Glossary

Definitions of key terms and concepts used throughout the Cycles documentation.

Core Concepts

Budget Authority

The role Cycles plays in an autonomous system: authorizing or denying execution based on whether sufficient budget is available. Unlike billing or observability, budget authority is enforced before work begins. See What Cycles Is Not for how this differs from adjacent categories.

Reservation

A temporary hold placed on a budget before work begins. Reservations lock an estimated amount so that concurrent operations cannot overspend the same budget. Every reservation must eventually be committed or released. See How Reserve-Commit Works.

Commit

Finalizing a reservation with the actual cost once work completes successfully. The committed amount replaces the original estimate, and any difference is returned to the available budget. See How Reserve-Commit Works.

Release

Freeing a reservation's held budget when the associated work fails, is cancelled, or is no longer needed. The full reserved amount is returned to the available budget. See How Reserve-Commit Works.

Estimate

The predicted cost used when creating a reservation. Estimates determine how much budget is held and should be calibrated to cover the worst-case execution cost. See How to Estimate Exposure Before Execution.

Actual

The real cost committed after execution completes. The actual amount may be less than, equal to, or greater than the original estimate, with the difference handled by the configured overage policy.

Decide

A preflight budget check that evaluates whether a reservation would be allowed, without actually creating one. Useful for UI gating, request routing, or early rejection of requests that would exceed budget. See How Decide Works.

Budget & Scope

Scope

A hierarchical path that identifies a specific budget. Scopes are built from subject fields and take the form tenant:acme/workspace:prod/agent:summarizer. Budgets are enforced at every level of the scope hierarchy. See How Scope Derivation Works.

Subject

The set of entity fields — tenant, workspace, app, workflow, agent, and toolset — that identify who is spending. Subjects are sent with every protocol request and used to derive the scope path.

Scope Derivation

The process by which Cycles builds hierarchical scope paths from the subject fields on a request. Each field maps to a level in the scope tree, enabling budget enforcement at any granularity from tenant-wide down to a single toolset. See How Scope Derivation Works.

Cap / Budget Cap

A constraint applied to execution when budget is running low but not yet exhausted. For example, a cap might reduce max_tokens on an LLM call so the request can still proceed at lower cost. Caps are returned as part of an ALLOW_WITH_CAPS decision. See Caps and the Three-Way Decision Model.

Three-Way Decision

The three possible responses to a reservation or decide request: ALLOW (proceed normally), ALLOW_WITH_CAPS (proceed with reduced limits), or DENY (reject the request). This model enables graceful degradation instead of hard pass/fail. See Caps and the Three-Way Decision Model.

Overage Policy

Configures what happens when the actual cost committed exceeds the original estimate. Three policies are available: REJECT (deny the commit), ALLOW_IF_AVAILABLE (permit if remaining budget covers the difference), and ALLOW_WITH_OVERDRAFT (permit even if it creates debt). See Commit Overage Policies.

Units

USD_MICROCENTS

One hundred-millionth of a dollar (10^-8 USD). This is the default monetary unit in Cycles, chosen for integer-precision arithmetic at sub-cent granularity. See Understanding Units.

TOKENS

A raw token count unit, typically used to track LLM input and output tokens directly rather than converting to monetary cost. See Understanding Units.

CREDITS

An abstract credit unit that lets teams define their own internal currency. Useful when monetary cost is not the right abstraction for a given budget. See Understanding Units.

RISK_POINTS

An abstract risk-scoring unit for budgeting non-monetary concerns such as safety risk, compliance exposure, or action severity. See Understanding Units.

Lifecycle

TTL (Time To Live)

The duration an active reservation remains valid before it auto-expires. If a reservation is neither committed nor released within its TTL (plus any grace period), the held budget is automatically reclaimed. See Reservation TTL, Grace Period, and Extend.

Grace Period

An additional window of time after a reservation's TTL expires before the held budget is fully reclaimed. The grace period provides a safety buffer for in-flight operations that slightly exceed their TTL. See Reservation TTL, Grace Period, and Extend.

Extend

Prolonging an active reservation's TTL before it expires. This is used when work is taking longer than originally anticipated and the reservation should remain active. See Reservation TTL, Grace Period, and Extend.

Heartbeat

An automatic TTL extension sent periodically by SDK clients to keep a reservation alive during long-running work. Heartbeats remove the need for callers to manually track and extend reservation lifetimes.

Operations

Shadow Mode / Dry Run

Evaluating budget policies and computing the decision result without persisting the reservation or affecting budget balances. Shadow mode is used during rollout to validate enforcement logic before turning it on in production. See Dry-Run / Shadow Mode Evaluation and Shadow Mode How-To.

Idempotency Key

A unique client-supplied key that ensures a protocol operation is processed exactly once, even if the request is retried due to network failures or timeouts. Each endpoint type has its own idempotency scope. See Idempotency, Retries, and Concurrency.

Debt / Overdraft

A negative budget balance that occurs when the actual cost committed exceeds the available budget. Debt is only permitted when the overage policy is set to ALLOW_WITH_OVERDRAFT. See Debt, Overdraft, and the Over-Limit Model.

Event / Direct Debit

Recording spend against a budget without a prior reservation. Events are used for costs that are known after the fact or that bypass the reserve-commit lifecycle entirely. See How Events Work.

Balance

The current state of a budget, including fields such as allocated, spent, reserved, remaining, and debt. Balances are computed across the full scope hierarchy and reflect all committed, reserved, and event-based spend. See Querying Balances.

Infrastructure

Cycles Server

The HTTP service that implements the Cycles Protocol and processes all budget authority requests — reserve, commit, release, decide, extend, events, and balances. See the API Reference.

Admin Server

The management API used to configure tenants, API keys, budgets, and policies. The Admin Server is separate from the Cycles Server and is not part of the protocol's hot path. See Authentication, Tenancy, and API Keys.

Cycles Protocol

The open specification defining the budget authority API. The protocol covers the complete reservation lifecycle, balance queries, event recording, and decision evaluation. See the API Reference.