportionally. Hybrid embodiments use coarse counting as a fast path and refine consumption against a fine-grained accumulator in parallel.

Embodiments differ in scope. A per-unit embodiment binds budget to a single actuator. A pooled embodiment binds budget to a cluster of actuators that share a credentialing authority, with consumption from the pool reflecting the aggregate preemption load on the cluster. A hierarchical embodiment combines per-unit budgets nested under a pool budget, so that local preemptions consume local budget but persistent or large preemptions also consume from the pool.

Embodiments differ in preemption mechanics. In an abort embodiment, the preempted action terminates and emits its safe-state output. In a defer embodiment, the preempted action pauses in its current state for the duration of the preempting request and resumes thereafter. In a reorder embodiment, the preempted action and the preempting request are re-sequenced under arbitration policy. The preemption budget composes uniformly across these embodiments because the unit accounted for is the preemption event itself, not the underlying mechanism by which the lower-priority action was displaced.

Embodiments differ in their treatment of backpressure. In a hard-backpressure embodiment, an exhausted unit refuses further preemption requests outright and the upstream layer must absorb the refusal. In a soft-backpressure embodiment, the unit signals saturation upstream while continuing to process at its non-preempting capacity. In a graceful-degradation embodiment, the unit transitions to a safe-mode controller that processes a restricted action set without consuming preemption budget, holding the system in a stable envelope until upstream attention restores capacity.

Composition With Other Subsystems

The preemption budget composes with composite admissibility by appearing as one term in the admissibility evaluation. The evaluator considers ordinary admissibility, preemption authority, available budget, and credentialing standing in a single composite decision. A request that would commit under preemption commits only when all four terms admit it. The budget is not a side-channel that bypasses admissibility; it is admitted into admissibility as a structural input.

The budget composes with the credentialed observation mesh by emitting every consumption, exhaustion, and replenishment as a credentialed observation. The mesh accumulates these observations into the unit's lineage, the issuing authority's lineage, and the broader system's audit record. A reviewer reconstructing the system's operation reads not only what actions occurred but how each emergency authority was used and how its envelope was managed across the mission.

The budget composes with the trust slope of the requesting identity. A requester whose slope reflects sustained reliability draws preemption against a more permissive policy than a requester whose slope reflects volatile or unverified history. A requester whose slope has degraded loses preemption authority before its budget is exhausted; the slope itself participates in the admissibility evaluation. The composition prevents preemption authority from becoming a static privilege that survives a deteriorating identity.

The budget composes with the governed actuation arbiter by surfacing budget state to the arbiter as a first-class signal. The arbiter, presented with multiple competing requests for a saturated unit, may route to alternate units, queue requests against expected replenishment, or escalate to upstream authority. The arbiter's decision is itself a credentialed action whose lineage records why it chose the routing it chose, anchoring the system's behavior under saturation in the same audit substrate that anchors its behavior under ordinary load.

Prior-Art Distinctions

Real-time priority preemption in conventional schedulers — fixed-priority preemptive scheduling, rate-monotonic scheduling, earliest-deadline-first — admits preemption whenever priority comparison admits it. There is no budget. A high-priority task may preempt arbitrarily often within its activation pattern. The disclosed apparatus differs in that preemption authority is itself a finite, credentialed resource, and exhaustion produces backpressure rather than continued silent override.

Token-bucket and leaky-bucket rate limiters meter request admission against a refilling capacity, but they do not distinguish ordinary admission from emergency override, and they do not emit credentialed observations on consumption. The disclosed apparatus differs in that the metered resource is specifically the override authority, the metering is bound to the actuation gate's admissibility evaluation rather than to an independent ingress filter, and consumption is admitted into the audit substrate as a first-class lineage event.

Capability-based access control systems carry capabilities that authorize specified operations, and capabilities may be revoked. The disclosed apparatus differs in that the budget is not a capability and is not revocable by simple removal; it is an enforced quantity that decrements with use, replenishes under credentialed policy, and surfaces upstream when saturated. The temporal dynamics of the budget are central, where capability revocation is structural and discrete.

Safety-instrumented system architectures in industrial control define safe-state behaviors and require that emergency stops not be inhibited. The disclosed apparatus does not inhibit safety responses; it bounds the use of operationally elective preemption, leaving non-elective safety responses governed by their own subsystems. The two architectures are complementary; preemption budget addresses the operational misuse of override that safety-instrumented architectures do not directly meter.

Disclosure Scope

This article forms part of the disclosure of Provisional Application 64/049,409 and supports claims directed to a per-unit preemption budget bounding the count, duration, and authority of preemptions an actuation unit may perform within a window, including the emission of credentialed observations on consumption, the production of structural backpressure rather than violation upon exhaustion, the composition of the budget with the composite admissibility evaluator, and the alternative embodiments differing in granularity, scope, and preemption mechanics. The disclosure further supports claims directed to the integration of the budget with the credentialed observation mesh, the trust slope subsystem, and the governed actuation arbiter disclosed elsewhere in the application.